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Nine phages of coagulase-negative staphylococci were studied carefully with regard to their electron microscopic morphology. Two different groups of phages were detected: the larger phages showed heads of 121 nm diameter on average and tails with 229 nm length and 23 nm width. The smaller phages were characterized with heads of about 76 nm diameter and tails of about 177 nm length and 13 nm width (negatively stained with KPT).

Selected 22 phages of coagulase-negative staphylococci were tested against group-specific antisera for Staphylococcus aureus phages using a neutralization test. Fourteen of the tested phages were classified into the serological group B and one into the group F. All other phages were resistant to the antisera against S. aureus phages but cross-reacted with the antisera produced against themselves. Therefore they could be joined together into a new serological group of the staphylococcal phages.

Our phage-set, published in 1975 (6) was modified in that other staphylococcal hoststrains were found more suitable for the propagation. This new typing set of 15 phages should replace our old phage-sets. In comparing the phage-sets of Dr. Verhoef, Dr. Parisi and Dr. Blouse with our phages, the advantages of our new phage-set could be demonstrated. Lysogeny induction experiment with mitomycin C and UV-rays showed all staphylococcal host strains to be lysogenic. Conclusions of the studies performed were derived from and discussed.

Concerning the chemical induction of lysogeny of Staphylococcus aureus only little is known. Therefore, we performed induction experiments on 43 Staph, aureus strains using nine mutagenic substances and 15 chemotherapeutics. Only three of the nine mutagenic substances (beta-propiolacton, nitrosoguanidin and mitomycin C) and six of the 15 chemotherapeutics (penicillin G, ampicillin, cephalothin, nebacetin, novobiocin and nalidixie acid) showed inducing effects. Our results demonstrated furtheron that the lysogeny inducing ability is dependent on strains and substances used.

A modification of the "one-plate method" for detection of staphylococcal hemolysins has been described. Bacterial strains of Staphylococcus aureus, Streptococcus agalactiae and Cornebacterium pseudotuberculosis were replaced by their prepurified hemolytically active exosubstances: beta-toxin, CAMP-factor, and, the exosubstance of Corynebacterium pseudotuberculosis called COREX. By means of the modification described, exact detection of hemolysins in possible with staphylococcal strains producing one type of hemolysin as well as with strains producing a combination of hemolysins.