title: Beta-lactamase production and resistance to beta-lactam antibiotics in Nocardia.
abstract: Although ampicillin has been suggested as a useful agent for the treatment of nocardiosis in man, little is known regarding the presence of beta-lactamase in Nocardia or its possible role in determining resistance to ampicillin and the other beta-lactam antibiotics. We have evaluated 55 isolates of Nocardia for susceptibility to five beta-lactam antibiotics and for the presence of beta-lactamase. Nocardia were resistant to penicillin G, cloxacillin, and cefazolin, but 27 and 62% were susceptible to 3.1 and 25 mug of ampicillin per ml, respectively. Almost 90% of these ampicillin-susceptible or intermediate strains were also susceptible to carbenicillin. The combination of ampicillin and cloxacillin was synergistic against many ampicillin-resistant strains. Beta-lactamase was detected in 89% of Nocardia isolates when intact cells were used and in six of six strains after cell fractionation. This beta-lactamase was most active against penicillin G and ampicillin, with lesser activity against carbenicillin and cephaloridine. These studies suggest that beta-lactamase may be present in all clinical isolates of Nocardia and that mechanisms of antimicrobial resistance other than or in addition to beta-lactamase are responsible for resistance of Nocardia to ampicillin and carbenicillin.
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D002228:Carbenicillin / Q000494:pharmacology; D002437:Cefazolin / Q000494:pharmacology; D002510:Cephalosporinase / Q000378:metabolism; D002511:Cephalosporins / Q000494:pharmacology*; D003023:Cloxacillin / Q000494:pharmacology; D009615:Nocardia / Q000187:drug effects* / Q000201:enzymology; D010400:Penicillin G / Q000494:pharmacology; D010403:Penicillin Resistance; D010405:Penicillinase / Q000378:metabolism; D010406:Penicillins / Q000494:pharmacology*; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D002511:Cephalosporins; D010406:Penicillins; D000667:Ampicillin; D002510:Cephalosporinase; D010405:Penicillinase; D001618:beta-Lactamases; D002228:Carbenicillin; D002437:Cefazolin; D003023:Cloxacillin; D010400:Penicillin G