Gordonia terrae USTCMS 1066: ITS TAXONOMY, ANTIMICROBIALS AND IMIDAZOLIUM SUSCEPTIBILITY AND EVALUATION AS AN INITIAL SCREENING AGENT FOR ANTI-TB COMPOUNDS AND NATURAL PRODUCTS

Abstract

The taxonomic classification and unique characteristics of an air-borne actinomycete exhibiting a dark orange pigmentation were determined by polyphasic analysis. The colony appeared as a contaminant in an agar plate culture of the marine luminous bacterium: Vibrio fischeri USTCMS 1026. Subsequent investigation identified the actinomycete contaminant as MP 1066 for Mycobacterium phlei USTCMS 1066 but was later found to have morphological, physiological, biochemical and genotypic characteristics compatible with member species of the genus Gordonia. BLAST comparison of MP 1066 yielded 100% 16S rDNA sequence alignment with Gordonia terrae so the strain was renamed as Gordonia terrae USTCMS 1066. Its antimicrobial susceptibility profile is similar to that of the pathogenic mycobacteria yielding small MICs and large inhibition zones against the antibiotics: ampicillin (AMP), azithromycin (AZT), amoxicillin-clavulanic acid (AUC), ciprofloxacin (CIP), ethambutol (ETHAM), isoniazid (INH), rifampicin (RIF), tetracycline (TET), sulfamethoxazole – trimethoprim (SXT), and streptomycin (STREP). In addition, the crude ethanolic extracts of Acanthella carteri, Alstonia scholaris Lunasia amara Blanco, Momordica charantia, Wrightia antidysenterica, Zingiber officinale and the pure synthetic imidazole: 1,3-bis(4-methylphenyl) imidazolium chloride likewise inhibited strongly the growth of Gordonia terrae USTCMS 1066. Substances that strongly inhibited Gordonia terrae USTCMS 1066 were also observed to be strongly inhibitory to Mycobacterium tuberculosis indicative of its suitability as an initial assay organism for the screening of anti-TB natural products and synthetic compounds most specially for laboratories that are not equipped with Biosafety Level III facilities. KEYWORDS: Gordonia; Mycobacterium; anti-TB; antibiotics; plant extracts