Modification of the minitek system for identification of lactobacilli

Seventy-eight strains of 23 Lactobacillus species, including 41 reference strains and 37 fresh isolates from faeces of men and pigs or caecal contents of mice, were used in comparing the conventional tube test with the Minitek system (BBL) to evaluate the feasibility of the latter to identify lactobacilli. In addition, the following parameters were tested: (i) the effect of variation in inoculum broth and cultural methods, (ii) the reproducibility of reactions on each substrate. The Minitek system includes a new lactobacilli inoculum broth (LIB) and three substrates: ribose, melezitose, and amygdalin. The overall correlation was 84% by the anaerobic steel-wool jar method and 72.5% by overlaying sterile oil with the Minitek inoculum broth (MIB) for the identification of anaerobes; whereas with LIB, the overall agreement was 95.4% by the anaerobic jar method and 84.4% by the oil procedure. The agreement of the identification between the Minitek systems and conventional tests was best (85.9%) with LIB by the anaerobic jar method and poorest with the MIB overlaid with oil. In the reproducibility of reactions, 247 (17.2%) of a total of 1,440 sets of disks gave variable reactions with MIB when incubated under the anaerobic jar method as compared to only 29 (2.0%) with LIB. The Minitek system for the identification of lactobacilli is more accurate and reliable when inoculated with LIB and incubated under the anaerobic jar method.