Bacteriology of necrotizing infections of soft tissues

Abstract

Background: Necrotizing infections of soft tissues (NIST) are being attributed to a large variety of organisms, besides the originally described beta-haemolytic Streptococcus. A detailed bacteriological study of these infections was thought worthwhile.

Methods: A prospective study of 55 patients with NIST was carried out. Analysis of surface swabs and debrided tissue for aerobic and anaerobic bacteria and fungal infection was performed. A detailed bacteriological profile was obtained in 50 patients.

Results: A total of 257 isolates (167 aerobic, 90 anaerobic) was obtained. One to nine strains of bacteria were isolated from each patient. Aerobic bacteria alone were isolated in 26 patients while the remaining patients grew both aerobic and anaerobic bacteria. Forty-two patients had at least one Gram-positive bacterium while 40 had at least one Gram-negative bacterium. Staphylococcus aureus was the organism isolated most frequently (52%), followed by Bacteroides fragilis (40%) and anaerobic cocci (38%). Group A beta-haemolytic streptococci were isolated in 16%. Blood cultures were positive in only eight patients. Fungal cultures were positive in six patients. Aspergillus fumigatus was the commonest pathogen.

Conclusions: Necrotizing infections of soft tissues are polymicrobial and no single bacterium is associated with a specific clinical entity. Importance should be placed on early recognition and treatment of the disease rather than on isolation of bacteria.