Characterization of serratia-marcescens strains surviving in disinfecting footbaths

Sammendrag

Aim:
To determine if disinfecting footbaths in food industry were contaminated with bacteria and characterise some of the bacteria present.

Methods and results:
Bacterial strains were isolated from disinfecting footbaths containing TEGO 103G (amphoteric disinfectant) or TP-99 (alkylaminoacetate-based disinfectant) in five out of six dairy factories. Fourteen strains identified as Cedecea spp. by their fatty acid composition were further characterised. The reactions in the Rapid ID 32 E API analysis and 16S-rDNA-sequensing showed that all strains were Serratia marcescens. In contrary to Ser. marcescens ATCC 13880 the isolates from disinfecting footbaths were not killed (<5 log reduction) by the recommended in-use concentration of TEGO 103G, TEGO 51 or benzalkonium chloride. Survival and multiplication in tap water with in-use concentration of TEGO 103G was demonstrated for one of the strains. All strains were killed by the in-use concentrations of commercial disinfectants based on peracetic acid, hypochlorite, quaternary ammonium compounds and alkyl aminoacetate (TP-99). There were no indications of cross-resistance between disinfectants and antibiotics.

Conclusion:
Serratia marcescens may survive and multiply in disinfecting footbaths containing TEGO 103G or alkylaminoacetate due to disinfectant resistance.

Significance and impact of the study:
Disinfecting footbaths may act as contamination sources in food factories and they should not be used without regular hygienic monitoring.