Factors affecting the inactivation of a bacterial virus by chemical antimicrobial agents

The course of the chemical inactivation of coliphage T6r was followed by a standardised plaque counting technique.The antimicrobial agents used were cetrimide, chloramine, formaldehyde and phenol.Dilution of the reaction mixture was used to prevent the residual virus inhibitory effect of phenol, while the residual action of the other three compounds was stopped by the use of suitable neutralising agents.The effects on the kinetics of inactivation of concentration of antimicrobial agent and of temperature were examined to compare the agents tested.The concentration exponent and temperature coefficient of chloramine and formaldehyde were alike but were different from both cetrimide and phenol.The course of inactivation was influenced more by the medium in which the phage was suspended than the medium in which it was cultivated.The effect of the presence of various extraneous materials in the reaction mixture was also investigated.In general the presence of extraneous matter reduced the activity of cetrimide, chloramine and phenol, whilst the activity of formaldehyde appeared to be enhanced.The stability of pha;e surviving inactivation from reaction mixtures containing peptone was examined.In the presence of peptone, formaldehyde inactivation seemed partly reversible.This phenomena was not observed with the other agents tested.Comparison with previously postulated modes of action of these antimicrobial agents suggests that formaldehyde inactivates the phage by damaging a portion of the tail structure.The other agents were thought to affect the other protein components of the phage.The action of chloramine was attributed to denaturation of the protein shell with the subsequent loss of DNA.The action of cetrimide may be due to lysis of the phage proteins and it is likely that phenol has a similar mode of action.ACITDVLEDGETTNTS I am deeply grateful to Dr. W. R. L. Brown for suggesting the topic studied and I appreciate the way he