Antimicrobial resistance of Listeria monocytogenes isolated from seafood and humans in Iran

Fourteen Listeria monocytogenes isolates previously collected from seafood (n = 7) and human patients (n = 7) were studied
for their antimicrobial susceptibility against eight common antimicrobials (ampicillin, penicillin, gentamicin, streptomycin,
tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, and cefotaxime). A high resistance level to ampicillin,
cefotaxime (100%), and pencillin (57% in seafood isolates and 71.4% in clinical isolates) was observed in this
study. However, all of the isolates were susceptible to trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline.
Simultaneous resistance was identified in 4 clinical isolates (57.1%). Genotypic characterization of fish isolates (isolated
from three fish species) was performed by pulsed-field gel electrophoresis (PFGE). A high diversity among fish isolates
was observed. PFGE analyses distinguished the 4 isolates into 4 reproducible pulsotypes. There was no correlation between
the antibiograms with pulsotypes. In conclusion, the resistance of seafood isolates to the antibiotics commonly
used to treat listeriosis could be a potential health hazard for consumers