Burkholderia pseudomallei Morphotypes that Form in vitro under Stress Conditions

Abstract

Objective of the study was to determine diversity of the morphotypes formed in vitro from the initial morphological variant of B. pseudomallei 110 under stressful conditions and to study some phenotypic characteristics of them. Materials and methods. Virulent strain Burkholderia pseudomallei 110 of Australian serotype was used. Burkholderia cultures were added to the axenic culture of Tetrahymena pyriformis in LB broth and sterile river water in the ratio of 100: 1 and incubated at 28 °C; the passage of monocultures and cultures in protozoa cells was repeated at intervals of 3–4 days. Morphotypes were identified on Ashdown’s medium after cultivation for 3–4 days at 32 °C, photographs were analyzed based on classification of Chantratita et al. In all morphotypes the activity of extracellular enzymes and virulence were determined on the model of golden hamsters. Results and conclusions. Seven B. pseudomallei 110 colony morphotypes were identified. Four of them with characteristics of I, III, IV and VII morphotypes, described by Chantratita et al., were named Chl (Chantratita like variant). The study of morphotypes in different samples revealed a variation in them, depending on the culture medium (LB broth or water), and their different ratios in individual samples. The greatest number of morphological variants (4 out of 7) was formed during the passage of the monocultures of B. pseudomallei 110 in LB broth; in water the initial culture was almost entirely (95 %) transformed into morphotype I Chl. Under other conditions of cultivation the dominant V morphotype was formed, and in the presence of protozoa it was combined predominantly with I Chl. Morphotypes differed in the production of extracellular enzymes, motility and reduced virulence.

Keywords

• burkholderia pseudomallei
• tetrahymena pyriformis
• morphotypes
• phenotypic characteristics