20 patients were treated with negative pressure wound therapy (NPWT) and 20 patients by cotton gauze dressings. Bacterial cultures were done on 0, 4th and 8th day. The bacterial inoculates were compared between these two groups. NPWT was found to decrease pseudomonas species more than the S. aureus or E. coli species. The number of isolates of Pseudomonas decreased from day 0 (n=7) to day 8 (n=2) by NPWT. In the gauze dressing group, the number of isolates marginally increased from day 0 (n=5) to day4 (n=6) and then decreased to the baseline at day 8 (n=5). The number of isolates of E coli under gauze dressings also decreased from day 0 (n=12) to day 8 (n=6). Under NPWT however, lead an only marginal decrease in the number of isolates of E coli from day 0 (n=7) to Day 8 (n=6). Thus, NPWT is more effective to control obligate aerobic bacteria.