Microbiological studies of tracheostomy site wounds.

Specimens were obtained from 25 patients who developed tracheostomy site wound infections. Aerobic bacteria only were isolated in 4 (16%) instances, anaerobic bacteria only in 2 (8%), and mixed aerobic and anaerobic isolates were recovered in 19 (76%). A total of 145 isolates (72 aerobes and 73 anaerobes) were recovered, an average of 5.8 isolates per specimen (2.9 aerobes and 2.9 anaerobes). The most frequently recovered isolates were Peptostreptococcus sp., Bacteroides sp., alpha-hemolytic streptococci, Fusobacterium sp., and Pseudomonas aeruginosa. Twenty-nine isolates recovered from 19 (72%) patients produced beta-lactamase. These included all isolates of Staphylococcus aureus and Bacteroides fragilis group and 4 of 11 (36%) of Bacteroides melaninogenicus group. The polymicrobial aerobic-anaerobic flora of tracheostomy site wound infection, and the presence of beta-lactamase-producing bacteria in most of these infections, may have important implications for their management.