Phosphatidylinositol-specific phospholipase C activity as a marker to distinguish between pathogenic and nonpathogenic Listeria species

Abstract

In this study, 468 Listeria strains were checked for the presence of phosphatidylinositol-specific phospholipase C (PI-PLC) activity by using a simple assay that consisted of overlaying colonies formed on agar plates with L-ft-phosphatidylinositol as substrate. In this assay, PI-PLC-active colonies show turbid halos around the colonies as a result of the release of insoluble diacylglycerol from the substrate. This activity was detected only in the pathogenic species Listeria monocytogenes and was not present in any of the 167 strains of Listeria seeligeri, Listeria welshimeri, Listeria innocua, Listeria murrayi, and Listeria grayi tested. Hence, screening for PI-PLC activity permits discrimination between pathogenic and nonpathogenic Listeria species. In particular, the hemolytic but nonpathogenic species L. seeligeri can now be separated from the hemolytic and pathogenic species L. monocytogenes and L. ivanovii. The use of this assay will improve the specific detection and/or isolation of pathogenic Listeria species from clinical samples or food enrichment cultures.

Phosphatidylinositol-specific phospholipase C activity in Lactobacillus rhamnosus with capacity to translocate

“…Thereafter, PI-PLC activity was detected by overlaying the plates with 20 mg l 31 L-K-phosphatidylinositol substrate in 1.4% (w/v) agarose and incubated at 37³C up to 5 days. PI-PLC active strains showed a turbid halo around the colony by the release of the insoluble diacylglycerol from the substrate [16].…”

Prevalence of Listeria spp Including Listeria monocytogenes from Apparently Healthy Sheep of Gujarat State, India

“…of Listeria, i.e. L. monocytogenes (Notermans et al, 1991a) andL. ivanovii (Leimeister-Wachter et al, 1991) and has been found to be a reliable marker for discrimination between pathogenic and non-pathogenic Listeria species (Notermans et al, 1991a).…”

“…The details of the primer sequences are shown in Table 1. The PCR was standardized for the detection of virulence-associated genes namely, plcA, prfA, hlyA, actA and iap of L. monocytogenes following the methodologies described (Notermans et al, 1991a;Paziak-Domanska et al, 1999;Furrer et al, 1991;Suarez and Vazquez-Boland, 2001) with suitable modifications. In brief, the standard strain of pathogenic L. monocytogenes (MTCC 1143) was grown overnight in brain heart infusion broth at 37°C.…”

“…Reliable diagnosis of listeriosis was made by cultural methods; however, the isolation as well as the differentiation of pathogenic and non-pathogenic Listeria remains a time consuming and tedious task. The pathogenic potential of Listeria isolates can be assessed by in vitro pathogenicity tests such as haemolytic activity, phosphatidylinositol-specific phospholipase C (PI-PLC) assay (Notermans et al, 1991a), phosphatidylcholine-specific phospholipase C (PC-PLC) assay and in vivo methods namely, chick embryo (Notermans et al, 1991b) and mouse inoculation tests (Menudier et al, 1991). However, in vivo methods need skilled personnel to perform and remain objectionable from animal ethics point of view.…”

“…The rapid and reliable diagnosis of listeriosis has been suggested to be ideally based on the detection of virulence markers of Listeria spp. by molecular techniques, and more preferably, on the expression of their activities by in vitro assays (Notermans et al, 1991a).…”