The API 50 CH identification system was evaluated for the identification of 97 strains of commensal lactobacilli. This system agreed with the species-level identifications for none of the 7 reference strains and only 4 of 90 vaginal isolates identified using whole-chromosomal DNA probes.Lactobacillus species maintain a healthy vaginal ecosystem and are associated with decreased acquisition of bacterial vaginosis (10), human immunodeficiency virus (13), and gonorrhea (13). There are over 50 species recognized in the genus Lactobacillus (7), and several of these species have been proposed as probiotics (4,14). In some instances, Lactobacillus strains found in food or probiotics have caused peritonitis (12) or endocarditis (9). Correct species identification of lactobacilli is essential to guide appropriate antibiotic therapy (12). Correct identification of lactobacilli is also relevant to studies of epidemiology (2, 3) and innate immunity (1).Phenotypic tests have been used as the primary methods for classifying Lactobacillus species. Klein et al. have reported that none of the commercial kits can be recommended and that some species of lactobacilli are incorrectly identified as Lactobacillus acidophilus (12). Using phenotypic techniques, L. acidophilus has been reported to be the most frequently isolated Lactobacillus species recovered from the vagina (1, 6, 16). However, using genotypic methods, studies done in the United States (2), Japan (18), and Europe (8,19) L. iners, L. gasseri, and L. vaginalis are the most common species of lactobacilli found in the vagina. This suggests that the phenotypic methods most commonly used for the identification of Lactobacillus species have poor concordance with genomics-based tests.Some investigators have relied on API 50 CH carbohydrate fermentation strips (bioMérieux, Inc., Marcy l'Etoile, France) to identify vaginal strains of Lactobacillus to the species level (1,15). In this study, we evaluate the use of API 50 CH carbohydrate fermentation strips for the identification of five common commensal Lactobacillus species isolates.Lactobacillus isolates (n ϭ 97) stored at Ϫ80°C in litmus milk (Becton Dickinson Microbiology Systems, Cockeysville, MD) were tested for species identification using the API 50 CH carbohydrate fermentation strips. Seven of these were reference strains: L. crispatus ATCC 33197 and ATCC 202225 (also known as CTV-05), L. jensenii ATCC 25258, L. gasseri ATCC 9857 and ATCC 4963, L. iners CCUG 28746, and L. vaginalis ATCC 49540. The remaining 90 isolates were recovered from vaginal specimens and identified to the species level using whole-chromosomal DNA probes (3). These included isolates of L. crispatus (n ϭ 16), L. jensenii (n ϭ 18), L. gasseri (n ϭ 18), L. iners (n ϭ 19), and L. vaginalis (n ϭ 19). These isolates were obtained from women in Seattle (n ϭ 26), Pittsburgh (n ϭ 28), and Uganda (n ϭ 36) from 1995 to 2002.Each isolate was inoculated onto a Columbia agar with 5% sheep blood (BA) (PML Microbiologicals, Portland, OR) plate, incubated at 37°C ...
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