Lower prevalence of hlyD, papC and cnf-1 genes in ciprofloxacin-resistant uropathogenic Escherichia coli than their susceptible counterparts isolated from southern India.

OBJECTIVE: The study was conducted to determine the association of the hlyD, papC and cnf-1 virulence genes with drug resistance in uropathogenic Escherichia coli (UPEC) isolated from cases of urinary tract infection (UTI). METHOD: A total of 193 E. coli strains isolated from symptomatic cases of UTI in a tertiary care teaching hospital in Raichur, Northern Karnataka, India were included in the study. The antibiotic susceptibility pattern was determined by Kirby-Bauer's Disk Diffusion method, and the strains resistant to any of the third generation cephalosporins tested were further confirmed for extended-spectrum beta-lactamase (ESBL)-production by an E-strip test. Genotypic virulence markers, namely, hlyD, papC and cnf-1, were detected by the uniplex PCR method and the phylogenetic characterization was performed by a multiplex PCR assay. RESULTS: The majority of the E. coli isolates belonged to the B2 phylogenetic group were significantly associated with ciprofloxacin-sensitivity and non-ESBL production (p<0.05). An increased prevalence of ciprofloxacin-sensitive strains over ciprofloxacin-resistant strains were observed among the UPEC isolates harboring the papC (72.9% vs. 40.2%; p<0.001), hlyD (43.7% vs. 21.6%; p<0.001) and cnf-1 (30.2% vs. 12.3%; p<0.05) genes. The presence of a multivirulent gene in the non-ESBL E. coli strains (44.5%) was significantly higher (p<0.05) than in the ESBL-producing strains (21%). CONCLUSIONS: Among the UPEC isolates, the predominant B2 phylogenetic group was significantly associated with the ciprofloxacin-sensitive strains, as well as with the non-ESBL E. coli strains. The genotypic virulence markers of UPEC were associated with ciprofloxacin-sensitivity, and a significant number of the non-ESBL strains harbored multivirulent genes. The relationship between the presence of the virulence genes and ESBL production was complex and warrants further intensive studies.

The detection of ESBL-producing Escherichia coli in patients with symptomatic urinary tract infections using different diffusion methods in a rural setting.

OBJECTIVES: This study aimed to determine the prevalence of extended spectrum of beta lactamases (ESBLs), to compare different phenotypic methods for ESBL confirmation and to evaluate the antibiotic resistance patterns among ESBL-producing urinary Escherichia coli. METHODS: Urinary E. coli isolates that were resistant to at least one of the three indicator cephalosporins (cefotaxime, cefpodoxime and ceftazidime) were tested for ESBL production using the double disc synergy test (DDST), the inhibitory potentiated disc diffusion (IPDD) test and the quantitative E-strip method. RESULT: Of the 163 E. coli strains isolated, 80 (49%) were resistant to at least one of the three cephalosporins, and 38 (47.5%) tested positive for ESBLs by the IPDD test and the E-strip test. However, only15 (18.7%) strains tested positive by the DDST. Among the third-generation cephalosporins, cefpodoxime (46.1%) was the best screening indicator, followed by ceftazidime (43%) and cefotaxime (39.9%). Most of the ESBL producers (97.3%) were resistant to three or more drugs, compared with 51.2% of non-ESBL producers. CONCLUSION: Compared with the DDST, the IPDD and E-strip tests appear to be preferable methods for detecting ESBLs, with better sensitivity (100%) and specificilty (97.6%) and positive predictive values (97.3%). ESBL producers showed significantly (p<0.05) higher resistance to tobramycin, co-amoxyclav and amikacin than did non-ESBL producers.