Listeria monocytogenes Associated with New Zealand Seafood Production and Clinical Cases: Unique Sequence Types, Truncated InlA, and Attenuated Invasiveness

Abstract

bListeriosis is caused by the food-borne pathogen Listeria monocytogenes, which can be found in seafood and processing plants. To evaluate the risk to human health associated with seafood production in New Zealand, multi-virulence-locus sequence typing (MVLST) was used to define the sequence types (STs) of 31 L. monocytogenes isolates collected from seafood-processing plants, 15 from processed foods, and 6 from human listeriosis cases. The STs of these isolates were then compared with those from a collection of seafood isolates and epidemic strains from overseas. A total of 17 STs from New Zealand clustered into two lineages: seafood-related isolates in lineages I and II and all human isolates in lineage II. None of the New Zealand STs matched previously described STs from other countries. Isolates (belonging to ST01-N and ST03-N) from mussels and their processing environments, however, were identical to those of sporadic listeriosis cases in New Zealand. ST03-N isolates (16 from mussel-processing environments, 2 from humans, and 1 from a mussel) contained an inlA premature stop codon (PMSC) mutation. Therefore, the levels of invasiveness of 22 isolates from ST03-N and the three other common STs were compared using human intestinal epithelial Caco-2 cell lines. STs carrying inlA PMSCs, including ST03-N isolates associated with clinical cases, had a low invasion phenotype. The close relatedness of some clinical and environmental strains, as revealed by identical MVLST profiles, suggests that local and persistent environmental strains in seafood-processing environments pose a potential health risk. Furthermore, a PMSC in inlA does not appear to give L. monocytogenes a noninvasive profile.

Characterization of Listeria monocytogenes from three countries and antibiotic resistance differences among countries and Listeria monocytogenes serogroups

“…; Cruz et al . ). All isolates in this study also carried the lmo2672 , which agrees with findings in food and cattle isolates (Wieczorek et al .…”

Virulence factors and resistance to antimicrobials inListeria monocytogenesserotype 1/2c isolated from food

“…Furthermore, a PMSC in inlA does not appear to give L. monocytogenes a noninvasive profile (Cruz et al . ). PMSCs are not always accompanied by a noninvasive phenotype.…”

Listeria monocytogenes in Aquatic Food Products—A Review

“…However, lineage III and IV isolates (mainly serotypes 4a and 4c) are generally underrepresented, potentially due to their attenuated pathogenic potential and different phenotypic properties compared to lineage I and II isolates (Liu ; Orsi and others ). The majority of human infections are linked to lineage I serotype 4b and 1/2b isolates, although lineage II serotype 1/2a isolates have caused some listeriosis outbreaks (Orsi and others ; Cruz and others ). Based on the geographical and temporal distribution of outbreaks, L. monocytogenes has been further classified into epidemic clones (ECs) I (lineage I), II (lineage II), III (lineage I), and IV (lineage I).…”

“…This differentiation enables discrimination of isolates from different serotypes based on their ecological compartments (Orsi and others ). Three highly clonal lineage I serotype 4b strains have caused recurrent global outbreaks (ECs I, Ia, and II) (Cruz and others ).…”

“…Internalins are responsible for the internalization of L. monocytogenes into epithelial cells ( Inl A); mutations in such virulence genes, which are components of the well‐documented virulence cycle, might attenuate the virulence potential (Orsi and others ; Kovacevic and others ). Cruz and others () screened for the presence of inl A mutations (premature stop codons [PMSCs]) in L. monocytogenes isolated from New Zealand (NZ) mussel‐processing environments to estimate the risk to human health. PMSCs might impact the environmental survival of L. monocytogenes .…”