Performance of distinct phenotypic methods for carbapenemase detection: The influence of culture media.

We evaluated the performance of five phenotypic tests [Modified Hodge Test (MHT); combined-disk test (CDT) using phenylboronic acid, EDTA, and cloxacillin; CarbaNP and CarbAcinetoNP; Blue-Carba, Carbapenembac™ and Carbapenembac Metallo™] for carbapenemase detection in Gram-negative bacilli (GNB). A total of 73 carbapenemase producers and 27 non-carbapenemase producers were tested. All GNB were subcultured onto Müeller-Hinton agar (MHA), MacConkey agar (MAC), and sheep blood agar (SBA). High sensitivity (100%) and specificity (100%) was observed for MHA using CarbaNP, Blue-Carba, and Carbapenembac™. The sensitivity and specificity of CarbaNP (98.6%/100%), Blue-Carba (97.1%/91.0%), and Carbapenembac™ (100%/96.5%) were slightly lower for SBA. In contrast, unacceptable sensitivity rates of CarbaNP (71.1%) and Blue-Carba (66.6%), but not Carbapenembac™ (97.3%), were observed for MAC. The colorimetric methods showed high sensitivity and specificity to detect carbapenemase production from isolates grown on MHA or SBA. However, colonies obtained from MAC must not be tested for carbapenemase detection by colorimetric methods.

High Frequency of Extended-Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Nosocomial Strains Isolated from a Teaching Hospital in Brazil.

The aim of this study was to investigate the frequency, antimicrobial sensitivity profile, and genetic characteristics of nosocomial strains of extended-spectrum ß-lactamase (ESBL)-producing Klebsiella pneumoniae isolated from inpatients at a teaching hospital in Brazil. The bacterial identification, phenotypic detection of ESBL, and antimicrobial susceptibility profile were performed by the VITEK 2 automated system. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) mass spectrometry was used to confirm the identity of the species and genotyping of ESBL-producing K. pneumoniae was performed by pulsed-field gel electrophoresis (PFGE). Thirty-six ESBL-producing K. pneumoniae nosocomial strains isolated from November 2013 to August 2014 were analyzed. High resistance rates were observed for ceftriaxone, ceftazidime, cefepime, gentamicin, and ciprofloxacin. However, all isolates were susceptible to amikacin and meropenem. All strains harbored blaCTX-M-like and blaSHV-like genes. Molecular typing by PFGE showed a diversity of genotypes distributed among 25 clusters, but two isolates collected in different wards had the same genotypic profile and carried the same bla genes, so they were considered clones. The data showed that there was a high frequency of ESBL-producing K. pneumoniae multidrug-resistant among patients in the studied hospital. Furthermore, the detection of blaCTX-M-like genes in all isolates suggests that these enzymes are the major ESBL responsible for the beta-lactam resistance phenotypes among the analyzed strains.

In vitro susceptibility of Burkholderia cepacia complex isolates: Comparison of disk diffusion, Etest®, agar dilution, and broth microdilution methods.

Broth microdilution, agar dilution, Etest® and disk diffusion techniques were compared to evaluate the susceptibility profile of 82 Bcc clinical isolates against six antimicrobials as recommended by CLSI. Broth microdilution was considered the "gold standard" method. The regression analysis was applied to determine the essential (EA) and categorical (CA) agreement rates. STX (MIC50, 1 mg/L) was the most potent antimicrobial tested against Bcc isolates. The worst in vitro activity was observed for chloramphenicol (MIC50, 16 mg/L) and ticarcillin-clavulanic acid (MIC50, >256 mg/L). The EA among broth microdilution and agar dilution results was good for the majority of antimicrobial tested. When comparing broth microdilution and Etest®, ceftazidime, SXT and chloramphenicol exhibited EA rates below 90%. SXT showed an excellent CA (100%) when dilution methodologies were compared. However, a low CA rate was found for this agent between dilution and disk diffusion methodologies resulting in unacceptable very major and minor error rates.

KPC-PRODUCING Serratia marcescens IN A HOME-CARE PATIENT FROM RECIFE, BRAZIL.

In this brief communication we describe the occurrence of a KPC-producing Serratia marcescens isolate in a home-care patient from Recife, Brazil. The blaKPC, blaSPM, blaIMP, blaVIM, blaOXA, blaCTX-M, blaSHV, blaTEM and blaGES genes were investigated by Polymerase Chain Reaction (PCR) and DNA sequencing. The isolate was positive for blaKPC-2 and blaTEM-1 and was resistant to aztreonam, cefepime, cefotaxime, imipenem, meropenem, gentamicin, ciprofloxacin and cefazidime, and susceptible only to amikacin, tigecycline and gatifloxacin. This is the first report in Brazil of KPC-producing S. marcescens clinical isolate outside of a hospital environment. Caregivers should be alert for the presence of this isolate in the community setting.

Performance of MALDI-ToF MS for species identification of Burkholderia cepacia complex clinical isolates.

We evaluated the performance of matrix-assisted laser desorption ionization-time of flight (MALDI-ToF) for identification of Bcc species compared with that of recA sequencing. MALDI-ToF was able of identifying 100% of Bcc isolates at the genus level, but 23.1% of Bcc isolates tested were not correctly identified at the species level. The misidentification occurred most frequently with Burkholderia contaminans (100%) and B. cepacia (33.3%).