There is a growing concern by regulatory authorities for the selection of antibiotic resistance caused by
the use of biocidal products. We aimed to complete the detailed information on large surveys by investigating the
relationship between biocide and antibiotic susceptibility profiles of a large number of Staphylococcus aureus isolates
using four biocides and antibiotics commonly used in clinical practice. The minimal inhibitory concentration
(MIC) for most clinically-relevant antibiotics was determined according to the standardized methodology for over 1600 clinical S. aureus
isolates and compared to susceptibility profiles of benzalkonium chloride, chlorhexidine, triclosan, and sodium hypochlorite. The relationship
between antibiotic and biocide susceptibility profiles was evaluated using non-linear correlations.
The main outcome evidenced was an absence of any strong or moderate statistically significant correlation when susceptibilities of either
triclosan or sodium hypochlorite were compared for any of the tested antibiotics. On the other hand, correlation coefficients for MICs of
benzalkonium chloride and chlorhexidine were calculated above 0.4 for susceptibility to quinolones, beta-lactams, and also macrolides.
Our data do not support any selective pressure for association between biocides and antibiotics resistance and furthermore do not allow
for a defined risk evaluation for some of the compounds. Importantly, our data clearly indicate that there does not involve any risk of selection
for antibiotic resistance for the compounds triclosan and sodium hypochlorite. These data hence infer that biocide selection for antibiotic
resistance has had so far a less significant impact than feared.