Diabetic foot ulcers—where do we stand microbiologically?

Foot ulcers in diabetics are prone to polymicrobial infection by bacteria as well as fungi. Infection retards healing of ulcers leading to gangrene and ultimately, amputation of the extremity. The choice of empiric antibiotic therapy is extrapolated from results of studies from other regions, western literature or infection at other sites which may be inappropriate. Thus, a study was conducted to determine microbial aetiology of diabetic foot ulcers and their susceptibility patterns. Pus aspirates or wound swabs were collected from foot ulcers of 70 diabetics at the time of admission and processed for isolation of bacteria (aerobic and anaerobic) and fungi according to standard protocols. Organisms were identified upto species level. Antimicrobial susceptibility testing was performed by Kirby Bauer disk diffusion method as per CLSI standards. One hundred forty-seven organisms were isolated from 70 specimens. Seventy-three percent showed polymicrobial growth. The proportion of Gram negative bacilli, Gram positive cocci, anaerobes and fungi were 57 %, 27 %, 4 % and 12 % respectively. Enterobacteriaceae were the predominant Gram negative bacilli and S.aureus, the predominant Gram positive cocci. Clostridium and Candida species were the commonest among anaerobes and fungi respectively. Twenty-three percent of S.aureus were MRSA and 23 % of Enterobacteriaceae were ESBL producers. Ps.aeruginosa strains demonstrated good susceptibility to antipseudomonal antimicrobials and 16.5 % strains were meropenem resistant. Due to the associated risk of increased morbidity and mortality in infected diabetic ulcers, the wide spectrum of organisms associated with it and their differing susceptibility profile, treatment should be individualised based on microbial culture and antimicrobial susceptibility results.