Lysogenic conversion of the lipase in Staphylococcus pyogenes group 3 strains

Staphylococcus pyogenes PS54, the propagating strain of the group III staphylococcal typing phage 54, manifests no lipase activity on egg yolk medium. This strain was found to harbor at least two prophages. One of these, designated as L54a, was demonstrated to be capable of suppressing lipase production by lysogenic conversion of strains of Staphylococcus pyogenes previously manifesting lipase activity.Suspensions of typing phage 54 were also found to contain substrains of phage having the same conversion property, with respect to lipase activity, as L54a. These converting phages differed from L54a with respect to their ultrastructure and their lytic spectra. They may have arisen by means of recombination between non-converting typing phage 54 and the prophage L54a carried in the propagating strain of Staphylococcus.

Segregation o co-transduced streptomycin and tetracycline resistance in Staphylococcus aureus

Extrachromosomal streptomycin and tetracycline resistance in Staphylococcus aureus E169 has been transduced to three different recipients. An analysis of the transductants demonstrates that: (1) in most cases the behaviour of the markers in the transductants is similar to that in the donor; (2) the markers are co-transduced at frequencies of 2–44% and the frequency is highest when the selected marker is streptomycin resistance; (3) in the co-transductants the markers segregate independently, suggesting that they are unlinked.

Transduction of tetracycline resistance in Staphylococcus epidermidis

Fourteen Staphylococcus epidermidis strains were biotyped according to the scheme of Baird-Parker and tested for their sensitivities to S. epidermidis typing phages. Tetracycline-susceptible strains were tested for the capacity to be transduced to resistance. Five strains, all of biotype 1, were lysed by one or more phages. Five of eight biotype 1 strains were transduced to tetracycline resistance with rates of 10(-8) to 10(-5). Three strains of other biotypes were not transduced, nor was PS 73, an unusual coagulase-negative strain. The transducing phage phi367 was isolated from the lysogenic tetracycline-resistant donor strain. The phage morphologically resembles serological group B S. aureus phages. Restriction and modification were indicated from the efficiency of plating on phage-sensitive strains.

Genetic analysis of resistance to erythromycin and oleandomycin in Staphylococcus aureus

Strains U9(pase, tet, ery, nov) and U9(pase, tet, ol, nov) of Staphylococcus aureus were used as donors of the ery and ol markers, respectively, to strain 152. Thirty-three erythromycin-sensitive (ery-s) mutants of strain 152(ery) and 19 oleandomycin-sensitive (ol-s) mutants of strain 152(ol) were isolated following diethyl sulfate mutagenesis. The results of reciprocal transductions involving these mutants are as follows: (a) the frequency at which the ery and ol markers were transduced into each mutant varied greatly, and was especially low in those mutants which yielded recombinants in reciprocal transductions between the mutants; (b) 13 of the 19 ol-s mutants yielded recombinants in reciprocal transductions between the ol-s mutants; (c) no recombinants were detected in reciprocal transductions between ery-s mutants; (d) antibiotic-resistant recombinants were obtained in reciprocal transductions between three ery-s mutants and three ol-s mutants. The results of this study demonstrate that there is only one genetic locus which controls resistance to erythromycin and oleandomycin in these strains, and that it exists in an inducible state (the ery marker) and a constitutive state (the ol marker).

Bacteriophage types and antibiotic susceptibility of Staphylococcus aureus

In vitro tests of 132 strains of Staphylococcus aureus, among which were 38 (28.7%) heteroresistant strains, were performed with 14 commonly used antibiotics, including gentamicin and vancomycin. Heteroresistant strains were found predominantly, but not only, with group 3 phage-typable strains; no heteroresistant strain was found in out-patients. Gentamicin appeared as a uniformly effective agent at low concentrations against oxacillin-sensitive and -resistant strains. It is suggested that gentamicin should be compared to vancomycin in future clinical therapeutic trials in severe staphylococcal infections, especially in cases due to oxacillin-resistant strains.