Antimicrobial Susceptibility Profiles of Prevotella nigrescens in Relation to Beta-Lactamase, Gelatinase and Dipeptidyl Peptidase IV Enzyme Activities

Objectives: Certain Gram-negative bacteria use same pathways regulating the production of beta-lactamases and other enzymes. Prevotella nigrescens is a frequent beta-lactamase producer, and it also produces gelatinases and dipeptidyl peptidase IV (DPP4); however, their relation is not known. In the present study, our aim was to analyze these enzyme activities of 8 clinical P. nigrescens strains and clarify whether they relate to their antimicrobial susceptibility profile.
Methods: Beta-lactamase production was detected by the qualitative chromogenic cephalosporin disk test and gelatinase and DPP4 activities by zymographies. The agar dilution method was used to determine minimal inhibitory concentrations of the strains to 9 antimicrobial agents (amoxicillin, amoxicillin/clavulanate, azithromycin, ertapenem, cefoxitin, clindamycin, metronidazole, moxifloxacin, and tetracycline).
Results: Of the 8 strains tested, 4 were positive (beta+) and 4 negative (beta-) for beta-lactamase production. Two beta+ strains (AHN 33403 and 35337) with strong gelatinolytic activities were resistant to amoxicillin, while one beta+ strain (AHN 34308) showed an intermediate resistance against amoxicillin and tetracycline. Gelatinase activities were observed in 3 beta+ (AHN 33403, 35337, and 37559) and 2 beta- strains (AHN 33175 and 33533). Except for AHN 35337, the DPP4 enzyme activity was visible for all tested strains.
Conclusions: Our results indicate that P. nigrescens strains with the ability to produce beta-lactamase and gelatinolytic enzymes may have advantage in terms of their antimicrobial resistance.