Comparative Analysis between Monophasic and Biphasic Methods of Blood Culture

Abstract

A biphasic blood (BiPB) culture bottle (GIBCO Laboratories, North Andover, USA) with an architectural design that physically separates the agar slant from the broth was compared with a conventional vented monophasic bottle (MPB) (GIBCO Laboratories, North Andover, USA) for routine blood culture. Monophasic bottles contained thioglycollate broth (BioAmerica Inc., USA) while the biphasic contained Brain heart infusion agar-BHIA/Brain heart infusion broth-BHIB (BioAmerica Inc., USA). 120 blood cultures were examined on either of monophasic and biphasic blood culture experimental set up.  Out of 240 sets collected, 157(65.4%) were positive for bacterial growth while 83(35.6%) were negative. After subculture a total of 8 isolates (from 154 plates for BiPB and 117 plates for MPB) were recovered during the study. Of these isolates, 4 (from 126 plates for BiPB and 91 plates for MPB) were recovered, 2 isolates (from 28 plates) grew in the BiPB but not in MPB, 2 isolates (from 26 plates) grew only in the MPB but not in BiPB. The BiPB allowed more rapid recovery of Escherichia coli, Staphylococcus spp., Klebsiella spp., Salmonella spp. and Proteus spp. While Pseudomonas spp. and Enterococcus faecalis were more readily isolated using MPB. BiPB subcultures was easy enough to permit both early and daily subculture which provided isolated colonies sooner than could be done by using the MPB. Bacteria organisms were recovered at a non-significantly (P > 0.025) more frequent rate in the BiPB than in the MPB-A. Either bottle, however, should be used in conjunction with an anaerobic bottle for optimal recovery of anaerobic bacteria.

Key words: Biphasic, Monophasic, Thioglycollate, Brain Heart Infusion Agar/Broth, blood culture.