Production of enterolysin A by a raw milk enterococcal isolate exhibiting multiple virulence factors.
Even though enterococci are a common cause of human infection they can readily be isolated from a range of food sources, including various meat and dairy products. An enterococcal strain, DPC5280, which exhibits a broad spectrum of inhibition against many Gram-positive bacteria was recently isolated from an Irish raw milk sample. Characterization of the inhibition revealed that the strain exhibits haemolytic activity characteristic of the two-component lantibiotic cytolysin and also produces a heat-labile antimicrobial protein of 34 kDa. The latter protein displayed cell wall hydrolytic activity, as evidenced by zymogram gels containing autoclaved lactococcal cells. N-terminal sequencing of the purified protein yielded the sequence ASNEWS which is 100 % identical to enterolysin A (accession no. AF249740), a protein which shares 28 and 29 % identity to the Gly-Gly endopeptidases, lysostaphin and zoocin A, respectively. Indeed, amplification of entL from DPC5280 and sequencing revealed that the protein is 100 % identical to enterolysin A. The DPC5280 strain also contained the determinants associated with multiple virulence factors, including gelatinase, aggregation substance and multiple antibiotic resistance. The linkage of this cell-wall-degrading enzyme to other virulence factors in enterococci may contribute to the competitiveness of pathogenic enterococci when found in complex microbial environments such as food and the gastrointestinal tract.
Hickey
Rita M
RM
Microbiology Department, University College Cork, Ireland.|Teagasc, Dairy Products Research Centre, Moorepark, Fermoy, Co. Cork, Ireland.
Twomey
Denis P
DP
National Food Biotechnology Centre, University College Cork, Ireland.|Teagasc, Dairy Products Research Centre, Moorepark, Fermoy, Co. Cork, Ireland.
Ross
R Paul
RP
Teagasc, Dairy Products Research Centre, Moorepark, Fermoy, Co. Cork, Ireland.
Hill
Colin
C
Microbiology Department, University College Cork, Ireland.|National Food Biotechnology Centre, University College Cork, Ireland.
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D001430:Bacteriocins; D001483:Base Sequence; D002473:Cell Wall / Q000378:metabolism; D003603:Cytotoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013293:Enterococcus faecalis / Q000378:metabolism* / Q000472:pathogenicity*; D006094:Gram-Positive Bacteria / Q000187:drug effects; D006461:Hemolysis; D008892:Milk / Q000382:microbiology*; D008969:Molecular Sequence Data; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism
D001426:Bacterial Proteins; D001430:Bacteriocins; D003603:Cytotoxins; D037521:Virulence Factors; C120351:cytolysin, Enterococcus faecalis