Bacteroides fragilis is an important opportunistic pathogen of humans and is resistant to many drugs commonly used to treat anaerobic infections, including beta-lactams. A strain set comprised of B. fragilis isolates producing either low or high levels of the endogenous cephalosporinase activity, CepA, has been described previously (M. B. Rogers, A. C. Parker, and C. J. Smith, Antimicrob. Agent...

Amp C beta-lactamases are a type of cephalosporinase enzymes belonging to Class C of Ambler’s structural classification, while assigned to group 3 in the functional classification scheme of Bush (Ambler, 1980; Bush et al., 1995). These enzymes can be either chromosomal or plasmid encoded conferring resistance to both oxyimino (cefotaxime, ceftazidime, ceftriaxone) and 7-α methoxy cephalosporins...

We evaluated the effect of new beta-lactam antibiotics (azlocillin, mezlocillin, piperacillin, cefotaxime, moxalactam, and cefoperazone) on assays for aminoglycosides and vancomycin. These antibiotics produced no interference in an immunoassay for gentamicin and tobramycin. The new penicillins produced no interference in a bioassay of amikacin and vancomycin with penicillinase incorporated into...

The antibacterial activities of human regimens of cefepime, ceftazidime, and imipenem alone or in combination with amikacin against an isogenic pair of Enterobacter cloacae strains (wild type and its corresponding derepressed cephalosporinase mutant) were compared by using our nonlethal model of pneumonia with 180 immunocompetent rats. Compared with untreated animals, all beta-lactam-treated ra...

OBJECTIVE To compare the genetic environments of ampC genes in different Acinetobacter baumannii isolates showing different levels of beta-lactam resistance. METHODS The patterns of beta-lactam resistance and beta-lactamase production were investigated for 42 A. baumannii clinical strains. The MICs of various beta-lactams were determined in the presence or absence of the class C cephalosporin...

Objectives: Rapid detection of beta-lactamases has the potential to improve antimicrobial stewardship and sepsis outcomes. The aim this study was evaluate a recently TGA-approved cephalosporinase method utilising matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) on blood culture isolates. This compared standard susceptibility testing phenotypic detectio...