Phenotypes of isolates of Pseudomonas aeruginosa in a diabetes care center

BACKGROUND: Pseudomonas aeruginosa is an invasive organism that frequently causes severe tissue damage in diabetic foot ulcers. A major problem in P. aeruginosa infection may be that this pathogen exhibits a high degree of resistance to a broad spectrum of antibiotics. Some researchers feel that P. aeruginosa is a homogeneous species, whereas others have suggested that they are panmictic. Here we characterized P. aeruginosa populations isolated from diabetic foot ulcer and from hospital environment specimens, both from a tertiary diabetes care center in Chennai, India. METHODS: Phenotypic methods like antibiotic susceptibility determinations using Kirby-Bauer's disc diffusion test and minimum inhibitory concentration (MIC) as well as outer membrane protein SDS-PAGE analysis of P. aeruginosa were performed. RESULTS: Twenty three isolates (29.8%) of P. aeruginosa from 77 diabetic foot ulcers and two environmental isolates (13.3%) from 15 different hospital fomites were detected. Both environmental isolates were sensitive to antibiotics than those isolated from clinical specimens by Kirby-Bauer's disk-diffusion method, which correlated the resistance levels by MIC determination. Outer membrane proteins (OMP) corresponding to 21, 23, 43, 46, 50, and 70 kDa were detected. CONCLUSIONS: The study is captivative as the resistance in P. aeruginosa from diabetic foot ulcers seems very common and because all the isolates were resistant to at least one or more antibiotics tested. Disk-diffusion and MIC results shows that piperacillin, amikacin and imipenem retain high levels of antipseudomonal activities and amikacin two times more active than the aforementioned antibiotics to enable itself as a potent antipseudomonal agent in diabetic foot infections. The OMP profile has revealed that clinical isolates were different from hospital environment isolates, which suggests that the origin of infections by P. aeruginosa is mainly due to growth of bacterial strains acquired by patients prior to hospital admission.