Colonización por microorganismos multirresistentes en servicio de oncología de Hospital de Niños Roberto del Río durante el 2016 / Colonization by multiresistant microorganisms in oncology service of Roberto del Río Children's Hospital during 2016

Los pacientes inmunocomprometidos presentan un riesgo aumentado de colonización e infecciones por microorganismos multirresistentes (MOR), entre ellos Enterococcus spp resistentes a vancomicina (ERV) y bacterias productoras de betalactamasas de espectro extendido (BLEE), las cuales son causa importante de morbimortalidad. OBJETIVO: Describir la prevalencia de MOR en Servicio de Oncología del Hospital Roberto del Río. MÉTODO: Se realizó un estudio descriptivo retrospectivo de los niños hospitalizados en el servicio de oncología desde enero a diciembre del 2016 a los cuales se les realizó vigilancia de portación de ERV y BLEE. RESULTADOS: De los 97 pacientes hospitalizados, se identificó un 8% de portación de ERV, un 13,7% de BLEE y un 6,8% presentó portación de ambos microorganismos. DISCUSIÓN: Entre enero 2012 a diciembre del 2013 se observó en nuestro centro que un 52% de los pacientes hospitalizados en oncología estaban colonizados por ERV, la disminución significativa de la portación podría deberse a la mejor adherencia de normas de prevención de infecciones asociadas a la atención en salud (IAAS), programa de uso racional de antimicrobianos y a la nueva infraestructura del servicio.

The inmunosupressed patients are at increased risk of colonization and infection with vancomycin resistant Enterococci (VRE) and extended- spectrum b-lactamase producing Enterobacteriaceae (ESBL), which can cause substantial morbidity and mortality. OBJECTIVE: Describe the prevalence of VRE and ESBL in the Oncology Unit of Roberto del Río Hospital. METHODS: Descriptive and retrospective study of hospitalized children since January to December 2016 in the Oncology Unit, that underwent VRE and ESBL colonization surveillance. RESULTS: From the 97 hospitalized patients, there were 8% of VRE colonization, 13.7% of ESBL and 6.8% of colonization from both microorganism. DISCUSSION: Between January 2012 and December 2013, we observed that 52% of hospitalized patients in the Oncology Unit were colonized by VRE. The significant decrease in colonization may be due to better fulfillment of healthcare-associated infections (HAI) normative, antibiotics stewardship and new infraestructure of our unit.

Infection related to Klebsiella pneumoniae producing carbapenemase in renal transplant patients / Infección relacionada con Klebsiella pneumoniae productora de carbapenemasa en pacientes trasplantados renales

ABSTRACT Objective: To evaluate the risk factors related to Klebsiella pneumoniae carbapenemase infection after renal transplantation. Methods: This was a retrospective epidemiological (case-control) study, conducted from October 2011 to march 2016. Transplanted patients with infection by this bacteria during hospitalization were selected as cases. The controls were paired by age, sex, type of donor and transplant time. The proportion of cases and controls was 1:2. Results: Thirty hundred and five patients were included in the study (45 cases and 90 controls). The risk factors found for infection by KPC were: time of hospitalization after the transplant (OR: 4.82; CI95% 2.46-9.44), delayed kidney function (OR: 5.60; CI95% 1.91-11.01) and previous infectious for another microorganism ( OR: 34.13 CI95% 3.52-132.00). Conclusion: The risk of acquisition of this bacterium was directly related to invasive procedures and exposure to the hospital environment. The findings reinforce the importance of prevention measures and control of infection by this microorganism.

RESUMEN Objetivo: Evaluar los factores de riesgo relacionados con la infección por Klebsiella pneumoniae carbapenemasa después del trasplante renal. Método: Estudio retrospectivo epidemiológico (caso-control), realizado de octubre de 2011 a marzo de 2016. Pacientes transplantados con infección por esa bacteria durante la internación fueron seleccionados como casos. Los controles se parearon por edad, sexo, tipo de donante y tiempo de trasplante. La proporción de casos y controles fue de 1: 2. Resultados: Treinta y cinco pacientes fueron incluidos en el estudio (45 casos y 90 controles). Los factores de riesgo para la infección encontrados por KPC fueron: tiempo de hospitalización después del trasplante (OR: 4,82, IC95% 2,46-9,44), función renal retardada (OR: 5,60, IC95% 1, 91-11,01) y anterior infecciosa para otro microorganismo (OR: 34,13 IC95% 3,52-132,00). Conclusión: El riesgo de adquisición de esta bacteria estuvo directamente relacionado a procedimientos invasivos y exposición al ambiente hospitalario. Los hallazgos refuerzan la importancia de medidas de prevención y control de la infección por ese microorganismo.

Performance of rapid tests for carbapenemase detection among Brazilian Enterobacteriaceae isolates

ABSTRACT The global emergence of carbapenemases led to the need of developing new methods for their rapid detection. The aim of this study was to evaluate the performance of the rapid tests for carbapenemase-producing and non-producing Enterobacteriaceae. Carbapenem non-susceptible Enterobacteriaceae from a surveillance study submitted to a multiplex real time PCR for carbapenemase detection were included in this study. The isolates were subjected to the rapid phenotypic tests Carba NP, Blue-Carba and Carbapenem Inactivation Method (CIM). A total of 83 carbapenemase-producing (43) and non-producing (40) isolates were included in the study. The sensitivity/specificity were 62.7%/97.5%, 95.3%/100%, and 74.4%/97.5% for Carba NP, Blue-Carba and CIM, respectively. Both Carba NP and Blue-Carba presented their final results after 75 min of incubation; the final results for CIM were obtained only after 8 h. Failure to detect OXA-370 carbapenemase was the main problem for Carba NP and CIM assays. As the Blue-Carba presented the highest sensitivity, it can be considered the best screening test. Conversely, CIM might be the easiest to perform, as it does not require special reagents. The early detection of carbapenemases aids to establish infection control measures and prevent carbapenemases to spread reducing the risk of healthcare associated infections and therapeutic failure.

Performance of "RESIST-3 O.K.N. K-SeT" immunochromatographic assay for the detection of OXA-48 like, KPC, and NDM carbapenemases in Klebsiella pneumoniae in Turkey

ABSTRACT In this study, the performance of the "RESIST-3 O.K.N. K-SeT" (Coris BioConcept, Gembloux, Belgium) immunochromatographic assay was evaluated in 132 Klebsiella pneumoniae comprising 102 carbapenem resistant and 30 carbapenem susceptible isolates. Genotypically known isolates of Gram negative bacteria (n = 22) including various species were also tested by the assay as controls. The isolates tested by the immunochromatographic assay and also were run PCR for bla KPC, bla IMP, bla VIM, bla NDM, and bla OXA-48. The rates of bla NDM, bla OXA-48, and bla KPC in carbapenem resistant isolates were found at 52.9%, 39.2%, and 2.0%, respectively. Both bla NDM and bla OXA-48 were found in six (5.9%) isolates. The results of the assay showed 100% concordance with those obtained by PCR in 132 K. pneumoniae. The agreement between the two methods was found to be identical at the isolate level. The assay also correctly detected all genotypically known isolates of Escherichia coli, Serratia marcescens, Citrobacter freundii, Enterobacter cloacae, K. pneumoniae carrying bla KPC, bla NDM, and/or bla OXA-48. On the other hand, the assay did not exhibit any cross-reaction in control isolates harboring bla IMP and bla VIM. We conclude that the RESIST-3 O.K.N. K-SeT is a reliable, rapid, and user friendly test and we recommend it for routine diagnostic laboratories.

Phenotypic and molecular detection of metallo-ß-lactamase-producing Pseudomonas aeruginosa isolates from patients with burns in Tehran, Iran

Abstract INTRODUCTION: Health care-associated infections caused by metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa are a significant growing concern in patients with burns worldwide. The aims of this study were to determine the antibiotic susceptibility of and detect the presence of MBLs among P. aeruginosa isolates and assess their clonal relationship using enterobacterial repetitive intergenic consensus (ERIC)-PCR. METHODS: Non-duplicated clinical isolates (160) of P. aeruginosa were collected from patients with burns at the Motahari Hospital in Tehran, Iran. All isolates were identified using standard laboratory methods and further characterized for antimicrobial susceptibility. Any carbapenem-resistant isolates were then examined for MBL production by the E-test and MBL-encoding genes were detected by PCR. The clonal relatedness of MBL-producing isolates was assessed by ERIC-PCR. RESULTS: For multidrug-resistant isolates, the highest rates of susceptibility were observed for colistin 160 (100%), polymyxin B 160 (100%), and ceftazidime 32 (20%). In total, 69 (43.7%) isolates were identified as MBL producers. Twenty-eight (17.5%) isolates were positive for the bla VIM-1 gene followed by the bla IMP-1 (15.6%) and bla SPM-1 (5.6%) genes. ERIC-PCR revealed three separate genotypes, where type A (76.8%) was the most prevalent, followed by B (20.3%), and then C (2.9%). CONCLUSIONS: Our present study found that the bla IMP-1 and bla VIM-1 genes were present at a significant frequency and also detected the bla SPM-1 gene in P. aeruginosa isolates for the first time, highlighting the need for establishing suitable infection control measures to successfully treat patients and prevent further spread of these resistant organisms among patients with burns.

pMEX01, a 70kb Plasmid Isolated From Escherichia Coli That Confers Resistance to Multiple ß-Lactam Antibiotics

Abstract Multidrug-resistant microorganisms are of great concern to public health. Genetic mobile elements, such as plasmids, are among the most relevant mechanisms by which bacteria achieve this resistance. We obtained an Escherichia coli strain CM6, isolated from cattle presenting severe diarrheic symptoms in the State of Querétaro, Mexico. It was found to contain a 70 kb plasmid (pMEX01) with a high similarity to the pHK01-like plasmids that were previously identified and described in Hong Kong. Analysis of the pMEX01 sequence revealed the presence of a blaCTX-M-14 gene, which is responsible for conferring resistance to multiple β-lactam antibiotics. Several genes putatively involved in the conjugative transfer were also identified on the plasmid. The strain CM6 is of high epidemiological concern because it not only displays resistance to multiple β-lactam antibiotics but also to other kinds of antibiotics.

Study of pandrug and heavy metal resistance among E. coli from anthropogenically influenced Delhi stretch of river Yamuna

Abstract Escalating burden of antibiotic resistance that has reached new heights present a grave concern to mankind. As the problem is no longer confined to clinics, we hereby report identification of a pandrug resistant Escherichia coli isolate from heavily polluted Delhi stretch of river Yamuna, India. E. coli MRC11 was found sensitive only to tobramycin against 21 antibiotics tested, with minimum inhibitory concentration values >256 µg/mL for amoxicillin, carbenicillin, aztreonam, ceftazidime and cefotaxime. Addition of certain heavy metals at higher concentrations were ineffective in increasing susceptibility of E. coli MRC11 to antibiotics. Withstanding sub-optimal concentration of cefotaxime (10 µg/mL) and mercuric chloride (2 µg/mL), and also resistance to their combinatorial use, indicates better adaptability in heavily polluted environment through clustering and expression of resistance genes. Interestingly, E. coli MRC11 harbours two different variants of blaTEM (blaTEM-116 and blaTEM-1 with and without extended-spectrum activity, respectively), in addition to mer operon (merB, merP and merT) genes. Studies employing conjugation, confirmed localization of blaTEM-116, merP and merT genes on the conjugative plasmid. Understanding potentialities of such isolates will help in determining risk factors attributing pandrug resistance and strengthening strategic development of new and effective antimicrobial agents.

Carbapenemases in Acinetobacter baumannii: Review of their dissemination in Latin America / Carbapenemasas en Acinetobacter baumannii: Revisión de su diseminación en América Latina

Carbapenem resistance in gram-negative bacteria by production of carbapenemases is one of the most challenging issues regarding healthcare worldwide. We review the epidemiology and prevalence of carbapenemases in carbapenem-resistant Acinetobacter baumannii isolates from Latin American countries. High resistance rates to antimicrobial agents, particularly to carbapenems, are observed in this region. OXA-23 is the most widely disseminated class D-carbapenemase; it is present in all the countries of the region and is frequently associated to endemic clones CC113/CC79, CC104/CC15, CC110/ST25 and CC109/CC1. The emergence of OXA-72 and NDM-1 represents a novel finding which is observed simultaneously and without clonal relatedness in different countries, some of which are distant from one another, whereas OXA-143 is only present in Brazil. Further collaborative intraregional studies would provide a better understanding of these issues in most of the countries and thus, policies to control the spread of these isolates could be implemented.

En bacilos gram negativos, la resistencia a carbapenemes por producción de carbapenemasas es uno de los mayores problemas en la atención de la salud a nivel mundial. Reseñamos en este artículo la epidemiologia y la prevalencia de las carbapenemasas descritas en aislamientos de Acinetobacter baumannii recuperados en América Latina. En esta región se ha observado un alto porcentaje de resistencia a los antimicrobianos, particularmente a los carbapenemes. La carbapenemasa más frecuentemente descrita es OXA-23, que ha sido recuperada en todos los países de la región y fue asociada a los clones endémicos CC113/CC79, CC104/CC15, CC110/ST25 y CC109/CC1. La emergencia de OXA-72 y NDM-1 representa un nuevo hallazgo en varios países, algunos de los cuales se encuentran muy distantes entre sí. Por el momento, OXA-143 solo se recuperó de aislamientos obtenidos en Brasil. Serían necesarios estudios colaborativos dentro de la región para lograr una mejor comprensión de la resistencia a carbapenemes en Acinetobacter baumannii, a fin de poder instaurar medidas de control que eviten una mayor diseminación de esta bacteria.

Isolation of blaNDM-producing Enterobacteriaceae in a public hospital in Salvador, Bahia, Brazil

ABSTRACT Carbapenemases have great importance in the global epidemiological scenario since infections with carbapenemase-producing bacteria are associated with high mortality, especially in hospitalized patients in intensive care units. This study describes two microorganisms producers of the New Delhi Metallo-b-lactamase, Klebsiella pneumoniae and Citrobacter freundii, from two patients admitted to a public hospital in Salvador, Bahia. These are the first clinical cases of New Delhi Metallo-b-lactamase described in microorganisms in the north and northeast Brazil. The isolates were characterized by antimicrobial susceptibility test, with resistance to all β-lactams including carbapenems, negative Modified Hodge Test and the synergy test with Ethylenediaminetetraacetic acid, Phenylboronic Acid and Cloxacillin was positive only with Ethylenediaminetetraacetic acid (difference of >5 mm in the inhibition zone between the disk without and with the inhibitor). Analysis by multiplex PCR for blaIMP, blaVIM, blaNDM, blaKPC and blaOXA-48 enzymes confirmed the presence of blaNDM gene. This report of two different New Delhi Metallo-b-lactamase-producing microorganisms in a different region of Brazil confirms the risk of spreading resistance genes between different species and emphasizes the need for prevention and control of infections caused by these pathogens, which have limited treatment options and have been linked to high mortality rates.

Detection of virulence and ß-lactamase encoding genes in Enterobacter aerogenes and Enterobacter cloacae clinical isolates from Brazil

ABSTRACT Enterobacter cloacae and E. aerogenes have been increasingly reported as important opportunistic pathogens. In this study, a high prevalence of multi-drug resistant isolates from Brazil, harboring several β-lactamase encoding genes was found. Several virulence genes were observed in E. aerogenes, contrasting with the E. cloacae isolates which presented none.

Factores predictores de mortalidad intrahospitalaria en pacientes adultos con infecciones por Klebsiella pneumoniae resistente a carbapenémicos y colistín: un estudio de cohorte retrospectivo / Risk factors for in-hospital mortality among adult patients infected with colistin-resistant carbapenemase producing Klebsiella pneumoniae: a retrospective cohort study

Resumen Introducción: La emergencia de Klebsiella productora de carbapenemasas resistente a colistín representa un desafío clínico y un problema emergente. Objetivo: Evaluar la mortalidad intrahospitalaria y sus potenciales factores de riesgo en pacientes internados con infecciones clínicas por Klebsiella pneumoniae productora de carbapenemasas (KPC) resistente a colistín. Material y Método: Realizamos un estudio de cohorte retrospectivo, incluyendo pacientes adultos admitidos a un hospital universitario de tercer nivel en Buenos Aires, infectados por KPC resistente a colistín. El evento primario considerado fue la mortalidad intrahospitalaria. Se utilizaron modelos generalizados lineales para evaluar potenciales predictores de dicho evento. Resultados: En total, se identificaron 18 pacientes hospitalizados que presentaron una infección clínica por esta bacteria durante el año 2016 y que fueron incluidos en el análisis final. La mortalidad intrahospitalaria en esta cohorte fue de 38,9%. La presencia de bacteriemia, la injuria renal aguda al momento del diagnóstico y la presencia de shock séptico se asociaron a la ocurrencia del evento primario. Conclusión: El desarrollo de infecciones clínicamente relevantes por KPC resistente a colistín en pacientes internados es frecuente y presenta una elevada mortalidad. En nuestra cohorte, la presencia de shock e injuria renal aguda al momento del diagnóstico se asociaron a un incrementado riesgo de mortalidad intrahospitalaria. Futuras investigaciones deberían corroborar estos hallazgos e investigar factores adicionales que permitan identificar tempranamente a aquellos pacientes que presentarán eventos desfavorables.

ABSTRACT Background: The emergence of colistin resistant carbapenemase-producing Klebsiella represents a therapeutic challenge and a worldwide problem. Aim: To estimate the in-hospital mortality and identify the associated risk factors among patients with colistin-resistant carbapenemase-producing Klebsiella pneumoniae (KPC) that present with a clinical infection. Methods: We carried a retrospective cohort study, including adult patients infected with colistin-resistant KPC hospitalized at a tertiary teaching hospital in Buenos Aires, Argentina during the year 2016. The main outcome was in-hospital mortality. We used generalized lineal models to evaluate potential predictors of mortality. Results: 18 patients that developed a colistin-resistant KPC clinical infection were identified and included in the final analysis. In-hospital mortality in this cohort was 38.9%. The presence of bacteremia, acute renal injury at the time of diagnosis and septic shock were associated with the main outcome. Conclusions: Infections due to colistin-resistant KPC among in-hospital patients was frequent and was associated with high mortality rate. In our cohort, both shock and acute kidney injury were associated with a higher likelihood of poor outcomes. Further studies are warranted to evaluate the role of these and others risk factors so as to aid in the early detection of high risk patients.

Klebsiella pneumoniae productora de carbapenemasas en Perú: reporte de caso y discusión de la resistencia a los antimicrobianos / Carbapenemase producing Klebsiella pneumoniae in Peru: a case report and antimicrobial resistance discussion

Las carbapenemasas son uno de los mecanismos enzimáticos de resistencia antimicrobiana, que compromete la mayor parte de los antibióticos betalactámicos. Por lo general, su producción se debe al uso indiscriminado de antimicrobianos. A nivel mundial, la expansión de este mecanismo de resistencia es inminente y las medidas de control son limitadas. Con el objeto de discutir los problemas relacionados a este mecanismo emergente de resistencia, reportamos un caso de Klebsiella pneumoniae productora de carbapenemasas en Huancayo, la Región de la Sierra Central de Perú.

Carbapenemases are one of the major mechanisms of antimicrobial resistance, usually due to the indiscriminate use of antibiotics. The expansion of this mechanism of resistance at world level is imminent and control measures are limited. In the region of the Central Sierra of Peru - Huancayo, we report a case of carbapenemase-producing Klebsiella pneumoniae, with the purpose of discussing the problems related to this emerging mechanism of antibiotic resistance.

Antimicrobial activity evaluation and comparison of methods of susceptibility for Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacter spp. isolates

Abstract The production of KPC (Klebsiella pneumoniae carbapenemase) is the major mechanism of resistance to carbapenem agents in enterobacterias. In this context, forty KPC-producing Enterobacter spp. clinical isolates were studied. It was evaluated the activity of antimicrobial agents: polymyxin B, tigecycline, ertapenem, imipenem and meropenem, and was performed a comparison of the methodologies used to determine the susceptibility: broth microdilution, Etest® (bioMérieux), Vitek 2® automated system (bioMérieux) and disc diffusion. It was calculated the minimum inhibitory concentration (MIC) for each antimicrobial and polymyxin B showed the lowest concentrations for broth microdilution. Errors also were calculated among the techniques, tigecycline and ertapenem were the antibiotics with the largest and the lower number of discrepancies, respectively. Moreover, Vitek 2® automated system was the method most similar compared to the broth microdilution. Therefore, is important to evaluate the performance of new methods in comparison to the reference method, broth microdilution.

Draft genome sequence of a GES-5-producing Serratia marcescens isolated in southern Brazil

Abstract Serratia marcescens is a Gram-negative rod intrinsically resistant to polymyxins and usually associated with wound, respiratory and urinary tract infections. The whole genome of the first GES-5-producing S. marcescens isolated from a Brazilian patient was sequenced using Ion Torrent PGM System. Besides blaGES-5, we were able to identify genes encoding for other β-lactamases, for aminoglycoside modifying enzymes and for an efflux pump to tetracyclines.

Draft genome sequence of a multidrug-resistant beta-lactamase OXA-357-producing Acinetobacter pittii ST865 clinical isolate from China

Abstract Worldwide increasing emergence of carbapenem-resistant Acinetobacter spp. has rendered the limited availability of effective antimicrobial agents and has become a major public health concern. In this study, we report the draft genome sequence of A. pittii TCM156, a multidrug-resistant isolate that harbored the blaOXA-357 gene. The genome sequence was further analyzed by various bioinformatics methods. The genome size was estimated to be 3,807,313 bp with 3508 predicted coding regions and G + C content is 38.7%. These findings have raised awareness of the possible emergence of OXA-type enzyme-producing A. pittii isolate in China.

Diversidad genética de cepas extraintestinales de Escherichia coli productoras de las betalactamasas TEM, SHV y CTX-M asociadas a la atención en salud / Genetic diversity of extraintestinal Escherichia coli strains producers of beta-lactamases TEM, SHV and CTX-M associated with healthcare

RESUMEN Introducción. En Venezuela existen pocos reportes que describan las bases genéticas del potencial patogénico y filogenético de las cepas de Escherichia coli provenientes de hospitales. Objetivo. Determinar la diversidad genética de cepas extraintestinales de E. coli productoras de las betalactamasas TEM, SHV y CTX-M asociadas a la atención de salud. Materiales y métodos. Se estudió una colección de 12 cepas extraintestinales de E. coli con sensibilidad disminuida a las cefalosporinas de amplio espectro. La sensibilidad antimicrobiana se determinó por concentración inhibitoria mínima. La detección de los grupos filogenéticos, de los factores de virulencia y de los genes que codifican la resistencia antimicrobiana se hizo mediante la técnica de reacción en cadena de la polimerasa y la relación clonal se estableció mediante reacción en cadena de la polimerasa de elementos palindrómicos extragénicos repetitivos (Repetitive Element Palindromic-PCR, rep-PCR). Resultados. Todas las cepas analizadas presentaron resistencia a las cefalosporinas, y resistencia conjunta a quinolonas y aminoglucósidos. La distribución filogenética evidenció que los grupos A y B1 fueron los más frecuentes, seguidos por D y B2; en este último, se detectaron todos los factores de virulencia evaluados, y el gen más frecuente fue el fimH. En todas las cepas analizadas, se encontró bla CTX-M, con predominio de las bla CTX-M-8, y en dos de estas cepas se evidenció la presencia simultánea de bla CTX-M-9, variantes bla CTX-M-65 y bla CTX-M-147. Conclusión. Las cepas estudiadas demostraron diversidad genética y albergaron diferentes genes de virulencia y betalactamasas de espectro extendido (BLEE) sin predominio de ningún filogrupo en particular. Este estudio constituye el primer reporte de la variante bla CTX-M-65 en Venezuela y de la variante bla CTX-M-147 en el mundo, en cepas no relacionadas genéticamente aisladas de hospitales, situación que merece atención y la racionalización del uso de los antimicrobianos.

ABSTRACT Introduction: There are few reports from Venezuela describing the genetic basis that sustains the pathogenic potential and phylogenetics of Escherichia coli extraintestinal strains isolated in health care units. Objective: To establish the genetic diversity of extraintestinal E. coli strains producers of beta-lactamases TEM, SHV and CTX-M associated with healthcare. Materials and methods: We studied a collection of 12 strains of extraintestinal E. coli with diminished sensitivity to broad-spectrum cephalosporins. Antimicrobial susceptibility was determined by minimum inhibitory concentration. We determined the phylogenetic groups, virulence factors and genes encoding antimicrobial resistance using PCR, and clonal characterization by repetitive element palindromic-PCR rep-PCR. Results: All strains showed resistance to cephalosporins and joint resistance to quinolones and aminoglycosides. The phylogenetic distribution showed that the A and B1 groups were the most frequent, followed by D and B2. We found all the virulence factors analyzed in the B2 group, and fimH gene was the most frequent among them. We found bla CTX-M in all strains,with a higher prevalence of bla CTX-M-8; two of these strains showed coproduction of bla CTX-M-9 and were genetically identified as bla CTX-M-65 and bla CTX-M-147 by sequencing. Conclusion: The strains under study showed genetic diversity, hosting a variety of virulence genes, as well as antimicrobial resistance with no particular phylogroup prevalence. This is the first report of bla CTX-M alleles in Venezuela and in the world associated to non-genetically related strains isolated in health care units, a situation that deserves attention, as well as the rationalization of antimicrobials use.

Correlation of phenotypic tests with the presence of the blaZ gene for detection of beta-lactamase

Abstract Staphylococcus aureus and Staphylococcus saprophyticus are the most common and most important staphylococcal species associated with urinary tract infections. The objective of the present study was to compare and to evaluate the accuracy of four phenotypic methods for the detection of beta-lactamase production in Staphylococcus spp. Seventy-three strains produced a halo with a diameter ≤28 mm (penicillin resistant) and all of them were positive for the blaZ gene. Among the 28 susceptible strain (halo ≥29 mm), 23 carried the blaZ gene and five did not. The zone edge test was the most sensitive (90.3%), followed by MIC determination (85.5%), but the specificity of the former was low (40.0%). The nitrocefin test was the least sensitive (28.9%). However, the nitrocefin test together with the disk diffusion method showed the highest specificity (100%). The present results demonstrated that the zone edge test was the most sensitive phenotypic test for detection of beta-lactamase, although it is still not an ideal test to detect this type of resistance since its specificity was low. However, the inhibition halo diameter of the penicillin disk can be used together with the zone edge test since the same disk is employed in the two tests. Combined analysis of the two tests shows a sensitivity of 90.3% and specificity of 100%, proving better sensitivity, especially for S. saprophyticus. This is a low-cost test of easy application and interpretation that can be used in small and medium-sized laboratories where susceptibility testing is usually performed by the disk diffusion method.

Carbapenem-resistant and cephalosporin-susceptible: a worrisome phenotype among Pseudomonas aeruginosa clinical isolates in Brazil

Abstract The mechanisms involved in the uncommon resistance phenotype, carbapenem resistance and broad-spectrum cephalosporin susceptibility, were investigated in 25 Pseudomonas aeruginosa clinical isolates that exhibited this phenotype, which were recovered from three different hospitals located in São Paulo, Brazil. The antimicrobial susceptibility profile was determined by CLSI broth microdilution. β-lactamase-encoding genes were investigated by PCR followed by DNA sequencing. Carbapenem hydrolysis activity was investigated by spectrophotometer and MALDI-TOF assays. The mRNA transcription level of oprD was assessed by qRT-PCR and the outer membrane proteins profile was evaluated by SDS-PAGE. Genetic relationship among P. aeruginosa isolates was assessed by PFGE. Carbapenems hydrolysis was not detected by carbapenemase assay in the carbapenem-resistant and cephalosporin-susceptible P. aueruginosa clinical isolates. OprD decreased expression was observed in all P. aeruginosa isolates by qRT-PCR. The outer membrane protein profile by SDS-PAGE suggested a change in the expression of the 46 kDa porin that could correspond to OprD porin. The isolates were clustered into 17 genotypes without predominance of a specific PFGE pattern. These results emphasize the involvement of multiple chromosomal mechanisms in carbapenem-resistance among clinical isolates of P. aeruginosa, alert for adaptation of P. aeruginosa clinical isolates under antimicrobial selective pressure and make aware of the emergence of an uncommon phenotype among P. aeruginosa clinical isolates.