Association of Listeria monocytogenes LIPI-1 and LIPI-3 marker llsX with invasiveness.

Listeria monocytogenes is an opportunistic pathogen that is widely distributed in the environment. The evolution of its genome has exhibited differences in virulence among strains of the same species. Listeria monocytogenes LIPI-3 (Listeria Pathogenicity Island 3) and LIPI-1 (Listeria Pathogenicity Island 1) are considered responsible for the increased virulence in some strains. The aim of this study was to detect LIPI-1 genes and the llsX gene belonging to LIPI-3 in invasive strains of L. monocytogenes and to establish whether there is a relationship among the invasiveness, presence of the llsX and LIPI-1 genes, and the source of the strains. The results showed that 70% of the strains were invasive, and all these strains except one possessed LIPI-1, which suggests that although there is a correlation between LIPI-1 and invasiveness, the independent mechanisms of LIPI-1 may contribute to invasiveness. In contrast, 35% of the total strains were positive for llsX and were invasive; thus, the results revealed that there is a strong association between llsX and the invasiveness of L. monocytogenes in HEp-2 cells (HeLa contaminant/epithelial in origin). In addition, there is no other association with any other variable in this study. Moreover, the authors found that LIPI-1 and llsX are more frequently found in fresh than in frozen vegetables. Together, the findings provide an approximation for the better understanding of Listeriolysin S (LLS) and its role in the pathogenesis of L. monocytogenes, and a possible relation between virulence factors and food-storage temperature.

Cultivation-independent approach for the direct detection of bacteria in human clinical specimens as a tool for analysing culture-negative samples: a prospective study.

Administration of empirical antibiotic therapy prior to microbiological diagnosis is thought to be associated the failure of subsequent bacterial growth in culture. The aim of this study was to detect bacterial pathogens via direct amplification and sequencing of the 16S rDNA gene in samples showing negative culture results as alternative diagnostic tools to troubleshoot difficult samples. Twenty-three (7.66 %) positive samples were detected, most of which were monomicrobial infections; 15 of the cases were identified as HAIs, 6 had catheter colonisation, and 2 had sample colonisation. The pathogens identified included Escherichia, Salmonella, Pseudomonas spp., Enterococcus spp. and coagulase-negative staphylococci (CoNS). The most frequent infections were bacteraemia and urinary tract infection, but meningitis, warm infection and soft tissue infection were also documented. These findings emphasise the efficacy and usefulness of molecular diagnosis, thus 16S rDNA gene analysis is strongly indicated by HAIs diagnostics.

Lactobacillus species isolated from vaginal secretions of healthy and bacterial vaginosis-intermediate Mexican women: a prospective study.

BACKGROUND: Lactobacillus jensenii, L. iners, L. crispatus and L. gasseri are the most frequently occurring lactobacilli in the vagina. However, the native species vary widely according to the studied population. The present study was performed to genetically determine the identity of Lactobacillus strains present in the vaginal discharge of healthy and bacterial vaginosis (BV) intermediate Mexican women. METHODS: In a prospective study, 31 strains preliminarily identified as Lactobacillus species were isolated from 21 samples collected from 105 non-pregnant Mexican women. The samples were classified into groups according to the Nugent score criteria proposed for detection of BV: normal (N), intermediate (I) and bacterial vaginosis (BV). We examined the isolates using culture-based methods as well as molecular analysis of the V1-V3 regions of the 16S rRNA gene. Enterobacterial repetitive intergenic consensus (ERIC) sequence analysis was performed to reject clones. RESULTS: Clinical isolates (25/31) were classified into four groups based on sequencing and analysis of the 16S rRNA gene: L. acidophilus (14/25), L. reuteri (6/25), L. casei (4/25) and L. buchneri (1/25). The remaining six isolates were presumptively identified as Enterococcus species. Within the L. acidophilus group, L. gasseri was the most frequently isolated species, followed by L. jensenii and L. crispatus. L. fermentum, L. rhamnosus and L. brevis were also isolated, and were placed in the L. reuteri, L. casei and L. buchneri groups, respectively. ERIC profile analysis showed intraspecific variability amongst the L. gasseri and L. fermentum species. CONCLUSIONS: These findings agree with previous studies showing that L. crispatus, L. gasseri and L. jensenii are consistently present in the healthy vaginal ecosystem. Additional species or phylotypes were detected in the vaginal microbiota of the non-pregnant Mexican (Hispanic-mestizo) population, and thus, these results further our understanding of vaginal lactobacilli colonisation and richness in this particular population.