Surgical infections: a microbiological study

Surgical infections are mostly polymicrobial, involving both aerobes and anaerobes. One hundred seventeen cases comprised of abscesses (n=51), secondary peritonitis (n=25), necrotizing fascitis (n=22) and wounds with devitalized tissues (n=19) were studied. The number of microorganisms isolated per lesion was highest in secondary peritonitis (2.32). The aerobe/ anaerobe ratio was 0.81 in secondary peritonitis and 1.8 in necrotizing fascitis. Most secondary peritonitis (80%), necrotizing fascitis (75%) and wounds with devitalized tissues (66.7%) were polymicrobial. Common microorganisms isolated in our study were E. coli, Staphylococcus aureus, Klebsiella spp., Pseudomonas aeruginosa, Bacteroides fragilis and Peptostreptococcus spp. The most effective antibiotics for S. aureus were clindamycin (79.1%) and cefuroxime (70.8%). For Gram-negatives (Klebsiella spp., E. coli and Proteus spp.), the most effective antibiotics were cefotaxime, ceftizoxime, amikacin and ciprofloxacin. Pseudomonas aeruginosa was maximally sensitive to amikacin (35.2%) and ciprofloxacin (35.2%). The greatest degree of multidrug resistance to all the drugs was found in P. aeruginosa (52.9%), followed by Klebsiella spp. (33.3%), Proteus spp. (33.3%), E. coli (22.2%), and S. aureus (12.5%). All the anaerobes that we isolated were 100% sensitive to metronidazole and chloramphenicol, followed by clindamycin (95% to 100%). Apart from antibiotic therapy, non-antimicrobial methods, such as hyperbaric oxygen therapy and debridement also play an important role in the treatment of surgical infections.