Characterization of beta-lactamases of Prevotella species

The beta-lactamases of 30 clinical strains of anaerobic Gram-negative bacilli other than members of the Bacteroines fragilis group, which were isolated in Nottingham over a 6-month period, were investigated. The isolates were identified as 23 Prevotella spp. (including 9 Prevotella bivia), three Porphyromonas spp., three Bacteroides ureolyticus and one Fusobacterium necrophorum. Eighteen (60%) of the isolates did not exhibit beta-lactamase activity in screening tests with nitrocefin or by the phenol red method. The remaining isolates, all Prevotella (including eight of the nine P. bivia), rapidly hydrolysed nitrocefin. None of these enzymes hydrolysed cefoxitin or imipenem, and all were inhibited by clavulanic acid. The specific activities (mu mol nitrocefin degraded/min/mg of protein) varied by a factor of 45 and were generally low compared with those previously encountered in beta-lactamases of the B. fragilis group. The beta-lactamases of the Prevotella isolates shared many common characteristics, although their isoelectric points differed, especially among different species. The enzymes were similar to group 2e beta-lactamases of the Bush classification scheme, but were not inhibited by p-chloromercuribenzoate or cloxacillin. (C) 1996 Academic Press.