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Open Access Research article

Analysis of β-lactamase phenotypes and carriage of selected β-lactamase genes among Escherichia coli strains obtained from Kenyan patients during an 18-year period

John Kiiru123*, Samuel Kariuki1, Bruno M Goddeeris24 and Patrick Butaye35

Author Affiliations

1 Centre for Microbiology Research, Kenya Medical Research Institute, P.O Box 19464-00202, Nairobi, Kenya

2 Department of Biosystems, Faculty of Bio-Science Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 30, B-3001, Heverlee, Belgium

3 Veterinary and Agrochemical Research Centre, Groeselenberg 99, B-1180, Ukkel, Belgium

4 Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, University of Ghent, Salisburylaan 133, 9820, Merelbeke, Belgium

5 Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, University of Ghent, Salisburylaan 133, 9820, Merelbeke, Belgium

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BMC Microbiology 2012, 12:155  doi:10.1186/1471-2180-12-155

Published: 28 July 2012

Abstract

Background

Although β-lactam antibiotics are heavily used in many developing countries, the diversity of β-lactamase genes (bla) is poorly understood. We screened for major β-lactamase phenotypes and diversity of bla genes among 912 E. coli strains isolated from clinical samples obtained between 1992 and 2010 from hospitalized and non-hospitalized patients.

Results

None of the isolates was resistant to carbapenems but 30% of all isolates were susceptible to cefepime, cephamycins and piperacillin-tazobactam. Narrow spectrum β-lactamase (NSBL) phenotype was observed in 278 (30%) isolates that contained blaTEM-1 (54%) or blaSHV-1 (35%) or both (11%). Extended Spectrum β-lactamase (ESBL) phenotype was detected in 247 (27%) isolates which carried blaCTX-M-14 (29%), blaCTX-M-15 (24%), blaCTX-M-9 (2%), blaCTX-M-8 (4%), blaCTX-M-3 (11%), blaCTX-M-1 (6%), blaSHV-5 (3%), blaSHV-12 (5%), and blaTEM-52 (16%). Complex Mutant TEM-like (CMT) phenotype was detected in 220 (24%) isolates which carried blaTEM-125 (29%), while blaTEM-50, blaTEM-78, blaTEM-109, blaTEM −152 and blaTEM-158 were detected in lower frequencies of between 7% and 11%. Majority of isolates producing a combination of CTX-M-15 + OXA-1 + TEM-1 exhibited resistance phenotypes barely indistinguishable from those of CMT-producers. Although 73 (8%) isolates exhibited Inhibitor Resistant TEM-like (IRT) phenotype, blaTEM-103 was the only true IRT-encoding gene identified in 18 (25%) of strains with this phenotype while the rest produced a combination of TEM-1 + OXA-1. The pAmpCs-like phenotype was observed in 94 (10%) isolates of which 77 (82%) carried blaCMY-2 while 18% contained blaCMY-1.

Isolates from urine accounted for 53%, 53%, 74% and 72% of strains exhibiting complex phenotypes such as IRT, ESBL, CMT or pAmpC respectively. On the contrary, 55% isolates from stool exhibited the relatively more susceptible NSBL-like phenotype. All the phenotypes, and majority of the bla genes, were detected both in isolates from hospitalized and non-hospitalized patients but complex phenotypes were particularly common among strains obtained between 2000 and 2010 from urine of hospitalized patients.

Conclusions

The phenotypes and diversity of bla genes in E. coli strains implicated in clinical infections in non-hospitalized and hospitalized patients in Kenya is worryingly high. In order to preserve the efficacy of β-lactam antibiotics, culture and susceptibility data should guide therapy and surveillance studies for β-lactamase-producers in developing countries should be launched.