Selection of Microbial Population in Chlortetracycline-treated Ocean Perch ( Sebastodes alutus )

Microorganisms isolated from chlortetracycline (CTC)-treated ocean perch were individually tested to determine their relative sensitivity to CTC by use of CTC-impregnated paper discs. The CTC sensitivity varied among isolates obtained from untreated fish. The proportion of CTC-resistant species increased with higher CTC concentration and the length of storage at 7 C. Among individual generic groups, “coryneforms” and yeasts were more resistant to CTC than other groups.Pseudomonas, Achromobacter, Flavobacterium, Bacillus , andLactobacillus all contained species either resistant or sensitive to CTC. More CTC-resistant species in these genera accumulated with the increased CTC concentrations and with the length of storage in the presence of CTC.