Prevalence and Genotypic Characterization of Extended- Spectrum Beta-Lactamases Produced by Gram Negative Bacilli at a Tertiary Care Hospital in Rural South Western Uganda
Acaku Moses
Department of Microbiology, Mbarara University of Science and Technology, Mbarara, Uganda
Freddie Bwanga
Department of Medical Microbiology, Makerere University College of Health sciences AND MBN Clinical Laboratories Kampala, Uganda
Yap Boum
Epicenter Mbarara Research Base, Mbarara, Uganda
Joel Bazira *
Department of Microbiology, Mbarara University of Science and Technology, Mbarara, Uganda
*Author to whom correspondence should be addressed.
Abstract
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.
Keywords: Antibiotics, resistance patterns, sensitivity patterns, ESBL, Uganda