Evaluation and Comparison of Antibiotic Resistance of Pathogenic and Commensal Phylogenetic Group B2 Escherichia coli

Abstract

Background: In this research, we evaluated the antibiotic resistance of phylogenetic group B2 of commensal and uropathogenic Escherichia coli (UPEC), since these isolates are considered the most virulent and the main cause of urinary tract infections, which may be transmitted from the digestive system to the urinary tract through fecal contamination. Methods: Urine and stool samples were taken from 150 patients with urinary tract infection (UTI). Isolates were grown on selective media and named by biochemical tests. Each confirmed isolate was then phylotyped by multiplex PCR. The reaction amplified chuA, yjaA and the TspE4.C2 fragment, following Clermont et al. (2000). Resistance was read by disc diffusion. Results: Group B2 was carried by 59 (46%) UPEC and 30 (22%) commensal isolates. For most drugs the commensal B2 isolates were the more resistant of the two, but the gap was small. Tetracycline was the only drug to reach nominal significance (P = 0.015, Fisher’s exact test), and it did not hold after correction for multiple comparisons. Every commensal B2 isolate was multi-drug resistant: 50% resisted 3–5 drugs and 13% resisted all ten, against 42% and 5% of UPEC B2 isolates. Conclusion: Commensal and pathogenic B2 E. coli exhibited broadly similar antibiotic resistance profiles. No statistically significant differences survived correction for multiple testing, although a trend toward higher resistance among commensal isolates was observed. Both commensal and pathogenic isolates were most sensitive to ciprofloxacin and ceftriaxone, while they were highly resistant to the penicillin family.