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Molecular and Phenotypic Analysis of Hemolytic Aeromonas Strains Isolated from Food in Egypt Revealed Clinically Important Multidrug Resistance and Virulence Profiles

Hammad, Ahmed M., Moustafa, Alaa-Eldin H., Mansour, Maha M., Fahmy, Bashier M., Hamada, Mohamed G., Shimamoto, Toshi, Shimamoto, Tadashi
Journal of food protection 2018 v.81 no.6 pp. 1015-1021
Aeromonas, aztreonam, beta-lactamase, cephalosporins, cheeses, diarrhea, fish, food contamination, genes, hemolysins, imipenem, milk, multiple drug resistance, phenotype, prediction, public health, raw milk, risk, screening, virulence, Egypt
The aim of this study was to determine the public health significance of hemolytic Aeromonas species isolated from 213 food samples in Egypt, based on their virulence and antimicrobial-resistance potential. We recovered 63 strains, isolated from fish, raw milk, karish cheeses, and ras cheese in 29 (31.18%) of 93, 10 (25.00%) of 40, 13 (32.50%) of 40, and 11 (27.50%) of 40 samples, respectively. The most prevalent virulence gene was alt (50.79%), followed by aerA (34.92%), asa1 (39.68%), ahh1 (20.63%), act (11.11%), and ast (3.17%). Thirteen strains screened in this study carried no hemolysin gene, but only the alt gene, and another eight hemolytic strains screened, carried no virulence gene. The virulence signatures “ahh1+aerA” and “alt+act,” in which the genes interact synergistically to induce severe diarrhea, were detected in two and four strains, respectively. Most showed resistance to third-generation cephalosporins, aztreonam, and imipenem, which indicates the complexity of the β-lactamase production in our hemolytic Aeromonas strains. Fourteen (22.22%) of 63 strains carried one or more antimicrobial-resistance markers, including the blaCTX-M, blaTEM, tet(A), tet(E), and intI1 genes, which were detected in 6.34, 3.17, 3.17, 4.76, and 14.28% of isolates, respectively. In conclusion, the majority of hemolytic Aeromonas strains isolated from the intestinal contents of healthy fish and naturally contaminated milk and cheeses were not commensal but had developed multidrug-resistance and virulence profiles, indicating an emerging potential health risk. Importantly, screening for certain hemolysin genes may not be reliable in predicting the pathogenic potential of Aeromonas species and, thereby, the safety of analyzed foods. Our findings indicate that specific criteria are required for the phenotypic and molecular analysis of Aeromonas species in food items, particularly those eaten without further treatment, to ensure their safety.