Genomic Characterization of mcr-1.1-Producing Escherichia coli Recovered From Human Infections in São Paulo, Brazil.

Polymyxins are one of most important antibiotics available for multidrug-resistant Gram-negative infections. Diverse chromosomal resistance mechanisms have been described, but the polymyxin resistance phenotype is not yet completely understood. The objective of this study was to characterize colistin resistant mcr-1-producing strains isolated from human infections over one year in a hospital setting (Hospital das Clínicas, São Paulo, Brazil). We isolated 490 colistin-resistant Gram-negative rods, of which eight were mcr-1.1-positive Escherichia coli, the only species with this result, indicating a low incidence of the mcr-1 production mechanism among colistin-resistant isolates. All mcr-1.1 positive isolates showed similarly low MICs for colistin and were susceptible to most antibiotics tested. The isolates showed diversity of MLST classification. The eight mcr-1.1-positive E. coli genomes were sequenced. In seven of eight isolates the mcr-1.1 gene is located in a contig that is presumed to be a part of an IncX4 plasmid; in one isolate, it is located in a contig that is presumed to be part of an IncHI2A plasmid. Three different genomic contexts for mcr-1.1 were observed, including a genomic cassette mcr-1.1-pap2 disrupting a DUF2806 domain-containing gene in six isolates. In addition, an IS1-family transposase was found inserted next to the mcr-1.1 cassette in one isolate. An mcr-1.1-pap2 genomic cassette not disrupting any gene was identified in another isolate. Our results suggest that plasmid dissemination of hospital-resident strains took place during the study period and highlight the need for continued genomic surveillance.

The effect of a rapid molecular blood test on the use of antibiotics for nosocomial sepsis: a randomized clinical trial.

BACKGROUND: Appropriate use of antimicrobials is essential to improve outcomes in sepsis. The aim of this study was to determine whether the use of a rapid molecular blood test-SeptiFast (SF) reduces the antibiotic consumption through early de-escalation in patients with nosocomial sepsis compared with conventional blood cultures (BCs). METHODS: This was a prospective, randomized, superiority, controlled trial conducted at Sao Paulo Heart Institute in the period October 2012-May 2016. Adult patients admitted to the hospital for at least 48 h with a diagnosis of nosocomial sepsis underwent microorganism identification by both SF test and BCs. Patients randomized into the intervention group received antibiotic therapy adjustment according to the results of SF. Patients randomized into the control group received standard antibiotic adjustment according to the results of BCs. The primary endpoint was antimicrobial consumption during the first 14 days after randomization. RESULTS: A total of 200 patients were included (100 in each group). The intention to treat analysis found no significant differences in median antibiotic consumption. In the subgroup of patients with positive SF and blood cultures (19 and 25 respectively), we found a statistically significant reduction in the median antimicrobial consumption which was 1429 (1071-2000) days of therapy (DOT)/1000 patients-day in the intervention group and 1889 (1357-2563) DOT/1000 patients-day in the control group (p = 0.017), in the median time of antimicrobial de-escalation (8 versus 54 h-p < 0.001), in the duration of antimicrobial therapy (p = 0.039) and in anti-gram-positive antimicrobial costs (p = 0.002). Microorganism identification was possible in 24.5% of patients (45/184) by SF and 21.2% (39/184) by BC (p = 0.45). CONCLUSION: This randomized clinical trial showed that the use of a rapid molecular-based pathogen identification test does not reduce the median antibiotic consumption in nosocomial sepsis. However, in patients with positive microbiological tests, the use of SeptiFast reduced antimicrobial consumption through early de-escalation compared to conventional blood cultures. These results were driven by a reduction in the consumption of antimicrobials used for Gram-positive bacteria. TRIAL REGISTRATION: The trial was registered at ClinicalTrials.gov (NCT01450358) on 12th October 2011.

Streptococcus pneumoniae: susceptibility to penicillin and moxifloxacin.

OBJECTIVE: To determine the minimum inhibitory concentrations (MICs) of parenteral penicillin and moxifloxacin against Streptococcus pneumoniae strains isolated at a hospital center. METHODS: In-vitro, prospective study involving 100 S. pneumoniae isolates collected from patients who had been treated, between October of 2008 and July of 2010, at the Hospital das Clínicas complex of the University of São Paulo School of Medicine, located in the city of São Paulo, Brazil. The isolates were obtained from respiratory tract cultures or blood samples unrelated to meningeal infections, and they were tested for penicillin and moxifloxacin susceptibility by E-test. The MIC category interpretations were based on updated standards. RESULTS: All isolates were fully susceptible to parenteral penicillin (MIC < 2 µg/mL), and, consequently, they were also susceptible to amoxicillin, ampicillin, third/fourth generation cephalosporins, and ertapenem. Of the S. pneumoniae strains, 99% were also susceptible to moxifloxacin, and only one strain showed an MIC = 1.5 µg/mL (intermediate). CONCLUSIONS: Our results showed high susceptibility rates to parenteral penicillin and moxifloxacin among S. pneumoniae isolates unrelated to meningitis, which differs from international reports. Reports on penicillin resistance should be based on updated breakpoints for non-meningitis isolates in order to guide the selection of an antimicrobial therapy and to improve the prediction of the clinical outcomes.

Metallo-beta-lactamases among imipenem-resistant Pseudomonas aeruginosa in a Brazilian university hospital.

INTRODUCTION: Imipenem-resistant Pseudomonas aeruginosa resulting from metallo-ß-lactamases has been reported to be an important cause of nosocomial infection and is a critical therapeutic problem worldwide, especially in the case of bacteremia. OBJECTIVES: To determine the frequency of metallo-ß-lactamases among imipenem-resistant Pseudomonas aeruginosa isolates and to compare methods of phenotypic and molecular detection. METHODS: During 2006, 69 imipenem-resistant Pseudomonas aeruginosa samples were isolated from blood and tested for metallo-ß-lactamase production using both phenotypic methods. Minimal Inhibitory Concentratrions (MIC) (µg/mL) was determined with commercial microdilution panels. Pulsed Field Gel Electrophoresis (PFGE) was performed among metallo-ß-lactamase producers. RESULTS: Of all the blood isolates, 34.5% were found to be imipenem-resistant Pseudomonas aeruginosa. Positive phenotypic tests for metallo-ß-lactamases ranged from 28%-77%, and Polymerase Chain Reaction (PCR) were positive in 30% (of note, 81% of those samples were bla(SPM)₋1 and 19% were bla(VIM)₋2). Ethylenediamine tetracetic acid (EDTA) combinations for the detected enzymes had low kappa values; thus, care should be taken when use it as a phenotypic indicator of MBL. Despite a very resistant antibiogram, four isolates demonstrated the worrisome finding of a colistin MIC in the resistant range. PFGE showed a clonal pattern. CONCLUSION: Metallo-ß-lactamases among imipenem-resistant Pseudomonas aeruginosa were detected in 30.4% of imipenem-resistant Pseudomonas aeruginosa isolates. This number might have been higher if other genes were included. SPM-1 was the predominant enzyme found. Phenotypic tests with low kappa values could be misleading when testing for metallo-ß-lactamases. Polymerase Chain Reaction detection remains the gold standard.

Streptococcus pneumoniae: sensibilidade a penicilina e moxifloxacina / Streptococcus pneumoniae: susceptibility to penicillin and moxifloxacin

OBJETIVO: Determinar a concentração inibitória mínima (CIM) de penicilina parenteral e moxifloxacina contra cepas de Streptococcus pneumoniae isoladas em um centro hospitalar. Métodos: Estudo in vitro prospectivo de 100 isolados de S. pneumoniae coletados de pacientes tratados entre outubro de 2008 e julho de 2010 no complexo do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, em São Paulo (SP). Os isolados foram obtidos de culturas do trato respiratório e de amostras de sangue não relacionadas a infecções meníngeas e foram testados quanto à suscetibilidade a penicilina e moxifloxacina por E test. As interpretações categóricas de CIM foram baseadas em padrões atualizados. RESULTADOS: Todos os isolados foram suscetíveis a penicilina parenteral (CIM < 2 µg/mL) e, consequentemente, eram também suscetíveis a amoxicilina, ampicilina, cefalosporinas de terceira e quarta geração e ertapenem. Quanto à moxifloxacina, 99 por cento das cepas de S. pneumoniae também foram suscetíveis, e somente uma teve CIM = 1,5 µg/mL (intermediário). Conclusões: Nossos resultados mostraram altas taxas de sensibilidade a penicilina parenteral e moxifloxacin nos isolados de S. pneumoniae não relacionados a meningite, o que difere de relatos internacionais. Relatos sobre resistência a penicilina devem ser baseados em pontos de corte atualizados para isolados não relacionados a meningite a fim de guiar a escolha terapêutica antimicrobiana e melhorar a predição dos desfechos clínicos.

OBJECTIVE: To determine the minimum inhibitory concentrations (MICs) of parenteral penicillin and moxifloxacin against Streptococcus pneumoniae strains isolated at a hospital center. METHODS: In-vitro, prospective study involving 100 S. pneumoniae isolates collected from patients who had been treated, between October of 2008 and July of 2010, at the Hospital das Clínicas complex of the University of São Paulo School of Medicine, located in the city of São Paulo, Brazil. The isolates were obtained from respiratory tract cultures or blood samples unrelated to meningeal infections, and they were tested for penicillin and moxifloxacin susceptibility by E-test. The MIC category interpretations were based on updated standards. RESULTS: All isolates were fully susceptible to parenteral penicillin (MIC < 2 µg/mL), and, consequently, they were also susceptible to amoxicillin, ampicillin, third/fourth generation cephalosporins, and ertapenem. Of the S. pneumoniae strains, 99 percent were also susceptible to moxifloxacin, and only one strain showed an MIC = 1.5 µg/mL (intermediate). CONCLUSIONS: Our results showed high susceptibility rates to parenteral penicillin and moxifloxacin among S. pneumoniae isolates unrelated to meningitis, which differs from international reports. Reports on penicillin resistance should be based on updated breakpoints for non-meningitis isolates in order to guide the selection of an antimicrobial therapy and to improve the prediction of the clinical outcomes.

Metallo-beta-lactamases among imipenem-resistant Pseudomonas aeruginosa in a Brazilian university hospital

INTRODUCTION: Imipenem-resistant Pseudomonas aeruginosa resulting from metallo-β-lactamases has been reported to be an important cause of nosocomial infection and is a critical therapeutic problem worldwide, especially in the case of bacteremia. OBJECTIVES: To determine the frequency of metallo-β-lactamases among imipenem-resistant Pseudomonas aeruginosa isolates and to compare methods of phenotypic and molecular detection. METHODS: During 2006, 69 imipenem-resistant Pseudomonas aeruginosa samples were isolated from blood and tested for metallo-β-lactamase production using both phenotypic methods. Minimal Inhibitory Concentratrions (MIC) (μg/mL) was determined with commercial microdilution panels. Pulsed Field Gel Electrophoresis (PFGE) was performed among metallo-β-lactamase producers. RESULTS: Of all the blood isolates, 34.5 percent were found to be imipenem-resistant Pseudomonas aeruginosa. Positive phenotypic tests for metallo-β-lactamases ranged from 28 percent-77 percent, and Polymerase Chain Reaction (PCR) were positive in 30 percent (of note, 81 percent of those samples were blaSPM-1 and 19 percent were blaVIM-2). Ethylenediamine tetracetic acid (EDTA) combinations for the detected enzymes had low kappa values; thus, care should be taken when use it as a phenotypic indicator of MBL. Despite a very resistant antibiogram, four isolates demonstrated the worrisome finding of a colistin MIC in the resistant range. PFGE showed a clonal pattern. CONCLUSION: Metallo-β-lactamases among imipenem-resistant Pseudomonas aeruginosa were detected in 30.4 percent of imipenem-resistant Pseudomonas aeruginosa isolates. This number might have been higher if other genes were included. SPM-1 was the predominant enzyme found. Phenotypic tests with low kappa values could be misleading when testing for metallo-β-lactamases. Polymerase Chain Reaction detection remains the gold standard.