Early detection and preliminary susceptibility testing of positive pediatric blood cultures with the Steers replicator

Abstract

Early replicator subculturing of blood specimens after 4 to 16 h of incubation detected 135 of 217 (59%) of all positive cultures, including 56 of 64 (87%) Haemophilus influenzae type b, 7 of 22 (32%) Staphylococcus aureus, 19 of 20 (95%) pathogenic streptococci, and 20 of 24 (83%) Enterobacteriaceae. The mean time to detection of the common pediatric pathogens (36 h) was significantly less than that of contaminants (85 h) (P less than 0.001). Blind subculturing to differential media aided in the rapid identification of isolates and the detection of mixed cultures. In addition, a method of obtaining rapid susceptibilities of blood and body fluid isolates to selected antibiotics by blind subculturing to antibiotic-containing media was evaluated. Immediate susceptibility information was obtained for 214 of the 245 (87.3%) isolate-antibiotic combinations. There was complete correlation with a standard Kirby-Bauer reading for 94.9% of these observations. Replicator blood subculturing before 24 h of incubation results in early detection of the majority of pediatric pathogens. The inoculation of additional differential and antibiotic-containing media with each blind subculture aids in rapid identification of isolates and may give limited, but clinically important, immediate susceptibility information.