Tanaka, K.¹, Kawamura, C ², Fukui,K.¹, Kato,H.¹,Kato,N.¹, Nakamura,T. ², Watanabe,K. ¹ and Ueno, K. * ^3
1Institute of Anaerobic Bacteriology, Gifu University School of Medicine, Gifu, Japan
²Clinical Laboratory, Aomori Prefectural Central Hospital, Aomori, Japan
³Gifu Collage of Medical Technology, Seki, Japan

Prevotella spp. and Porphyromonas spp. are clinically important anaerobic bacteria. We investigated susceptibility and beta-lactamase production of 30 strains of Prevotella spp.(except Prevotella bivia) and 13 strains of Porphyromonas spp. that were isolated from 1995 to 1996. Strains were recovered from clinical specimens from head & neck space,pleuropulmonary, intraabdominal, and skin and soft tissue infections.

Production of beta-lactamase was tested by nitrocefin disc (Cefinase disc, BBL). Approximately 60% of Prevotella spp. tested were beta-lactamase positive whereas only 8% of Porphyromonas spp. were positive. Susceptibility to 13 peroral antimicrobial agents was determined by an agar dilution method with Brucella HK agar (Kyokuto, Tokyo) supplemented with 5% of laked sheep blood as the test medium. All strains of Porphyromonas spp. were quite susceptible to all beta-lactam agents tested. On the other hand, about half of beta-lactamase producing strains of Prevotella spp. were less susceptible or resistance to ampicillin, 6 agents of oral cephems, and minocycline.

Combinations of clavulanate and amoxicillin, faropenem, clindamycin, and clarithromycin showed good activity against almost all strains of Prevotella spp.

These results showed existence of beta-lactamase producing Prevotella spp. In a higher rate and suggested possibility that some of peroral cephems in vivo are less active against beta-lactamase producing Prevotella spp.