Previous laboratory studies have implicated triclosan as a possible selective force driving resistance to multiple antibiotics and have identified a number of triclosan resistance mechanisms in Salmonella enterica. The aim of this work was to determine the prevalence of decreased susceptibility to triclosan in a panel of human and animal isolates of S. enterica and to identify the mechanisms of triclosan resistance in these strains. Over 400 animal and human isolates of non-typhoidal Salmonella were screened for decreased susceptibility to triclosan and a panel of antibiotics. The prevalence of decreased susceptibility to triclosan was ca. 4%. Of the isolates with decreased triclosan susceptibility, 56% were multidrug-resistant (MDR) compared with 12% of triclosan-sensitive isolates. MDR and triclosan-resistant strains showed increased efflux activity compared with strains with reduced susceptibility to triclosan alone. No high-level triclosan resistance was seen in this panel of isolates. A reservoir of strains with low-level decreased triclosan susceptibility is present in animals and humans. These isolates are MDR as a result of generic mechanisms of antimicrobial resistance and do not carry specific mutations within fabI.
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