| Abstract: | 
                    
                        
                         Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic bacterium that is widely distributed in 
aquatic environments and causes major economic losses in fish and public health hazards.This study 
aimed to identify the occurrence of P. aeruginosa in samples collected from fish and fish handlers, 
and to investigate the antimicrobial susceptibility, virulence determinants, and biofilm genes of P. 
aeruginosa isolates. A total of 276 samples were cross-sectionally collected from Nile tilapia (53), 
Golden grey mullet (52), Mediterranean horse mackerel (50), Striped red mullet (71), and fish handlers 
(50) at five different retail fish markets in Damietta Governorate, Egypt. Pseudomonas species (spp.) 
were biochemically identified in 57.9% of the total examined samples. Peudomonas aeruginosa were 
the most prevalent species isolated from the fish and human samples via PCR technique. Peudomonas 
aeruginosa isolates exhibited full resistance (100%) to tobramycin (TOB), gentamicin (CN), and colistin 
(CL), with a high level of susceptibility (88.5%) to imipenem (IPM) using the disk diffusion method. 
Most P. aeruginosa isolates (84.6%) exhibited drug resistance, with 61.5% were multidrug resistance 
(MDR) and 23.1% were extensive drug resistance (XDR). Most isolates had at least four virulenceassociated genes (lasB, toxA, exoU, and oprL) and three biofilm genes (psIA, peIA, and lasR) by using 
uniplex PCR. The lasI, and rhlR Quorum Sensing (QS) genes were identified in 84.6% and 61.5% in the 
examined P. aeruginosa isolates, respectively. The highest mortality rate in Nile tilapia experimentally 
infected with P. aeruginosa isolate encoding most of virulent genes. Multivariate analyses revealed 
high heterogeneity among the examined isolates. This study revealed the emergence of virulent 
and drug resistant P. aeruginosa isolates in fish, poses high risks to consumers and food. Thus, strict 
hygienic measures should be considered when catching, handling, and storing fish, in addition to the 
routine application of antimicrobial susceptibility testing. 
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