Isolation of bacillus HB-1 from human clinical sources.

Abstract

Seventeen recent isolates from a variety of human clinical sources of organisms designated as HB-1 according to the subgrouping of King and Tatum11,12 were studied with respect to their morphologic, cultural, and biochemical characteristics, as well as their experimental pathogenicity in mice. These nonfermentative, Gram-negative rods produced striking, dry, flat, radially-spreading colonies consisting of a clear, moist center circled by a highly refractile, speckled, pearl-like zone of growth resembling mercury droplets, surrounded in turn by an outer nonrefractile perimeter of spreading growth. Growth of all HB-1 strains was enhanced by the concomitant presence of X factor (hemin) and Co2, but growth was not influenced by V factor (NAD). However, on brain–heart infusion agar alone, in the absence of hemin, growth was obtained under anaerobiosis which was comparable to that observed on blood and chocolate agar. Biochemically, all strains were nonfermentative, and only oxidase and nitrate were positive. All of the isolates were susceptible to most of the commonly employed antibiotics with the exception of lincomycin and oxacillin. Experimental mouse pathogenicity could not be demonstrated, but microorganisms of the HB-1 group may conceivably possess pathogenic potential, as evidenced by their derivation from human pathologic sources.