Clinical Investigations

Summary 1. The type clieracteristics of H. injluenzae were studied. The typing procedure for encapsuled strains was improved e.g. by employing slide cultures for capsule swelling tests. The serological cross‐reaction with encapsuled pneumococci, especially type 6, was confirmed. No hyaluronidase production could be demonstrated in H. influenxae (I). 2. The relations between encapsuled, converted rough, and primarily rough strains of H. influenzae were studied in trar:sformation experiments. By varying the experimental conditions and Watching carefully for all emerging variants, including non‐capsulated ones, which were subsequently tested in new experiments, it was possible to transfer capsule formation ability and type specificity to a number of strains isolated in the non‐capsulated state (II). No change of tho antigenic composition of the bacilli could be observed, by gel precipitation experiments, in transformed strains, except that the acquisition of a capsular antigen was demonstrated (V). 3. The susceptibility of Ei. influenzae to six commonly used chemotherapeutics was investigated. hureomycin, chloramphenicol, and terramycin were found most effective (III). 4. By the gel precipitation method, the presence in influenza bacilli of antigenic factors common to, or widely distributed within, the species was demonstrated (V). Unlike other tested bacteria, liaemopliilic organisms were easily dissolved by 1% sodium carbonate solution, which was used for the preparation of an extract rich in the widely distributed antigenic factors (IV). 5. The use of a sodium carbonate extract as the antigen of a complement fixation test (AHI) resulted in a reaction which, unlike tests used formerly for the recording of 11. influenzae immunity, was fairly independent of the type and capsulation of the immunizing strains (IV). 6. A convenient routine method for the determination of nritipneiimolysin (RPI) was noiked out. KO significant overlapping versus antistreptolysiii was noted (VI). 7. The transfer of APl, AS, AHI, and ASta from mother to foetus was studied. The transmission was more effective with regard to the antilysins than to the antibaeterial complement fixing antibodies to H. influenzae (IV, VI). 8. The content of AP1, AS, AHI, and ASta in infants and children of different ages was found to be rising with increasing age, though with different rates for the separate antibodies (IV, VI). 9. Maxillary sinusitis was found on one or more occasions during one winter season in 60 of apparently healthy children. Pnenrnococci and influenza bacilli were the prevailing pathogens, whereas staphylococci were comparatively rare. Haernolytic streptococci were never found. These obscrvations deviated from most previous investigations and could be ascribed to the adequate methods used for collecting and examining the antral discharges. The antibody titers in nasal carriers of the separate pathogens were higher than in non‐carriers but significantly increasod only when the pathogens were present in inflamed sinuses. The importance of the immunization exerted by sinus processes is stressed (VII). 10. In suppurative otitis, pneumococci were common in all ages up to seven years, while pyogenic staphylococci as primary pathogens were rare and largely restricted to infants and very small children. Influenza bacilli were frequent up to four years of age, and hacrnolytic streptococci increased their incidence with increasing age. This prevalence of different pathogens in the separate ages was paralleled by a corresponding difference in the evolution of the ability to produce antibodies to the same pathogens. The respiratory infection which generally preceded the otitis was found often to involve bacteria other than those found in the aural secretion. The El. influenzae otitis displayed a characteristic picture and tended towards recurrence. Further, the significance of age and of treatment for the occurrence of relapses was studied (VIII). 11. In the discussion, the pathogenicity of encapsuled influenza bacilli with regard to otitis is compared to that of non‐capsulated strains. The main antibody titer levels and the antibody responses to acute infections in diiferent ages are correlated to the variation according to age of the incidence of infections by the corresponding pathogens. The high antibody titers, and espccially the high A111 rates, observed in maxillary sinusitis are discussed. The antibody production is pointed out as one of the factors which influence the course of infections and, with regard to otitis, the incidence of relapses.