Rapid antimicrobial resistance screening method for Bacteroides intermedius

Abstract

The purpose of the study was to validate a rapid resistance screening (RRS) method for antimicrobial susceptibility testing of a selected periodontopathic microorganism using the standard broth dilution method as a control. Twenty-five subgingival plaque samples from gingivitis or periodontitis sites were plated on Trypticase soy agar supplemented with 5% rabbit blood with antibiotic discs (RRS method) and without (control). The antibiotics tested were: Augmentin, clindamycin, erythromycin, metronidazole, penicillin G and tetracycline hydrochloride. Bacteroides intermedius isolated from both groups of plates were placed onto antibiotic supplemented Trypticase soy broth. The antibiotic susceptibilities of B. intermedius isolated from the plates with antibiotic discs and the standard broth method were compared. The results showed high sensitivity and predictability for the RRS method compared with the control. The percentage of agreement was: 100% for Augmentin 30 micrograms, clindamycin 2 micrograms and tetracycline 30 micrograms; 96% for erythromycin 15 micrograms, metronidazole 80 micrograms and penicillin 10 IU; 92% for penicillin 2 IU; 88% for erythromycin 2 micrograms and 84% for tetracycline 5 micrograms. The results of this study document the feasibility of the RRS method for testing antimicrobial resistance of whole samples if its efficacy can be demonstrated for other bacteria. This method may be a quick and useful test for the periodontal practitioner in determining the antibiotic susceptibility of periodontal plaque pathogens.