Detection of extended spectrum beta-lactamase Escherichia coli and histamine contents in raw mackerel (Scomber japonicus) sold in open markets in Sagamu, Nigeria.

Abstract

Background: A food borne sickness called histamine fish poisoning is frequently brought on by eating some fish species that have high levels of histamine and other biogenic amines in their tissues. When fish is improperly stored and preserved, its natural makeup makes it polluted. Objectives: This study was carried out to examine the histamine contents, determine the extended spectrum beta-lactamase producing isolates of Escherichia coli from the gut of raw mackerel fish obtained in Sagamu markets and relate the plasmid isolated, if present, with Extended Spectrum Beta Lactamase (ESBL). Materials and Methods: Fifty (50) mackerel fish were dissected and their guts were removed for the isolation of E. coli on eosin methylene blue agar medium. The isolates obtained were Gram stained, biochemically characterized, and thereafter plated on Mueller Hinton agar impregnated with ESBL discs by double disc synergy methods. Ten gram (10 g) of each part of fish weighing 100 g was blended for histamine determination by spectrophotometry and plasmid analysis of some selected ESBL resistance amongst the isolates were determined. Results: Escherichia coli were found in all fifty mackerel fish and 31 (62%) of those were ESBL producers. All of these were plasmid-free. In 14 (28%) of the 50 fish analysed, histamine concentrations of more than 100mg/100g exceeded the tolerance threshold of 10mg/100g. Conclusion: The results from the study showed that some of the fish sold in the markets of Sagamu contain ESBL producing Escherichia coli which may be considered as reservoirs for resistant bacteria. Significant level of histamine recorded surpassed histamine tolerance level in fish for human consumption. There is a need to provide storage facilities and raise hygiene awareness in markets where fish is sold.