Virulence markers in Aeromonas hydrophila and Aeromonas veronii biovar sobria isolates from freshwater fish and from a diarrhoea case.
OBJECTIVE
To evaluate the public health significance of representative strains of two Aeromonas spp., mainly from freshwater fish, on the basis of production of virulence-associated factors and presence of the haemolytic genes aerA and hlyA.


RESULTS
Eleven strains of Aer. hydrophila, three strains of Aer. veronii biovar sobria (all from freshwater fish) and one strain of Aer. hydrophila from human diarrhoea were tested for potential virulence traits and for the presence of the haemolytic genes aerA and hlyA. Ten Aer. hydrophila isolates were aerA(+)hlyA(+) and two aerA(+)hlyA(-). Aeromonas veronii biovar sobria isolates were aerA(-)hlyA(-). Strains from the three genotypes showed enterotoxic activity in the suckling mouse assay. At 28 degrees C, four Aer. hydrophila fish strains could be considered as potentially virulent (possessing at least two of these characteristics: haemolytic, cytotoxic and enterotoxic). One Aer. veronii biovar sobria strain and the clinical isolate were cytotoxic on Vero cells. When grown at 4 degrees C, these six isolates fulfilled virulence criterion, but at 37 degrees C, only one fish strain, an Aer. hydrophila, did.


CONCLUSIONS
The potential health risk derived from the presence of Aer. hydrophila and Aer. veronii biovar sobria in ice-stored freshwater fish should not be underestimated.


CONCLUSIONS
Expression of virulence factors is affected by temperature incubation and not always related to the presence of haemolytic genes.
González-Serrano
C J
CJ
Department of Food Hygiene and Food Technology, Veterinary Faculty, University of León, León, Spain.
Santos
J A
JA
García-López
M L
ML
Otero
A
A
D000333:Aeromonas / Q000145:classification / Q000302:isolation & purification / Q000472:pathogenicity*; D016980:Aeromonas hydrophila / Q000302:isolation & purification / Q000472:pathogenicity; D000818:Animals; D000833:Animals, Suckling; D001426:Bacterial Proteins / Q000633:toxicity; D001427:Bacterial Toxins / Q000633:toxicity; D002522:Chlorocebus aethiops; D003967:Diarrhea / Q000382:microbiology*; D017859:Esocidae / Q000382:microbiology*; D005393:Fish Diseases / Q000382:microbiology*; D005618:Fresh Water; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology* / Q000662:veterinary; D006460:Hemolysin Proteins / Q000633:toxicity; D006801:Humans; D051379:Mice; D017686:Oncorhynchus mykiss / Q000382:microbiology*; D052899:Pore Forming Cytotoxic Proteins; D013696:Temperature; D018675:Toxicity Tests; D014709:Vero Cells; D014774:Virulence
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D052899:Pore Forming Cytotoxic Proteins; C032676:aerolysin