Bacterial coinfections in COVID-19-hospitalized patients

SUMMARY OBJECTIVE: The aim of this study was to assess the rate of bacterial infections in COVID-19-hospitalized patients and to analyze the most prevalent germs, sources, risk factors, and its impact on in-hospital mortality. METHODS: This observational retrospective study was conducted on 672 patients hospitalized between April and August 2020 in Nossa Senhora da Conceição Hospital, a public hospital located in Porto Alegre, Brazil. The inclusion criterion was adult patients hospitalized with confirmed COVID-19. Data were collected through chart review. Risk factors for bacterial infection and mortality were analyzed using both univariate and multivariate robust Poisson regression models. RESULTS: Bacterial coinfection was observed in 22.2% of patients. Risk factors for bacterial infections were dementia (RR=2.06 (1.18-3.60); p=0.011), cerebrovascular disease (RR=1.75 (1.15-2.67); p=0.009), active cancer (RR=1.52 (1.082-2.15); p=0.01), need for noninvasive ventilation (RR=2.320 (1.740-3.094); p<0.01), invasive mechanical ventilation (RR=4.63 (2.24-9.56); p<0.01), and renal replacement therapy (RR=1.68 (1.26-2.25); p<0.01). In the adjusted model, bacterial infections were not associated with mortality (0.96 (0.75-1.24); p=0.79). The most common source of infection was due to respiratory, blood, and central venous catheters, with 69 (29.36%), 61 (25.96%), and 59 (25.11%) positive cultures, respectively. CONCLUSION: We observed a high rate of bacterial infections in COVID-19-hospitalized patients, most commonly of respiratory source. Neurologic and oncologic morbidities and need for ventilation and renal replacement therapy was associated with risk factors for bacterial infections. Nevertheless, an association between bacterial infections and hospital mortality was not established.

Sequencing and multiple antimicrobial resistance of Pseudomonas fluorescens isolated from Nile tilapia fish in Egypt

Abstract Pseudomonas fluorescens is one of the main causes of septicemic diseases among freshwater fish, causing severe economic losses and decreasing farm efficiency. Thus, this research was aimed to investigate the occurrence of P. fluorescens in Nile Tilapia (O. niloticus) fish in Egypt, gene sequencing of 16SrDNA gene, and antimicrobial susceptibility. P. fluorescens strains were detected in 32% (128/400) of apparently healthy (9%; 36/400) and diseased (23%; 92/400) Nile tilapia fish. The highest prevalence was observed in gills of fish, 31.3% followed by intestine 26.9%, liver 24.2%, and kidneys 17.6%. The PCR results for the 16SrDNA gene of P. fluorescens showed 16SrDNA gene in 30% of examined isolates. Moreover, Homogeny and a strong relationship between strains of P. fluorescens was confirmed using 16SrDNA sequences. Beside the responsibility of 16SrDNA gene on the virulence of P. fluorescens. The results of antimicrobial susceptibility tests revealed that all strains were resistant to piperacillin (100%), followed by ceftazidime (29.7%), and cefepime (25.8%). The strains of P. fluorescence were highly sensitive to cefotaxime (74.2%), followed by ceftriaxone and levofloxacin (70.3% each). Interestingly, 29.7% of strains of P. fluorescens were multiple antimicrobial-resistant (MAR).

Resumo Pseudomonas fluorescens é uma das principais causas de doenças septicêmicas em peixes de água doce, causando graves perdas econômicas e diminuindo a eficiência da fazenda. Assim, esta pesquisa teve como objetivo investigar a ocorrência de P. fluorescens em peixes de tilápia-do-nilo (O. niloticus) no Egito, sequenciamento do gene 16S rDNA e suscetibilidade antimicrobiana. Cepas de P. fluorescens foram detectadas em 32% (128/400) de peixes tilápia-do-nilo aparentemente saudáveis (9%; 36/400) e doentes (23%; 92/400). A maior prevalência foi observada nas brânquias dos peixes, 31,3%, seguida pelo intestino 26,9%, fígado 24,2% e rins 17,6%. Os resultados da PCR para o gene 16SrDNA de P. fluorescens mostraram o gene 16SrDNA em 30% dos isolados examinados. Além disso, a homogeneidade e uma forte relação entre cepas de P. fluorescens foi confirmada usando sequências de 16SrDNA. Além da responsabilidade do gene 16SrDNA na virulência de P. fluorescens. Os resultados dos testes de suscetibilidade antimicrobiana revelaram que todas as cepas foram resistentes à piperacilina (100%), seguida pela ceftazidima (29,7%) e cefepima (25,8%). As cepas de P. fluorescens foram altamente sensíveis à cefotaxima (74,2%), seguida pela ceftriaxona e levofloxacina (70,3% cada). Curiosamente, 29,7% das cepas de P. fluorescens eram multirresistentes a antimicrobianos (MAR).

Sequencing and multiple antimicrobial resistance of Pseudomonas fluorescens isolated from Nile tilapia fish in Egypt / Sequenciamento e resistência antimicrobiana múltipla de Pseudomonas fluorescens isoladas de tilápia-do-nilo no Egito

Pseudomonas fluorescens is one of the main causes of septicemic diseases among freshwater fish, causing severe economic losses and decreasing farm efficiency. Thus, this research was aimed to investigate the occurrence of P. fluorescens in Nile Tilapia (O. niloticus) fish in Egypt, gene sequencing of 16SrDNA gene, and antimicrobial susceptibility. P. fluorescens strains were detected in 32% (128/400) of apparently healthy (9%; 36/400) and diseased (23%; 92/400) Nile tilapia fish. The highest prevalence was observed in gills of fish, 31.3% followed by intestine 26.9%, liver 24.2%, and kidneys 17.6%. The PCR results for the 16SrDNA gene of P. fluorescens showed 16SrDNA gene in 30% of examined isolates. Moreover, Homogeny and a strong relationship between strains of P. fluorescens was confirmed using 16SrDNA sequences. Beside the responsibility of 16SrDNA gene on the virulence of P. fluorescens. The results of antimicrobial susceptibility tests revealed that all strains were resistant to piperacillin (100%), followed by ceftazidime (29.7%), and cefepime (25.8%). The strains of P. fluorescence were highly sensitive to cefotaxime (74.2%), followed by ceftriaxone and levofloxacin (70.3% each). Interestingly, 29.7% of strains of P. fluorescens were multiple antimicrobial-resistant (MAR).

Pseudomonas fluorescens é uma das principais causas de doenças septicêmicas em peixes de água doce, causando graves perdas econômicas e diminuindo a eficiência da fazenda. Assim, esta pesquisa teve como objetivo investigar a ocorrência de P. fluorescens em peixes de tilápia-do-nilo (O. niloticus) no Egito, sequenciamento do gene 16S rDNA e suscetibilidade antimicrobiana. Cepas de P. fluorescens foram detectadas em 32% (128/400) de peixes tilápia-do-nilo aparentemente saudáveis ​​(9%; 36/400) e doentes (23%; 92/400). A maior prevalência foi observada nas brânquias dos peixes, 31,3%, seguida pelo intestino 26,9%, fígado 24,2% e rins 17,6%. Os resultados da PCR para o gene 16SrDNA de P. fluorescens mostraram o gene 16SrDNA em 30% dos isolados examinados. Além disso, a homogeneidade e uma forte relação entre cepas de P. fluorescens foi confirmada usando sequências de 16SrDNA. Além da responsabilidade do gene 16SrDNA na virulência de P. fluorescens. Os resultados dos testes de suscetibilidade antimicrobiana revelaram que todas as cepas foram resistentes à piperacilina (100%), seguida pela ceftazidima (29,7%) e cefepima (25,8%). As cepas de P. fluorescens foram altamente sensíveis à cefotaxima (74,2%), seguida pela ceftriaxona e levofloxacina (70,3% cada). Curiosamente, 29,7% das cepas de P. fluorescens eram multirresistentes a antimicrobianos (MAR).

Pseudomonas aeruginosa: una bella oportunista / Pseudomonas aeruginosa: a beautiful opportunist

Las bacterias son infinitamente más antiguas que el hombre y se reproducen más rápido, cada quince minutos y en una hora tienen cuatro generaciones, mientras que el hombre necesita un siglo para ello, de modo que en la larga existencia bacteriana somos apenas un minúsculo accidente. Toda la maravillosa maquinaria reunida en una sola bacteria de la especie Pseudomonas aeruginosa no fue planeada contra nosotros, incluyendo señales de quorum, bombas de expulsión, integrones, biofilm y piocinas, ya presentes en su vida natural o planctónica. Su adaptación a la vida nosocomial forzó a estudiarla y la organización de sus múltiples capacidades hace plantear que en su vida hay un propósito, una suerte de "inteligencia bacteriana" en contraposición a la tesis de Jacques Monod que estima la vida en este planeta como fruto del azar y de la necesidad.

Bacteria are infinitely older tan man and reproduce faster, every fifteen minutes and in one hour they have four generations, while man needs a century for have the same, so that in the long bacterial existence we are just a tiny accident. All the wonderful machinery assembled in a single bacterium of the species Pseudomonas aeruginosa it was not planned against us, including quorum sensing, efflux pumps, integrons, biofilm and pyocins, already presents in their natural or planktonic life. Her adaptation to hospital life forced to study this wonderful creature, and the organization of such multiple capacities suggests the existence of a vital purpose, a kind of bacterial intelligence, contrary to Jacques Monod's thesis, which estimate life in this planet as the result of chance and necessity.

Respuesta de procalcitonina ante co-infección e infección secundaria por bacterias multirresistentes en pacientes COVID -19 / Procalcitonin response in co-infection and secondary infection by multidrug resistant bacteria in COVID -19 patients

INTRODUCCIÓN. La procalcitonina, es un biomarcador que puede usarse como apoyo diagnóstico en infecciones bacterianas y la monitorización del tratamiento antibiótico, sobre todo en pacientes con sepsis. De ahí que, fue utilizado durante la pandemia COVID-19 OBJETIVO. Determinar los valores de procalcitonina en pacientes con COVID-19 y definir una p osible correlación entre su incremento y vinculación en coinfección o infección secundaria por Klebsiella pneumoniae y Pseudomonas aeruginosa con multidrogo resistencia y resistencia extendida a los antibióticos. MATERIALES Y MÉTODOS. Estudio retrospectivo observacional, descriptivo transversal, realizado del 1 de mayo al 31 de octubre del 2020 en el Hospital de Especialidades Carlos Andrade Marín sobre 7028 pacientes adultos, hospitalizados, con diagnóstico de COVID-19, y resultados de procalcitonina, cuyas muestras de secreción traqueal y/o hemocultivo presentaron desarrollo de Klebsiella pneumoniae y Pseudomonas aeruginosa. Su análisis estadístico fue desarrollado mediante la prueba Chi Cuadrado de Pearson. RESULTADOS. Se recibieron 861 muestras de hemocultivo y 391 de secreción traqueal, obteniéndose: 32% aislamientos de Klebsiella pneumoniae y Pseudomonas aeruginosa multidrogo y extremadamente resistente. Entre los pacientes COVID-19 que fallecieron, 34,4% mostraron incrementos de procalcitonina. Al contrario, entre los pacientes que sobrevivieron sólo en 8,8% se observó incrementos de procalcitonina evidenciándose un vínculo entre el incremento de procalcitonina y mortalidad. CONCLUSIONES. No existe diferencia en relación al incremento en los valores de procalcitonina en pacientes COVID-19 con co-infección o infección secundaria por Klebsiella pneumoniae y Pseudomonas aeruginosa multidrogo y extremadamente resistente y los valores de procalcitonina en pacientes con coinfección e infección secundaria con otro tipo de aislamientos bacterianos.

INTRODUCTION. Procalcitonin is a biomarker that can be used as a diagnostic support in bacterial infections and the monitoring of antibiotic treatment, especially in patients with sepsis. Hence, it was used during the COVID-19 pandemic OBJECTIVE. To determine the values of procalcitonin in patients with COVID-19 and to define a possible correlation between its increase and linkage in co-infection or secondary infection by Klebsiella pneumoniae and Pseudomonas aeruginosa with multidrug resistance and extended resistance to antibiotics. MATERIALS AND METHODS. Retrospective observational, descriptive cross-sectional study, conducted from May 1 to October 31, 2020 at the Hospital de Especialidades Carlos Andrade Marín on 7028 adult patients, hospitalized, with diagnosis of COVID-19, and procalcitonin results, whose tracheal secretion and/or blood culture samples presented development of Klebsiella pneumoniae and Pseudomonas aeruginosa. Their statistical analysis was developed using Pearson's Chi-squared test. RESULTS. We received 861 blood culture and 391 tracheal secretion samples, obtaining: 32% isolates of Klebsiella pneumoniae and multidrug-resistant and extremely resistant Pseudomonas aeruginosa. Among the COVID-19 patients who died, 34.4% showed increased procalcitonin levels. On the contrary, among patients who survived, only 8.8% showed increased procalcitonin levels, showing a link between increased procalcitonin levels and mortality. CONCLUSIONS. There is no difference in relation to the increase in procalcitonin values in COVID-19 patients with co-infection or secondary infection by Klebsiella pneumoniae and multidrug-resistant and extremely resistant Pseudomonas aeruginosa and procalcitonin values in patients with co-infection and secondary infection with other types of bacterial isolates.

Use of topical colistin in bacterial keratitis caused by extensively drug-resistant Pseudomonas Aeruginosa: a case report / Uso de colistina tópica em ceratite bacteriana causada por Pseudomonas Aeruginosa extensivamente resistente a medicamentos: relato de caso

ABSTRACT Bacterial keratitis caused by multidrug-resistant strains of Pseudomonas aeruginosa is a therapeutic challenge due to a limited number of active antimicrobials and rapid progression to corneal necrosis and perforation. To report the use of topical colistin and surgical tarsorrhaphy in a case of keratitis caused by extensively drug-resistant Pseudomonas aeruginosa in a patient with severe coronavirus disease-2019 (COVID-19) pneumonia. A 56-year-old male was admitted to the intensive care unit with clinical symptoms of severe COVID-19 pneumonia. During his stay in the unit, he developed rapidly progressive keratitis with Pseudomonas aeruginosa resistant to all drugs except for colistin on culture. Due to incomplete lid closure, a temporary tarsorrhaphy was performed, and a regimen of descending-dose topical colistin was initiated. After five weeks, keratitis resolved completely. Extensively drug-resistant Pseudomonas aeruginosa is an unusual cause of bacterial keratitis. We describe the safe and effective use of topical colistin in a case with severe corneal involvement.

RESUMO A ceratite bacteriana causada por cepas multirresistentes de Pseudomonas aeruginosa é um desafio terapêutico, devido à disponibilidade limitada de antimicrobianos e à rápida progressão para necrose e perfuração da córnea. O objetivo deste artigo é relatar o uso de colistina tópica e tarsorrafia cirúrgica em um caso de ceratite por Pseudomonas aeruginosa amplamente resistente a medicamentos em um paciente com pneumonia grave por COVID19. Um homem de 56 anos foi internado em uma unidade de terapia intensiva com sintomas clínicos de pneumonia grave por COVID19. Durante sua permanência na unidade de terapia intensiva, o paciente desenvolveu uma ceratite rapidamente progressiva, cuja cultura foi positiva para Pseudomonas aeruginosa resistente a todos os antimicrobianos, exceto colistina. Devido ao fechamento incompleto da pálpebra, foi realizada uma tarsorrafia temporária e foi instituído um esquema de colistina tópica em doses decrescentes. Após cinco semanas, a resolução completa da ceratite foi alcançada. Pseudomonas aeruginosa amplamente resistente a medicamentos é uma causa incomum de ceratite bacteriana. Este relato descreve o uso seguro e eficaz da colistina tópica em um caso com comprometimento corneano grave.

Caracterización de la utilización de colistín en un hospital de alta complejidad / Evaluation of colistin use in a highly complex hospital

RESUMEN: El aumento de la resistencia y la escasez de nuevos antibacterianos ha requerido la reintroducción de antiguos antimicrobianos entre ellos colistín. OBJETIVO: Caracterizar la utilización de colistín durante el año 2017 en un hospital universitario, mediante la descripción de los pacientes, los tratamientos, la microbiología asociada y efectos adversos. PACIENTES Y MÉTODOS: Trabajo observacional retrospectivo. Se revisaron los datos de todos los pacientes que recibieron colistín intravenoso (IV) por al menos 48 horas, durante el año 2017. RESULTADOS: Se incluyeron 53 pacientes, equivalentes a 91 tratamientos. El foco respiratorio fue el principal (46,2%). El 68,1% de los tratamientos fue iniciado en la UCI. La mayoría de los pacientes tenía una hospitalización reciente (83,5%), y presentaban uso previo de antibacterianos (89%). Los dos patógenos mayoritariamente identificados fueron Pseudomonas aeruginosa y Klebsiella spp. El consumo promedio de colistín fue de 2,4 DDD/100 camas/día. El servicio que más consumió colistín fue la UCI, con 45,5 DDD/100 camas/día, usando generalmente la dosis de 3 MUI cada 8 horas IV y con una baja utilización de dosis de carga. CONCLUSIÓN: Colistín corresponde a un antimicrobiano de uso restringido a infecciones sospechadas o confirmadas por agentes bacterianos multi resistentes. En esta serie, su uso inicial fue principalmente empírico, en pacientes con factores de riesgo para resistencia antibacteriana; se usó en forma asociada a otros antimicrobianos, siendo el foco principal el respiratorio.

BACKGROUND: The increase in resistance and the shortage of new antibiotics has led to the reintroduction of old antimicrobials such as colistin. AIM: To evaluate the use of colistin during 2017 in a university hospital, through the characterization of patients and treatment, associated microbiology, response to treatment and adverse effects. METHODS: Retrospective observational design. The data of all patients who received colistin for at least 48 hours during the year 2017 were reviewed. RESULTS: 55 patients were included, equivalent to 144 treatments. The respiratory focus was the main one (57.9%). 64% of the treatments began in the ICU, while 7% in the ward. Most of the patients has a recent hospitalization (86.8%) and has previous use of antibiotics (90.4%). The two main pathogens identified were Pseudomonas aeruginosa and Klebsiella spp. In 87.1% of the cases with microbiological justifications for the use of colistin, a favorable response was obtained. The average consumption of colistin was 2.4 DDD/100 beds/day. The department that consumed the most colistin was the ICU, with 45,5 DDD/100 beds/day, generally using a dose of 3 MIU every 8 hours IV and with low use of loading doses. CONCLUSION: Colistin corresponds to an antibiotic whose use is restricted to infections suspected or confirmed by multi-resistant bacterial agents. Its initial use in this serie was mainly empirical, in patients with risk factors for antibiotics resistance, it was used in association with other antimicrobials, being the respiratory the main infectious focus.

Otitis externa maligna con diseminación hematógena de Pseudomonas aeruginosa resistente a carbapenémicos

Pseudomonas aeruginosa en una bacteria Gram negativa no fermentadora que produce diversos tipos de infecciones severas en inmunocompetentes e inmunodeprimidos. Una de estas infecciones es la otitis externa maligna, la cual se presenta principalmente en personas con diabetes mellitus y puede tener una evolución tórpida cursando con osteomielitis de base de cráneo y parálisis de nervios craneales. El tratamiento es individualizado y principalmente conservador con antibioticoterapia guiada por cultivo. La bacteria aislada en la mayoría de los casos reportados es sensible a los antibióticos anti-pseudomónicos. Reportamos un caso de presentación inusual de otitis externa maligna por Pseudomonas aeruginosa resistente a carbapenémicos con evidencia sugerente de compromiso bilateral y en el cual se aisló al mismo germen en urocultivo y hemocultivos, lo que indicaría una diseminación hematógena del microorganismo.

Pseudomonas aeruginosa is a non-fermenting Gram-negative bacterium that produces several types of severe infections in immunocompetent and immunosuppressed patients. One of these infections is malignant otitis externa, which occurs mainly in people with diabetes mellitus and can have a torpid evolution coursing with osteomyelitis of skull base and cranial nerve palsies. Treatment is individualized and mainly conservative with culture-guided antibiotic therapy, with isolated pseudomonas being sensitive to anti-pseudomonal antibiotics in the majority of reported cases. We report a case of unusual presentation of malignant otitis externa caused by Pseudomonas aeruginosa resistant to carbapenems with suggestive evidence of bilateral involvement and in which the same germ was isolated in urine and blood cultures, which would indicate hematogenous dissemination of the microorganism.

Calidad microbiológica: detección de Aeromonas sp y Pseudomonas sp en garrafones provenientes de pequeñas plantas purificadoras de agua / Microbiological quality: detection of Aeromonas sp and Pseudomonas sp in jugs from small water purification establishments

RESUMEN Las plantas purificadoras de agua que carecen de un adecuado sistema de control de calidad pueden generar problemas de salud pública. El objetivo de este estudio fue examinar la calidad microbiológica del agua proveniente de pequeñas plantas purificadoras de la ciudad de Puebla, así como, determinar la existencia de bacterias Aeromonas sp y Pseudomonas sp, y caracterizar si presentan un fenotipo patógeno oportunista. Se recolectaron 70 muestras de garrafones de agua de 25 establecimientos. La cuantificación bacteriana se realizó mediante el método de goteo en placa. Se comprobaron los géneros microbianos mediante análisis bioquímico. En las cepas que mostraron discrepancia se utilizó la identificación molecular con base a secuencias parciales del gen 16S rRNA para confirmar su especie y se les evaluaron sus características de patogenicidad: multirresistencia a antibióticos, producción de biopelícula y actividad hemolítica. El 40 % de las plantas purificadoras no cumplieron con la calidad microbiológica del agua para consumo humano. El 41.4 % de los garrafones de agua muestreados incumplió la normativa, presentando coliformes totales 35.7 %, Pseudomonas 30 %, Enterococcus faecalis 8.6 % y bacterias coliformes fecales el 5.7 %. Se obtuvieron 56 aislados, provenientes de los 29 garrafones contaminados; 10 de ellos se caracterizaron molecularmente, resultando 7 aislados relacionados con especies diferentes de P. aeruginosa y 3 con especies de Aeromonas. De los aislados de Pseudomonas, 5 presentaron resistencia a 2 familias de antibióticos y 2 mostraron multirresistencia. El 36 % de los 10 aislados produjeron hemólisis y biopelícula. Dos cepas de Aeromonas mostraron resistencia a Cefalosporina 3a generación pero no produjeron hemólisis. Los 10 aislados analizados fueron clasificados como no patógenos. Es necesario un seguimiento sanitario más estricto para lograr el cumplimiento de las normas nacionales e internacionales relacionadas con el consumo de agua purificada, para evitar dañar la salud de los consumidores.

ABSTRACT Water purification establishments that lack an adequate quality control system can cause public health problems. The objective of this study was to examine the microbiological quality of water from small purification establishments in the city of Puebla, as well as to determine the existence of Aeromonas sp and Pseudomonas sp bacteria, and to characterize whether they present an opportunistic pathogenic phenotype. 70 water jug samples were collected from 25 establishments. Bacterial quantification was performed using the drop plate method. Microbial genera were determined by biochemical analysis using the standard methodology. In the strains that showed discrepancy, molecular identification based on partial sequences of the 16S rRNA gene was used to confirm their species, and their pathogenic characteristics were evaluated: multiresistance to antibiotics, biofilm production, and hemolytic activity. The results showed that 40 % of the purification establishments did not comply with the microbiological quality of water for human consumption. Similarly, 41.4 % of the jugs of water sampled failed to comply with the regulations, presenting total coliforms 35.7 %, Pseudomonas 30 %, Enterococcus faecalis 8.6 % and fecal coliform bacteria 5.7 %. Likewise, 56 isolates were obtained from the 29 contaminated jugs, of which 10 were molecularly characterized, resulting in 4 different species for P. aeruginosa and 3 for Aeromonas. Of the 7 Pseudomonas isolates, 5 presented resistance to 2 families of antibiotics and 2 showed multiresistance. In total, 36 % of the 10 isolates produced hemolysis and biofilm. Two Aeromonas strains showed resistance to 3rd generation Cephalosporin but did not produce hemolysis. The 10 isolates analyzed were classified as non-pathogenic. A stricter sanitary monitoring is necessary to achieve compliance with national and international standards related to the consumption of purified water, to avoid harming the health of consumers.

Antibacterial Activity of Lawsonia inermis Leaf Extracts against Multidrug-resistant Pseudomonas aeruginosa from Infected Wounds

Background: Wound infection comprises numerous different organisms that have the ability to surface colonization of wounds. Multidrug-resistant Pseudomonas aeruginosa is one of the pathogenic bacteria associated with wound infections. Aim: This study isolated and identified multidrug-resistant Pseudomonas aeruginosa from infected wounds and determine the antibacterial activity of Lawsonia inermis leaf extracts against it. Design: This is a Clinical and laboratory-based study involving patients with defined cases of wound infections. Place and Duration of Study: This study was conducted in the Microbiology (Bacteriology) laboratory of Specialist Hospital, Bauchi, Nigeria, from February to November 2021. Methods: Twenty-eight (28) Pseudomonas aeruginosa isolates were recovered from 179 wound swabs using standard laboratory procedures and were screened for multidrug-resistant patterns according to the Kirby-Bauer disc diffusion method. Antibacterial efficacy of the aqueous, ethanolic, and methanolic leaf extracts of Lawsonia inermis was tested against the multidrug-resistant isolates using agar well diffusion techniques. The zone of inhibition was measured and the differences between means were statistically analyzed (p<0.05). Results: A total of twenty-eight (28) multidrug-resistant Pseudomonas aeruginosa were confirmed, showing resistance to Amoxicillin (64.3%), Ceftazidime (85.71%), and Cefotaxime (78.57%) but sensitivity to Imipenem (95.5%). The phytochemical screening revealed the presence of flavonoids, glycosides, saponins, steroids, and tannins among others. MDR P. aeruginosa was inhibited at varied concentrations of the extracts with the diameter mean zone of inhibition increasing as the concentration increased. The Methanol extracts showed the highest antibacterial activity against MDR P. aeruginosa with a mean zone of inhibition of 9.500±0.288mm at 400mg/ml. Conclusion: These results indicated that Lawsonia inermis leaf extracts possess antibacterial activities on Multidrug-resistant Pseudomonas aeruginosa which could be a good source for the production of plant-based antibacterial drugs., although somewhat less than the synthetic standard drugs (Imipenem) having a mean of 13.83±0.288mm.

Absceso en miocardio secundario a neumonía adquirida en la comunidad por Pseudomona aeruginosa en lactante inmunocompetente: reporte de caso / Myocardial abscess secondary to community acquired Pseudomona aeruginosa pneumonia in an immunocompetent infant: case report

La Pseudomona aeruginosa es una causa importante de infecciones asociadas a la atención de la salud y en las neumonías adquiridas en la comunidad, rara vez se identifica como el agente patógeno, siendo estas de progresión rápida y de mal pronóstico. Se trata de un menor de un año de edad inmunocompetente el cual fallece en casa una semana después de una lesión en la planta del pie derecho que según familiares le sacaron "pus", tratado con antinflamatorios y analgésicos. Se le realizó necropsia que evidenció cicatriz en planta de pie derecho sin lesiones traumáticas. Pulmones de consistencia indurada, con adherencias y áreas que impresionan necróticas, asociada a efusión pleural. El estudio histológico reportó un proceso infeccioso pulmonar agudo abscedado que se diseminó por continuidad a tejido cardiaco y en estudios microbiológicos de pulmón y bazo se reportó Pseudomona aeruginosa.

Pseudomona aeruginosa is an important cause of health care-associated infections and in community-acquired pneumonias, it is rarely identified as the pathogenic agent, being of rapid progression and poor prognosis. This is a one-year-old immunocompetent minor who died at home one week after a lesion in the sole of the right foot which, according to family members, caused "pus", treated with anti-inflammatory and analgesic drugs. A necropsy was performed, which showed a scar on the sole of the right foot with no traumatic lesions. Lungs of indurated consistency, with adhesions and areas that appear necrotic, associated with pleural effusion. The histological study reported an abscessed acute pulmonary infectious process that spread by continuity to cardiac tissue and microbiological studies of lung and spleen reported Pseudomona aeruginosa.

Evaluation of toxin-antitoxin genes, antibiotic resistance, and virulence genes in Pseudomonas aeruginosa isolates

SUMMARY OBJECTIVE: Toxin-antitoxin genes RelBE and HigBA are known to be involved in the formation of biofilm, which is an important virulence factor for Pseudomonas aeruginosa. The purpose of this study was to determine the presence of toxin-antitoxin genes and exoenzyme S and exotoxin A virulence genes in P. aeruginosa isolates and whether there is a relationship between toxin-antitoxin genes and virulence genes as well as antibiotic resistance. METHODS: Identification of the isolates and antibiotic susceptibilities was determined by a VITEK 2 (bioMérieux, France) automated system. The presence of toxin-antitoxin genes, virulence genes, and transcription levels were detected by real-time polymerase chain reaction. RESULTS: RelBE and HigBA genes were detected in 94.3% (82/87) of P. aeruginosa isolates, and exoenzyme S and exotoxin A genes were detected in all of the isolates (n=87). All of the isolates that harbor the toxin-antitoxin and virulence genes were transcribed. There was a significant increase in the RelBE gene transcription level in imipenem- and meropenem-sensitive isolates and in the HigBA gene transcription level in amikacin-sensitive isolates (p<0.05). There was a significant correlation between RelBE and exoenzyme S (p=0.001). CONCLUSION: The findings suggest that antibiotic resistance may be linked to toxin-antitoxin genes. Furthermore, the relationship between RelBE and exoenzyme S indicates that toxin-antitoxin genes in P. aeruginosa isolates are not only related to antibiotic resistance but also play an influential role in bacterial virulence. Larger collections of comprehensive studies on this subject are required. These studies should contribute significantly to the solution of the antibiotic resistance problem.

SCREENING AND CHARACTERISATION OF SIDEROPHORE PRODUCING RHIZOBACTERIA FROM PADDY FIELD OF POONDI

To enhance the crop production and to manage plant diseases, many chemicals are being used. The use of such agrochemicals is hazardous to environment. To identify a viable alternate, biocontrol agent is necessary. Keeping this in point, the present investigation was undertaken to isolate PGPR bacteria from paddy rhizospheric soil. A total of 100 bacteria were isolated. On the basis of morphological, physiological and biochemical characterisation most of the isolates belong to Pseudomonas aeruginosa. The isolates were further screened for siderophores production by CAS method. In this 10 isolates showed positive results in siderophore production. The produced siderophore were further characterised based on their classi?cation such as hydroxylate, catecholate and carboxamate depending on the iron ligating group. In the present study, the effect of culture media components in the yield of siderophore was studied. Among the 10 isolates, 3 of were produced catecholate type of siderophore ef?ciently in succinate medium at neutral pH in low iron concentration. Potential siderophore producing isolates was further applied on Vigna radiata (Green gram). There was a signi?cant increase in the shoot and root length by roll towel method and Pot assay method

Quantification and Diversity of Cultivated Bacteria in Root Endosphere and Rhizosphere of Bamboo Species Fargesia nitida in Association with the Tree Succession

Fargesia nitida is a cold-resistant evergreen bamboo and is a pioneer plant in the secondary succession after the native trees were destroyed in the eastern Tibetan Plateau. However, little is known about the effects of this plant on soil conditions and about its microbiomes. Aiming at learning the interactions among the soil characteristics, the plants and the microbes in relation to the plant succession, a study on cultivated microbes associated with the rhizocompartments of F. nitida was performed in the present study to reveal the preference of this plant to the root associated microbes, in comparison with that associated with the successive spruce (Picea asperata Mast.) trees. The results demonstrated that growth of F. nitida could improve the soil nutrient contents, especially increasing total nitrogen, NH4+-N, total carbon, and microbial biomass carbon, and maintained more soil bacteria than the successive spruce trees. Based upon the study of F. nitida root-associated cultivated microbial community, the nutrient improvement in F. nitida growing soils might be from the root endophytic bacteria, which presented greater abundance (3.8, 1.7, and 12.6 folds) than that of bacteria in its rhizosphere, root zone soil, and spruce root zone soil, respectively. Pseudomonas members, especially species related to P. baetica and P. vancouverensis, were strongly selected by F. nitida as root endophytes.

Antibacterial activity of Mangifera indica seed extracts combined with common antibiotics against multidrug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii isolates

In this project, we employed ethanolic (EMI) and aqueous (AMI) extracts of mango (Mangifera indica L., Anacardiaceae) fruit seeds as a modulator of antibiotic resistance against multidrug-resistant (MDR) Pseudomonas aeruginosa and Acinetobacter baumannii to evaluate natural compounds isolated from by-products or waste of edible plants. We also investigated the effect of these extracts alone and in combination with standard classes of antibiotics in the desired strains. M. indica seeds were processed and exploited using ethanol and water. The minimum inhibitory concentrations (MICs) of clinical isolates were examined against EMI and AMI extracts, followed by seven antibiotics of ceftazidime, ciprofloxacin, penicillin, amikacin, meropenem, ampicillin, and colistin. The checkerboard method evaluated the synergistic action between mango kernel extract (EMI) and seven antibiotics. EMI extract significantly revealed antimicrobial properties against MDR A. baumannii and P. aeruginosa with synergistic effects with the applied antibiotics. The considerable antibacterial efficacy of ethanolic extract of M. indica seeds can have great curative value as antibacterial drugs against infections caused by MDR P.aeruginosa and A. baumannii.

Ação antimicrobiana e antibiofilme dos extratos combinados de canela e própolis sobre cepas clínicas de Acinetobacter baumannii e Pseudomonas aeruginosa multirresistentes / Antimicrobial and antibiofilm action of combined extracts of cinnamon and propolis on multiresistant clinical strains of Acinetobacter baumannii and Pseudomonas aeruginosa

Os microrganismos resistentes a diferentes classes de agentes antimicrobianos têm se tornado cada vez mais comuns e atualmente são denominados como multirresistentes. Nos hospitais, tais microrganismos apresentam maior perigo, pois são causadores de infecções nosocomiais e a higienização bucal deficiente dos pacientes internados pode tornar a cavidade bucal um sítio para proliferação desses microrganismos multirresistentes. Diante do exposto, novos compostos com ação antimicrobiana precisam ser estudados. O objetivo deste estudo foi avaliar quimicamente o extrato hidroalcóolico de própolis verde de Baccharis dracunculifolia e de Cinnamomum verum (canela) que foram obtidos a partir da extração da matériaprima, analisar a atividade antimicrobiana e antibiofilme dos extratos isolados e combinados contra quatro cepas clínicas multirresistentes de Pseudomonas aeruginosa e Acinetobacter baumannii e verificar a citotoxicidade dos produtos vegetais in vitro em linhagem celular de queratinócitos humanos (HaCat). Para tanto, os extratos vegetais foram preparados a partir da matéria-prima da canela em casca e da própolis bruta. Em seguida, foram caracterizados quimicamente por cromatografia líquida de alta eficiência (HPLC-DAD) para identificação dos principais compostos e a análise do teor de sólidos solúveis dos extratos vegetais também foi realizada. Para avaliação antimicrobiana, foram performados o teste de microdiluição em caldo de acordo com a Clinical and Laboratory Standards Institute (CLSI) e a análise de Checkerboard, para avaliar o efeito combinado dos extratos. A atividade antibiofilme dos extratos combinados foi realizada por meio do teste de MTT, no qual diferentes tempos de contato (5 e 30 min) e diferentes modalidades (inibição na formação do biofilme bacteriano e erradicação do biofilme bacteriano já formado) foram testadas. Para ação citotóxica, as células foram cultivadas em meio DMEM e semeadas na placa de 96 poços. Após aderência inicial, aplicou-se os extratos em diferentes concentrações baseadas nas análises microbiológicas para avaliação da viabilidade celular por meio do teste de MTT. Os dados foram analisados por ANOVA e teste de Tukey, ou Kruskal-Wallis e Dunn, considerando um nível de significância de 5%. Os compostos identificados no extrato de própolis verde de B. dracunculifolia foram ácido clorogênico, derivado do ácido cinâmico e apigenina. O aldeído cinâmico foi o principal composto identificado no extrato de C. verum. Os extratos vegetais apresentaram ação bactericida sobre todas as cepas analisadas e, quando combinados, os extratos atuaram de modo aditivo e algumas combinações sinérgicas foram encontradas. O protocolo de inibição da formação do biofilme promoveu percentuais de redução superiores quando comparado ao protocolo de erradicação. Valores expressivos de 83,86% (p < 0,05) de inibição da formação de biofilme de uma cepa clínica de A. baumannii e 89,31% (p < 0,05) de inibição em uma cepa clínica de P. aeruginosa foram encontrados com a aplicação dos extratos combinados. A atuação dos produtos vegetais foi estatisticamente semelhante a atuação da clorexidina 0,12%. Em conclusão, os extratos de própolis verde e canela na forma isolada ou combinada apresentaram ação antimicrobiana e antibiofilme sobre cepas clínicas de A. baumannii e P. aeruginosa multirresistentes. Dessa forma, os produtos vegetais são promissores agentes antissépticos para futuras formulações odontológicas. (AU)

Microorganisms resistant to different classes of antimicrobial agents have become increasingly common and are currently called multidrug resistant. In hospitals, such microorganisms are more dangerous, as they cause nosocomial infections and poor oral hygiene in hospitalized patients can make the oral cavity a site for the proliferation of these multiresistant microorganisms. Given the above, new compounds with antimicrobial action need to be studied. The objective of this study was to chemically evaluate the hydroalcoholic extract of green propolis from Baccharis dracunculifolia and Cinnamomum verum (cinnamon) that were obtained from the extraction of the raw material, to analyze the antimicrobial and antibiofilm activity of the isolated and combined extracts against four clinical strains multiresistant strains of Pseudomonas aeruginosa and Acinetobacter baumannii and verify the cytotoxicity of plant products in vitro in human keratinocyte cell lineage (HaCat). For this purpose, plant extracts were prepared from raw cinnamon bark and raw propolis. Then, they were chemically characterized by high performance liquid chromatography (HPLC-DAD) to identify the main compounds and the analysis of the soluble solids content of the plant extracts was also performed. For antimicrobial evaluation, the broth microdilution test according to the Clinical and Laboratory Standards Institute (CLSI) and the Checkerboard analysis were performed to evaluate the combined effect of the extracts. The antibiofilm activity of the combined extracts was performed using the MTT test, in which different contact times (5 and 30 min) and different modalities (inhibition of bacterial biofilm formation and eradication of already formed bacterial biofilms) were tested. For cytotoxic action, cells were cultured in DMEM medium and seeded in the 96-well plate. After initial adhesion, the extracts were applied at different concentrations based on microbiological analyzes to assess cell viability through the MTT test. Data were analyzed by ANOVA and Tukey's test, or Kruskal-Wallis and Dunn, considering a significance level of 5%. The compounds identified in the green propolis extract of B. dracunculifolia were chlorogenic acid, cinnamic acid derivative and apigenin. Cinnamic aldehyde was the main compound identified in the C. verum extract. The plant extracts showed bactericidal action on all strains analyzed and, when combined, the extracts acted additively and some synergistic combinations were found. The biofilm formation inhibition protocol promoted higher reduction percentages when compared to the eradication protocol. Significant values of 83.86% (p < 0.05) inhibition of biofilm formation in a clinical strain of A. baumannii and 89.31% (p < 0.05) inhibition in a clinical strain of P. aeruginosa were found with the application of the combined extracts. The performance of plant products was statistically similar to the performance of 0.12% chlorhexidine. In conclusion, extracts of green propolis and cinnamon, in isolated or combined form, showed antimicrobial and antibiofilm action on multiresistant clinical strains of A. baumannii and P. aeruginosa. Thus, plant products are promising antiseptic agents for future dental formulations. (AU)

Ação antimicrobiana de extratos de gengibre (Zingiber officinale) e quilaia (Quillaja saponaria) isolados e associados sobre Pseudomonas aeruginosa resistente a antibióticos / Antimicrobial action of isolated and associated extracts of ginger (Zingiber officinale) and quilaia (Quillaja saponaria) on antibiotic-resistant Pseudomonas aeruginosa

Extratos de plantas têm demonstrado diversos efeitos positivos para a saúde, incluindo ação antimicrobiana, no entanto, o uso clínico da fitoterapia ainda é discreto, de modo que mais estudos sobre os efeitos benéficos do sinergismo farmacológico de extratos poderiam contribuir para sua aplicação terapêutica. O objetivo deste estudo foi avaliar os efeitos dos extratos glicólicos de gengibre (EG) e quilaia (EQ) isolados e em associação sobre 7 cepas clínicas de Pseudomonas aeruginosa e uma cepa padrão em forma planctônica e biofilmes monotípicos. Para a análise antimicrobiana sobre cultura planctônica foram feitos testes para determinação de Concentração Inibitória Mínima (CIM) e Concentração Microbicida Mínima (CMM) (CLSI, M07-A9) dos extratos isolados, além do Índice de Concentração Inibitória Fracionada (ICIF) e do Índice de Concentração Microbicida Fracionada (ICMF) para os extratos combinados. A análise estatística foi feita com método ANOVA e teste de Tukey para dados com distribuição normal e Kruskall-Wallis com Teste de Comparação Múltipla de Dunn para dados sem distribuição normal (significância de 5%). Para cepa padrão foram determinadas CIM igual a 3,12 mg/mL e CMM igual a 6,25 mg/mL para ambos os extratos. Para cepas clínicas as CIM do EG foram 3,12 ou 6,25 mg/mL e de EQ 1,56 ou 3,12 mg/mL, enquanto os valores de CMM foram de 6,25 mg/mL para EG e de 1,56, 3,12 ou 6,25 mg/mL para EQ. Os resultados de ICIF indicaram 15 associações sinérgicas e 4 associações aditivas dos extratos contra a cepa padrão e, dentre cepas clínicas, foram obtidos 15 resultados aditivos. A partir dos resultados de ICMF foram identificadas 6 associações sinérgicas e 1 associação aditiva contra a cepa padrão, além de 8 associações com efeito aditivo contra cepas clínicas. A partir dos resultados de testes em culturas planctônicas foi avaliada a ação antibiofilme sobre as cepas em que foram observadas reduções de viabilidade de 36,7 e 34% para o EG (50 e 25 mg/mL) e 51,3 e 51,4% para EQ (25 e 12,5 mg/mL) contra cepa padrão. As reduções em cepas clínicas variaram de 43 a 73% com EG e de 36 a 79% para EQ. As associações dos extratos promoveram reduções de viabilidade de 8 a 35% contra 5 das 7 cepas clínicas. Conclui-se que os extratos glicólicos de gengibre e quilaia apresentam ação antimicrobiana de forma isolada e combinados com efeito aditivo sobre a forma planctônica de cepas clínicas resistentes de P. aeruginosa. De forma isolada, os extratos apresentaram importante ação preventiva na formação dos biofilmes dessas cepas, podendo ser considerados potenciais fitoterápicos com aplicações terapêuticas para o combate das infecções por P. aeruginosa. (AU)

Plant extracts have demonstrated several positive health effects, including antimicrobial action, however, the clinical use of phytotherapy is still discreet, so that more studies on the beneficial effects of pharmacological synergism of extracts could contribute to its therapeutic application. The aim of this study was to evaluate the effects of glycolic extracts of ginger (EG) and quilaia (EQ) alone and in combination on 7 clinical strains of Pseudomonas aeruginosa and a standard strain in planktonic form and monotypic biofilms. For the antimicrobial analysis on planktonic culture, tests were performed to determine the Minimum Inhibitory Concentration (MIC) and Minimum Microbicidal Concentration (MMC) (CLSI, M07-A9) of the isolated extracts, in addition to the Fractional Inhibitory Concentration Index (FICI) and the Fractionated Microbicidal Concentration Index (FICM) for the combined extracts. Statistical analysis was performed using the ANOVA method and Tukey's test for data with normal distribution and Kruskall-Wallis with Dunn's Multiple Comparison Test for data without normal distribution (5% significance). For the standard strain, MIC were determined equal to 3.12 mg/mL and MMC equal to 6.25 mg/mL for both extracts. For clinical strains the MIC of EG were 3.12 or 6.25 mg/mL and 1.56 or 3.12 mg/mL of EQ, while the MMC values were 6.25 mg/mL for EG and 1.56, 3.12 or 6.25 mg/ml for EQ. The FICI results indicated 15 synergistic and 4 additive associations of the extracts against the standard strain and, among clinical strains, 15 additive results were obtained. From the FICM results, 6 synergistic and 1 additive association against the standard strain were identified, in addition to 8 associations with additive effect against clinical strains. Based on the results of tests on planktonic cultures, the antibiofilm action were evaluated on the strains in which viability reductions of 36 and 34% were observed for EG (50 and 25 mg/mL) and 51% were observed for EQ (25 and 12, 5 mg/mL) against the standard strain. Reductions in clinical strains ranged from 43 to 73% with EG and from 36 to 79% for EQ. Associations of extracts promoted viability reductions of 8 to 35% against 5 out of 7 clinical strains. It is concluded that the glycolic extracts of ginger and quilaia have antimicrobial action in isolation and combined with additive effect on the planktonic form of resistant clinical strains of P. aeruginosa. Isolated, the extracts showed an important preventive action in the formation of biofilms of these strains and may be considered potential herbal medicines with therapeutic applications to combat P. aeruginosa infections. (AU)

Prevalence of multi-drug resistant Pseudomonas aeruginosa isolated from selected residential sewages in Dutsin-Ma, Katsina State, Nigeria

The global surge in Multidrug resistant (MDR) bacteria is an issue of great concern. Pseudomonas aeruginosa has been implicated in several nosocomial infections, where it has caused grave complications in immunocompromised patients. This is the first study to report the prevalence of MDR P. aeruginosa isolated from residential sewage in Dutsin-Ma, Katsina State, Nigeria. Pseudomonads count, isolation, biochemical characterization and antibiogram were carried out using standard microbiological procedures. This study examined sixty (60) samples from selected residential sewage in the study site collected at different intervals between July and September 2021. A total of 40 (66.7%) P. aeruginosa were isolated from the analyzed sewage samples. The highest (2.84x104) pseudomonad count was recorded from sewage samples collected from Kadangaru. Pseudomonas aeruginosa isolates from this sample site showed the highest (100%) resistance to cephalosporins (cefuroxime) and nitrofurantoin. Similarly, isolates from Miami area also demonstrated the highest (95%) resistance to a cephalosporin (ceftazidime). All (100%) isolates used in this study showed MDR resistance to tested antibiotics. The occurrence of MDR P. aeruginosa from a residential sewage site that may contaminate drinking water sources in the study area is of public health threat to the inhabitants. Surveillance and molecular epidemiology of antibiotics resistant bacteria are urgently needed in the study area.

In vitro activity of imipenem/relebactam against non-Morganellaceae Enterobacterales and Pseudomonas aeruginosa in Latin America: SMART 2018‒2020

Abstract Carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa are being isolated from patient specimens with increasing frequency in Latin America and worldwide. The current study provides an initial description of the in vitro activity of imipenem/relebactam (IMR) against non-Morganellaceae Enterobacterales (NME) and P. aeruginosa infecting hospitalized patients in Latin America. From 2018 to 2020, 37 clinical laboratories in nine Latin American countries participated in the SMART global surveillance program and contributed 15,466 NME and 3408 P aeruginosa isolates. MICs for IMR and seven comparators were determined using CLSI broth microdilution and interpreted by CLSI M100 (2022) breakpoints. β-lactamase genes were identified in selected isolate subsets. IMR (96.9% susceptible), amikacin (95.9%), meropenem (90.7%), and imipenem (88.7%) were the most active agents against NME. Among piperacillin/tazobactam-nonsusceptible NME (n= 4124), 90.4% of isolates were IMR-susceptible (range by country, 97.2 [Chile] to 67.0% [Guatemala]) and among meropenem-nonsusceptible NME isolates (n= 1433), 74.0% were IMR-susceptible (94.1% [Puerto Rico] to 5.1% [Guatemala]). Overall, 6.3% of all collected NME isolates carried a KPC (metallo-β-lactamase [MBL]-negative), 1.8% an MBL, 0.4% an OXA-48-like carbapenemase (MBL-negative), and 0.1% a GES carbapenemase (MBL-negative). Amikacin (85.2% susceptible) and IMR (80.1%) were the most active agents against P. aeruginosa; only 56.5% of isolates were imipenem-susceptible. Relebactam increased susceptibility to imipenem by 22.0% (from 23.9% to 45.9%) in piperacillin/tazobactam-nonsusceptible isolates (n= 1031) and by 35.5% (from 5.5% to 41.0%) in meropenem-nonsusceptible isolates (n= 1128). Overall, 7.6% of all collected P. aeruginosa isolates were MBL-positive and 0.7% carried a GES carbapenemase. In conclusion, in 2018‒2020, almost all NME (97%) and most P. aeruginosa(80%) isolates from Latin America were IMR-susceptible. Continued surveillance of the in vitro activities of IMR and comparator agents against Gram-negative pathogens, and monitoring for β-lactamase changes (in particular for increases in MBLs), is warranted.

Epidemiology and in vitro activity of ceftazidime-avibactam and comparator agents against multidrug-resistant isolates of Enterobacterales and Pseudomonas aeruginosa collected in Latin America as part of the ATLAS surveillance program in 2015‒2020

Abstract Introduction The incidence of antimicrobial resistance is increasing in many parts of the world. The focus of this report is to examine changes in antimicrobial resistance epidemiology among clinical isolates of Enterobacterales and Pseudomonas aeruginosa collected in six Latin American countries as part of the Antimicrobial Testing Leadership and Surveillance (ATLAS) program from 2015 to 2020, with a focus on the in vitro activity of ceftazidime-avibactam against Multidrug-Resistant (MDR) isolates. Methods Non-duplicate, clinical isolates of Enterobacterales (n= 15,215) and P. aeruginosa (n= 4,614) collected by 40 laboratories in Argentina, Brazil, Chile, Colombia, Mexico, and Venezuela, from 2015 to 2020, underwent centralized Clinical Lab Standards Institute (CLSI) broth microdilution susceptibility testing. Minimum Inhibitory Concentration (MIC) values were interpreted using 2022 CLSI breakpoints. An MDR phenotype was defined by resistance to ≥ 3 of seven sentinel agents. Results In total, 23.3% of Enterobacterales and 25.1% of P. aeruginosa isolates were MDR. Annual percent MDR values for Enterobacterales were stable from 2015 to 2018 (21.3% to 23.7% year) but markedly increased in 2019 (31.5%) and 2020 (32.4%). Annual percent MDR values for P. aeruginosa were stable from 2015 to 2020 (23.0% to 27.6% year). Isolates were divided into two 3-year time-periods, 2015‒2017 and 2018‒2020, for additional analyses. For Enterobacterales, 99.3% of all isolates and 97.1% of MDR isolates from 2015‒2017 were ceftazidime-avibactam-susceptible compared to 97.2% and 89.3% of isolates, respectively, from 2018‒2020. For P. aeruginosa, 86.6% of all isolates and 53.9% of MDR isolates from 2015‒2017 were ceftazidime-avibactam-susceptible compared to 85.3% and 45.3% of isolates, respectively, from 2018‒2020. Among individual countries, Enterobacterales and P. aeruginosa collected in Venezuela showed the greatest reductions in ceftazidime-avibactam susceptibility over time. Conclusion MDR Enterobacterales increased in Latin America from 22% in 2015 to 32% in 2020 while MDR P. aeruginosa remained constant at 25%. Ceftazidime-avibactam remains highly active against all clinical isolates of both Enterobacterales (97.2% susceptible, 2018‒2020) and P. aeruginosa (85.3%), and inhibited more MDR isolates (Enterobacterales, 89.3% susceptible, 2018‒2020; P. aeruginosa, 45.3%) than carbapenems, fluoroquinolones, and aminoglycosides.