1. COURSE: MLSM 505 TOPIC: SPIROCHAETES: LEPTOSPIRA

2. Characteristics   Leptospiras are tightly coiled, thin spirochaetes, measuring about 0.1 x 6-12 u. They are not easily stained with bacteriological stains but can be examined by darkground microscopy. Optimum temperature of growth is C aerobically.

3. Members of this genus of spirochaetes differ from other genera in their motility which is very vigorous and in their having hooks in one or both ends. They grow in media containing serum. Classification There are two main species of Leptospira: L. interrogans: subdivided into over 100 serovars which are usually pathogenic.

4.  L. biflexa: subdivided into about 60 serovars which are usually non pathogenic. Habitat   Leptospiras are present in several animals which act as their reservoirs e.g. L. interrogans serovar icterohaemorrhagiae in rats, L. canicola in dogs and L. pomona in pigs.

5. Pathogenicity   Leptospiras are important human pathogens which are found in various animals in different locations in the world: common in rats and other rodents, domestic animals such as dogs and cats, and pigs. The animals excrete the organisms in urine which contaminates soil and water. Swimming in contaminated water or consuming of contaminated food and drink can lead to human infection.

6. When leptospiras are ingested or pass through mucous membranes or skin, they circulate in the blood, multiply in various organs, producing fever and dysfunction of liver (jaundice), kidney(uraemia) and central nervous system ( aseptic meningitis). L. interrogans serovar icterohaemorrhagiae is the major cause of leptospirosis; Weil’s disease is the several forms of jaundice caused by this species. Farmers and people who work in sewers and miners are most at risk of contracting the disease.

7. Laboratory Diagnosis Specimens: Blood for blood culture (during the first week of infection), urine ( second – third week).   Microscopy: Routine staining is not useful. Demonstrate in wet preparation of blood and urine with DG microscope. For blood, place a drop of blood on a clean microscope slide, cover with cover slip. With a fine tipped pasteur pipette, introduce distilled water from the side into the preparation.

8. The red cells will be lysed and watch for actively motile spirochaetes
The red cells will be lysed and watch for actively motile spirochaetes. For urine, centrifuge fresh urine at 300 rpm, make a wet prep and examine under the DG microscope Culture: Liquid and semi solid media enriched with animal protein such serum are employed to isolate Leptospiras.

9. The most popular ones are the Stuart’s and Korthof’s media and they contain buffered salts and rabbit serum. Inoculate the media and incubate aerobically at 300C.   Serology: Serological tests are valuable in the diagnosis of leptospirosis as antibodies appear by the end of the first week of infection. Two types of serological tests are available:

10. Genus-specific tests: These are positive whatever the serovar of the infecting strain may be. The tests include the Macroscopic slide agglutination test. It is tested against the heated antigen of saprophytic strain of Patoc 1 serovar patoc whose antigen is common to most of the strains. Other genus-specific tests that can be used are CFT, HA and ELISA.

11. .      Serogroup-specific tests: These are reactive with strains of the same sero-group as the infecting strain. These tests include the microscopic agglutination test (MAT) and ELISA. The IgG antibodies remain in the body for sometime, so a rise in titre has to been demonstrated to confirm current infection.  

12. Antibiotic sensitivity Penicillin and tetracycline are very active against the organism.