In vivo Consequences of the Interaction between Antibiotic-damaged Pathogens and Host Animal Defences
Streptococcus pyogenes is recognised as an important cause of infection in man and much of its virulence can be attributed to the possession of both structural and soluble antigens. Although the properties of pathogenic bacteria are often studied after in vitro growth, there is evidence that organisms grown in vivo may differ from those grown in vitro [1,2]. Under these circumstances it is conceivable that the host response may be determined by the expression of virulence factors of the pathogen. It is known that S. pyogenes cells can lose some of their normal complement of M antigen during in vitro culture. Only by exposing such cells to human or animal leukocytes  can one enrich the numbers of M-positive organisms within a culture. These bacteria are much less susceptible to serum opsonization and subsequent phagocytosis by leukocytes [4,5]. The presence of M protein as a surface “fuzz” prevents the activation of complement by the alternative pathway and renders the streptococcus resistant to phagocytic adherence and ingestion .
KeywordsFusidic Acid Phagocytic Ingestion Chemotactic Index Antigen Synthesis Alternate Complement Pathway Activation
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