Production of Thiol-dependent Haemolysins by Listeria monocytogenes and Related Species

Abstract

Twenty-six strains belonging to the five main species of the genus Listeria were examined for production of thiol-dependent exotoxins. All strains of L. monocytogenes cultured in charcoal-treated broth secreted a haemolytic factor at a level ranging from 200 to 800 haemolytic units (HU) ml-1, except for the strain EGD (1500 HU ml-1) and the type strain CIP 82110T (10 HU ml-1). The haemolytic activity reached a maximum level by 8-10 h and then rapidly declined as soon as bacterial exponential growth ceased. The titres of haemolytic activity were markedly reduced when bacteria were grown in charcoal-untreated broth. The haemolytic factor produced by L. monocytogenes strains was characterized as listeriolysin O (Mr about 60,000), a member of the group of thiol-dependent exotoxins. Strains of Listeria ivanovii also produced high levels of thiol-dependent exotoxin (about 2500 HU ml-1), in both charcoal-treated and untreated broth. Small amounts of haemolytic factor (about 9-30 HU ml-1) were also produced by Listeria seeligeri in charcoal-treated broth. The haemolysin produced by L. seeligeri was identified for the first time as a thiol-dependent exotoxin of Mr about 60,000, antigenically related to listeriolysin O. As expected, we failed to detect thiol-dependent exotoxin in the two nonhaemolytic species, Listeria innocua and Listeria welshimeri.

Effect of eugenol on growth and listeriolysin o production by Listeria monocytogenes

“…A stock solution was prepared by dissolving 100 mg of eugenol in 10 mL of 95% ethanol. Aliquots were added to sterilized and cooled proteose peptone broth -PPG (Geoffroy et al, 1989) to give the final concentrations of 100, 300, 500, 800 and 1000 µg mL -1 . In order to detect the absence of antibacterial activity of ethanol, the experiments were performed with a control, with the solvent added to the medium.…”

Listeriolysin genes: complete sequence of ilo from Listeria ivanovii and of lso from Listeria seeligeri

“…These toxins include the species-specific types of Iisteriolysin 0 produced by the three Listeria species which are hemolytic on blood agar: Listeria monocytogenes (pathogenic for man anct animals), Listeria ivanoL·ii (animal pathogen) and Listeria seeligeri (apathogenic). Their Iisteriolysins have previously bet!n characterized biochemically [6,10],and it has also been shown that they vary in cytolytic activity.The gene for Iisteriolysin 0 (h/y) from 1.4. monocytogenes has been cloned and sequenced [4,13] and homologous DNA sequences have been detected in the chromosome of the two other hemolytic Listeria species [11]. lt has been firmly established, that Iisteriolysin 0 (LLO) is an essential virulence factor of L. monocytogenes (reviewed in Refs.…”

“…These toxins include the species-specific types of Iisteriolysin 0 produced by the three Listeria species which are hemolytic on blood agar: Listeria monocytogenes (pathogenic for man anct animals), Listeria ivanoL·ii (animal pathogen) and Listeria seeligeri (apathogenic). Their Iisteriolysins have previously bet!n characterized biochemically [6,10],and it has also been shown that they vary in cytolytic activity.…”

Molecular basis of listeriolysin O pH dependence

“…LLO is a virulence factor of LM and is essential for its escape from the phagocytic vesicle of the macrophage (1)(2)(3)(4)(5)(6). LLO, a member of the large family of CDCs, was first characterized by Geoffrey et al (7), and its pore-forming activity was shown to have a marked pH optimum. LLO exhibits very little cytolytic activity at neutral pH but substantial activity at pH Ͻ6.…”