Association of Toxic Capsule and Cell Wall Mucopeptide with Virulence in Gaffkya tetragena

Abstract

Nine strains of organisms morphologically and physiologically identified as Gaffkya tetragena were obtained from various sources to study their pathogenicity. Initial virulence analysis of all strains by mouse intraperitoneal injection of viable cells revealed that only three strains, recently isolated from and associated with respiratory infections in hospitalized patients, caused death of mice within 48 hr. The ld 50 for these virulent, encapsulated strains was 1 × 10 7 to 6 × 10 7 viable organisms. To associate virulence with a toxic component, the following fractions were purified from all strains: capsular material, cell walls, mucopeptide preparations from cell walls and whole cells, grouplike material, cytoplasmic material, and culture filtrate with and without added reducing agent. Rabbit and mouse dermal toxicity testing of these fractions revealed that the capsular material, cell walls, and mucopeptide preparations of the virulent strains were toxic. None of the nonvirulent strains contained toxic components, with the exception of one strain which yielded capsular material equal in toxicity to that of the virulent strains. The capsular material induced a soft pustular lesion persisting for approximately 22 days. Cell walls and mucopeptide preparations produced a hard nodular lesion, identical to that produced by autoclaved whole cells, that persisted for 25 to 30 days. One strain may represent a virulence intermediate between the virulent and nonvirulent strains, since it contains toxic capsular material but nontoxic cell wall mucopeptide. The results indicate that the virulence of this organism is associated with toxic capsular material and cell wall mucopeptide.