Kinetic studies on the interaction of bacteriophage type 71 staphylococcal bacteriocin with susceptible bacteria

Kinetic studies on the interaction of the bacteriocin produced by phage type 71 Staphylococcus aureus with susceptible bacterial cells were undertaken. Survivors among susceptible bacteria to which the bacteriocin has been added can be rescued after trypsin treatment. The bacteriocin adsorbs very rapidly to susceptible streptococcal cells at a time when killing of the cells is only minimal. Heat-killed or mechanically disrupted cells are also effective in adsorbing the bacteriocin. Adsorption is comparable at 37 C and 25 C, but is less pronounced at 4 C. Elution of adsorbed bacteriocin could not be achieved by heating, by varying pH, or by using different concentrations of sodium chloride solutions. Surface M protein of streptococcal cells plays no role in the adsorptive process. Adsorption is specific in that only susceptible bacteria, but not resistant ones, are capable of adsorbing the bacteriocin.

Relationship of antigen k to Staphylococcus aureus bacteriophage type 187, of human and of canine origins

Similarities as well as differences have been observed between phage type 187 Staphylococcus aureus cultures of human and of canine origins. Thus, all strains susceptible to phage 187, regardless of their host specificity, were agglutinated by absorbed serum k. (Furthermore, agglutinability of the autoclaved bacteria indicated a reaction with the k(1) component of the k-antigen complex.) On the other hand, the strains of canine biotype were in addition agglutinated by absorbed serum 61218, and they possessed biochemical features which distinguished them from human strains of S. aureus.

Competence for transfection in Staphylococcus aureus

Lysogenicity with phage P11 is a requirement for competence in the presence of calcium ions in Staphylococcus aureus 8325N. The wild-type strain 8325N, lysogenic for the phages P11, P12, and P13, is also competent, but strain 8325-4, a nonlysogenic derivative of strain 8325N, as well as strains 8325-4 (P12) and 8325-4 (P13) could not develop competence. Preincubation of strain 8325-4 with culture filtrates from a competent strain can induce competence, but rabbit anti-P11 serum can neutralize the competence factor. Superinfection of competent strain 8325-4 (P11) with phage P11 at high multiplicities increases the transfection frequency. Uptake of deoxyribonucleic acid by competent cells is dependent on calcium ion concentration, pH, and temperature. Inhibition of energy metabolism or protein synthesis before and during incubation with deoxyribonucleic acid affects the binding and uptake. The ability to develop competence during bacterial growth differs between the wild-type strain (8325N) and a nuclease-deficient mutant (8325N nuc). The wild-type strain has a narrow competence maximum in the early exponential growth phase where no extracellular nuclease activity is produced. The nuc strain shows in addition competence maxima later in the exponential growth phase.

Natural history of impetigo. II. Etiologic agents and bacterial interactions

Intensive observations on 37 children in a population with endemic skin infections provided an opportunity to study the interrelationships between and the significance of the bacterial genera commonly associated with impetigo. Cultures of the respiratory tract, three normal skin sites, and lesions, when present, were taken three times weekly from July to October 1969. Impetigo developed in all 37 children. Group A streptococci alone were recovered from 21% of 361 lesions, Staphylococcus aureus alone from 8%, Staphylococcus epidermidis alone from 5% and mixtures of streptococci and staphylococci from 61%. Vesicular or pustular lesions were more often pure streptococcal than pure staphylococcal. Streptococci alone were more often recovered from early stage lesions rather than from later ones. The pure staphylococcal lesions characteristically occurred early in the season whereas streptococcal or mixed lesions had later peaks.Serial observations on 74 lesions revealed longer persistence of streptococci than staphylococci in mixed lesions. In 85% of the instances the same streptococcal serotype was recovered repeatedly from an individual lesion, whereas staphylococcal types changed in 57% of instances. Phage type 75 accounted for the majority of staphylococcal isolates from all sites, whereas phage type 54 was recovered only from skin lesions. In contrast to streptococci, the site sequence of staphylococcal spread was from the nose to normal skin to skin lesions. These studies reveal important differences in the migration of staphylococci (as compared with streptococci) to various body sites and suggest a subsidiary role for staphylococci in nonbullous impetiginous lesions yielding both organisms.

Genetic studies on plasmid-linked cadmium resistance in Staphylococcus aureus

The genetic basis of cadmium resistance conferred by three penicillinase plasmids, PI(524), PI(258), and PII(147), of Staphylococcus aureus was examined by mutation, recombination, and deletion analysis. Three separate loci were identified: cadA, responsible for high-level resistance; cadB, giving a low-level resistance, nonadditive to cadA; and mad, a locus marginally decreasing the cadmium resistance of plasmid-positive staphylococci. The loci cadA and mad were present on all three plasmids, but cadB was only found on PII(147). Spontaneous deletions of mad involved up to three-fourths of the plasmid genome, which allowed derivation of a partial deletion map of PII(147), a plasmid with a contour length of 10.9 mum, corresponding to a molecular weight of 20.4 x 10(6).