Abstract
Background:
The bacterial load in fresh and frozen fish is a major public health concern.

Aim:
This study aimed to determine the prevalence of human pathogenic foodborne bacteria and their antibioticresistance profiles in fresh and frozen chub mackerel (Scomber japonicus) fish.

Methods:
A total of 60 samples of fresh and imported frozen chub mackerel (Scomber japonicus) were randomly collected from anglers on boats in the Bab-Albahr market in Tripoli, Libya. Bacterial isolation from muscles was performed using a suitable culture media. Biochemical identification of the isolated bacteria was performed using the API 20E and its antibiogram.

Results:
The total number of bacterial isolates from 30 fresh samples was 53, and from 30 imported frozen samples was 26. The most frequently occurring species in fresh fish were Vibrio cholera (32%), Proteus mirabilis (26.4%), Vibrio alginolyticus (22.6%), and Escherichia coli (18.8%), while in frozen fish were E. coli (50%), Citrobacter freund (23.07%), Klebsiella pneumoniae (15.3%), and V. alginolyticus (11.5%). The isolates exhibited high resistance to β-lactam antibiotics.

Conclusion:
The microbial assessment of chub mackerel (Scomber japonicus) provides insights into the sanitary conditions along the Tripoli coast. In addition, the results of the present study indicate that imported frozen fish sold in Tripoli’s fish markets could pose a public health threat. This research is considered a preliminary microbial assessment of S. japonicus contamination in the Tripoli market and along the Tripoli Coast. The incidence of S. aureus infections emphasized the presence of an issue in husbandry practices, insufficient adherence to basic hygiene protocols, and the random use of antibiotics.

Key words: Phylogenetic analysis tree, S. aureus, Sheep milk, Virulence factors