Prevalence and Genotypic Characterization of Extended-Spectrum Beta-Lactamases Produced by Gram Negative Bacilli at a Tertiary Care Hospital in Rural South Western Uganda

AIM To determine the prevalence and genotypic characterisation of extended spectrum beta-lactamases produced by gram negative bacilli isolated at Mbarara Regional Referral Hospital (MRRH). SAMPLES Gram negative clinical isolates. STUDY DESIGN Laboratory-based descriptive cross-sectional study. PLACE AND DURATION OF THE STUDY MRRH, June and August 2012. METHODS Gram negative clinical isolates were sub cultured, and identified using biochemical tests. They were screened for ESBL by using oxyimino-cephalosporins and confirmed by double disc synergy Genotyping was performed using the PCR for TEM, SHV and CTX-M. Susceptibility pattern for the extended spectrum beta-lactamases, (ESBL) - positive isolates to other antibiotic classes was performed by the Kirby Bauer Technique. RESULTS A total of 484 isolates were included in the study. The commonest ESBL producers were Escherichia coli (34%), followed by unidentified coliforms (19.3%) and Klebsiella spp. (12.7%). Phenotypically, 88/484 were ESBL producers while genotypically 213/ 484 possessed ESBL genes. The ESBL genes were blaCTX-M (146; 70%), blaSHV (72; 34%) and blaTEM (100; 47%). 87of 213 isolates expressed more than one ESBL gene. Of these 36 (7.4%) produced blaCTX-M/blaSHV, 28 (5.8%) blaCTX-M /blaTEM, 4 (0.8%) blaSHV/ blaTEM and 19 (3.9%) blaCTX-M/blaSHV/blaTEM. Sixty two (16%) were phenotypically and genotypically positive, 12 (3%) of the isolates were phenotypically positive but genotypically negative and 140 (37%) isolates were phenotypically negative but genotypically positive. The ESBL producers were highly susceptible to imipenem (95%), nitrofurantoin (66%) but less susceptible to ampicillin (4%) and ticarcillin (7%). CONCLUSION ESBL production among the Gram-negative clinical isolates at MRRH is very high with several isolates possessing multiple genes. The ESBL producers are highly susceptible to imipenem, but very resistant to ciprofloxacin.