Isolation and characterization of Streptococcus uberis of bovine mastitis origin
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"Thin, watery, large mucoid colonies on blood agar plates, gram variable cocci in long chains, inability to grow in common laboratory media--these were among the un usual observations made in May, 1968 in the investigation of an outbreak of mastitis. At one milking visibly abnor mal milk appeared in 33% of the quarters of the herd. Counts of the causative organism were often 10^6/ml. Due to mastitis, acute in nature, most of the animals had to be sold during two years time. The organism was penicillin sensitive, but treat ment with penicillin did not eliminate the malady. Milk samples taken 12 months apart yielded two mucoid strains, biochemically classified as Streptococcus uberis. The recurring attacks resulted in severe economic loss to the owner. The problem was so intriguing and baffling that it was decided to investigate the outbreak, to identify the causative organism and to suggest remedial measures. Because the isolates were very unusual, it was chosen to study them in detail. Two non-mucoid strains were evolved from the wild types making comparisons to the mucoid strains possible. Study of the gram reaction was planned using various media and reagents. Sensitivities to various antibiotics were observed. Persistency of the outbreak, in spite of treatment, demanded an epidemiological survey. Attempts were made to study the immunological behavior and the pathogenicity for experimental animals. Although Str. uberis ranks second to Str. agalactiae in the etiology of mastitis, it has so far evaded a logical classification. Str. agalactiae, being more common and comparatively more easily identified, has usually been the subject of mastitis investigations rather than Str. uberis. No single Lancefield serum will type all its strains. Much of the literature on this organism is contradictory in nature, and most workers have been primarily interested in taxonomy. Str. uberis causes severe outbreaks of bovine mastitis and elicits poor immunological response. Mere mention of its name along with other organisms as the causative agent of mastitis does not mean much. Thus the organism was studied in detail, and the results of this investigation are embodied in this thesis. It is hoped that this work will clear up some of the confusion existing about this organism."--Introduction.
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