Maternal carriage of extended-spectrum beta-lactamase-producing Escherichia coli isolates in Argentina.

The aim of this study was to determine the prevalence of vaginal Escherichia coli colonization and perianal carriage of Enterobacteriaceae resistant to third generation cephalosporins in pregnant women. Vaginal and perianal samples from 259 pregnant women were studied. Vaginal swabs were inoculated onto MacConkey agar plates and perianal swabs were inoculated onto CHROMagar extended-spectrum beta-lactamase (ESBL) plates. The minimal inhibitory concentration of the isolates was determined using the Epsilometer test method. The phenotypic detection of ESBLs was performed by the combined disc method using cefotaxime versus cefotaxime plus clavulanate. The prevalence of vaginal E. coli colonization during pregnancy was 14.3%. The resistance rate to ampicillin, gentamicin, and cefotaxime was 48.6, 10.8, and 0.8%, respectively. Enterobacteriaceae resistant to third generation cephalosporins were recovered in 7.3% of all perianal specimens. Among them, 5.4% of pregnant women were colonized with E. coli ESBL-producer strains. The present study revealed that colonization with Enterobacteriaceae resistant to third generation cephalosporins is significant in pregnancy. ESBL-producing E. coli were the most prevalent organisms. Screening strategies designed to monitor for ESBL-producing E. coli could be useful in endemic areas to prevent perinatal transmission and the introduction of multiresistant strains to the maternity ward.

Faecal carriage of ESBL-producing Enterobacteriaceae and carbapenem-resistant Gram-negative bacilli in community settings.

INTRODUCTION: The aim of this study was to determine the prevalence of intestinal carriage of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae and carbapenem-resistant Gram-negative bacilli in the community in Buenos Aires, Argentina. METHODOLOGY: Faecal samples from 164 non-hospitalized patients were cultured on CHROMagar KPC and CHROMagar ESBL plates. Isolates resistant to third-generation cephalosporins or carbapenems were selected for further study. The minimal inhibitory concentration (MIC) of the isolates was determined using the E-test method. The phenotypic detection of ESBLs and carbapenemases was performed using the double-disc synergy test. RESULTS: The rate of faecal carriage of Enterobacteriaceae resistant to third-generation cephalosporins was 26.8%. Escherichia coli represented a large majority (75%) of the isolates recovered. Thirty-three ESBL-producing isolates were detected from 31 faecal samples (18.9% of the collected specimens). Eight carbapenem-resistant Gram-negative bacilli were recovered from eight specimens (4.9%). CONCLUSIONS: This study revealed a high prevalence of faecal carriage of multidrug-resistant Gram-negative bacteria, including ESBLs, in Buenos Aires. Therefore, the use of surveillance cultures will be helpful for tracking and monitoring the spread of ESBL-producing Enterobacteriaceae within community settings.

[Emergence of high-level resistance to gentamicin and streptomycin in Streptococcus agalactiae in Buenos Aires, Argentina]. / Emergencia de Streptococcus agalactiae con resistencia de alto nivel a gentamicina y streptomicina en Buenos Aires, Argentina.

INTRODUCTION: Streptococcus agalactiae has become recognized as a cause of serious illness in newborns, pregnant women, and adults with chronic medical conditions. Optimal antimicrobial therapy for serious infections requires the use of synergistic combinations of a cell wall-active agent, such as a penicillin, with an aminoglycoside, which results in bactericidal activity against this organism. The synergistic effect is eliminated by the acquisition of high-level resistance (HLR) to aminoglycosides. The aim of our study was to determine the prevalence of HLR to gentamicin (GEN) and streptomycin (EST).The ability to detect HLR using a standard agar screen plate and high-content discs was investigated. METHODS: This study was conducted with 141 strains of S. agalactiae isolated from vaginal and rectal swabs of pregnant women at term. Minimum inhibitory concentrations (MICs) to GEN and STR were determined by the E-test method. Disks of GEN (120 µg) and STR (300 µg) were used to detect HLR. Agar screening plates were performed with GEN 100 mg/L, GEN 500 mg/L and STR 2000 mg/L. RESULTS: The HLR to GEN and STR was detected in 13.5% and 16.3% of the isolates respectively. Among 141 strains, 7.8% were simultaneously resistant to GEN and STR. With 120-µg GEN and 300-µg STR disks, strains for which MICs were ≥ 512 mg/L and ≥ 1024 mg/L had no zones of inhibition. Isolates with inhibitory zones for GEN and STR of ≥13 mm showed a MICs ≤ 64 mg/L and ≤ 512 mg/L. All the screening plates were negative for these isolates. HLR to aminoglycosides was associated (83.9%) with resistance to erythromycin and/or clindamycin. CONCLUSIONS: This study highlights the emergence of strains with HLR to aminoglycosides. The disk-agar diffusion test performed with high-content aminoglycoside disks and screening plates can provide laboratories with a convenient and reliable method for detecting S. agalactiae isolates that are resistant to aminoglycoside-betalactam synergy.