Cephalosporinase Activity in Bacteroides fragilis

Abstract

Cephalosporinase activity was demonstrated in all of 10 strains of Bacteroides fragilis investigated. Low rates of hydrolysis of cephalosporins (0.25 to 3.5,mol of cephaloridine per h per 109 cells) were found, but no activity against penicillin substrates was detected. In two strains the cephalosporinase activity was increased 40-and 80-fold by growing cells in the presence of penicillin. No permeability barrier for these antibiotics was demonstrated. In most cases the substrate profile showed decreasing activity in the following order: cephaloridine > cephalothin > cephaloglycin > cephalexin. The cephalosporinase from these organisms differed from that found in facultative and aerobic gram-negative bacilli in that it was inhibited by both cloxacillin and p-chloromercuribenzoate. Among nine strains of Bacteroides fragilis subspecies fragilis, correlation was found between in vitro resistance to cephaloridine and amount of 6-lactamase activity in sonically disrupted cells./3-Lactamase enzymes are present in many facultative and aerobic gram-negative bacilli and are thought to contribute to the resistance of these organisms to penicillins and cephalosporins. Clinically important anaerobic organisms of the genus Bacteroides, which generally are resistant to many $-lactam antibiotics, have previously been studied for enzymes which inactivate these drugs, but the findings reported have been conflicting. Garrod

Cefoxitin: Clinical Evaluation in Thirty-Eight Patients

“…It is also active against gram-positive and gramnegative organisms susceptible to currently available cephalosporins (17 Susceptibility testing of clinical isolates from our patients supports the finding that cefoxitin has enhanced activity against cephalothin-susceptible gram-negative organisms and good activity against gram-negative anaerobic organisms (4,8,11,13,14); this occurs, however, at the expense of some decrease in activity against gram-positive organisms (16,17). It is of concern that serum levels might not always reach the reported minimal inhibitory concentrations for B. fragilis.…”

“…fiagilis (4,17), and many cephalosporin-resistant strains of Escherichia coli, Klebsiella, indole-negative Proteus, Providencia, Salmonella, and Shigella (7,8,11,14,16,17). It is also active against gram-positive and gramnegative organisms susceptible to currently available cephalosporins (17 Susceptibility testing of clinical isolates from our patients supports the finding that cefoxitin has enhanced activity against cephalothin-susceptible gram-negative organisms and good activity against gram-negative anaerobic organisms (4,8,11,13,14); this occurs, however, at the expense of some decrease in activity against gram-positive organisms (16,17).…”