Brucella

Abstract

Bru. cel' la . L. dim. ending ‐ ella ; M.L. fem. n. Brucella named after Sir David Bruce, who first recognized the organism causing undulant (Malta) fever. Proteobacteria / Alphaproteobacteria / Rhizobiales / Brucellaceae / Brucella Cocci , coccobacilli , or short rods , 0.5–0.7 × 0.6–1.5 µm. Arranged singly and, less frequently, in pairs, short chains, or small groups. True capsules are not produced. Do not usually show true bipolar staining. Resting stages are not known. Gram negative. Nonmotile ; do not produce flagella. Aerobic , possessing a respiratory type of metabolism and having a cytochrome‐based electron transport system with oxygen or nitrate as the terminal electron acceptor. Nitrate reductase is produced. Many strains require supplementary CO 2 for growth , especially on primary isolation. Colonies on serum‐dextrose agar or other clear media are transparent, raised, convex, with an entire edge and a smooth, shiny surface. They appear a pale honey color by transmitted light. Smooth strains produce perosamine synthetase and a distinctive lipopolysaccharide (LPS). Nonsmooth variants of the smooth species occur, but there are also stable nonsmooth nomenspecies with a distinctive host range. Optimal temperature for growth 37°C. Growth occurs between 20 and 40°C. Optimal pH for growth 6.6–7.4. Catalase positive . Usually oxidase positive, but negative strains occur. Chemoorganotrophic. Most strains require complex media containing several amino acids, thiamin, nicotinamide, iron, and magnesium ions; some strains may be induced to grow on minimal media containing an ammonium salt as the sole nitrogen source. Growth is improved by serum or blood , but hemin ( X‐factor ) and nicotinamide adenine dinucleotide ( NAD : V‐factor ) are not essential . Acid production does not occur from carbohydrates in conventional media , except for B . neotomae . Do not produce indole. Do not liquefy gelatin or inspissated serum. Do not lyse erythrocytes. Do not produce acetyl methyl carbinol (Voges–Proskauer test.) The methyl red test is negative . Intracellular parasites, transmissible to a wide range of animal species including man. The genome typically comprises two circular chromosomes, but a single large chromosome is present in B . suis biovar 3. The mol % G + C of the DNA is : 57.9–59. Type species : Brucella melitensis (Hughes 1893) Meyer and Shaw 1920, 179 ( Streptococcus melitensis Hughes 1893, 235.)