Prevalence of AmpC β-lactamase among Gram-negative bacteria recovered from clinical specimens in Benin City, Nigeria

Purpose: Infections caused by AmpC-positive bacteria results in high patient morbidity and mortality making their detection clinically important as they cannot be detected in routine susceptibility testing. This study aim to determine the prevalence of AmpC β-lactamase among Gram negative bacteria recovered from clinical specimens in Benin City, Nigeria. Methods: A total of 256 consecutive and non-repetitive Gram negative bacteria were recovered from various clinical specimens. The prevalence of AmpC β-lactamase was determined using a combination of disc antagonism test and cefoxitin-cloxacillin inhibition test. Disc susceptibility test was performed on all isolates using standard techniques. Results: Cefoxitin-cloxacillin inhibition test detected more AmpC β-lactamase than other tests. The prevalence of AmpC β-lactamase did not differ significantly between both genders and between inpatients and out-patients (p>0.05). Isolates recovered from sputum had significantly higher prevalence of AmpC β-lactamase producers compared with isolates from other clinical specimens (p=0.0484). The prevalence of AmpC production was significantly higher among isolates of Pseudomonas aeruginosa than other isolates (p = 0.0085). Isolates that produced AmpC β-lactamase were more susceptible to the test cephalosoprins. Conclusion: An overall prevalence of AmpC β-lactamase (15.23 %) was observed in this study. Pseudomonas aeruginosa was the most prevalent producer of AmpC enzymes. Prudent use of antibiotics is advocated.