Evaluation of acridine orange stain for detection of microorganisms in blood cultures

Abstract

A pH 4.0 buffered solution of the fluorochrome acridine orange was used to stain samples of 2,704 blood cultures that failed to yield visible evidence of growth after 1 day of incubation. Results obtained by the staining method were compared with those obtained by aerobic and anaerobic subcultures simultaneously performed upon the same cultures. Of the 109 culture-positive blood specimens initially detected by the acridine orange and the subculture methods, 85 (78%) were detected by both acridine orange and subculture techniques, 14 acridine orange alone. The differences between the subculture and acridine orange methods were not found to be statistically significant (P > 0.1). The acridine orange method represents a rapid and inexpensive alternative to conventional subculture techniques for the detection of bacteria in blood cultures that fail to yield visible evidence of growth after 1 day of incubation.