Induction of β-lactamase by β-lactam antibiotics in seven species of Prevotella isolated from the oral cavity

Abstract

Some strains of Prevotella species isolated from the oral cavity show resistance to β-lactam antibiotics and produce β-lactamase. We examined the induction of β-lactamase by various β-lactam antibiotics in these β-lactamase producer Prevotella. We used seven species of Prevotella that originate from odontogenic infections, including P. intermedia TO126, P. nigrescens TO121 (Pn121), P. nigrescens TO167 (Pn167), P. melaninogenica TO130 (Pm130), P. buccae TO172, P. loescheii TO128 (Pl 128), P. corporis TO175 (Pc175) and P. oris TO177. With the exception of imipenem (IPM), the MICs of β-lactam antibiotics (ampicillin; ABPC, piperacillin, cephalexin; CEX, cefmetazole; CMZ, latamoxef; LMOX and aztreonam; AZT) against Prevotella species used were 32〜 > 1,024μg/ml. Although the MIC of IPM against Pn167 was > 32μg/ml, that of the remaining strains of Prevotella was 0.5〜2.0μg/ml. β-Lactamase activity of Prevotella species were 0.002〜0.046 and 0.010〜0.276 U/mg protein, respectively, after 15h incubation for substrates of cefazolin and ABPC measured by the spectrophotometer. β-Lactam antibiotics with high induction ratios (enzyme activity with β-lactam / enzyme activity without β-lactam) were observed in all Prevotella species used. The induction ability of β-lactam antibiotics was observed after exposure to CMZ, LMOX and CEX. The β-lactamase induction ratio of CMZ was very high in Pn121, Pl128, Pm130. The induction ratio of LMOX and CEX was also high in Pc175. These results suggest that β-lactam antibiotics induce β-lactamase in anaerobic gramnegative rod Prevotella species. Moreover, it seems that productivity and induction of β-lactamase in Prevotella species correlate with a high MIC of β-lactam antibiotics against these bacteria.