In vitro detection of bacterial contamination in platelet concentrates by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: a preliminary study

Molecular Routes to Specific Identification of the Lactobacillus Casei Group at the Species, Subspecies and Strain Level

The genus Lactobacillus includes, among others, Lactobacillus casei, Lactobacillus paracasei and Lactobacillus rhamnosus, species that are collectively referred to as the Lactobacillus casei group. Many studies have shown that strains belonging to this group may decrease lactose intolerance, the effects of inflammatory bowel disease, diarrhea, constipation, food allergies and even colon cancer. Moreover, evidences exists of positive effects of these bacteria on mucosal immunity and blood cholesterol level. Because of their beneficial influence on human health, many of them are used as food additives and probiotic pharmaceuticals. It should be stressed that health-promoting properties are not attributed at the species level, but to specific strains. Therefore, procedures are necessary to allow specific identification at each phylogenetic level-genus, species and strain. In this paper we present a practical overview of molecular methods for the identification and differentiation of L. casei bacteria. The research included 30 bacterial strains belonging to three species: L.casei, L. paracasei and L. rhamnosus. Among the tested procedures were genus- and species-specific PCR, multiplex-PCR, Real-Time HRM analysis, RFLP-PCR, rep-PCR, RAPD-PCR, AFLP-PCR, and proteomic methods such as MALDI-TOF MS typing and SDS-PAGE fingerprinting. The obtained results showed that multiplex-PCR and MALDI-TOF MS turned out to be the most useful methods to identify the tested bacteria at the species level. At the strain level, the AFLP-PCR method showed the highest discriminatory power. We hope that the presented results will allow for the easy selection of an appropriate procedure, depending on the experiment conducted and the equipment capabilities of any given laboratory.

MALDI-TOF MS and point of care are disruptive diagnostic tools in Africa

We review reviewing our experience of point-of-care and mass spectrometry in Senegal as two disruptive technologies promoting the rapid diagnosis of infection, permitting better medical management of patients.

Comparing two blood culture systems for the detection of bacterial contamination in platelet concentrates

BACKGROUND

The transfusion of platelet concentrates (PCs) contaminated with bacteria may cause serious, and even fatal, septic reactions in patients. The aim of this study was to compare the VersaTREK with the BACTEC FX automated culture systems for screening bacterial contamination, directly after the delay of 24 hours of preparation to obtain the final pooled buffy coat PCs, to prevent transfusion-transmitted bacterial infections.

STUDY DESIGN AND METHODS

Seven bacterial strains were each inoculated into five replicate pooled buffy coat PCs at approximately 100 colony-forming units/unit, and 5- or 10-mL samples were inoculated into duplicate aerobic culture bottles. The time and detection rates were compared between BACTEC FX, as a reference method, and VersaTREK.

RESULTS

Time to detection was significantly shorter using VersaTREK for most species detected by both systems for the volumes tested. Of 70 VersaTREK cultures, 69 (98.57% detection rate) were positive after 24 hours of incubation with the 5-mL sample. In contrast, the BACTEC FX system detected all positive samples in PCs for the volume of 10 mL, although seven samples were false negatives for the 5-mL volume.

CONCLUSION

The VersaTREK system compared favorably to the BACTEC FX system for 5-mL volumes (p < 0.05) and could be considered a potential method for detecting bacterial contamination in PC samples directly after 24 hours of preparation of the final pooled buffy coat PCs.