Bacteria isolated from surgical infections and its susceptibilities to antimicrobial agents - Special references to bacteria isolated between April 2010 and March 2011

Abstract This is an integrated summary of the results obtained from a 3-decade multicenter study on bacteria isolated from surgical infections in Japan between July 1982 and March 2012. During the 3-decade study, 11,196 strains were isolated from 4,787 patients consisting of 2,132 patients with primary infection and 2,655 patients with surgical site infection. Almost half of the primary infection was peritonitis, which accounted for 42.3%-55.5%. In contrast, most of the surgical site infection was wound infection, which accounted for 49.3%-66.1%. The most commonly isolated bacteria throughout three decades were Escherichia coli (1,164 strains), Enterococcus faecalis (842), Staphylococcus aureus (833), Pseudomonas aeruginosa (706), Bacteroides fragilis (705), Klebsiella pneumoniae (498), Enterobacter cloacae (391) and coagulase-negative staphylococci (CNS) (325). Overall, S. aureus and CNS had sensitivity for vancomycin, whose MIC90s were 0.78 to 3.13 μg/mL; E. faecalis had sensitivity for vancomycin and imipenem, whose MIC90s were 0.78-4 μg/mL; E coli, E. cloacae, K. pneumoniae, and B. fragilis had preferable sensitivity for imipenem. No antibacterial agents had a long-term good activity (e.g. MIC90 < 2 μg/mL) for P aeruginosa and Bilophila wadsworthia. Among antibacterial agents tested, ciprofloxacin had most bactericidal activity for P. aeruginosa; its MIC90 varied from 0.5 to 8 μg/mL. The MIC90s of all antibacterial agents tested except levofloxacin and minocycline were at least 128 μg/mL for B. wadsworthia. S. aureus accounted for approximately 20% to 60% of bacteria isolated after clean operation. Overall, at least 55% of the bacteria isolated after clean operation consisted of S. aureus, CNS, E. faecalis, E. coli, E. cloacae, K. pneunoniae, P. aeruginosa, B. fragilis, and B. wadsworthia throughout three decades. However, the percentage of other Gram-positive and negative bacteria increased with the worse of sterile condition in surgical operation. E. faecalis tended to be most commonly isolated from patients having host-compromised factors including carcinoma, diabetes, anticancer agents, steroids, immunosuppressants, and radiation, while E. coli was commonly isolated from patients having no such factors. Two-drug-resistant P. aeruginosa was first isolated in 1987, thereafter was frequently isolated, and reached 69 strains for 30 years. Three-drug-resistant P. aeruginosa was isolated in 1990, 1996, and 1998 to reach 5 strains, but not isolated in remaining 13 years. Methicillin-resistant S. aureus was highly frequently isolated between 1988 and 1991. Subsequently, the isolation frequency declined, sometimes increased in 1998, 2005, and 2006, and thereafter maintained lower levels by 2011.