Impact of the national shortage of polymyxin B in critically ill patients during the COVID-19 pandemic / Impacto da escassez nacional de polimixina B em pacientes gravemente enfermos durante a pandemia de COVID-19 / Impacto del desabasto nacional de polimixina B en pacientes críticos durante la pandemia de COVID-19

Background and Objectives: during the COVID-19 pandemic, the number of critical patients requiring intensive care increased considerably, resulting in an increase in infections due to multi-resistant microorganisms. In Brazil, in 2021, due to the high demand for polymyxin B use, there was a national shortage of the medication. One strategy used to overcome this situation was aminoglycoside use. The work aimed to analyze the impact of replacing polymyxin B with amikacin and gentamicin in the final stage of patients. Method: an analytical study with an observational, cross-sectional design, with a quantitative approach, through a retrospective analysis through the analysis of medical records, with the primary stages being discharges or deaths. Results: mortality was similar between the group treated with aminoglycoside and the group treated with polymyxin B. Within the aminoglycoside group, mortality was higher in the group that had bacteria resistant to the drug than in the group that had infection with an organism sensitive to this drug. Mortality was not affected by comorbidities, age, or number of hospital infections. The main factor that led to the need for dialysis was the combination of two nephrotoxic medications. Conclusion: two hypotheses emerged: the first would be that replacing polymyxin B with aminoglycosides did not impact mortality; the other would be that, regardless of the antibiotic group used, patients had a high risk of death. Despite sample limitations, the study corroborates the adoption of strategies for the rational use of antimicrobials.(AU)

Justificativa e Objetivos: durante a pandemia de COVID-19, o número de pacientes críticos que necessitaram de cuidados intensivos aumentou consideravelmente, resultando em aumento de infecções por microrganismos multirresistentes. No Brasil, em 2021, devido à grande demanda pelo uso da polimixina B, houve escassez nacional do medicamento. Uma estratégia utilizada para superar essa situação foi o uso de aminoglicosídeos. O trabalho teve como objetivo analisar o impacto da substituição da polimixina B por amicacina e gentamicina na fase final dos pacientes. Método: estudo analítico com desenho observacional, transversal, com abordagem quantitativa, por meio de análise retrospectiva por meio de análise de prontuários, sendo as etapas primárias as altas ou óbitos. Resultados: a mortalidade foi semelhante entre o grupo tratado com aminoglicosídeo e o grupo tratado com polimixina B. Dentro do grupo aminoglicosídeo, a mortalidade foi maior no grupo que apresentava bactérias resistentes ao medicamento do que no grupo que apresentava infecção por organismo sensível a este medicamento. medicamento. A mortalidade não foi afetada por comorbidades, idade ou número de infecções hospitalares. O principal fator que levou à necessidade de diálise foi a combinação de dois medicamentos nefrotóxicos. Conclusão: surgiram duas hipóteses: a primeira seria que a substituição da polimixina B por aminoglicosídeos não impactou a mortalidade; a outra seria que, independentemente do grupo de antibióticos utilizado, os pacientes apresentavam alto risco de morte. Apesar das limitações amostrais, o estudo corrobora a adoção de estratégias para o uso racional de antimicrobianos.(AU)

Antecedentes y Objetivos: durante la pandemia de COVID-19, el número de pacientes críticos que requirieron cuidados intensivos aumentó considerablemente, resultando en un aumento de infecciones por microorganismos multirresistentes. En Brasil, en 2021, debido a la alta demanda del uso de polimixina B, hubo escasez nacional del medicamento. Una estrategia utilizada para superar esta situación fue el uso de aminoglucósidos. El trabajo tuvo como objetivo analizar el impacto de la sustitución de la polimixina B por amikacina y gentamicina en la etapa final de los pacientes. Método: estudio analítico con diseño observacional, transversal, con enfoque cuantitativo, mediante un análisis retrospectivo mediante el análisis de historias clínicas, siendo las etapas primarias las altas o defunciones. Resultados: la mortalidad fue similar entre el grupo tratado con aminoglucósido y el grupo tratado con polimixina B. Dentro del grupo de aminoglucósido, la mortalidad fue mayor en el grupo que tenía bacterias resistentes al fármaco que en el grupo que tenía infección con un organismo sensible a este. droga. La mortalidad no se vio afectada por las comorbilidades, la edad o el número de infecciones hospitalarias. El principal factor que llevó a la necesidad de diálisis fue la combinación de dos medicamentos nefrotóxicos. Conclusión: surgieron dos hipótesis: la primera sería que la sustitución de polimixina B por aminoglucósidos no impactó la mortalidad; la otra sería que, independientemente del grupo de antibióticos utilizado, los pacientes tenían un alto riesgo de muerte. A pesar de las limitaciones de la muestra, el estudio corrobora la adopción de estrategias para el uso racional de antimicrobianos.(AU)

Rapid bacterial identification by MALDI-TOF MS directly from blood cultures and rapid susceptibility testing: A simple approach to reduce the turnaround time of blood cultures

Abstract Antimicrobial treatment of patients with bloodstream infections (BSI) is time-sensitive. In an era of increasing antimicrobial resistance, rapid detection and identification of bacteria with antimicrobial susceptibility are critical for targeted therapy early in the disease course. This study describes the performance of a rapid method for identifying and testing antimicrobial susceptibility of Gram-negative bacteria performed directly from blood culture bottles in a routine microbiology laboratory. A total of 284, 120, and 24 samples were analyzed by rapid identification (Rid), rapid susceptibility testing (RAST), and rapid broth microdilution for polymyxin B (rMIC), respectively, and compared with standard methods. Our protocol was able to identify 93% of isolates at the species level using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). We obtained 100% agreement for RAST compared to the standard method and 96% agreement for rMIC. Our protocol has proven to be an excellent tool for rapid identification of Gram-negative bacilli causing BSIs. It can also be used in microbiology laboratory routine along with RAST and faster polymyxin microdilution, especially for carbapenemase-producing bacteria, allowing for rapid, simple, accurate, and cost-effective diagnosis.

Chinese consensus guidelines for therapeutic drug monitoring of polymyxin B, endorsed by the Infection and Chemotherapy Committee of the Shanghai Medical Association and the Therapeutic Drug Monitoring Committee of the Chinese Pharmacological Society / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Polymyxin B, which is a last-line antibiotic for extensively drug-resistant Gram-negative bacterial infections, became available in China in Dec. 2017. As dose adjustments are based solely on clinical experience of risk toxicity, treatment failure, and emergence of resistance, there is an urgent clinical need to perform therapeutic drug monitoring (TDM) to optimize the use of polymyxin B. It is thus necessary to standardize operating procedures to ensure the accuracy of TDM and provide evidence for their rational use. We report a consensus on TDM guidelines for polymyxin B, as endorsed by the Infection and Chemotherapy Committee of the Shanghai Medical Association and the Therapeutic Drug Monitoring Committee of the Chinese Pharmacological Society. The consensus panel was composed of clinicians, pharmacists, and microbiologists from different provinces in China and Australia who made recommendations regarding target concentrations, sample collection, reporting, and explanation of TDM results. The guidelines provide the first-ever consensus on conducting TDM of polymyxin B, and are intended to guide optimal clinical use.

Efficacy and safefy of Polymyxin B treatment for neutropenic patients suffering from refractory Gram-negative bacterial bloodstream infection / 中华血液学杂志

Objective: To assess the efficacy and safety of polymyxin B in neutropenic patients with hematologic disorders who had refractory gram-negative bacterial bloodstream infection. Methods: From August 2021 to July 2022, we retrospectively analyzed neutropenic patients with refractory gram-negative bacterial bloodstream infection who were treated with polymyxin B in the Department of Hematology of the First Affiliated Hospital of the Soochow University between August 2021 to July 2022. The cumulative response rate was then computed. Results: The study included 27 neutropenic patients with refractory gram-negative bacterial bloodstream infections. Polymyxin B therapy was effective in 22 of 27 patients. The median time between the onset of fever and the delivery of polymyxin B was 3 days [interquartile range (IQR) : 2-5]. The median duration of polymyxin B treatment was 7 days (IQR: 5-11). Polymyxin B therapy had a median antipyretic time of 37 h (IQR: 32-70). The incidence of acute renal dysfunction was 14.8% (four out of 27 cases), all classified as "injury" according to RIFLE criteria. The incidence of hyperpigmentation was 59.3%. Conclusion: Polymyxin B is a viable treatment option for granulocytopenia patients with refractory gram-negative bacterial bloodstream infections.

Nephrotoxicity caused by polymyxin in the treatment of drug-resistant Gram-negative bacterial infections：a meta-analysis / 中国药房

OBJECTIVE To evaluate the incidence of nephrotoxicity in patients with drug-resistant Gram-negative bacterial infections after the use of polymyxin， and to provide evidence-based reference for clinical rational drug use. METHODS PubMed， Embase， Web of Science， the Cochrane Library， Wanfang database， CNKI， VIP and SinoMed were searched to collect randomized controlled trials （RCTs） or cohort studies about the polymyxin （trial group） versus other antibiotics （control group） or polymyxin B （trial group） versus polymyxin E （control group）. After literature screening， data extraction and quality evaluation， RevMan 5.4.1 software was used for meta-analysis. RESULTS A total of 37 studies were included， including 4 RCTs and 33 cohort studies， with a total of 5 871 patients. The meta-analysis results showed that in RCT [RR＝2.64，95%CI （1.43，4.87），P＝0.002] and in cohort studies [RR＝1.59， 95%CI （1.27， 1.98）， P＜0.000 1]， the incidence of nephrotoxicity in the trial group was significantly higher than control group. The results of the subgroup analysis of cohort studies showed that the incidence of nephrotoxicity in the trial group （receiving polymyxin） was significantly higher than control group （receiving new β-lactam and β-lactamase inhibitors and tigecycline）； when Kidney Disease Improving Global Outcomes （KDIGO）， renal replacement therapy or 0.5 times increase in serum creatinine were used as the standard of nephrotoxicity， the incidence of nephrotoxicity in the trial group was significantly higher than the control group （P＜0.05）. The incidence of nephrotoxicity in patients receiving polymyxin E was significantly higher than those using polymyxin B [RR＝0.57， 95%CI （0.39，0.84）， P＝0.005]. CONCLUSIONS In the treatment of drug-resistant Gram-negative bacteria infections， the incidence of nephrotoxicity caused by polymyxin is relatively high. The TYU108F）； incidence of nephrotoxicity caused by polymyxin E is higher than polymyxin B.

Mechanism of polymyxin resistance related to lipopolysaccharide modification in carbapenem-resistant Klebsiella pneumoniae / 中华微生物学和免疫学杂志

Objective:To investigate the mechanism of polymyxin resistance related to lipopolysaccharide modification in carbapenem-resistant Klebsiella pneumoniae (CRKP). Methods:Plasmid-mediated drug resistance genes in seven CRKP strains were detected by conjugation assay and mcr gene detection. The expression of polymyxin resistance-related genes was measured using quantitative real-time PCR. The complete genomes of CRKP strains were sequenced. Silver staining and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were performed to analyze the changes in lipopolysaccharide (LPS). Results:The seven CRKP strains were negative for mcr genes and the results of conjugation assay were also negative. Moreover, no mobile genetic elements related to drug resistance were detected. Compared with wild-type strain, all seven CRKP strains that were resistant to polymyxin showed increased expression of pmrA, pmrB and pmrC genes at the transcriptional level; six showed increased expression of phoP/ phoQ genes; three showed decreased expression of crrA/ crrB genes; four showed decreased expression of mgrB gene. The missense mutation sites in drug-resistant strains were mainly in KPHS_09430, KPHS_35900, KPHS_39520 and KPHS_52420. IS Kpn14 insertion sequence was detected in CRKP-6 strain. MALDI-TOF-MS reveals the modification of natural lipid A with L-Ara4N in CRKP LPS. Conclusions:LPS modification induced by chromosome-mediated mutation in the two-component regulatory system was the main molecular mechanism of polymyxin resistance in CRKP isolates in this study. Effects of the mutation in the two-component system on polymyxin resistance varied in different strains.

Analysis and evaluation of the application of polymyxin B in inpatients based on clinical guidelines and consensuses / 中国药房

OBJECTIVE To evaluate the rationality of clinical application of polymyxin B in the inpatients of a third grade class A hospital，so as to provide evidence for the optimization of clinical scheme of the drug. METHODS A retrospective method was conducted on the electronic medical records of inpatients treated with Polymyxin B sulfate for injection from January 2020 to March 2022 to collect the basic information of patients， inpatient departments and time， infection diagnosis， results of pathogenic bacteria test， laboratory test indicators， usage and dosage， and combined medication，etc. Based on the drug instructions， according to relevant guidelines and consensus， the rationality， efficacy and safety of polymyxin B in inpatient were evaluated. RESULTS & CONCLUSIONS A total of 101 inpatients were included， respiratory system infection was the main cause （62.4%）. All patients had received the etiological examination， and the pathogen with the highest detection rate was carbapenem‑resistant Acinetobacter baumannii （40.6%）. One hundred patients were treated by intravenous drip， and 4 patients were treated by combination of aerosol inhalation or intrathecal injection； 99 patients were given the dose of 500 thousand units by continuous intravenous infusion， q12 h. Totally 51.5% of patients were treated for 7-14 days； and 77 patients were treated with other anti-Gram-negative drugs. There were unreasonable phenomena including too short time of medication （29.7%）， no combination of medication （23.8%）， and no indication of medication （17.8%）. The clinical effective rate of 101 patients treated with polymyxin B was 49.5%， and 16 patients （15.8%） had acute kidney injury during the treatment. Clinical pharmacists should actively participate in the clinical treatment of polymyxin B， formulate individualized treatment plans according to the guidelines/consensus and in combination with the patient’s condition and infection status to improve the rationality of clinical medication.

Determination of polymyxin B concentration in plasma and its application in critically ill patients / 中国药房

OBJECTIVE To establish a method for the determination of polymyxin B concentration in plasma and apply it to clinical practice. METHODS After precipitated with 5% trichloroacetic acid solution， using polymyxin E2 as internal standard， the concentrations of polymyxin B1 and B2 in plasma sample were determined by UPLC-MS/MS. The determination was performed on BEH C18 chromatographic column with water （0.1% formic acid）-acetonitrile （0.1% formic acid） as mobile phase （gradient elution） at the flow rate of 0.5 mL/min. The sample size was 10 µL. The detection was accomplished with electrospray ionization operated in positive ion scanning by multi-reaction monitoring mode. The ion pairs for quantitative analysis were m/z 603.2→101.2 （polymyxin B1）， m/z 595.7→101.1 （polymyxin B2） and m/z 578.5→101.1 （internal standard）. The plasma concentration of polymyxin B in 79 critically ill patients was measured by the above method， the occurrence of acute renal injury （AKI） was recorded and the relationship of polymyxin B concentration in plasma with AKI was analyzed. RESULTS The linear ranges of polymyxin B1 and polymyxin B2 were 200-20 000， 50-5 000 ng/mL （r＞0.995）， and the lower limits of quantification were 200 and 50 ng/mL， respectively. RSDs of intra‐day and inter‐day precision tests were not higher than 12.06%， the average extraction recovery was 103.04%-117.44%， and RSDs of matrix effect test and stability test were all not higher than 7.42%. Steady state trough and peak plasma concentration were （2.54±2.52） and （8.17±5.20） mg/L for 79 clinical patients using polymyxin B. Eighteen patients out of 27 included patients developed AKI， with an incidence of 66.67%. The peak concentration of polymyxin B of patients without AKI was significantly lower than that of patients with AKI （P＜0.05）， but there was no significant difference in the trough concentration between two groups （P＞0.05）. CONCLUSIONS The established UPLC-MS/MS has the advantages of simple operation and high sensitivity， and can be used to monitor the plasma concentration of polymyxin B in patients. The occurrence of AKI is correlated with the peak concentration of polymyxin B.

Clinical observation of polymyxin B in the treatment of CRKP-BSI in patients with hematological malignancies / 中国药房

OBJECTIVE To analyze the efficacy and safety of polymyxin B in the treatment of carbapenem-resistant Klebsiella pneumoniae （CRKP）-bloodstream infection （BSI） in patients with hematologic malignancies. METHODS The medical records of patients with hematologic malignancies with CRKP-BSI who received polymyxin B for at least 3 days in our hospital from September 2019 to June 2021 were retrospectively analyzed. All patients were initially treated with a triple therapy namely polymyxin B+tigecycline+carbapenems for anti-infection therapy. RESULTS A total of 10 patients were enrolled as the study subjects. Eleven strains of CRKP were cultured in blood， including 10 strains of CRKP produced Klebsiella pneumoniae carbapenemase（KPC） and 1 strain of CRKP produced both KPC and metal-beta-lactamase； 9 strains were sensitive to colistin， 7 strains were sensitive to tigecycline， 5 strains were sensitive to amikacin and 2 strains were sensitive to compound sulfamethoxazole. All patients were accompanied by neutropenia， with an average duration of （14.1±6.4） days. They were all characterized by fever， chills and fatigue. After treatment， 6 patients were cured and discharged， 4 patients died of ineffective treatment of septic shock. No serious adverse events related to polymyxin B occurred in all patients. CONCLUSIONS Polymyxin B can be used as a therapeutic drug for CRKP-BSI in patients with hematological malignancies. No serious adverse event related to polymyxin B occurs during the treatment.

Capacidade de formação de biofilmes e perfil de resistência de Acinetobacter baumannii isolados em unidades de terapia intensiva: uma revisão sistemática

Introdução: Acinetobacter baumanni é um cocobacilo Gram negativo responsável por elevadas taxas de infecções relacionadas à assistência à saúde (IRAS). Apresenta alto nível de resistência intrínseca a antimicrobianos, além da capacidade de adquirir resistência a carbapenêmicos e polimixinas. Ainda, A. baumannii possui habilidade para produzir biofilmes em superfícies abióticas e bióticas, o que favorece a infecção de pacientes gravemente enfermos internados em unidades de terapia intensiva (UTI). Deve ser ressaltado que bactérias envolvidas em biofilmes apresentam maior resistência aos antimicrobianos, atribuída a fatores bioqúmicos, moleculares e as condições dos hospedeiros, o que dificulta o tratamento dessas infecções. Objetivos: Avaliar a produção de biofilme por isolados de A. baumannii recuperados de pacientes internados em UTIs, bem como operfil de susceptibilidade a antimicrobianos (aminoglicosídeos, tigeciclina, carbapenêmicos e polimixinas) entre esses isolados. Métodos: Foi realizada uma revisão sistemática de acordo com os critérios Prisma nos bancos de dados Pubmed/Medline, Scopus, Lilacs, Scielo, e Web of Science. Resultados: Foram incluídos um total de 12 artigos que avaliaram 1006 isolados clínicos de A. baumannii, os quais todos foram resistentes aos carbapenê-micos. No entanto, a maioria dos isolados permaneceu sensível as polimixinas B e E(94,46%). A porcentagem dos isolados produtores de biofilme foi alta (96,3%), e neste estudo não fica clara a relação entre a habilidade de produzir biofilmes e a resistência aos antimicrobianos analisados. Conclusão: Mais estudos devem ser conduzidos para monitorar a resistência aos antimicrobianos em A. baumannii, sobretudo em produtores de biofilme, visto que o manejo terapêutico das infecções ocasionadas por essas linhagens torna-se mais complexo e desafiador.

SUMMARY Introduction: Acinetobacter baumanni is a Gram-negative coccobacillus responsible for high rates of healthcare-related infections (HAI). It has a high level of intrinsic resistance to antimicrobials, in addition to the ability to acquire resistance to carbapenems and polymyxins. Furthermore, A. baumannii has the ability to produce biofilms on abiotic and biotic surfaces, which favors the infection of critically ill patients admitted to intensive care units (ICU). It should be noted that bacteria involved in biofilms have greater resistance to antimicrobials, attributed to biochemical and molecular factors and the conditions of the hosts, which makes the treatment of these infections difficult. Objectives: To evaluate the biofilm production by A. baumannii isolates recovered from ICU patients, as well as the antimicrobial susceptibility profile (aminoglycosides, tigecycline, carbapenems and polymyxins) among these isolates. Methods: A systematic review was performed according to PRISMA criteria in the PUBMED/MEDLINE, Scopus, LILACS, SciELO, and Web of Science databases. Results: A total of 12 articles that evaluated 1006 clinical isolates of A. baumannii, all of which were resistant to carbapenems, were included. However, most isolates remained sensitive to polymyxins B and E (94.46%). The percentage of biofilm-producing isolates was high (96.3%), and in this study the relationship between the ability to produce biofilms and resistance to the analyzed antimicrobials is not clear. Conclusion: More studies should be conducted to monitor antimicrobial resistance in A. baumannii, especially in biofilm producers, as the therapeutic management of infections caused by these strains becomes more complex and challenging.

Introducción: Acinetobacter baumanni es un cocobacilo gramnegativo responsable de altas tasas de infecciones relacionadas con la salud. Tiene un alto nivel de resistencia intrínseca a los antimicrobianos, además de la capacidad de adquirir resistencia a los carbapenémicos y polimixinas. Además, A. baumannii tiene la capacidad de producir biopelículas en superficies abióticas y bióticas, lo que favorece la infección de pacientes críticos ingresados en unidades de cuidados intensivos (UCI). Cabe señalar que las bacterias involucradas en biofilms tienen mayor resistencia a los antimicrobianos, atribuida a factores bioquímicos y moleculares y a las condiciones de los hospedadores, lo que dificulta el tratamiento de estas infecciones. Objetivos: Evaluar la producción de biofilm por aislamientos de A. baumannii recuperados de pacientes de UCI, así como el perfil de susceptibilidad antimicrobiana (amino-glucósidos, tigeciclina, carbapenémicos y polimixinas) entre estos aislamientos. Métodos: Se realizó una revisión sistemática según los criterios Prisma en las bases de datos Pubmed / Medline, Scopus, Lilacs, SciELO y Web of Science. Resultados: Se incluyeron un total de 12 artículos que evaluaron 1006 aislamientos clínicos de A. baumannii, todos ellos resistentes a carbapenémicos. Sin embargo, la mayoría de los aislados permanecieron sensibles a las polimixinas B y E (94,46%). El porcentaje de aislamientos productores de biopelículas fue alto (96,3%), y en este estudio no está clara la relación entre la capacidad de producir biopelículas y la resistencia a los antimicrobianos analizados. Conclusión: Se deben realizar más estudios para monitorear la resistencia a los antimicrobianos en A. baumannii, especialmente en productores de biopelículas, ya que el manejo terapéutico de las infecciones causadas por estas cepas se vuelve más complejo y desafiante.

Polymyxin Acute Kidney Injury: a case of severe tubulopathy / Nefropatia por polimixina B: a tubulopatia pode ser muito séria!

Abstract Polymyxins are antibiotics developed in the 1950s. Polymyxin-induced neurotoxicity has been often described in medical literature. The same cannot be said of nephrotoxicity or tubulopathy in particular. This report describes the case of a patient prescribed polymyxin B to treat a surgical wound infection, which led to significant increases in fractional excretion of calcium, magnesium, and potassium and subsequent persistent decreases in the levels of these ions, with serious consequences for the patient. Severe hypocalcemia, hypomagnesemia, and hypokalemia may occur during treatment with polymyxin. Calcium, magnesium and potassium serum levels must be monitored during treatment to prevent life-threatening conditions.

Resumo Polimixinas são um grupo de antibióticos desenvolvidos na década de 1950. Seus efeitos neurotóxicos são comumente descritos na literatura, porém há menos relatos sobre seus efeitos nefrotóxicos, especialmente tubulopatias. O objetivo deste relato é descrever o uso de polimixina B em uma paciente para tratamento de infecção de ferida operatória, promovendo grande aumento das frações de excreção de cálcio, magnésio e potássio e acarretando reduções graves e persistentes desses íons, com sérias consequências para a paciente. Hipocalcemia, hipomagnesemia e hipocalemia severas podem ocorrer durante terapia com polimixina e é sugerido que sejam monitorizadas as concentrações séricas desses eletrólitos durante o tratamento como forma de evitar condições de risco à vida.

Progress in resistance mechanism of Klebsiella pneumoniae to polymyxin / 中国药房

With th e massive use of antibiotics ，Klebsiella pneumoniae has shown a trend of multiple drug resistance ， especially carbapenem-resistant K. pneumoniae ，which means that fewer and fewer antibiotics can be used to treat K. pneumoniae infection. Polymyxin has become the last line of defense for the treatment of carbapenem-resistant K. pneumoniae infection due to its unique antibacterial mechanism. However ，with the increase of its use ，the reports of drug-resistant K. pneumoniae strains at home and abroad are also on the rise ，seriously endangering the lives of patients . The author summarizes the resistance mechanism of K. pneumoniae to polymyxin ，and find that the resistance mechanism of K. pneumoniae to polymyxin mainly includes the structural modification of lipopolysaccharide in bacterial outer membrane ，the overexpression of capsular polysaccharide and the overexpression of multidrug efflux pump ，which can provide a basis for the rational use of the drug and the prevention and treatment of drug-resistant K. pneumoniae .

Progress in the study of polymyxin resistance and its mechanism / 上海预防医学

Drug-resistant bacteria have become a serious threat to human health. Polymyxin has shown strong bactericidal activity to some Gram-negative and Gram-positive bacteria that are resistant to antibiotics， and has become a last-resort treatment option against a variety of multi-drug resistant bacteria. However， due to the abuse of polymyxin in animal breeding， the drug resistance rate of polymyxin in human population has significantly increased. In order to further understand the mechanism of polymyxin resistance， and to take measures to reduce the incidence of polymyxin resistance in the population， this paper reviewed the progress in research of the antibacterial mechanism of polymyxin， the prevalence of polymyxin resistance in the population， the mechanism of polymyxin resistance， and its transmission mode.

Progress in the study of polymyxin resistance and its mechanism / 上海预防医学

Drug-resistant bacteria have become a serious threat to human health. Polymyxin has shown strong bactericidal activity to some Gram-negative and Gram-positive bacteria that are resistant to antibiotics， and has become a last-resort treatment option against a variety of multi-drug resistant bacteria. However， due to the abuse of polymyxin in animal breeding， the drug resistance rate of polymyxin in human population has significantly increased. In order to further understand the mechanism of polymyxin resistance， and to take measures to reduce the incidence of polymyxin resistance in the population， this paper reviewed the progress in research of the antibacterial mechanism of polymyxin， the prevalence of polymyxin resistance in the population， the mechanism of polymyxin resistance， and its transmission mode.

Combination of polymyxin B and Aquilaria malaccensis extract enhanced the killing and inhibited the growth of Acinetobacter baumannii and Klebsiella pneumoniae

Aims@#Polymyxins are an important last-line treatment for infections caused by multidrug-resistant Gram-negative bacteria. Nonetheless, the emergence of polymyxin-resistance and the limiting of polymyxin monotherapy urgently demands its optimisation. Aquilaria malaccensis (Agarwood) has been widely used as traditional medicine. Many parts of the plant including leaves exhibit a considerable in vitro antibacterial activity against microbial pathogens. Exploiting A. malaccensis in combination with polymyxins provides a novel strategy in fighting antimicrobial resistance. The objective of this study was to evaluate the combination effects of A. malaccensis extract with polymyxins against Acinetobacter baumannii and Klebsiella pneumoniae.@*Methodology and results@#In vitro time-kill studies and GC-MS analysis were performed to evaluate the bacterial killing of polymyxin B and extract combination and analyse chemical compounds of the extract, respectively. The combination of polymyxin B (1 mg/L) and A. malaccensis extract (32 mg/mL and 64 mg/mL) treatments exhibited enhanced bacterial killing compared to polymyxin B alone at 4 h and 24 h. Combination treatments also inhibited the bacterial growth of both A. baumannii and K. pneumoniae observed throughout the 24 h. More than sixty compounds including phytol, 9,12-octadecadienal, fatty acid, alkanes and terpenoids were putatively identified as the compounds that likely contributed to the antibacterial activity.@*Conclusion, significance and impact of study@#This study was the first to report the potential application of A. malaccensis extract in combination with polymyxin B in treatment against A. baumannii and K. pneumoniae and can be further investigated and optimized for the treatment of bacterial infectious diseases.

Clinical efficacy of polymyxin B in combination with tigecycline in pneumonia caused by pan-drug resistant Klebsiella pneumoniae / 国际生物医学工程杂志

Objective:To investigate the clinical efficacy of injectable polymyxin B combined with tigecycline in pneumonia caused by pan-drug resistant Klebsiella pneumonia (PDR-KP). Methods:The retrospective analysis utilized clinical data of 71 patients with PDR-KP admitted to the Neurointensive Care Unit of Beijing Chaoyang Integrative Medicine Emergency Medical Center between September 2018 and August 2021. All patients received injectable polymyxin B combined with tigecycline. The response rate, bacterial clearance rate, and safety of this therapeutic option were evaluated according to the clinical symptoms and biochemical parameters before treatment (baseline), 7 days after the treatment, and at the end of the treatment.Results:The treatment time of 71 patients ranged from 8 to 14 days, with an average of 11 days. The symptoms, signs, laboratory tests, and chest CT findings of most patients significantly improved after the treatment using polymyxin B combined with tigecycline. On the 7th day after the treatment, 37 patients were clinically effective, with a total effective rate of 52.1%(37/71); 41 patients obtained bacteriological clearance, with a bacterial clearance rate of 57.7%(41/71). At the end of treatment, 51 patients were clinically effective, with a total effective rate of 71.8%(51/71); 56 patients obtained bacteriological clearance, with a bacterial clearance rate of 78.9%(56/71). Compared with the results on the 7th day after the treatment, the total effective rate ( χ2=5.86, P=0.016) and bacterial clearance rate ( χ2=7.32, P=0.007) of patients at the end of treatment were significantly increased. Skin pigmentation occurred in 39.4%(28/71) of patients during the treatment. Conclusions:Polymyxin B combined with tigecycline can be tried as a treatment option for pneumonia caused by PDR-KP, but more reliable clinical evidence is still needed.

Overview of polymyxin resistance in Enterobacteriaceae

ABSTRACT Polymyxin antibiotics are disfavored owing to their potential clinical toxicity, especially nephrotoxicity. However, the dry antibiotic development pipeline, together with the increasing global prevalence of infections caused by multidrug-resistant (MDR) gram-negative bacteria, have renewed clinical interest in these polypeptide antibiotics. This review highlights the current information regarding the mechanisms of resistance to polymyxins and their molecular epidemiology. Knowledge of the resistance mechanisms and epidemiology of these pathogens is critical for the development of novel antibacterial agents and rapid treatment choices.

Efficacy and nephrotoxicity of high-dose polymyxin B in treatment of multidrug-resistant Gram-negative bacterial infections / 中华全科医师杂志

Objective:To investigate the efficacy and nephrotoxicity of high-dosepolymyxin B (PMB) in treatment of patients with multidrug-resistant Gram-negative bacteria (MDR-GNB) infections.Methods:Clinical data of 90 patients with MDR-GNB infections who admitted to the Affiliated Huaian First People′s Hospital from January 2018 to December 2020 were retrospectively analyzed. Thirty one patients receivedhigh-dose PMB(≥25 000 U·kg?1·d?1) for treatment (high-dose group) and 59 patients received standard-dose PMB(<25 000 U·kg?1·d?1) for treatment (control group). The curative effect and renal function of the two groups were compared. The factors related toacute kidney injury (AKI) were analyzed with logistic regression.Results:The daily PMB dose and treatment course in high-dose group were (29 800±4 500) U/kg and (9.16±4.15) d, while those of the control group were (17 300±3 500)U/kg and (7.32±3.87) d ( P<0.01). The effective rate of the high-dose group was higher than that of control group (83.9% vs. 61.0%, χ2=4.95, P<0.05).The creatinine levels in high-dose group were increased significantly from 69.40(47.00, 94.70)μmol/L before treatment to 116.20(59.20, 213.20)μmol/L after treatment ( Z=-2.99, P<0.01); while there were no significant changesin control group before and after treatment [55.00(37.00, 92.47)μmol/L vs. 50.10(34.00, 156.00)μmol/L, Z=-1.78, P=0.78]. The 30-day mortality rate in the high-dose group was 32.3% (10/31), that in the standard-dose group was 49.2% (29/59)(χ2=2.36, P=0.12). The AKI incidence rate in high-dose group was higher than that in standard-dose group [ 67.7% (21/31) vs. 45.8% (27/59), χ2=3.94, P=0.04]. There were 4 and 10 deaths due to AKI in the high-dose and standard-dose groups, respectively (χ2=0.25, P=0.61). Logistic regression analysis showed that daily high-dose PMB was independently associated with AKI( OR=2.662, 95% CI:1.082-6.549, P=0.03). Conclusion:Thehigh-dose PMB is effective in treatment of patients with multidrug-resistant Gram-negative bacteriainfections, but the incidence of AKI is also significantly increased. Therefore, when using daily high-dose PMB, the pros and cons must be weighed to avoid increasing the risk of AKI.

Efficacy and Safety of Atomization Inhalation of Polymyxin in the Adjunctive Treatment of Ventilator-associated Pneumonia：A Meta-analysis / 中国药房

OBJECTIVE：To evaluate the efficacy and safety of atomization inhalation of polymyxin combined in the adjunctive treatment for ventilator-associated pneumonia ，and to provide evidence-based reference for clinical treatment. METHODS ： Retrieved from Cochrane Library ，Embase，PubMed，Web of Science ，CNKI，CBM，VIP and Wanfang database （from their inception to March 2021），randomized controlled trials （RCTs）about efficacy and safety of atomization inhalation of polymyxin combined with conventional treatment （trial group ） versus conventional treatment （control group ） for ventilator- associated pneumonia were collected. After data extraction and quality evaluation of included literatures met inclusion and exclusion criteria ， Meta-analysis was performed by using Rev Man 5.4 software. RESULTS ：A total of 13 clinical studies were included ，involving 2 RCTs and 11 cohort studies with a total of 1 066 patients. The results of Meta-analysis showed that clinical response rate [OR ＝ 1.53，95％CI（1.17，2.00），P＝0.002]，microbial clearance rate [OR ＝1.46，95％CI（1.11，1.91），P＝0.007] of trial group were significantly higher than those of control group ，with statistical significance. There was no statistical significance in the mortality rate [OR ＝0.88，95％CI（0.68，1.14），P＝0.32] and the incidence of renal impairment [OR ＝1.04，95％CI（0.72，1.49），P＝0.85] between 2 groups. CONCLUSIONS ：Based on current evidence ，atomization inhalation of polymyxin combined with conventional treatment can significantly improve clinical response rate and microbial clearance rate of patients with ventilator- associated pneumonia. However ， more strictly-designed ， long-term follow-up and large-scale RCTs are needed.

Application progress of polymyxin in bloodstream infection of drug-resistant Acinetobacter baumannii / 中华危重病急救医学

In recent years, the bloodstream infection rate of Gram-negative bacilli has continued to increase. Among them, drug-resistant bacteria have a higher mortality rate and longer hospital stay, especially the bloodstream infection of carbapenem-resistant Acinetobacter baumannii (CRAB). Polymyxin began to be used clinically in the 1950s and has antibacterial activity against multidrug resistant and poly drug-resistant Gram-negative bacilli. It can also be used as an effective permeation agent for the cell envelope of Gram-negative bacilli. Polymyxin is reserved for microbiologically clear drug-resistant Gram-negative bacilli infections. The World Health Organization classifies polymyxin as an antimicrobial drug with clinical significance for human infections and can be used to treat drug-resistant Acinetobacter baumannii infection. This article reviews the clinical treatment of polymyxin in bloodstream infections of drug-resistant Acinetobacter baumannii, to provide reference for clinical medication.