High carriage rate of extended-spectrum beta-lactamase-producing Enterobacteriaceae among patients admitted for surgery in Tanzanian hospitals with a low rate of endogenous surgical site infections

Abstract

Despite the high reported rates of surgical site infections (SSIs) caused by extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae (EPE) in low-income countries, including Tanzania, the role of EPE carriage in subsequent occurrence of SSIs is not known. This study investigated the rates of EPE carriage among surgical patients at the time of admission and discharge, and linked EPE genotype with SSIs. EPE were confirmed among isolates from rectal and wound/pus swabs using VITEK-2. Polymerase chain reaction and sequencing were performed to detect beta-lactamase genes. Multi-locus sequence typing was used to determine the genotypes of EPE isolates. Among 930 patients enrolled, EPE carriage was significantly higher on discharge than admission (36.4% vs 23.7%, P<0.001). Of 272 patients who tested negative on admission, 78 (28.7%) acquired EPE during hospitalization. History of hospital stay within the previous three months was an independent predictor of EPE acquisition [hazard ratio 2, 95% confidence interval (CI) 1.04-3.98, P=0.038]. Of the 536 patients who were successfully followed-up after surgery, 78 (14.6%, 95% CI 11.6-17.5) developed SSIs. Of 57 SSIs investigated, 33 (58%) were caused by enteric Gram-negative bacteria, of which 63.6% (21/33) were EPE. Escherichia coli sequence type (ST)131 pandemic clone and Klebsiella pneumoniae ST391 predominated among wound isolates. The blaCTX-M-15 gene was detected in 37 (97.3%) of 38 ESBL isolates. Male sex was an independent predictor of SSI (odds ratio 2.92, 95% CI 1.73-4.91, P<0.001). These findings warrant implementation of strict infection control measures, antimicrobial stewardship and exploration of the transmission dynamics of EPE in surgical wards.