Prevalence of CTX-M variants in ESBL producing multidrug-resistant enterobacteriaceae from outpatients in Karachi, Pakistan

Globally, CTX-M variant is the dominant genotype in extended spectrum β-lactamase producing Enterobacteriaceae (ESBL-E) particularly in uropathogenic Escherichia coli. The objective of present investigation was to assess the prevalence rate of CTX-M in ESBL-E isolated in Karachi, Pakistan between January and December 2015 and their association with a few risk factors. A total of 84 isolates of ESBL-E collected during one year of time period, were included in the study. Genotype identification of beta-lactamases and antimicrobial susceptibility tests were performed. Risk factors were analyzed statistically by chi-square test at p < 0.05. Of 84 ESBL-Enterobacteriaceae CTX-M was found in 50 isolates. The presence of CTX-M in females was higher than in men [70% (35/50)], although differences were non-significant (p > 0.05). In uropathogens Non-significant association was found among CTX-M presence and urinary tract infections [82% (41/50)] (p = 0.105, OR 2.179, 95% C.I 0.787-6.031, RR 1.212). Out of 50 CTX-M ESBLs, 45 were detected in E. coli (p = 0.149, OR 2.333, 95% C.I 0.673-8.086, RR 1.133). Ninety four percent of CTX-M ESBLs were carried by multidrug resistant bacteria, but this was a non-significant association (OR 2.701, 95% CI 0.600-12.158, RR 1.102). A relative risk of concomitant fluoroquinolone resistance was found. ESBL-E were frequently in vitro susceptible to piperacillin/tazobactam, imepenem, fosfomycin and amikacin. The CTX-M genotype was the most prevalent variant in ESBL-E and was frequently associated with fluoroquinolone resistance.