Morphological and physiological changes of Staphylococcus aureus exposed to hypochlorous acid

To characterize hypochlorous acid (HOCl) stress resistance of Staphylococcus aureus and to assess physiological state and changes in cell morphology.

Clinical wild-type strain of S. aureus was used in the stress with HOCl at concentrations ranging from 0 to 4 mg l(-1). Concentrations below 1.5 mg l(-1) caused no significant drop in viability. During 2 h of HOCl stress at 2 mg l(-1), there was appearance of minicells capable of passing through the 0.45 microm pores of filtration membranes. Intracellular proteins increased gradually to reach a level of 51% of dry weight and an enhanced synthesis of at least two proteins of 23 and 220 kDa was concluded.

Staphylococcus aureus can undergo morphological and physiological changes during 2 h of exposure to 2 mg l(-1) of HOCl, which represents an adaptative response towards the hypochlorous acid stress. This evolution limits the use of 0.45 microm pores size membrane filters for research on S. aureus in waters and the clinical environment.