A total of 66 serovars of potentially pathogenic Leptospira species were examined by slot blot hybridization, and 57 of these serovars were classified in six DNA homology groups. In cases in which common serovars were studied, the results were in general agreement with the results of previous workers, who used different DNA homology methods. However, we propose a new species, Leptospira kirschneri, comprising the following serovars: bulgarica, butembo, cynopteri, dania, grippotyphosa, kabura, kambale, ramisi, and tsaratsovo. Seven of these serovars have not had their DNAs studied by other workers.Differentiation of strains within Leptospira species based upon variations in antigenic composition was introduced nearly 40 years ago. A total of 223 Leptospira serovars have been identified, and for convenience these serovars are grouped into 23 serogroups (10). Haapala et al. in 1969 (5) and Brendle et al. in 1974 (1) reported DNA base compositions of and measured levels of DNA homology between selected leptospire strains. The methods which these authors used had the potential to indicate the genetic structure of the genus Leptospira and to provide information that could be used to produce a phylogenetic classification. The results of a comprehensive study of 45 serovars in which quantitative DNA-DNA hybridization experiments were performed were published in 1987 (17). A total of 40 pathogenic strains were placed in five homology groups and were described as new species of the genus Leptospira. Leptospira interrogans was restricted to serovars icterohaemorrhagiae, copenhageni, canicola, pomona, saxkoebing, wolffi, pyrogenes, autumnalis, bataviae, jalna, australis, smithi, schueffneri, zanoni, grippotyphosa, djasiman, and hebdomadis; Leptospira noguchi comprised serovars panama, fortbragg, and louisiana; Leptospira weilii comprised serovars celledoni and sarmin; Leptospira santarosai comprised serovars shermani, borincana, peru, hawaiin, bananal, atlantae, bakeri, and navet; Leptospira borgpetersenii comprised serovars javanica, ballum, mini, tarassovi, and sejroe; and Leptospira inadai comprised serovar lyme. Yasuda et al. (17) determined levels of relatedness at 55 and 70°C by using the hydroxyapatite method (2). In this study we found that it was impractical to obtain the quantities of leptospire DNA that are required by this method for an extensive survey and instead used slot blot hybridization at 60°C. We found that the results obtained with slot blot hybridization were accurate and reproducible. Our results are in good agreement with those of Yasuda et al. (17).In this paper we describe the use of a quantitative slot blot hybridization method to determine the levels of DNA relatedness of 66 pathogenic leptospire serovars; to do this, we used 16 strains as sources of labeled reference DNA. * Corresponding author. MATERIALS AND METHODSLeptospira serovars and culture conditions. Cultures of Leptospira strains were obtained either from the WHO/FAO Collaborating Leptospirosis Laboratory, Brisbane, Australia, or fro...

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PLATE XVIIRE SEARCH on gonorrhoea has been hampered by the lack of suitable animal models. Although human volunteers have been infected with urethral pus and with gonococci grown in vitro (Hill, 1943;Kellogg et al., 1968) such experiments are limited by ethical considerations. An animal model would not only facilitate investigations of the pathogenicity of Neisseria gonorrhoeae but might also act as an assay system for testing the anti-gonococcal activity of drugs and vaccines. Recently, Brown, Lucas and Kuhn (1972) infected the urethra of male chimpanzees with N. gonorrhoeae isolated from human pus and from culture, and demonstrated transmission of infection from a male to a female chimpanzee by coitus. This system seems to parallel the human situation but is expensive. However, similar experiments might be accommodated by a model in small laboratory animals that has been developed by Ark0 (1972) from a method used in virology (Tosi et al., 1970). Perforated polyethylene practice golf-balls were implanted subcutaneously into rabbits, and stainless-steel springs into guinea-pigs, rats, hamsters and mice. The chambers became encapsulated with connective tissue and filled with a sterile transudate. Gonococci were inoculated into the chambers and persistent infections established in all five species. An anti-inflammation agent (dexamethasone) was used in the rabbits, rats and guinea pigs but not in hamsters and mice. Rats were the most difficult animals to infect. Using a similar system, Flynn and Waitkins (1 973) implanted annular plastic chambers subcutaneously in mice. They did not use anti-idlammation drugs and achieved only fleeting infections. Many years before, N. gonorrhoeae had been grown in vivo in collodion sacs (Harris, 1939) and in the anterior chamber of the rabbit eye (Miller, 1948). However, for use in studies of pathogenicity and immunity the latter system has technical drawbacks, and collodion sacs exclude host defence-mechanisms, especially the idammatory response. The Ark0 system seemed convenient

SUMMARY. Various strains of Leptospira interrogans were compared by bacterial restriction-endonuclease DNA analysis (BRENDA). Field strains of serovar harq'jo isolated from domestic animals in New Zealand, Australia and Northern Ireland were indistinguishable from one another but differed strikingly from the hardjo reference strain Hardjoprajitno. Similarly, field isolates of balcanica and tarassovi differed from their serovar reference strains, probably owing to a difference in epidemiological niche. Subdivision of these serovars into distinct subtypes as defined by BRENDA is therefore useful and justified. In contrast, analysis of serovars pomona, ballurn and copenhageni shows that field and reference strains were identical, or differed only by a single band.It is suggested that BRENDA will overcome many of the problems associated with serological methods of identifying serovars and allow more precise definition of epidemiological relationships between strains and their hosts.