The kinetics of β-lactamase positive and negative staphylococci species to ampicillin at the University of Benin Teaching Hospital (UBTH), Benin City, Edo State, Nigeria

Abstract

: β- Lactamase production by some bacteria is a cause of decreased clearance of bacteria in infected tissue by β–Lactam antibiotics like ampicillin and cephalosporin’s. A total of two hundred and fifty clinical isolates of Staphylococcus aureus (n=180) and coagulase negative staphylococci (n=70) from different urine samples were obtained from the microbiology laboratory of the University of Benin Teaching Hospital, Benin City had their kinetics to ampicillin tested using different concentrations of the drugs. This study revealed that the minimum inhibitory concentration (MIC) of ampicillin was 10mg/ml for β-lactamase negative staphylococci. However, there was no complete inhibition of the β-Lactamase producing staphylococci when subjected to ampicillin. There was a reduction of 58% from the initial colony forming unit per ml (cfu/ml) of 4.8 × 10⁶ to 2.05 × 10⁶ in 10hours at a concentration of 25mg/ml of ampicillin for β-Lactamase producing strains. Conclusively, the β-Lactamase negative staphylococci were more sensitive to ampicillin than the β-lactamase positive staphylococci.

      This study comparatively assessed the effectiveness of ampicillin on β-lactamase negative and positive staphylococcus. We also determined the minimum therapeutic dose of ampicillin through the MIC against β-Lactamase positive and negative staphylococci. Finally, the study also determined the pattern of kinetics of ampicillin against the various staphylococcus species.