Emergence of β-lactamase- and carbapenemase- producing Enterobacteriaceae at integrated fish farms

Samples were collected from fish, fishpond water inlets, tap water, outlet water, and workers at sites of integrated agriculture-aquacultures. Samples were also taken from inhabitants of the aquaculture surrounding areas. All samples were cultured on MacConkey agar, the Enterobacteriaceae isolates were tested for susceptibility to cephalosporins and carbapenems, and screened for bla_CTX-M-15, bla_SHV, bla_OXA-1, bla_TEM, bla_PER-1, bla_KPC, bla_OXA-48, and bla_NDM. Strains having similar resistance phenotype and genotype were examined for the presence of Incompatible (Inc) plasmids.

A major proportion of the Enterobacteriaceae isolates were resistant to cephalosporins and carbapenems. Among the 66 isolates from fish, 34 were resistant to both cephalosporin and carbapenem groups, 26 to carbapenems alone, and 4 to cephalosporins alone. Of the 15 isolates from fishpond water inlets, 8 showed resistance to both groups, 1 to carbapenems alone, and 5 to cephalosporins alone. Out of the 33 isolates from tap water, 17 were resistant to both groups, and 16 to cephalosporins alone. Similarly, of the 16 outlet water isolates, 10 were resistant to both groups, and 6 to cephalosporins alone. Furthermore, of the 30 examined workers, 15 carried Enterobacteriaceae resistant strains, 10 to both groups, and 5 to cephalosporins alone. Similar strains were isolated from the inhabitants of the aquaculture surrounding areas. Irrespective of source of samples, strains resistant to all examined antibiotics, carried predominantly the carbapenemase gene bla_KPC either alone or with the β-lactamase genes (bla_CTX-M-15, bla_SHV, bla_TEM, and bla_PER-1). The isolates from fish, water, and workers harboured a wide-range of multi-drug-resistance Inc. plasmids, which were similar among all isolates.