Aerobic and anaerobic infection associated with malignancy.

The goal of this work was to study the microbiology and clinical characteristics of patients with infections associated with malignancy treated over a period of 17 years. A total of 668 specimens were obtained from 605 patients. The malignancies include 224 hematological malignancies and 381 nonhematogenic malignancies. Anaerobic bacteria only were isolated in 201 (30%) specimens, aerobic bacteria in 226 (34%), mixed aerobic-anaerobic bacteria in 231 (35%) and Candida spp. in 10 (1%). A total of 683 anaerobic (1.0 isolates per specimens) and 592 aerobic or facultative (0.9 per specimen) organisms were recovered. The predominant anaerobic bacteria included Bacteroides fragilis group isolates (181), Peptostreptococcus spp. (166), Prevotella spp. (106), Clostridium spp. (70), and Fusobacterium spp. (43). The predominant aerobic bacteria included Escherichia coli (133), Staphylococcus aureus (100), Klebsiella pneumoniae (48), and Pseudomonas aeroginosa (45). The type of infections included abscesses (221), bacteremia (198), wounds (175), including 61 cellulitis, 24 post-surgical wounds and 23 decubitus ulcers), peritonitis (48), empyema (12), cholecystitis (6) and thrombophlebitis (5). S. aureus and Peptostreptococcus spp. were isolated from all sites. However, organisms of the oropharyngeal flora (Prevotella and Fusobacterium spp.) predominated in local infections and bacteremia that originated from this site (head and neck wounds and abscesses and pulmonary infections), and organisms of the gastrointestinal tract flora predominated in infections that originated from this site (peritonitis, abdominal abscesses and decubitus ulcers). This retrospective study demonstrates polymicrobial features of many infections associated with malignancies.