Quantitative aerobic and anaerobic bacteriology of infected diabetic feet

Quantitative aerobic and anaerobic cultures of deep tissue were performed on amputated infected lower limbs of 13 diabetic patients immediately after surgery. Dissection was made through intact skin distant from any preexisting ulcer. The results were compared with those obtained from: (i) ulcer swabs (pre- and postamputation), (iii) curettage of the ulcer base, and (iii) needle aspiration after normal saline injection. Anaerobic transport media were used for anaerobic cultures before prompt transfer to the anaerobic chamber. A mean of 4.7 bacterial species per specimen was seen (2.3 aerobes, 2.4 anaerobes). Mean log10 growth per gram of tissue was as follows: (i) aerobes plus anaerobes = 6.99, (ii) aerobes = 6.42, and (iii) anaerobes = 7.65. There was poor concordance between the deep tissue culture results and the results from other modalities of culture collection, though the results from other modalities of culture collection, though the results from curettage and saline aspiration were slightly better than those obtained from ulcer swabs. The most frequently isolated organisms were enterococci, anaerobic streptococci, and species of Proteus, Clostridium, and Bacteroides. When anti-microbial therapy is indicated for this patient population, the possibility of the concomitant presence of aerobes as well as anaerobes should be considered.