Aims: To investigate the susceptibility of 221 Listeria spp. (86 Listeria monocytogenes, 41 Listeria innocua and 94 Listeria seeligeri‐Listeria welshimeri‐Listeria ivanovii) isolated from catfish fillets and processing environment to 15 antibiotics.
Methods and Results: Listeria isolates were analysed by disc‐diffusion assay for their resistance to 15 drugs. All isolates were resistant to cefotaxime and clindamycin but were sensitive to ampicillin, cephalothin, chloramphenicol, erythromycin, gentamycin, kanamycin, rifampin, streptomycin, sulfamethoxazole/trimethoprim and vancomycin. Unlike L. monocytogenes and L. seeligeri‐L. welshimeri‐L. ivanovii isolates, 22% of L. innocua isolates displayed tetracycline/oxytetracycline resistance. Screening of tet genes by PCR identified tet(M) gene in the chromosome of all tetracycline/oxytetracycline‐resistant L. innocua. However, this gene was not associated with the integrase gene of Tn1545. Repetitive extragenic palindromic‐ and enterobacterial repetitive intergenic consensus‐PCR typing methods showed no genotype‐specific tetracycline resistance in the tet(M)‐positive strains.
Conclusions: Catfish fillets and processing environment were currently free of L. monocytogenes resistant to antibiotics commonly used in human listeriosis treatment. However, the presence of tet(M) gene in L. innocua raises the possibility of future acquisition of resistance by L. monocytogenes.
Significance and Impact of the Study: These data will be helpful in improving background data on antibiotics resistance strains isolated from food and processing environment.
Use of an agglomerated phosphate blend with a high pH (AGSP) maximized the yield of catfish fillets that were marinated through multineedle injection. In addition, STP and agglomerated phosphate blends increased the yield and tenderness of catfish fillets when compared to the nonmarinated control.
Hybrid striped bass (HSB) strips were dipped in chlorine or distilled water and packaged in 60% CO*, 6% Oa, and 34% N2 (MAP) or in AIR. APC reached lo* CFU/g after 4 days for AIR and 10 days for MAP fish. Sensory panelists detected a whiter color flesh in fish treated with chlorine. Hypoxanthine increased while IMP decreased and ADP and ATP did not change throughout. If inosine was excluded in the predictor, a modified K value (K*) could be applicable as a freshness indicator of freshwater HSB but storage environment should be specified. K* values correlated highly with APC for AIR (R2 = 0.84) and MAP packs (R* = 0.85).
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