Methods to determine virulence of Listeria strains

Ralovich, B

doi:10.1016/0168-1605(89)90025-1

Cited by 4 publications

(3 citation statements)

References 2 publications

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“…Three nonpathogenic Listeria strains, L. innocua LMG 11387, L. innocua M58 (isolated from Greek raw milk) and the avirulent L. monocytogenes no.10 strain (meat isolate, serotype 4ab) previously used as indicators of the behavior of L. monocytogenes in milk and cheese challenge studies (Samelis et al, ), were also used in this study. The avirulent meat strain no.10 (Ralovich, ) was used because it shares several main properties with L. monocytogenes Scott A (clinical isolate, serotype 4b), including their biochemical identification profile and sensitivity to acid, nisin, and enterocins (Samelis et al, ; Vandera et al, in press). Nonpathogenic Listeria strains were selected for the artificial contamination of the model cheeses in a local dairy plant (Pappas Bros., Filippiada, Epirus, Greece) because the use of pathogenic L. monocytogenes strains was not permitted under commercial conditions (Samelis et al, ).…”

Section: Methodsmentioning

confidence: 99%

Behavior of artificial listerial contamination in model Greek Graviera cheeses manufactured with the indigenous nisin A‐producing strain Lactococcus lactis subsp. cremoris M104 as costarter culture

Samelis

Giannou

Pappa

et al. 2016

Journal of Food Safety

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Growth of Listeria monocytogenes during processing of traditional Greek Graviera cheese is inhibited, but the pathogen may survive ripening. Therefore, this study used Lactococcus lactis subsp. cremoris M104, a nisin A‐producing (NisA+) raw milk isolate, to enhance inactivation of a nonpathogenic Listeria cocktail contaminated in model Graviera mini cheeses. Cheeses were manufactured from thermized milk with a commercial starter culture (CSC) or the CSC plus strain M104 (CSC + M104), ripened at 18 °C and 90% RH for 20 days and stored at 4 °C in vacuum for 60 days. Listeria populations declined 10‐fold in all fermenting cheeses but then survived with little death during ripening and storage. NisA+ M104 colonies were prevalent and the nisA gene was detected, but nisin activity was weak to undetectable, in all CSC + M104 cheeses. Thus, Graviera cheese processing should be optimized to ensure nisA gene expression by strain M104 at levels sufficient to increase inactivation of L. monocytogenes. Practical applications This study provided important preliminary evidence that the in situ NisA+ antilisterial activity of L. lactis subsp. cremoris M104 during Graviera cheese fermentation increased by reducing the curd cooking temperature from 48 °C to 42 °C. This indicated the feasibility to increase nisin production and activity by suitably modifying selected technological factors during traditional cooked hard cheese processing. Apart from its bioprotective potential, this NisA+ L. lactis subsp. cremoris genotype (represented by the indigenous strains M104 and M78) possesses desirable sugar fermentation capabilities and enzymatic activities similar to those of the best performing industrial L. lactis or L. cremoris strains in commercial starters (Parapouli et al., ). Since 2015 this novel lactococcal genotype has been applied as hand‐made, costarter culture for the production of commercial Greek Graviera cheeses characterized by specific flavor characteristics and improved textural properties than counterpart cheeses produced with CSCs only (Pappas Bros. collaborating cheese plant, Epirus; private communication).

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Section: Methodsmentioning

confidence: 99%

Behavior of artificial listerial contamination in model Greek Graviera cheeses manufactured with the indigenous nisin A‐producing strain Lactococcus lactis subsp. cremoris M104 as costarter culture

Samelis

Giannou

Pappa

et al. 2016

Journal of Food Safety

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“…(2018) . Strain no.10, originally described by Ralovich (1989) as avirulent in Anton's and mouse tests, is a meat strain of L. monocytogenes (serotype 4ab) of high bacteriocin (enterocin) sensitivity but moderate acid sensitivity; therefore, it is routinely used as a highly convenient target and/or indicator Listeria strain in our dairy studies, too ( Samelis et al., 2009 ; Vandera et al., 2018 , 2020 ).…”

Section: Methodsmentioning

confidence: 99%

Antilisterial activity of raw sheep milk from two native Epirus breeds: Culture-dependent identification, bacteriocin gene detection and primary safety evaluation of the antagonistic LAB biota

Sioziou,

Kakouri,

Bosnea

et al. 2024

Current Research in Microbial Sciences

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“…The fact that Listeria produces haemolysis on blood agar was observed for the first time in 1934 (Anton, 1934). β-haemolysis has been considered as an important diagnostic feature (Ralovich, 1989).…”

Section: Discussionmentioning

confidence: 99%

Application of Specific Media, API Technique and PCR for Rapid Confirmation of Listeria monocytogenes in Foodstuffs and Water

Farouk¹,

Abdel-Shaf²,

Shalaby³

et al. 2015

Research J. of Microbiology

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Listeria monocytogenes is responsible for causing the serious infectious disease listeriorosis which occurs due to food contaminated with Listeria. The study employed herein concerned with the isolation and identification of L. monocytogenes from foodstuffs and water. Hundred different food stuffs samples (milk, cheese and meat) and 50 fresh water samples were surveyed for presence of L. monocytogenes. These samples were inoculated into two enrichment media and cultivated on Oxford agar. Presumptively positive isolates were determined by morphology of colonies, gram stain, catalase test, haemolysis on sheep blood agar and motility test. The isolates were further identified to species level by 10300 API Listeria strips, PCR was done for all specimens to evaluate its accuracy. Out of 100 foodstuffs samples, 15 samples were showed positive results for Listria species. Out of 50 fresh water samples, 5 samples were showed positive results. Antibiotic susceptibility was done for all identified strains. All isolates were sensitive to penicillin G, ampicillin, tetracycline, amikacin and erythromycin.

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Methods to determine virulence of Listeria strains

Cited by 4 publications

References 2 publications

Behavior of artificial listerial contamination in model Greek Graviera cheeses manufactured with the indigenous nisin A‐producing strain Lactococcus lactis subsp. cremoris M104 as costarter culture

Behavior of artificial listerial contamination in model Greek Graviera cheeses manufactured with the indigenous nisin A‐producing strain Lactococcus lactis subsp. cremoris M104 as costarter culture

Antilisterial activity of raw sheep milk from two native Epirus breeds: Culture-dependent identification, bacteriocin gene detection and primary safety evaluation of the antagonistic LAB biota

Application of Specific Media, API Technique and PCR for Rapid Confirmation of Listeria monocytogenes in Foodstuffs and Water

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