Isolation and identification of bacteria associated with diabetic foot infections

Abstract

Bacteriological investigations were carried out for fourty patients presented with diabetic foot wounds, during Jan. 2004 – Jan. 2005 at the Police University Teaching Hospital, Khartoum Teaching Hospital and at the Health & Medical services centre of the University of Khartoum. Swab samples were collected from thirty patients with diabetic foot wounds before and after surgical debridements. In addition 10 tissue samples were excised from infected amputated parts following surgery. A total of 71 clinical bacterial isolates were identified to the species level on the basis of microscopical examination, Gram-reaction, cultural characteristics and biochemical tests. These isolates represented nine genera including Gram-positive bacteria (42.25%) and Gram-negative bacteria (57.75). Poly-microbial infection was obtained in 60% of diabetic foot wounds (24 patients) and only 40% of diabetic wounds had mono-microbial aetiology (16 patients). Mixed infection contained 2 to 6 isolates. However, the spectrum of microorganism isolated from superficial and deep tissue swab cultures were identical. In this investigation surface wound swabbing and deep tissue swabbing were found reliable procedure for the collection of sample for bacteriological studies from diabetic foot wound. Staphylococcus species were isolated at a rate of 28.17% and it represented the most common cause of diabetic food infection in this study. S. delephini a coagulase positive Staphylococci were isolated for the first time from diabetic wound (8.45%). Streptococci species were isolated at a frequency of (5.63%) and Coryne bacterium species at a rate of 8.45%. iii The Gram-negative isolated included E. coli (12.67%), Serratia marcescens (7.04%), Serratia plymuthica (1.41%), Klebsiella pneumoniae (2.82%), Proteus vulgaris biogroup 3(1.40%) and Proteus mirabilis (9.86%). Serratia marcescens and Serratia plymuthca were reported for the first time to be involved in diabetic foot infection. Serratia marcescens was found to tolerate 4% glucose. Other Gram-negative bacteria include Vibrio species (8.45%), Aeromonas species (4.23%) and Shewanella putrefaciens (2.8%). All our 71 isolates that include nine genera were resistant to penicillin, 83% were resistant to chloramphenicol and only 42.3% of the isolates were found sensitive to gentamycin. About 50% of E. coli and Staphylococci isolates were found resistant to gentamycin. All Streptococci isolate were resistant to various antibiotics used.