Antibiotic challenge of meat starter cultures and effects upon fermentations

Abstract

The principal bacterial strains present in 10 different commercial meat starter cultures were isolated and identified. These 22 strains (pediococci, lactobacilli and staphylococci) were examined for their sensitivity to a group of 21 antibiotics in solid and liquid media. Minimum inhibitory concentrations (MIC) of antibiotics were calculated and a select group was used at 1 2 , 1,2 and 5 times their MIC in broth media amended by glucose, salt and nitrite addition to study effects upon fermentation rate by the reconstituted starter culture mixtures. Four antibiotics often used in clinical therapy of large domestic animals were used in meat fermentations at 28 °C to evaluate their ability to inhibit the fermentation process. Patterns of antibiotic susceptibility of the lactic acid bacteria were consistent with those seen for similar organisms isolated from different environments. Pediococcus pentosaceus and the lactobacilli were more resistant to antibiotic challenge than P.acidilactici. Staphylococci were most sensitive to the antibiotics tested. The lactic acid bacteria were resistant to sulfa drugs, vancomycin, dihydrostreptomycin and synergistin, were fairly resistant to carbadox, but showed substantial sensitivity to erythromycin, β-lactams, the tetracyclines, clindamycin, excenel, lincomycin, bacitracin, tylosin tartrate, and virginiamycin. Erythromycin, penicillin G, tylosin tartrate and excenel were evaluated for their ability to affect fermentation performance and growth of the mixed starter cultures in a dry sausage meat formulation. These antibiotics at concentrations ≥0.125μgg −1, ≥2 IUg −1, ≥0.5μgg −1 and ≥4μgg −1, respectively, negatively influenced fermentations. It is suggested that these concentrations may be used as targets for development of rapid tests for detection of residue levels that could inhibit starter culture performance in meat.