Aerobic and anaerobic microbiology of surgical-site infection following spinal fusion

The aerobic and anaerobic microbiology of surgical-site infections (SSI) fo llowing spinal fusion was retrospectively studied. This was done by reviewi ng the clinical and microbiological records at the Naval Hospital in Bethes da, Md., from 1980 to 1992. Aspirates of pus from 25 infection sites showed bacterial growth. Aerobic bacteria only were recovered from 9 (36%) specim ens, anaerobic bacteria only were recovered from 4 (16%), and mixed aerobic and anaerobic bacteria were recovered from 12 (48%). Sixty isolates were r ecovered: 38 aerobes (1.5 isolates per specimen) and 22 anaerobes (0.9 isol ate per specimen). The predominant aerobes were Escherichia coli (n = 8) an d Proteus sp. (n = 7). The predominant anaerobes were Bacteroides fragilis group (n = 9) and Peptostreptococcus sp. (n = 6) isolates. An increase in r ecovery of E. coli and B. fragilis was noted in patients with bowel or blad der incontinence. This study highlights the polymicrobial nature of SSI and the importance of anaerobic bacteria in SSI following spinal fusion.