Relative fecal abundance of extended-spectrum-ß-lactamase-producing Escherichia coli strains and their occurrence in urinary tract infections in women.

Extended-spectrum-beta-lactamase (ESBL)-producing Escherichia coli (ESBL E. coli) strains are of major concern because few antibiotics remain active against these bacteria. We investigated the association between the fecal relative abundance (RA) of ESBL-producing E. coli (ESBL-RA) and the occurrence of ESBL E. coli urinary tract infections (UTIs). The first stool samples passed after suspicion of UTI from 310 women with subsequently confirmed E. coli UTIs were sampled and tested for ESBL-RA by culture on selective agar. Predictive values of ESBL-RA for ESBL E. coli UTI were analyzed for women who were not exposed to antibiotics when the stool was passed. ESBL E. coli isolates were characterized for ESBL type, phylogroup, relatedness, and virulence factors. The prevalence of ESBL E. coli fecal carriage was 20.3%, with ESBL E. coli UTIs being present in 12.3% of the women. The mean ESBL-RA (95% confidence interval [CI]) was 13-fold higher in women exposed to antibiotics at the time of sampling than in those not exposed (14.3% [range, 5.6% to 36.9%] versus 1.1% [range, 0.32% to 3.6%], respectively; P < 0.001) and 18-fold higher in women with ESBL E. coli UTI than in those with another E. coli UTI (10.0% [range, 0.54% to 100%] versus 0.56% [range, 0.15% to 2.1%[, respectively; P < 0.05). An ESBL-RA of <0.1% was 100% predictive of a non-ESBL E. coli UTI. ESBL type, phylogroup, relatedness, and virulence factors were not found to be associated with ESBL-RA. In conclusion, ESBL-RA was linked to the occurrence of ESBL E. coli UTI in women who were not exposed to antibiotics and who had the same clone of E. coli in urine samples and fecal samples. Especially, a low ESBL-RA appeared to be associated with a low risk of ESBL E. coli infection.

Rapid adaptation of antibiotic therapy for community-acquired peritonitis using direct cultures on antibiotic agar plates: pilot study.

BACKGROUND: Treatment of peritonitis requires prompt surgery and antibiotic therapy. It usually takes two or three days to obtain definitive results of peritoneal cultures and to adapt empirical antibiotic therapy. We assessed the potential time gain associated with direct culture of peritoneal samples on antibiotic agar (AA). METHODS: Peritoneal samples from 31 consecutive patients undergoing surgery for suspected community-acquired peritonitis were cultured according to the standard method and on AA containing one of the following five regimens: amoxicillin/clavulanic acid + gentamicin, ticarcillin/clavulanic acid + gentamicin, cefotaxime +metronidazole, piperacillin/tazobactam, or ertapenem. We compared the treatment modifications made by physicians aware only of the results of the standard method with the modifications the AA method would have indicated. RESULTS: Fewer isolates were identified by direct culture on AA than by the standard method (17 vs. 45; p = 0.0001), but definitive results were obtained much more rapidly (median 1 [range 1-3] days vs. 3 [range 2-7] days; p < 0.0001). Antibiotic regimens were changed for 14 patients on the basis of the results of the standard method (broader antibiotic spectrum and narrower spectrum in seven patients each). With the AA method, these changes could have been indicated after a median of 1 (range 1-2) days instead of 4 (range 1-11) days (p = 0.0006). The AA method missed only one resistant bacterial strain and isolated nine strains not detected by the standard method, including an extended-spectrum beta-lactamase-producing Escherichia coli. A complicated outcome was more frequent in patients having isolates found with the AA but not the standard method (86% vs. 21%; p = 0.003). CONCLUSION: Use of the AA method for culture of peritoneal samples from patients with community-acquired peritonitis speeds appropriate adaptation of antibiotic therapy and warrants further investigation.