[Preparation and properties of chlorination-damaged P. aeruginosa suspensions]

The preparation of suspensions of bacterial cells impaired by the action of chlorine require a very accurate standardization of all the procedural detail of controlled experimental impairment by chlorine. All measures suitable to spread the kinetics of reduction of bacterial numbers in time will facilitate the reproducibility of results. The exact amount of hypochlorite--determined experimentally prior to the actual test--is transformed to chloramine at 0 degrees C then a defined quantity of bacteria is added. After different periods of contact samples are taken and stabilized by adding thiosulphate of sodium. When the bactericidal action is not abrupt but sufficiently drawn out a relatively high proportion of bacteria impaired by chlorine but still viable is obtained (50-90%). In suspension the proportion remains relatively stable during storage in the refrigerator (4 degrees -6 degrees C). Resuscitation experiments carried out with suspensions of organisms damaged as explained above showed resuscitation times of 3 h in casein soy broth not to grow as well as those after 24 h of resuscitation. Obviously the process of reparation after impairment by chlorine must be assumed to be relatively slow under these conditions.