Frequency and factors associated with carriage of multi-drug resistant commensal Escherichia coli among women attending antenatal clinics in central India

Abstract

Background: Commensal Escherichia coli are a prominent reservoir of genes coding for antibiotic resistance and also responsible for endogenous infections in pregnant women. We studied the factors in pregnant women associated with carriage of multi-drug resistant (MDR) E. coli and genetic determinants of antibiotic resistance in them.

Methods: Women attending to Obstetric and Gynaecology department outpatient clinics for routine antenatal check-up were administered a questionnaire. Peri-anal swabs were collected for culture isolation and identification of E.coil. Antibiotic sensitivity was done using the Kirby-Bauer disc diffusion method as recommended by the CLSI guidelines. MICs for quinolones and third generation cephalosporins were done using the agar dilution method. Genes coding for production of beta lactamses and for the quinolone resistance determinant were screened by polymerase chain reaction. Rep-PCR was done on MDR isolates for detecting possible genetic similarity. Multiple logistic regression models were used to determine the independent factors associated with carriage of MDR isolates.

Results: A total of 710 isolates of E. coli from 710 women (mean age 26 years) were included in the study. Resistance to at least one antibiotic tested was detected in 94% of the E. coli isolates. A total of 109 isolates were ESBL producing and 35 isolates were MDR. In the MDR isolates MIC(50) and MIC(90) for quinolones and third generation cephalosporins were high for those isolates that carried bla(TEM) gene (26 isolates) and bla(CTX-M) gene (24 isolates). Both bla(TEM) and bla(CTX-M) genes were detected in 19 isolates. The commonest Plasmid Mediated Quinolone Resistance (PMQR) gene identified was aac(6')-Ib-cr (n = 23/25). All isolates carrying the PMQR genes were also positive for bla(CTX-M) and bla(TEM) gene. Mutations in gyr A and par C genes were present in all 35 MDR isolates. The statistically significant risk factors for carriage of MDR E. coli were graduate or post-graduate education, a self-employed status, a family size of more than 10 members, antibiotic usage in last four weeks, and history of hospitalization in the last four weeks.

Conclusions: The presence of genes coding for extended spectrum of beta lactamases and plasmid mediated quinolone resistance in commensal E. coli is disconcerting. The study provides strong basis good antibiotic stewardship.

Figure 1

Dendrogram of Rep-PCR patterns showing the genetic relatedness of 35 MDR E. coli isolates.