Variability in the susceptibility pattern of Bacteroides fragilis in four Detroit area hospitals.

Recent clinical isolates of Bacteroides fragilis selected at random from four Detroit area hospitals were collected over a 3-month period, and the minimum inhibitory concentrations were determined within several days. The levels of antimicrobial agents used in this survey breached the concentration attainable in the patient's serum. The antimicrobial susceptibility patterns of these isolates to five antimicrobial agents suggest that there is a 20% variation in the resistance to clindamycin and also up to 20% variation among the other four antibiotics in the four area hospitals. The changing susceptibility pattern of B. fragilis to antibiotic resistance suggests that minimum inhibitory concentrations should be determined for all isolates from serious clinical infections.