Antibiotic resistance in bacteria isolated from fish in Serbia

Abstract

Introduction. Bacteria isolated from skin, gills, and fish intestines from aquaculture ponds, ornamental fish stores/aquariums and live fish markets were investigated.

Materials and Methods. Disk diffusion and E-test were used for susceptibility testing to carbapenems, ureidopenicillins with or without ß-lactamase inhibitor, 3^rd and 4^th generation cefalosporins, aminoglycosides, colistin, fluoroquinolones, and chloramphenicol. PCR was used to detect resistance genes in the bacterial isolates.

Results and Conclusions. Among the total number of bacteria tested, regardless of the genus and species, 56.7% of isolates were found to be sensitive to all antibiotics, 23.1% of isolates were resistant to one or two antibiotics, and 20.2% of isolates were resistant to three and up to 16 antibiotics. In A. hydrophila isolated from a guppy (Poecilia reticulata) sampled in an ornamental fish store aquarium, 16S rRNA methyltransferase was confirmed by finding the rmtB gene. Pseudomonas isolates showing phenotypic resistance to carbapenems, ureidopenicillins with or without ß-lactamase inhibitor and 3^rd and 4th generation cephalosporins were tested and found negative for different resistance genes by PCR (MßL, ESBL, KPC, OXA-23, OXA-24, OXA-40, OXA-58, VIM, IMP, SPM, GIM, NDM, TEM, SHV, CTX-M-1, CTX-M-9, OXA-1, OXA-9 and the AmpC group, as well as single genes, MOXM, CITM, ACCM, EBCM, FOXM, DHAM). Based on E-test results, three Pseudomonas isolates from common carp (Cyprinus carpio) were found to be resistant to colistin with MIC values of 4  μg/mL.