RESUMEN
Carbohydrate fermentation test is a well-established technique for speciation of bacteria and fungi. However, long incubation period, cost and procedural complexity may limit its use. Here, we describe a simple modification of conventional carbohydrate fermentation technique using microtitre plate. Thirty-one yeast isolates were identified based on their fermentation property by microtitre plate method and results were compared with conventional method. The modified method had 85.7% sensitivity and 100% specificity. The average time taken to produce positive reaction was 24 hours. When compared with conventional method, modified method reduced turn-around time and cost of processing without significant increase in discordant results.
RESUMEN
Identification of Lactobacillus sp. strains by phenotypic methods may lead to doubtful results possibly interfering in the reliability of the epidemiological and probiotics studies. Therefore this study aimed to determine the best methodology for the identification of the large diversity of lactobacilli species found in the vagina by comparing two techniques, one based on their biochemical profile and other employing molecular biology. A carbohydrate fermentation test (API 50 CH) was compared with multiplex polymerase chain reaction (PCR) for the identification of species of vaginal lactobacilli from 135 healthy women. The kappa index was used to evaluate agreement between the methods. Using the molecular technique, L. crispatus (32.6 percent), L. jensenii (25 percent) and L. gasseri (20.6 percent) were the most frequent species. However, using the biochemical technique, the most frequent species were: L. acidophilus (34.8 percent), L. crispatus (27.2 percent) and L. fermentum (13 percent). Although L. acidophilus was the most frequent specie found by biochemical tests, no strain of this microorganism was detected by PCR. Agreement between the methods was low for identification of all the most common species. Although rates of L. crispatus detected were similar using both methods (32.6 percent and 27.2 percent), agreement between them was relatively low (kappa = 0.52). Conclusions: Our results confirmed the limitation of the biochemical method and the applicability of a previously published molecular method (Multiplex PCR) for the identification of lactobacilli in the vaginal tract, focusing on further necessity of its improvement for also targeting L. vaginalis and L. iners.