One hundred fifteen strains of Diplo-coccus pneumoniae were randomly isolated from septic lesions not associated with the respiratory tract, and sputum, throat and nose in 16 centers throughout Poland. All strains were typed and 92.2 % of them proved typable. Most frequently occurring types were: 19, 6B, 23, 6A, 17, 18C, 7, 14 and 35 listed here in order of frequency; these types constituted 51.3 % of typable strains. Together 40 serological types were found among the 115 strains. Investigation of susceptibility of these strains to 30 antibiotics, revealed very high sensitivity to the penicillins, cephaloridine and rifamycins, as well as to lincomycin, pristinamycin, novobiocin and tyrothricin. Sixteen strains (14 %) were tetracycline-resistant, one strain was erythromycin- and spiramycin-resistant, 3 oleandomycin-resistant and 9 chlor-amphenicol-resistant. All resistant strains were type 23, 19, 6A, 6B and 14, two first types occurring most frequently. Fucidin, bacitracin, streptomycin and the neomycin group of antibiotics were not effective.

Antistaphylococcal activity of normal serum against strains exhibiting various patterns of coagulase, clumping-factor, and staphylokinase production is not connected with the presence of these factors. Purified coagulase does not influence this property of serum. Coagulase-negative strains with clumpingfactor activity grow in normal serum as typical pathogenic staphylococci. Serum bacteriostatic activity against staphylococci may be reversed by several nonspecific factors, such as sterile broth, supernatant fluids of coagulase-negative strains, and ammonium sulfate precipitates of culture supernatant fluids of various staphylococci. Immune sera with a high agglutinating titer for staphylococcal cells do not prevent growth of serum-resistant strains; serum-susceptible strains are inhibited as in normal serum control. Activation or blocking of the serum fibrinolytic system does not influence serum bacteriostatic activity. The growth rate of serum-resistant strains is identical in serum and in Todd-Hewitt broth; serum-susceptible strains are inhibited to the inoculum level, but decreases and increases in viable count are noted during a 24-hr observation period. Observations made with sera of 10 animal species clearly demonstrated differences in serum bacteriostatic activity, mouse serum being completely noninhibitory and cat serum only weakly inhibitory. The technique of quantitative determination of serum susceptibility of staphylococci is described, and the importance of serum antistaphylococcal activity in vitro is discussed. Experimental staphylococcal infection produced in rabbits by intravenous injection of different Staphylococcus aureus strains did not result in significant changes in serum antistaphylococcal activity. The technique of experimental infection used caused chronic infection, with a peak on the 14th day; this was proved by means of a newly developed 5'-nucleotidase test. At the same time, sera of infected animals exhibited slight inhibitory properties, which returned to initial values 1 week later. Infection was produced by strains recognized as nonpathogenic and was inhibited in vitro by sera from both normal and infected rabbits. It is concluded that antistaphylococcal activity of serum should be considered as an "in vitro" phenomenon, which seems to have no importance in defense mechanisms of rabbits infected intravenously with staphylococci. Coagulase-positive strains of Staphylococcus aureus isolated from pathological material multiply readily in normal human serum, whereas nonpathogenic strains are inhibited (19, 20, 21). This phenomenon was found to be independent of complement and lysozyme and to be produced by a thermostable factor present in fresh serum (8, 18). Resistance of pathogenic staphylococci to the action of normal sera has aroused interest in the mechanism of nonspecific resistance to infection by these strains, especially after presentation 953 of a hypothesis on reversing of serum antistaphylococcal activity by coagulase (5). According to Ekstedt (3, 4), this activity depen...

SYNOPSISThe growth of 100 staphylococcal strains in normal rabbit serum was studied. Determinations were carried out by the tube method previously described and by a new plate method, and the results agreed in both cases. The strains of staphylococci used differed in the production of bound coagulase, clumping factor, and staphylokinase, and exhibited different phage patterns. Their multiplication in serum was not dependent on any of the above-mentioned characteristics. The newly elaborated plate test is characterized by easy and quick performance and allows for the determination of 25 to 36 strains on one Petri plate.

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