Lysogenic Conversion of Staphylococci to Loss of -Toxin

Abstract

SUMMARY Staphylococci may produce β-toxin and staphylokinase (fibrinolysin). In clinical material there is a preponderance of strains which are β-toxin negative and kinase positive (β –K+), but β +K–, β –K– and β +K+ strains also occur. Strains which are β +K– can be converted by lysogenization with certain phages to loss of β-toxin and gain of kinase (β –K+). This is true conversion, since every lysogenized coccus carries the new characters. All the phages which produced this double conversion (β –K+ phages) belong to the serological group F. The conversion is due to two separate loci on the phage which are active in the prophage state. These loci have not been found in phages of other serological groups (β 0K0 phages). The β-toxic and fibrinolytic properties of staphylococci are not always phage-dependent; strains which do not carry detectable phages or carry only β 0K0 phages can be either β +K–, β –K+, β +K+ or β –K–, implying the occurrence of structural loci on the bacterial genome. Several strains with the phage-typing pattern 80/81 or a related pattern, which are β –K+, were found to carry converting phages. On loss of these phages the strains became β +K–. and showed a change of typing-pattern, gaining sensitivity for phages of group III.