Genomic Divisions/Lineages, Epidemic Clones, and Population Structure

Cheng, Ying; Siletzky, Robin M.; Kathariou, Sophia

doi:10.1201/9781420051414.ch11

Cited by 44 publications

(71 citation statements)

References 75 publications

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“…Outbreaks of listeriosis tend to involve a relatively small number of closely related strains ("epidemic clones"), primarily of serotype 4b. Several major outbreaks have been attributed to epidemic clone I (ECI) and epidemic clone II (ECII), both of serotype 4b (5,21).…”

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Role of Growth Temperature in Freeze-Thaw Tolerance of Listeria spp

Azizoglu

Osborne

Wilson

et al. 2009

Appl Environ Microbiol

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The food-borne pathogen Listeria monocytogenes can grow in a wide range of temperatures, and several key virulence determinants of the organism are expressed at 37°C but are strongly repressed below 30°C. However, the impact of growth temperature on the ability of the bacteria to tolerate environmental stresses remains poorly understood. In other microorganisms, cold acclimation resulted in enhanced tolerance against freezing and thawing (cryotolerance). In this study, we investigated the impact of growth temperature (4, 25, and 37°C) on the cryotolerance of 14 strains of L. monocytogenes from outbreaks and from food processing plant environments and four strains of nonpathogenic Listeria spp. (L. welshimeri and L. innocua). After growth at different temperatures, cells were frozen at ؊20°C, and repeated freeze-thaw cycles were applied every 24 h. Pronounced cryotolerance was exhibited by cells grown at 37°C, with a <1-log decrease after 18 cycles of freezing and thawing. In contrast, freeze-thaw tolerance was significantly reduced (P < 0.05) when bacteria were grown at either 4 or 25°C, with log decreases after 18 freeze-thaw cycles ranging from 2 to >4, depending on the strain. These findings suggest that growth at 37°C, a temperature required for expression of virulence determinants of L. monocytogenes, is also required for protection against freeze-thaw stress. The negative impact of growth at low temperature on freeze-thaw stress was unexpected and has not been reported before with this or other psychrotrophic microorganisms.

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confidence: 99%

Role of Growth Temperature in Freeze-Thaw Tolerance of Listeria spp

Azizoglu

Osborne

Wilson

et al. 2009

Appl Environ Microbiol

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“…DNA sequence-based subtyping methods, such as multilocus sequence typing (MLST) (3,8,10) and multi-virulence-locus sequence typing (MVLST) (2,14), have also been used for phylogenetic studies and to categorize isolates into higher-level groups, such as evolutionary lineages, clonal complexes, and epidemic clones. The term epidemic clone has been defined as a group of genetically related isolates implicated in geographically and temporally unrelated outbreaks that are presumably of a common ancestor (1,2,4,7,14).…”

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Sequence Typing Confirms that a Predominant Listeria monocytogenes Clone Caused Human Listeriosis Cases and Outbreaks in Canada from 1988 to 2010

et al. 2012

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Human listeriosis outbreaks in Canada have been predominantly caused by serotype 1/2a isolates with highly similar pulsedfield gel electrophoresis (PFGE) patterns. Multilocus sequence typing (MLST) and multi-virulence-locus sequence typing (MV-LST) each identified a diverse population of Listeria monocytogenes isolates, and within that, both methods had congruent subtypes that substantiated a predominant clone (clonal complex 8; virulence type 59; proposed epidemic clone 5 [ECV]) that has been causing human illness across Canada for more than 2 decades.

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“…ECI, ECIa, and ECII have been responsible for repeated outbreaks of food-borne listeriosis (9,19,28). ECI and ECIa were recognized in the earliest epidemiologically characterized outbreaks of listeriosis (e.g., coleslaw outbreak in the Maritime Provinces in 1979 and Mexican-style cheese outbreak in California in 1985, both involving ECI, as well as an outbreak in Massachusetts in 1983, involving ECIa) (2,9,19,24). In contrast, ECII was not recognized until the hot dog-associated multistate outbreak in the United States in 1998-1999 (4, 5, 16, 28).…”

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DNA Probes for Unambiguous Identification of Listeria monocytogenes Epidemic Clone II Strains

Cheng

Kim

Lee

et al. 2010

Appl Environ Microbiol

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Listeria monocytogenes epidemic clone II (ECII) strains have been responsible for two major multistate outbreaks of food-borne listeriosis in the United States, but their prevalence and ecology remain poorly understood. In this study, we describe DNA probes that unambiguously identify this clonal group. These probes were able to differentiate ECII strains of outbreak, sporadic, or environmental origin from other L. monocytogenes strains of the same serotype (4b).Most outbreaks of food-borne listeriosis have involved a small number of well-defined clonal groups. Population genetic and epidemiologic studies have revealed three serotype 4b clonal groups, designated epidemic clones (ECs). ECI, ECIa, and ECII have been responsible for repeated outbreaks of food-borne listeriosis (9,19,28). ECI and ECIa were recognized in the earliest epidemiologically characterized outbreaks of listeriosis (e.g., coleslaw outbreak in the Maritime Provinces in 1979 and Mexican-style cheese outbreak in California in 1985, both involving ECI, as well as an outbreak in Massachusetts in 1983, involving ECIa) (2,9,19,24). In contrast, ECII was not recognized until the hot dog-associated multistate outbreak in the United States in 1998-1999 (4, 5, 16, 28). A subsequent multistate outbreak in 2002 was attributed to contaminated turkey deli meats and also involved ECII strains (6,20). In addition, ECII strains have contributed to sporadic human listeriosis and were isolated from environmental samples of food-processing plants (13,18,25,26).Our understanding of the epidemiology and ecology of ECII remains limited, partially due to the unavailability of tools for unambiguous detection of these strains by using relatively simple formats (e.g., hybridizations with specific DNA probes or PCR with specific primers). ECII strains were found to have diverged in a genomic region ("region 18") that was otherwise specific to serotype 4b and conserved among other serotype 4b strains (14). The genome of ECII strain H7858 (1998-1999 outbreak) has been sequenced (23), and DNA probes derived from region 18 of this strain hybridized with genomic DNA of all tested ECII strains (20). However, hybridization was also observed with two serotype 4b strains with pulsed-field gel electrophoreses (PFGE) profiles clearly different from ECII, suggesting that region 18 sequences of H7858 were also harbored by certain unrelated serotype 4b strains (20). Similar findings were reported by Chen and Knabel, who employed PCR with primers derived from region 18 of H7858 (8). Thus, a continuing need for DNA-based tools for unambiguous detection of ECII strains exists. This would supplement other subtyping tools (e.g., PFGE) to facilitate rapid detection and monitoring of clones of L. monocytogenes for epidemiological and risk assessment purposes.In this study, we assessed the ECII specificity of selected DNA probes derived from four different genomic regions present in the chromosome of ECII strain H7858 but not in the fully sequenced genome of epidemic clone I strain F2365, al...

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Genomic Divisions/Lineages, Epidemic Clones, and Population Structure

Cited by 44 publications

References 75 publications

Role of Growth Temperature in Freeze-Thaw Tolerance of Listeria spp

Role of Growth Temperature in Freeze-Thaw Tolerance of Listeria spp

Sequence Typing Confirms that a Predominant Listeria monocytogenes Clone Caused Human Listeriosis Cases and Outbreaks in Canada from 1988 to 2010

DNA Probes for Unambiguous Identification of Listeria monocytogenes Epidemic Clone II Strains

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