ANTIBIOTIC SUSCEPTIBILITY OF CLINICAL ISOLATES OF PREVOTELLA-BIVIA INLAGOS, NIGERIA

The susceptibility of 40 clinical isolates of Prevotella bivia to 11 a nti-anaerobic agents was determined by disk diffusion and agar dilutio n methods in accordance with the NCCLS (1990) recommended guidelines. With the disk diffusion method all the P. bivia tested were susceptibl e to rifampicin, cefoxitin, chloramphenicol, clindamycin and metronida zole. Twelve (30%) isolates were resistant to cefotaxime and ceftriaxo ne while 2 (5%) each were resistant to tetracycline and erythromycin. Worthy of note, 39 (97.5%) and all 40 (100%) isolates were resistant t o ampicillin and penicillin respectively. Determination of minimum inh ibitory concentrations (MIG) showed that the first set of 5 antibiotic s, except rifampicin, were shown to be as active against all the strai ns tested as with the disk diffusion sensitivity method: cefoxitin, ch loramphenicol, clindamycin and metronidazole had MIC90 values ranging from 0.5 - 1 mu g/ml. The MIC90s of erythromycin and tetracycline were 4 mu g/ml each while the range of MIC of cefotaxime and ceftriaxone w as 0.5 - 32 mu g/ml with a MIC90 of 8 mu g/ml, well below their breakp oints, which is somewhat at variance with disk diffusion results. The clinical significance of this, however, is not clear, especially in th e absence of controlled clinical trials. Ampicillin and penicillin MIC 90 values were 64 mu g/ml and 80 U/ml respectively which essentially c onfirmed the resistance observed by the disk method. All the P, bivia isolates were beta-lactamase producers, hence the resistance of these isolates to penicillin and ampicillin. It is conceivable that in infec tions with monoculture of P. bivia, agents like tetracycline, or eryth romycin may still be a useful alternative for treatment.