Clinical features and aerobic and anaerobic microbiological characteristics of cellulitis.

Abstract

To investigate the aerobic and anaerobic microbiological characteristics of cellulitis and correlate them with the infection site. Of 342 specimens, 64 obtained using needle aspiration and 278 using swabs were studied over 10 years. Bacterial growth was noted in 15 (23%) of the 64 needle aspirates and 259 (93%) of the 278 swab aspirates. The microbial results of the 15 specimens obtained through needle aspiration are separately presented. Aerobic or facultative bacteria only were present in 138 (53%) of swab samples, anaerobic bacteria only in 69 (27%), and mixed aerobic-anaerobic flora in 52 (20%). In total, there were 582 isolates, 247 aerobic or facultative and 335 anaerobic bacteria, with an average of 2.2 isolates per specimen. The predominance of certain isolates in different anatomical sites correlated with their distribution in the normal flora adjacent to the infected site. The highest recovery rates of anaerobes was from the neck, trunk, groin, external genitalia, and leg areas. Aerobes outnumbered anaerobes in the arm and hand. The predominant aerobes were Staphylococcus aureus, group A streptococci, and Escherichia coli. The predominant anaerobes were Peptostreptococcus sp, Bacteroides fragilis group, Prevotella and Porphyromonas sp, and Clostridium sp. Certain clinical findings correlated with the following organisms: swelling and tenderness with Clostridium sp, Prevotella sp, S aureus, and group A streptococci; regional adenopathy with B fragilis group; bulbous lesions with Enterobacteriaceae; gangrene and necrosis with Peptostreptococcus sp, B fragilis group, Clostridium sp, and Enterobacteriaceae; foul odor with Bacteroides sp; and gas in tissues with Peptostreptococcus sp, B fragilis group and Clostridium sp. Certain predisposing conditions correlated with the following organisms: trauma with Clostridium sp; diabetes with Bacteroides sp, Enterobacteriaceae, and S aureus; and burn with Pseudomonas aeruginosa. These data highlight the polymicrobial nature of cellulitis.