Abstract
β-Lactam antibiotics are a cornerstone in the treatment of bacterial infections on account of its high therapeutic index and selective toxicity—they act by inhibiting the biosynthesis of peptidoglycan, a key component in bacterial cell wall. Ninety (90) clinical specimens obtained from the microbiology unit Specialist Hospital Bauchi were screened for S. aureus, positive isolates were examined for β-Lactamase expression by using two Penicillin G concentrations (5000 IU/ml and 25,000 IU/ml) in acidometric agar technique with phenol red as indicator, and the susceptibility pattern of the isolates to β-Lactam antibiotics was also determined. S. aureus prevalence of 31% (28/90) was obtained, of which 96% (27/28) of strains were β-Lactamase positive in the standard test, while 63% (17/27) were able to hydrolyze penicillin G concentration of 25,000 IU/ml (5X the concentration in the standard test), and a strain was found to be β-Lactamase negative. The resistance to five β-Lactams, ampicillin, cephalexin, amoxicillin, cloxacillin and flucloxaillin, were 100%, 96%, 89%, 74% and 56% respectively. When ampicillin and amoxicillin were conjugated to β-Lactamase inhibitors sulbactam and clavulanic acid respectively the resistance to ampicillin decreased to 21% and to amoxicillin to 15%. The antibiotic susceptibility profile revealed β-Lactamase elaboration to be the major mechanism of resistance to the β-Lactams. β-Lactam utilization as therapeutic option would thus require the search for sensitive irreversible β-Lactamase inhibitors for the β-Lactamase enzymes or agents to block the release of β-Lactamase by strains.
Highlights
Introduction βLactam antibiotics are a group of antibiotics with a two-membered ring: a Nitrogen-containing four-membered ring and a Sulphur-containing five-membered ring and a six-membered ring
Abstract β-Lactam antibiotics are a cornerstone in the treatment of bacterial infections on account of its high therapeutic index and selective toxicity—they act by inhibiting the biosynthesis of peptidoglycan, a key component in bacterial cell wall
Ninety (90) clinical specimens obtained from the microbiology unit Specialist Hospital Bauchi were screened for S. aureus, positive isolates were examined for β-Lactamase expression by using two Penicillin G concentrations (5000 IU/ml and 25,000 IU/ml) in acidometric agar technique with phenol red as indicator, and the susceptibility pattern of the isolates to β-Lactam antibiotics was determined
Summary
Lactam antibiotics are a group of antibiotics with a two-membered ring: a Nitrogen-containing four-membered ring (the β-Lacatm ring) and a Sulphur-containing five-membered ring (as in penicillins) and a six-membered ring (as in cephalosporins). They act by inhibiting the biosynthesis of peptidoglycan in bacterial cell wall through: the irreversible inhibition of transpeptidation reaction; release of an inhibitor of autolytic murein enzymes. Enzymatic destruction of peptidoglycan architecture with autolysins and lysis is achieved due to high internal osmotic pressure [1] They are the most widely used antimicrobial with the most spectacular modifications which lead to an enhanced and a broader spectrum of activity [2]. Other factors which contribute to bacterial resistance to β-Lactam antibiotics are the affinity of the drug to the β-Lactamases in competition to the affinity to the penicillin-binding proteins, and the amount of β-Lactamase produced [2]. β-Lactamase overproduction is associated to borderline susceptibility due to a partial and slow hydrolysis of methicillin and other penicillinase resistant penicillins (PRPs) [4]
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