Detection of Brucella melitensis by BACTEC 9050 system

OBJECTIVES. To evaluate BACTEC 9050 system capacity for detection of bacter emia due to Brucella spp. MATERIAL AND METHODS. 16 febrile patients were studied during an epidemic i nfection for Brucella spp. Suspicious of brucellosis was serologically conf irmed with Rose Bengal test and agglutination tube test. Only one blood culture was processed per patient. Ten millilitres of blood were inoculated in a Bactec Plus aerobic/F bottle and incubated in BACTEC 9 050 automatic system. The bottles were kept in incubation during 21 days, a nd they were subcultured when the machine detected its growth; if not, a bl ind subculture was performed after 21 days. RESULTS. 13 of 16 patients showed bacteriemia (81.2%): 11 patients were det ected by BACTEC 9050 system and 2 patients by blind subculture after 21 day s. A positive result appeared in 149.8 hours (6.2 days) as a mean. Earlier detections were seen in 83 hours (3.4 days) and the latest ones at 245 hour s (10.2 days). The aetiology agent of the epidemic infection was Brucella m ellitensis biotype 1. We found significative differences comparing the BACT EC 9050 with BACTEC 9120/9240 systems (p<0.03). CONCLUSIONS. Incubation protocols of 5 days are not useful for BACTEC 9050 system in the case brucellosis suspicious. Protocols of 7 would detect only 69.2% of the cases.