Comparison of BACTEC MYCO/F LYTIC and WAMPOLE ISOLATOR 10 (lysis-centrifugation) systems for detection of bacteremia, mycobacteremia, and fungemia ina developing country

In less-developed countries, studies of bloodstream infections (BSI) have b een hindered because of the difficulty and costs of culturing blood for bac teria, mycobacteria, and fungi. During two study periods (study period I [1 997] and study period II [1998]), we cultured blood from patients in Malawi by using the BACTEC MYCO/F LYTIC (MFL), ISOLATOR 10 (Isolator), Septi-Chek AFB (SC-AFB), and Septi-Chek bacterial (SC-B) systems. During study period I, blood was inoculated at 5 mi into an MFL bottle, 10 mi into an Isolator tube for lysis and centrifugation, and 10 mi into an SC-B bottle. Next, 0. 5-ml aliquots of Isolator concentrate were inoculated into an SC-AFB bottle and onto Middlebrook 7H11 agar slants, chocolate agar slants, and Inhibito ry Mold Agar (IMA) slants. During study period II, the SC-B and chocolate a gar cultures were discontinued. MFL growth was detected by fluorescence cau sed by shining UV light (lambda = 365 nm) onto the indicator on the bottom of the bottle. During study period I, 251 blood cultures yielded 44 bacteri al isolates. For bacteremia, the MFL was similar to the Isolator concentrat e on chocolate agar (33 of 44 versus 27 of 44; P, not significant [NS]), bu t more sensitive than the SC-B bottle (34 of 44 versus 24 of 44; P = 0.05), For both study periods combined, 486 blood cultures yielded 37 mycobacteri al and 13 fungal isolates. For mycobacteremia, the sensitivities of the MFL and Isolator concentrate in the SC-AFB bottle were similar (30 of 37 versu s 29 of 37; P, NS); the MFL bottle was more sensitive than the concentrate on Middlebrook agar (30 of 37 versus 15 of 37; P = 0.002), For fungemia, th e MFL bottle was as sensitive as the SC-B bottle or Isolator concentrate on chocolate agar or IMA slants. We conclude that the MFL bottle, inoculated with just 5 mi of blood and examined under UV light, provides a sensitive a nd uncomplicated method for comprehensive detection of BSI in less-develope d countries.