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Diverse cadmium resistance determinants in Listeria monocytogenes isolates from the turkey processing plant environment.

ABSTRACT: Two different cadA cadmium resistance determinants (cadA1, first identified in Tn5422, and cadA2, associated with pLM80) were detected among cadmium-resistant Listeria monocytogenes strains from turkey processing plants. Prevalence of cadA1 versus cadA2 was serotype associated. Cadmium-resistant isolates that were also resistant to benzalkonium chloride (BC) were more likely to harbor cadA2 alone or together with cadA1 than isolates that were cadmium resistant but BC susceptible.

SUBMITTER: Mullapudi S

PROVIDER: S-EPMC2805206 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Diverse cadmium resistance determinants in Listeria monocytogenes isolates from the turkey processing plant environment.

Mullapudi S S Siletzky R M RM Kathariou S S

Applied and environmental microbiology 20091130 2

Two different cadA cadmium resistance determinants (cadA1, first identified in Tn5422, and cadA2, associated with pLM80) were detected among cadmium-resistant Listeria monocytogenes strains from turkey processing plants. Prevalence of cadA1 versus cadA2 was serotype associated. Cadmium-resistant isolates that were also resistant to benzalkonium chloride (BC) were more likely to harbor cadA2 alone or together with cadA1 than isolates that were cadmium resistant but BC susceptible. ...[more]

PMID: 19948870

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Project description:Listeria monocytogenes is a foodborne pathogen that can cause severe disease (listeriosis) in susceptible individuals. It is ubiquitous in the environment and often exhibits resistance to heavy metals. One of the determinants that enables Listeria to tolerate exposure to cadmium is the cadAC efflux system, with CadA being a P-type ATPase. Three different cadA genes (designated cadA1 to cadA3) were previously characterized in L. monocytogenes A novel putative cadmium resistance gene (cadA4) was recently identified through whole-genome sequencing, but experimental confirmation for its involvement in cadmium resistance is lacking. In this study, we characterized cadA4 in L. monocytogenes strain F8027, a cadmium-resistant strain of serotype 4b. By screening a mariner-based transposon library of this strain, we identified a mutant with reduced tolerance to cadmium and that harbored a single transposon insertion in cadA4 The tolerance to cadmium was restored by genetic complementation with the cadmium resistance cassette (cadA4C), and enhanced cadmium tolerance was conferred to two unrelated cadmium-sensitive strains via heterologous complementation with cadA4C Cadmium exposure induced cadA4 expression, even at noninhibitory levels. Virulence assessments in the Galleria mellonella model suggested that a functional cadA4 suppressed virulence, potentially promoting commensal colonization of the insect larvae. Biofilm assays suggested that cadA4 inactivation reduced biofilm formation. These data not only confirm cadA4 as a novel cadmium resistance determinant in L. monocytogenes but also provide evidence for roles in virulence and biofilm formation.IMPORTANCEListeria monocytogenes is an intracellular foodborne pathogen causing the disease listeriosis, which is responsible for numerous hospitalizations and deaths every year. Among the adaptations that enable the survival of Listeria in the environment are the abilities to persist in biofilms, grow in the cold, and tolerate toxic compounds, such as heavy metals. Here, we characterized a novel determinant that was recently identified on a larger mobile genetic island through whole-genome sequencing. This gene (cadA4) was found to be responsible for cadmium detoxification and to be a divergent member of the Cad family of cadmium efflux pumps. Virulence assessments in a Galleria mellonella model suggested that cadA4 may suppress virulence. Additionally, cadA4 may be involved in the ability of Listeria to form biofilms. Beyond the role in cadmium detoxification, the involvement of cadA4 in other cellular functions potentially explains its retention and wide distribution in L. monocytogenes.

Project description:The eradication of Listeria monocytogenes from food chains is still a great challenge for the food industry and control authorities since some clonal complexes (CCs) are either better adapted to food processing environments (FPEs) or are globally widespread. In this work, we focus on the in-house evolution of L. monocytogenes genotypes collected from a heavily contaminated FPE whose contamination pattern underwent a massive and yet unexplained change. At the beginning of the sampling in 2010, a high variety of most likely transient L. monocytogenes genotypes was detected belonging to sequence type (ST) 1, ST7, ST21, ST37. After several efforts to intensify the hygiene measures, the variability was reduced to L. monocytogenes ST5 that was dominant in the following years 2011 and 2012. We aimed to elucidate possible genetic mechanisms responsible for the high abundance and persistence of ST5 strains in this FPE. Therefore, we compared the genomes of six L. monocytogenes ST5 strains to the less frequently occurring transient L. monocytogenes ST37 and ST204 from the same FPE as well as the highly abundant ST1 and ST21 isolated in 2010. Whole genome analysis indicated a high degree of conservation among ST5 strains [average nucleotide identity (ANI) 99.93-99.99%; tetranucleotide correlation 0.99998-0.99999]. Slight differences in pulsed field gel electrophoresis (PFGE) patterns of two ST5 isolates could be explained by genetic changes in the tRNA-Arg-TCT prophages. ST5 and ST204 strains harbored virtually identical 91 kbp plasmids related to plasmid group 2 (pLM80 and pLMUCDL175). Interestingly, highly abundant genotypes present in the FPE in 2010 did not harbor any plasmids. The ST5 plasmids harbored an efflux pump system (bcrABC cassette) and heavy metal resistance genes possibly providing a higher tolerance to disinfectants. The pLM80 prototype plasmids most likely provide important genetic determinants for a better survival of L. monocytogenes in the FPE. We reveal short-term evolution of L. monocytogenes strains within the same FPE over a 3 year period and our results suggest that plasmids are important for the persistence of ST5 strains in this FPE.

Dataset Information

Diverse cadmium resistance determinants in Listeria monocytogenes isolates from the turkey processing plant environment.

Publications

Diverse cadmium resistance determinants in Listeria monocytogenes isolates from the turkey processing plant environment.

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