High-frequency endonuclease (REA) typing: results from the WHO collaborative study group on subtyping of Listeria monocytogenes.
ABSTRACT Eighty isolates of Listeria monocytogenes were typed by high-frequency restriction endonuclease analysis. Two laboratories participated in the study with two restriction enzymes each. The enzymes used were EcoRI, Hae1II, HhaI. and its isoschizomer Cfo1. EcoRI was less discriminatory than the other enzymes. The profiles generated by Hha1 and CfoI were not fully stable for some closely related isolates. The size and the number of restriction bands generated by Hha1 in one laboratory and its isoschizomer Cfo1 in another laboratory were directly comparable. This indicates that REA-typing may be used as a definitive typing method for Listeria monocytogenes if the typing procedure is standardized. The stability of the REA-types needs further elucidation in order to establish firm differentiation criteria for comparison of isolates.
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ABSTRACT: Listeria monocytogenes strains responsible foroutbreaks oflisteriosis were studied byusing serotyping and phagetyping. Anadditional approach based on restriction endonuclease analysis (REA)ofthechromosomal DNA was usedtocharacterize L.monocytogenes strains collected fromvarious sourcesduring andafter aSwiss outbreak oflisteriosis (1983 to1987). Amongthe169wild-type strains ofListeria spp.that were examined, 161 (95%) belonged tothespecies L.monocytogenes, ofwhich109wereofhumanorigin. Tendifferent REAprofiles wereobtained fromthe120L.monocytogenes serotype4bstrains tested. AUl57serotype 4bstrains that were identified asSwiss epidemic strains byphagetyping clustered intwoclosely related REAprofiles. Inparticular, 10L.monocytogenes 4bstrains isolated fromthebrandofsoft cheese responsible fortheoutbreak andfrom itsdirect environment were indistinguishable fromisolates from40patients bybothphagetyping andREA analysis. However, 5ofthe17non-phage-typeable L.monocytogenes strains and18L.monocytogenes strains with a phagetypedifferent fromthose oftheSwiss epidemic typesshowedthesame profile. REA enabled the characterization ofnon-phage-typeable strains and,thus, seemsapromising tool forL.monocytogenes typing, especially during epidemiological investigations. Amongthesevenrecognized species ofthegenus Listeria (15), whichareallwidespread intheenvironment andcan occasionally becarried byhealthy people andanimals (6), mainly Listeria monocytogenes cancausesevere disease in adults andnewborn infants (11). Contaminated food(diary products, vegetables, andmeat)hasbeenimplicated in several recent outbreaks (4,9,17)andseemstobethemost important vehicle inthespread ofthis infection inhumans. Until now,epidemic strains ofListeria havebeencharacter- izedbyserotyping (18) andphagetyping (15). InSwitzer- land, alocally madesoft cheese wasimplicated inabout 100 casesofhumanlisteriosis between 1983and1987(1,10). Serotype 4bisolates werelargely predominant amongthose humanstrains (95%), andtwoparticular phagetypes were frequently observed (80%). However, thephagetypesin somestrains could notbedetermined. Thisprompted the application ofmolecular typing methods forL.monocyto- genes. Multilocus enzymeelectrophoresis (MEE)(19) was previously applied toasizable partofthestrains fromthe Swiss outbreak (14), andinthis report wedescribe theuseof restriction endonuclease analysis (REA)ofchromosomal DNA toclassify L.monocytogenes isolates. REA hasbeen usedpreviously tosubtype different microorganisms (5,8, 20)andhasbeenapplied successfully during various epi- demicsituations (3,13,21,22). Thisstudy mainly focused onL.monocytogenes serotype 4bstrains, including moststrains fromhumansinvolved in theSwiss outbreak, aswellasisolates fromvarious origins andofvarious serotypes andphagetypes, inorderto evaluate REAasanewmethod fortyping L.monocytogenes strains involved inanoutbreak.
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ABSTRACT: The rDNA gene restriction patterns of 134 isolates of Listeria species were determined with pKK3535--a pBR322 derived plasmid containing an Escherichia coli rRNA operon--used as a probe following digestion of chromosomal DNA by EcoRI endonuclease. Nineteen reference and type strains representing all species and serotypes of Listeria showed 17 distinct ribotypes. One hundred and fifteen wild strains of Listeria monocytogenes were ribotyped and the results were compared to those of serotyping, phage typing, multilocus enzyme electrophoresis (MEE) and restriction endonuclease analysis (REA). Ninety-six Listeria monocytogenes serotype 4b wild strains displayed six distinct ribotypes (I-VI), 72% (69/96) of them clustering in two very close rDNA patterns (I and II) of eight and nine bands, respectively. The same 96 strains displayed six REA patterns and eight MEE electrotypes. Among the 96 Listeria monocytogenes 4b isolates, the 34 epidemic strains defined by phage typing and by epidemiological data all belonged to one ribotype (ribotype I) representing 56% of the strains belonging to this ribotype. These same 34 epidemic strains were also grouped by REA and MEE typing in a unique profile (REA-A) and MEE electrotype (ET 1). Twenty-two Listeria monocytogenes strains of serogroup 1/2 analyzed by rDNA typing showed nine distinct ribotypes. For the 96 Listeria monocytogenes 4b strains studied, the discriminatory index was highest for phage typing and for any combination including phage typing. Ribotyping appears to be a well reproducible molecular typing method and could be a useful complement to other typing methods for the epidemiological study of listeriosis.European Journal of Clinical Microbiology 04/1993; 12(3):162-9. · 3.02 Impact Factor
- The Lancet 12/1988; 2(8622):1247-8. · 39.06 Impact Factor