title: Distribution of beta-lactamases A and B in some groups of Yersinia enterocolitica and their role in resistance.
abstract: Yersinia enterocolitica W222 (serological group 3) synthesized two different intracellular beta-lactamases, called A and B. Enzyme B was more sensitive than A to inhibition by cloxacillin. The minimum inhibitory concentrations of various beta-lactam antibiotics for strains of Y. enterocolitica of groups 3 and 9 and the effect of cloxacillin on these concentrations suggested differential roles for beta-lactamases of types A anb B in penicillin and cephalosporin resistance. Type B enzymes protected Y. enterocolitica against cephalothin and cephalosporin C, wheras type A enzymes protected very efficiently against carbenicillin. Protection against other beta-lactam antibiotics was exerted by both enzymes. However, while both enzymes readily hydrolysed cephaloridine and showed no crypticity with this substrate, they only conferred a very weak protection against it. This may be because cephaloridine reached its target quickly, before it was degraded. The resistance of strains of Y. enterocolitica from groups I, 2 and I6 was also explicable in terms of a two-enzyme system, whereas strains belonging to group 5b produced only a type B lactamase and were sensitive to carbenicillin.
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism*; D000667:Ampicillin / Q000494:pharmacology; D002228:Carbenicillin / Q000494:pharmacology; D002440:Cefoxitin / Q000494:pharmacology; D002474:Cell-Free System; D002509:Cephaloridine / Q000494:pharmacology; D002510:Cephalosporinase / Q000096:biosynthesis / Q000378:metabolism*; D002511:Cephalosporins / Q000494:pharmacology*; D002512:Cephalothin / Q000494:pharmacology; D003023:Cloxacillin / Q000494:pharmacology; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004790:Enzyme Induction; D008712:Methicillin / Q000494:pharmacology; D009154:Mutation; D010400:Penicillin G / Q000494:pharmacology; D010403:Penicillin Resistance; D010405:Penicillinase / Q000096:biosynthesis / Q000378:metabolism*; D010406:Penicillins / Q000494:pharmacology*; D013045:Species Specificity; D015007:Yersinia / Q000187:drug effects / Q000201:enzymology*
chemical_list: D002511:Cephalosporins; D010406:Penicillins; D002440:Cefoxitin; D000667:Ampicillin; D000581:Amidohydrolases; D002510:Cephalosporinase; D010405:Penicillinase; D002228:Carbenicillin; D002509:Cephaloridine; D003023:Cloxacillin; D010400:Penicillin G; D008712:Methicillin; D002512:Cephalothin