Systematic Veterinary Bacteriology and Mycology

DIAGNOSIS

• It involves clinical, microscopical and bacteriological examination.

Clinical examination

• Palpation of the udder and supramammary lymphnodes will be helpful in distinguishing the chronic and insidious form of mastitis produced by S.agalactiae and S.uberis.
• In contrast S.dysgalactiae and S. zooepidemicus causes sudden onset of acute inflammation of one quarter only with an acute systemic disturbance followed by joint infections and lameness.

Microscopical examination

• When long chains of organisms are detected in milk samples from chronic mastitis, it is caused by S. agalactiae.

Based on type of haemolysis on blood agar

Bacteriological examination

• When 0.1 ml of secretions inoculated on Edward’s medium (blood agar, crystal violet and aesculin) S.agalactiae produces bluish-grey colonies and S.uberis produces dark color colonies.
• CAMP test (Christie, Atkins, Munch and Peterson, 1944)
  • This test is based on the observation that ruminant red blood cells lysed by the beta toxin of staphylococci at 370C are completely lysed in the presence of S.agalactiae (group B).
  • Differentiation between the pneumococcus and S.viridans organisms can be achieved by bile solubility and the optochin test.
• Bile solubility test
  • Autolysis of pneumococcal cultures takes place within 15 minutes at 370C in the presence of 10 per cent sodium deoxycholate.
  • These substances have no effect on S. viridans organisms.
• The optochin test
  • The majority of pneumococcal strains are sensitive to optochin (Ethyl hydrocuprein hydrochloride). Whereas S.viridans organisms are not.
  • This test consists of placing a small circular piece of filter paper, impregnated with 1:4000 aqueous solution of optochin, in the center of a blood agar plate after inoculating the test cultures in streaks across the full width of the medium.
  • The growth of pneumococcal strains will be inhibited to a distance of some 5 mm from the circumference of the filter paper.