Serologic studies on cases of leptospirosis, that were observed in outbreaks among British security forces or sporadically among military and civilian personnel in Malaya from the end of 1953 through 1955, are reported. Paired or serial serum samples from 230 and single serum samples from seven proved or suspected cases of this disease were tested for the presence of agglutinins against 17 to 25 diverse serotype antigens. Significant titers were demonstrated in all but nine cases. In addition, leptospiral isolates from 93 of the above patients and 17 isolates from additional patients were identified through cross-agglutination and agglutinin-absorption tests. These studies disclosed the presence of jungle foci of infection with multiple leptospiral serotypes. The identity of the infecting strain by serotype or serogroup could be established either by cultural identification or serologic tests for 222 of 245 cases. In the remaining 23 cases, heterologous rises in titers, of the same order, against multiple serotypes precluded identification. A considerable proportion of patients showed agglutinins against heterologous “unrelated” serotypes. In many instances this may reflect simultaneous infections with multiple serotypes.
Specific limitations in the current scheme (Wolff and Broom, 1954) for classifying pathogenic leptospires pertinent to this study were noted, and modifications related to the recognition of “serotypes” and to the designation of serotypes were proposed.
The antigenic analysis of 110 leptospiral isolates disclosed the presence of 30 distinct serotypes. On the basis of modified criteria of the Wolff-Broom scheme 15 serotypes were identified as follows: Leptospira schuffneri (7 strains), L. canicola (2 strains), L. malaya (1 strain), L. mankarso (4 strains), L. pyrogenes (13 strains), L. australis B (2 strains), L. celledoni (6 strains), L. bangkinang (4 strains), L. autumnalis A (2 strains), L. pomona (1 strain), L. australis A (3 strains), L. grippotyphosa AB (9 strains), L. paidjan (11 strains), L. bataviae (1 strain) and L. wolffi A (7 strains). The antigenic characteristics of the remaining 15 serotypes have not hitherto been described and were designated and classified into the following serogroups: Canicola group—L. jonsis (7 strains), L. sumneri (1 strain); icterohemorrhagiae group—L. smithii (3 strains), L. birkini (1 strain); pyrogenes group—L. abramis (1 strain), L. biggis (8 strains), L. hamptoni (1 strain); javanica group—L. celledoni II (2 strains), L. coxus (2 strains); autumnalis group—L. mooris (2 strains); australis A group—L. fugis (1 strain); djasiman group—L. gurungi (1 strain); hebdomadis group—L. hemolyticus (4 strains), L. worsfoldi (2 strains), L. ricardi (1 strain).