Prevalence and antibiotic resistance of <i>Aeromonas hydrophila</i> and <i>Staphylococcus aureus</i> isolated from seafood in Egypt

Abstract

Objective: To investigate prevalence of Aeromonas. hydrophila and Staphylococcus aureus in seafood, and to detect the consistent  virulence genes as well as to assess the antimicrobial susceptibility.

Design: Observational study.
Samples: 280 marketed seafood samples (178 shrimp, 54 oysters, 26 crabs, 18 squid, and 4 octopuses).

Procedures: Isolation and identification of Aeromonas hydrophila and Staphylococcus aureus were performed using conventional  methods. The identified isolates were examined for virulence genes (aer and hly genes for A. hydrophila as well as nuc and sea genes for  S. aureus) as well as for antimicrobial susceptibility.

Results: A. hydrophila was isolated from 40 of the 280 seafood samples (14.3%), with  the highest prevalence (22.2%) in oyster samples, whereas S. aureus occurred in 50 samples (17.9%) with the highest prevalence (20.2%)  in shrimp samples. Moreover, aer and hly genes were detected in all isolates of A. hydrophila, and thermonuclease (nuc) gene was  detected in all tested S. aureus strains, whereas staphylococcal enterotoxin A (sea) gene was found in only 44% of S. aureus strains. A.  hydrophila strains were absolutely resistant to amoxicillin (100%), followed by ceftriaxone (80%), chloramphenicol (77.5%), trimethoprim- sulfamethoxazole (65%), and tetracycline (55%), whereas S. aureus strains showed high resistance to penicillin (86%), followed by  amoxicillin-clavulanic acid (72%), and trimethoprimsulfamethoxazole (58%). Multidrug resistance (MDR) to more than two classes of  antibiotics was found in 77.5% (31/40) of A. hydrophila strains and 66% (28/50) of S. aureus isolates.

Conclusion and clinical relevance:  Our data highlights the importance of awareness of virulent strains of MDR A. hydrophila and S. aureus strains of seafood samples in  Egypt. Consequently, the continuous surveillance of these bacteria in seafood with a strong focus on their antibiotic resistance  characteristics should be considered in further studies.