Associations among Listeria monocytogenes genotypes and distinct clinical manifestations of listeriosis in cattle.
OBJECTIVE
To determine whether specific strains of Listeria monocytogenes, as determined by genetic characteristics and virulence phenotypes, were associated with distinct clinical manifestations of listeriosis in cattle and thus may potentially have tissue specificity.


METHODS
32 cattle.


METHODS
DNA sequence data for the virulence genes actAand inlAwere used to infer the phylogeny of L. monocytogenes and to test for positive selection. Isolates were screened for the presence or absence of internalin genes and assigned an internalin profile. Plaquing assays were performed to determine the relative cytopathogenicity of each isolate. Categorical data analyses were performed to describe associations among L. monocytogenes genotypes, virulence phenotypes, and clinical manifestations of listeriosis.


RESULTS
Results confirmed that L. monocytogenes represents 2 deeply separated evolutionary lineages. Genes actA and inlA contained amino acid sites under positive selection, and specific residues at some sites were associated with lineage and manifestation of listeriosis. Whereas lineage I was clonal and predominantly composed of isolates from cases of encephalitis, lineage II was more genetically diverse and equally represented by isolates from cases of encephalitis versus septicemia and fetal infection. Lineage I isolates also had greater cytopathogenicity in vitro, compared with lineage II isolates.


CONCLUSIONS
Results indicated that L. monocytogenes virulence genes underwent positive selection that is consistent with the diversification of 2 evolutionary lineages: lineage I is clonal and associated with encephalitis, and lineage II is more genetically diverse and equally likely to cause both major forms of listeriosis in cattle.
Department of Food Science, Cornell University, Ithaca, NY 14853, USA.
Mary Ann
MA
Pohl
Martin
M
Wiedmann
Kendra K
KK
Nightingale
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004196:Disease Outbreaks; D005798:Genes, Bacterial; D005838:Genotype; D008089:Listeria monocytogenes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D008088:Listeriosis / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D010802:Phylogeny; D018805:Sepsis / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary; D014774:Virulence
D004269:DNA, Bacterial