The genus Veillonella was first isolated by Veillon and Zuber in 1898. Prevot further described these bacteria in 1933. Morphology: • Gram-negative anaerobic cocci , 0.3-0.5 um in diameter • Non motile • non spore forming Habitat: • mouth • upper respiratory tract • Intestine • vagina Characteristic: • pH Optimum pH, 6.5-8.0. • Temperature Optimum temperature, 30-37`C. • usually isolated mixed with other bacteria (These organisms are hypothesised to form a cooperative metabolic system in which a waste product, lactic acid, produced by S. mutans is utilised by V. dispar.) • Chemoautotrophs (Chemoautotrophs obtain their energy as well as their carbon from inorganic sources; they do this by the oxidation of inorganic molecules such as sulphur or nitrite.) • Non-fermentative. • produce a highly endotoxic lipopolysaccharide • are generally resistant to tetracycline Species: Veillonella atypica, V. dispar are found in humans V. parvula V. caviae V. criceti in rodents. V. ratti V. rodentium Diseases: Dental caries Abscesses of teeth and gums. sinusitis Osteomyelitis Endocarditis Laboratory diagnosis: Are small, spherical, gram-negative cocci appearing as pairs, masses, and short chains. Non hemolytic Growth may be improved by adding 1% sodium pyruvate and 0.1% potassium nitrate to the basal medium. Colonies grow slowly on normal laboratory media, their growth being encouraged by factors such as lactate, pyruvate and nitrate. enriched thioglycollate broth Some form catalase. Small white colonies. Colony produce of a red fluorescence at a wavelength of 365 nm. This fluorescence is better observed in a Veillonella selective medium (Rogosa medium) and disappears in contact with oxygen. Growth is usually visible after 48 hours in appropriate anaerobic conditions. glucose or any other carbohydrate is not fermented; indole -ve nitrate is reduced. H2S is produced propionic and acetic acids, C02, and H2 are produced from lactate during growth. Lactate 2 propionate + acetate + CO2 Oxidase-negative. Catalase-negative, but some species produce an atypical catalase lacking porphyrin.