The usefulness of molecular techniques to assess the presence of Aeromonas spp. harboring virulence markers in foods.
A total of 78 raw and 123 processed and ready-to-eat retail food samples were used to assess the presence of motile Aeromonas spp. harboring virulence genes (cytotoxic enterotoxin and hemolysin genes) using a recently described PCR method in comparison with the conventional cultivation method based on the use of Ampicillin-Dextrin Agar (ADA) medium. With the ADA-based method, 65/201 (32.3%) samples showed presumptive Aeromonas spp. colonies whereas the PCR method revealed the presence of Aeromonas spp. harboring the targeted virulence genes in 51/201 (25.4%) of the tested samples. The rate of contaminated samples and the presence of pathogenic Aeromonas were significantly lower with both methods for processed than in case of raw samples. A polyphasic identification approach including biochemical and molecular techniques was applied to a selection of 34 PCR-positive presumptive Aeromonas isolates. Following fatty acid methyl ester (FAME) analysis and amplified fragment length polymorphism (AFLP) fingerprinting, a total of 33 isolates (97%) could be identified to the DNA hybridization group (HG) level. The majority of these isolates belonged to the species Aeromonas hydrophila HG3 (50%) and Aeromonas veronii biovar sobria (HG8/10) (38%). Molecular characterization of PCR amplicons obtained from these strains by PCR-Restriction Fragment Length Polymorphism (PCR-RFLP) fingerprinting and PCR-Amplicon Sequence Analysis (PCR-ASA) allowed classification of all strains in a known PCR-RFLP and PCR-ASA type. In conclusion, the current findings demonstrate that the combined use of PCR-based virulence marker detection, PCR-RFLP and PCR-ASA offers a rapid, sensitive, and specific system to assess the presence and prevalence of Aeromonas spp. harboring virulence markers in food samples.
Bin Kingombe
César I
CI
Department of Microbiology, Swiss Federal Veterinary Office, Scharzernburgstrasse 161, CH-3003 Liebefeld-Bern, Switzerland. ckingomb@hc-sc.gc.ca
Huys
Geert
G
Howald
Denise
D
Luthi
Elisabeth
E
Swings
Jean
J
Jemmi
Thomas
T
D000333:Aeromonas / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity*; D001427:Bacterial Toxins / Q000235:genetics; D015169:Colony Count, Microbial; D016172:DNA Fingerprinting; D004269:DNA, Bacterial; D005504:Food Analysis; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D012680:Sensitivity and Specificity; D014774:Virulence / Q000235:genetics
D001427:Bacterial Toxins; D004269:DNA, Bacterial