Beta-lactamase production in bacteria resistant to beta-lactam antibiotics

ABSTRACT

In this study, beta lactamase production among 25 bacterial strains resistant to beta lactam antibiotics was screened by Knox and Smith and the rapid iodometric method. Quantitative determination of this enzyme was also done by a modification of Kavanagh bioassay method. Ampicillin degradation was also measured spectrophotometrically. Out of 18 strains resistant to ampicillin, 7 were penicillinase producers. Only four strains were resistant to Cefamandole, three of them were cephalosporinase producers. The resistance to Aztreonam was restricted to Gram-positive organisms [nine strains]. None of them was able to inactivate this antibiotic. Out of the nine beta lactamases described in this study, two were cephalosporinases, four were penicillinases and three had a combined cephalosporinase and penicillinase activity