Evaluation of inhibitors for development of a selective medium for isolation of Leptospira spp. from clinical samples

This study was conducted to develop a selective medium for the detection of Leptospira spp. in clinical samples. Serovars of Leptospira spp., environmental bacteria and the fungus from contaminated cultures of patients with suspected leptospirosis were inoculated into EMJH medium containing amphotericin B, 5-fluorouracil (5-FU), furazolidone and neomycin used singly or combined. Medium with 5-FU at the concentration of 200 μg ml^-1 did not show any inhibitory effect against the fungus, Gram-negative bacilli and any of the leptospira strains except serovar Pyrogenes. The highest concentration of neomycin and furazolidone that did not inhibit the growth of leptospires was 4 μg ml^-1 . All strains of Leptospira spp. grew on 5-FU (100 μg ml^-1 ) in combination with neomycin (4 μg ml^-1 ) and on 5-FU (100 μg ml^-1 ) in combination with furazolidone (4 μg ml^-1 ). The highest concentration of amphotericin B (500 μg ml^-1 ) that inhibited the growth of the fungus also inhibited the bacteria and most of serovars of Leptospira spp. The most effective antibiotic combinations that inhibited the majority of environmental bacteria growth without affecting leptospiral growth were EMJH with 5-FU (100 μg ml^-1 ) in combination with neomycin (4 μg ml^-1 ). In conclusion, these findings will help the development of new selective media to isolate leptospires.

Leptospirosis is one of the most widespread zoonotic diseases in the world. Since certain serovars are often associated with the symptoms and severity of the disease, the isolation and identification of the leptospires usually permits the prediction of sources of infection. Attempts to isolate Leptospira spp. from clinical specimens are often frustrated by overgrowth of the slow-growing bacteria by more rapidly growing contaminants. In this study, we evaluated selective agents to develop a new selective medium to isolate leptospires. The results demonstrated that the association of drugs in concentrations that allowed the growth of leptospires is to be more effective in inhibiting bacterial contaminants.