Antibiotic Resistance, Virulence Gene Detection, and Biofilm Formation in Aeromonas spp. Isolated from Fish and Humans in Egypt

SIMPLE SUMMARY: Despite significant advancements in food safety and cleanliness, there is still a risk of food supply chain contamination. Fish are susceptible to infection from bacterial pathogens, especially Aeromonas spp. Aeromonas spp. are dangerous to people because they can spread illnesses like septic arthritis, gastroenteritis with diarrhea, skin and soft tissue infections, meningitis, and bacteremia through the consumption of infected fish. Therefore, the present study was conducted to detect the prevalence of, antibiotic resistance, virulence, and biofilm formation by Aeromonas spp. in raw fish markets and humans in Zagazig, Egypt. In the current study, 11 isolates were confirmed as Aeromonas spp. and 4 isolates were confirmed as Aeromonas hydrophila using biochemical PCR assays. In addition, the antimicrobial resistance profile of the Aeromonas isolates was tested against 16 antibiotics, the result of which indicates the susceptibility of all isolates to imipenem followed by chloramphenicol, and a high multiple antibiotic resistance (MAR) index range between 0.142–0.642 was detected. In addition, it was illustrated that two isolates of the four identified A. hydrophila isolates were positive for the aer gene and that one isolate only had the hly gene. Additionally, biofilm formation was detected in two isolates from tilapia muscles and mugil viscera. Based on the information provided, control measures might be implemented to stop the high-risk contamination of a specific area and protect individuals from multidrug-resistant strains that might be transmitted through the food chain or incorrect handling. ABSTRACT: The genus Aeromonas is widely distributed in aquatic environments and is recognized as a potential human pathogen. Some Aeromonas species are able to cause a wide spectrum of diseases, mainly gastroenteritis, skin and soft-tissue infections, bacteremia, and sepsis. The aim of the current study was to determine the prevalence of Aeromonas spp. in raw fish markets and humans in Zagazig, Egypt; identify the factors that contribute to virulence; determine the isolates’ profile of antibiotic resistance; and to elucidate the ability of Aeromonas spp. to form biofilms. The examined samples included fish tissues and organs from tilapia (Oreochromis niloticus, n = 160) and mugil (Mugil cephalus, n = 105), and human skin swabs (n = 51) and fecal samples (n = 27). Based on biochemical and PCR assays, 11 isolates (3.2%) were confirmed as Aeromonas spp. and four isolates (1.2%) were confirmed as A. hydrophila. The virulence genes including haemolysin (hyl A) and aerolysin (aer) were detected using PCR in A. hydrophila in percentages of 25% and 50%, respectively. The antimicrobial resistance of Aeromonas spp. was assessed against 14 antibiotics comprising six classes. The resistance to cefixime (81.8%) and tobramycin (45.4%) was observed. The multiple antibiotic resistance (MAR) index ranged between 0.142–0.642 with 64.2% of the isolates having MAR values equal to 0.642. Biofilm formation capacity was assessed using a microtiter plate assay, and two isolates (18.1%) were classified as biofilm producers. This study establishes a baseline for monitoring and controlling the multidrug-resistant Aeromonas spp. and especially A. hydrophila in marine foods consumed in our country to protect humans and animals.