Genetic Determinants for Cadmium and Arsenic Resistance among Listeria monocytogenes Serotype 4b Isolates from Sporadic Human Listeriosis Patients

Lee, Sangmi; Rakić-Martinez, Mira; Graves, Lewis M.; Ward, Todd J.; Siletzky, Robin M.; Kathariou, Sophia

doi:10.1128/aem.03551-12

Cited by 47 publications

(63 citation statements)

References 39 publications

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“…L. monocytogenes strain F8027 (hereafter F8027) was originally derived from fresh celery and has been used as model in studies for produce colonization by L. monocytogenes (21). It grew at 35 but not at 50 g/ml cadmium chloride, hence its MIC (50 g/ml) is below the 70 g/ml threshold for resistance used in previous studies (11,12,22). PCR with previously described primers (8) indicated that F8027 was negative for previously identified cadmium resistance determinants cadA1, cadA2, and cadA3 (data not shown).…”

Section: Resultsmentioning

confidence: 99%

“…70% identity at the amino acid (aa) sequence level, cadA4 is noticeably divergent, exhibiting only ca. 36% identity with these other cadA determinants (11). Nonetheless, the deduced CadA encoded by cadA4 harbored all three key motifs characteristic of the CadA protein family (25): CXXC, responsible for metal binding; DKTGT, associated with ATP binding; and CXC, specifically CPC, serving as a membranebound ion transport channel (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Strains F2365 and H75550-Cd s chosen for heterologous expressions of cadA4C belong to clonal complexes CC1 (also known as ECI) and CC6 (also known as ECII), respectively, markedly distinct from either F8027 (CC315) or Scott A (CC2). H75550-Cd s is a plasmid (pPL80)-cured derivative of strain H7550, implicated in the 1998 to 1999 hotdog outbreak (26); pLM80 harbors cadA2C (24), and H7550 grew at cadmium concentrations Ͼ140 g/ml, similar to other cadA2-harboring strains (11). However, upon acquisition of cadA4C, cadmium MICs for both F2365 and H75550-Cd s increased to only 50 g/ml, i.e., a level characteristic for F8027 and other strains that naturally harbor cadA4.…”

Section: Resultsmentioning

confidence: 99%

“…Three members of the CadAC family were previously identified in L. monocytogenes. Of these, CadA1 and CadA2 were found to be harbored by plasmids and to be widely distributed among different strains and serotypes of L. monocytogenes (4,(10)(11)(12)(13), while CadA3 is encoded chromosomally and has only been identified in strain EGD-e and a few others (11,14,15). The expression of cadC (Lmo1102) from strain EGD-e was markedly upregulated in vivo in a murine infection model and experimentally confirmed to be required for virulence in that model (16).…”

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confidence: 99%

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Novel Cadmium Resistance Determinant in Listeria monocytogenes

Parsons

Lee

Jayeola

et al. 2017

Appl Environ Microbiol

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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.IMPORTANCE Listeria 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.KEYWORDS Listeria monocytogenes, cadmium resistance, cadA, biofilm, virulence L isteria monocytogenes is a Gram-positive rod-shaped bacterium widely distributed in nature (1). As a facultative intracellular foodborne pathogen causing the disease listeriosis, L. monocytogenes organisms are responsible for numerous hospitalizations and deaths in the United States every year (2). T...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Novel Cadmium Resistance Determinant in Listeria monocytogenes

Parsons

Lee

Jayeola

et al. 2017

Appl Environ Microbiol

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“…The serotype was determined at the CDC as previously described (24) and reexamined at North Carolina State University using a multiplex PCR serotyping scheme (25), which also allowed identification of the recently recognized 4b subset IVb-v1 (Table 1) (26,27). Resistance to arsenic, cadmium, and BC was determined as described previously (28) with the modification that cadmium-resistant isolates were those growing at Ն35 g/ml cadmium chloride, reflecting our recent discovery of the association between a cadmium resistance determinant (cadA4) and growth at 35 g/ml (but not at 70 g/ml) cadmium chloride (29).…”

Section: Methodsmentioning

confidence: 99%

Population Structure of Listeria monocytogenes Serotype 4b Isolates from Sporadic Human Listeriosis Cases in the United States from 2003 to 2008

Lee

Ward

Graves

et al. 2014

Appl Environ Microbiol

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c Listeria monocytogenes can cause severe food-borne disease (listeriosis). Numerous outbreaks have involved three serotype 4b epidemic clones (ECs): ECI, ECII, and ECIa. However, little is known about the population structure of L. monocytogenes serotype 4b from sporadic listeriosis in the United States, even though most cases of human listeriosis are in fact sporadic. Here we analyzed 136 serotype 4b isolates from sporadic cases in the United States, 2003 to 2008, utilizing multiple tools including multilocus genotyping, pulsed-field gel electrophoresis, and sequence analysis of the inlAB locus. ECI, ECII, and ECIa were frequently encountered (32, 17, and 7%, respectively). However, annually 30 to 68% of isolates were outside these ECs, and several novel clonal groups were identified. An estimated 33 and 17% of the isolates, mostly among the ECs, were resistant to cadmium and arsenic, respectively, but resistance to benzalkonium chloride was uncommon (3%) among the sporadic isolates. The frequency of clonal groups fluctuated within the 6-year study period, without consistent trends. However, on several occasions, temporal clusters of isolates with indistinguishable genotypes were detected, suggesting the possibility of hidden multistate outbreaks. Our analysis suggests a complex population structure of serotype 4b L. monocytogenes from sporadic disease, with important contributions by ECs and several novel clonal groups. Continuous monitoring will be needed to assess long-term trends in clonality patterns and population structure of L. monocytogenes from sporadic listeriosis.

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