APPEARANCE OF BLACK PIGMENTS IN THE EMJH SEMISOLID MEDIUM – CULTURAL CONFUSION

Prabhusaran Nagarajan*, Natarajaseenivasan Kalimuthusamy, Joseph Pushpa Innocent Danialas

ABSTRACT

Culturing Leptospira is the difficult and challenging task for the bacteriologists. But for maintaining leptospiral cultures and to cultivate this spirochete from the infective samples, it is mandatory to prepare the EMJH semisolid medium without any contaminations. There are more chances to get the EMJH medium contaminated. Some major reasons are summarized in this paper. More scientists working in leptospiral research confused themselves by observing the black deposits on the EMJH medium due to some metabolic process of the leptospires and few suggested contamination is the major reason for this issue. This controversy induced us to perform the laboratory test by taking three sets of EMJH semisolid medium. First set of medium inoculated with five leptospiral strains aseptically, second set inoculated with same five leptospiral strains as defined in first set in contaminatable manner and the third set without leptospiral inoculation but induced contamination by artificial open tube method. After incubation, the tubes were analyzed for Dinger’s ring formation and black pigments. The uncontaminated set of EMJH cultures showed Dinger’s ring only without any black pigmentation. Among the second set of medium, the tubes inoculated with Javanica, Patoc and Australis showed black pigments to black deposits and black threads found. This may be due to biochemical metabolic reactions by the contaminant mainly due to Bacillus sp (a common laboratory contaminant). More analysis required to incubate further, compare with more leptospiral strains and variations in EMJH semisolid medium composition to confirm the issue.

Keywords: Leptospira, EMJH semisolid medium, black pigments, contamination.