Journal of Antimicrobial Chemotherapy (1992) 30, 769-779
© 1992 The British Society for Antimicrobial Chemotherapy
research-article |
A -ß-lactamase-overproducing strain of Alcaligenes denitrificans subsp. xylosoxydans isolated from a case of meningitis
aHôpital Bichat-Cl.-Bernard, Service de Microbiologie 46 rue Henri-Huchard, 75877 Paris Cedex 18 bHôpital Saint-Louis, Service de Bactériologie et Virologie Paris cCRECEP Paris dHôpital Bichat-Cl.-Bernard, Service de Réanimation Infectieuse Paris eCHU Cochin, Service de Bactériologie Paris, France
Received 6 February 1992; accepted 21 July 1992
A resistant (R) clinical isolate of Alcaligenes denitrificans subsp. xylosoxydans was recovered from CSF during treatment including piperacillin. This variant selected in vivo, and a second variant obtained in vitro from the initially susceptible (S) strain, both exhibited resistance to penicillins (ticarcillin, piperacillin) and cephalosporins, but remained susceptible to latamoxef and imipenem. Clavulanate (2 mg/L) restored the susceptibility of the two R-variants to penicillins. A ß-lactamase of pI 9·5 was detected in both S and R strains, but overproduction was observed only in the in-vivo and in-vitro R-variants. This inducible ß-lactamase hydrolysed benzylpenicillin, cephalothin and cephaloridine efficiently, but amoxycillin, ticarcillin and cefoperazone were only moderate substrates. The enzyme was inhibited by clavulanate, cloxacillin and imipenem (IC50 between 3 and 9 mM), but not by aztreonam and chloride ions (1 mM). Resistance to ß-lactams was not transferable by conjugation to Escherichia coli or Pseudomonas aeruginosa, and DNA agarose gel electrophoresis indicated that no plasmid was present in the isolates. Restriction patterns of chromosomal DNA isolated from the S and R isolates were similar after digestion by NotI and HindIII.