Some of the characteristics of 42 clinical isolates of Haemophilus ducreyi are reported. Only six of the 42 strains were able to grow on horse-blood agar. All strains gave a positive oxidase test with tetramethyl-p-phenylenediamine and a negative result with dimethyl-p-phenylenediamine. All of 15 test strains were negative in the porphyrin test. Tests for haemin requirement were inconclusive because of difficulties encountered in obtaining growth on a basal medium.
Strains of thermophilic campylobacters of human origin were examined for bacteriocine activity and for susceptibility to R-type pyocines of Pseudomonas aeruginosa. None of 50 strains inhibited the growth of any other strain, but 13 of 80 strains (16%) were sensitive to R-type pyocines. Absorption of one of the partially purified pyocine preparations with a sensitive strain resulted in the removal of pyocine activity and a decrease in viable count of the organism by 85%.
Culture filtrates of all eight strains of Bacteroides gingivalis and all five strains of B. asaccharolyticus were toxic for Vero cells. Cytotoxicity was in general greater with material from cultures of B. gingivalis than from B. asaccharolyticus but none of the culture filtrates from eight strains of B. melaninogenicus showed activity in this test. The toxic material was released during prolonged incubation and more detailed study of preparations from one strain indicated that it had a molecular weight of less than 3500 and was heat stable.
CBA/N mice, which could not produce antibodies against lipopoly-saccharide (LPS) from either Escherichia coli or Leptospira interrogans serovar pomona, produced levels of agglutinating antibodies against leptospires similar to those produced by immunologically normal CBA mice. CBA/N mice were thus resistant to acute leptospiral infection and CBA/N immune serum passively protected immunosuppressed mice from infection. The results suggest that antibodies against LPS are not important in protection against experimental leptospiral infection in mice.
The thiosulphate: cyanide sulphurtransferase (rhodanese) test of Vandenbergh, Bawdon and Berk (1979) has been simplified and 2469 strains from a wide variety of sources representing different biochemical, serological or phage-pattern entities were tested. The percentages of rhodanese-producing strains were: Escherichia coli 98%, Shigella flexneri serovars 1–5%, X and Y 0%, other shigellae 73–100%, Yersinia spp. 0%, Salmonella subgenera I–IV 0%, Citrobacter freundi 16%, Klebsiella 37%, Enterobacter 4%, Hafnia alvei 61%, Proteus spp. 0%, Pseudomonas spp. 98–100%. Rhodanese production by S. flexneri serovar 6 supports the view that this group of bacteria should be removed from S. flexneri and placed in another species of Shigella.
The in-vitro bactericidal effect of serum for Klebsiella rhinoscleromatis was tested. Experiments with C2-deficient and hypogammaglobulinaemic human sera suggested that killing depended on activation of the classical complement pathway, although the alternative pathway probably amplified the effect. Serum from a patient with active rhinoscleroma, and another cured of the disease, showed normal killing.