Inhibiting plasmid mobility: the effect of isothiocyanates on bacterial conjugation.

Bacterial conjugation is the main mechanism for the transfer of multiple antibiotic resistance genes among pathogenic microorganisms. This process could be controlled by compounds that inhibit bacterial conjugation. In this study, the effect of allyl isothiocyanate, L-sulforaphane, benzyl isothiocyanate, phenylethyl isothiocyanate and 4-methoxyphenyl isothiocyanate on the conjugation of broad host range plasmids, which harbor various resistance genes in Escherichia coli were investigated; pKM101 (IncN), TP114 (IncI2 ), pUB307 (IncP) and the low copy number IncW plasmid R7K. Benzyl isothiocyanate (32 mg/L) significantly reduced the conjugal transfer of pKM101, TP114 and pUB307 to 0.3±0.6%, 10.7±3.3% and 6.5±1.0%, respectively. L-sulforaphane (16 mg/L, transfer frequency 21.5±5.1%) and 4-methoxyphenyl isothiocyanate (100 mg/L, transfer frequency 5.2±2.8%) were the only compounds that showed anti-conjugal specificity by actively reducing the transfer of R7K and pUB307, respectively.