Detection of Extended-Spectrum β-Lactamases (ESBL) Producing Enterobacteriaceae from Fish Trapped in the Lagoon Area of Bizerte, Tunisia

Extended-spectrum β-lactamase and their molecular mechanism in Enterobacteriaceae were analyzed in 126 fish samples of 9 various wild species, living in the lagoon of Bizerte in Tunisia. Fifty-nine (59) Gram-negative strains were isolated and identified as Escherichia coli (n = 24), Klebsiella pneumonia (n = 21), Citrobacter freundii (n = 8), and Shigella boydii (n = 6). Forty-seven ESBL producers were identified using the synergic test. β-Lactamase genes detected were bla(CTX-M-1) (E. coli/15; K. pneumonia/8; C. freundii/1; Sh. boydii/1), bla(CTX-M-1)+ bla(OXA-1) (E. coli/4; K. pneumonia/3), bla(CTX-M-1)+ bla(TEM-1-a) (K. pneumonia/2), bla(CTX-M-15)+ bla(TEM-1-a) (K. pneumonia/1; Sh. boydii/1), bla(CTX-M-15)+ bla(OXA-1) (K. pneumonia/1), bla(CTX-M-15) (E. coli/3; K. pneumonia/1; Sh. boydii/3), and bla(CTX-M-9) (C. freundii/3). Most strains (84.7%) showed a multiresistant phenotype. qnrA and qnrB genes were identified in six E. coli and in ten E. coli+one K. pneumonia isolates, respectively. The resistance to tetracycline and sulfonamide was conferred by the tet and sul genes. Characterization of phylogenic groups in E. coli isolates revealed phylogroups D (n = 20 strains), B2 (n = 2), and A (n = 2). The studied virulence factor showed prevalence of fimA genes in 9 E. coli isolates (37.5%). Similarly, no strain revealed the three other virulence factors tested (eae, aer, and cnf1). Our findings confirmed that the lagoons of Bizerte may be a reservoir of multidrug resistance/ESBL-producing Enterobacteriaceae. This could lead to indisputable impacts on human and animal health, through the food chain.