RESISTANCE OF PSEUDOMONAS-AERUGINOSA PAO1 PHAGE F116 TO SODIUM-HYPOCHLORITE

The development of viral resistance to sodium hypochlorite was investi gated using the Pseudomonas aeruginosa bacteriophage F116 as a model s ystem. This phage was chosen because of its structural characteristics and former investigations conducted in this laboratory. F116 mas show n to be sensitive to a sodium hypochlorite concentration of 0.0075 g l (-1) (available chlorine) which produced a 5 log(10) reduction in titr e in a suspension test. Survival bacteriophages challenged with this s odium hypochlorite concentration were isolated, propagated and challen ged again with the same and higher concentrations of the biocide. It w as observed that progeny virions were becoming increasingly resistant to sodium hypochlorite challenges up to a concentration of 0.0175 g l( -1) of available chlorine. It was also noticed that 1-2 log(10) of F11 6 virions from resistant phage lysates remained sensitive to the bioci de. An electron microscopical investigation of F116 resistant lysates showed that the phage resistance to sodium hypochlorite was not caused by F116 particles aggregation. Furthermore, no morphological differen ce between the sensitive and resistant F116 particles to sodium hypoch lorite was identified.