Isolation of Legionella pneumophila from blood with the BACTEC system: a prospective study yielding positive results

Abstract

In a prospective study of 16 patients with Legionnaires disease confirmed by cultural isolation of Legionella pneumophila from the respiratory tract, 38% (6 of 16) had positive blood cultures. Daily subcultures were made onto buffered charcoal-yeast extract plates from 6B aerobic and 7C anaerobic BACTEC blood culture bottles (Johnston Laboratories, Inc., Towson, Md.). Isolation of L. pneumophila was achieved from both aerobic and anaerobic bottles. L. pneumophila growth indices failed to exceed the BACTEC threshold limits; thus, the organism would have been overlooked despite its presence in the blood culture bottles. Bacteremic patients had statistically significant higher quantities of L. pneumophila isolated from sputum and visualized on direct fluorescent antibody stains. Thus, the potential exists for improved diagnosis of Legionella infection by a relatively noninvasive procedure (blood culture) with an instrument already in use in many hospital laboratories.

Update on detection of bacteremia and fungemia

“…Single isolations have been reported by using biphasic blood culture media and supplemented proteose peptone broth (45,101,105,106). The BACTEC 460 instrument recovered isolates variably: in one study, aerobic 6B bottles were positive by growth index and subculture whereas the anaerobic 7D bottles were negative (32); in another study, the 7D bottles were positive by blind subculture whereas the aerobic bottles were negative (145). In this prospective study of 16 patients with Legionnaires' disease, 6 had positive BACTEC blood cultures, all determined by blind subculture of the anaerobic bottles (145).…”

Update on detection of bacteremia and fungemia.

“…Single isolations have been reported by using biphasic blood culture media and supplemented proteose peptone broth (45,101,105,106). The BACTEC 460 instrument recovered isolates variably: in one study, aerobic 6B bottles were positive by growth index and subculture whereas the anaerobic 7D bottles were negative (32); in another study, the 7D bottles were positive by blind subculture whereas the aerobic bottles were negative (145). In this prospective study of 16 patients with Legionnaires' disease, 6 had positive BACTEC blood cultures, all determined by blind subculture of the anaerobic bottles (145).…”

“…The BACTEC 460 instrument recovered isolates variably: in one study, aerobic 6B bottles were positive by growth index and subculture whereas the anaerobic 7D bottles were negative (32); in another study, the 7D bottles were positive by blind subculture whereas the aerobic bottles were negative (145). In this prospective study of 16 patients with Legionnaires' disease, 6 had positive BACTEC blood cultures, all determined by blind subculture of the anaerobic bottles (145). Since that report, additional positive blood cultures have been reported from four patients with endocarditis by performing subcultures of BACTEC bottles; none of these were detected by growth index (182).…”

Prevention of Legionnaires' disease in transplant recipients: recommendations for a standardized approach

“…The fact that blood cultures for Legionella are not used in most clinical microbiology laboratories is due to the fastidious nature of the organism. However, Rihs et al (4) have isolated it from blood cultures; in patients with Legionnaires' disease in whom blood was subcultured to BCYE agar, 38% had positive cultures for L. pneumophila .…”