The outcome of the host- parasite relationship depends on a balance between the virulence of the parasite and the resistance of the host.
Aggressive mechanisms of the parasite 1. Adherence factors
. Pili: Hair-like appendages extending from the bacterial cell surface.
Invasiveness of micro-organism A high degree of bacterial invasiveness is usually associated with severe infection.
Bacterial toxins These are of two types.
Table 4.1 Characteristics of bacterial toxins
Character . Composition . Action . Antigenicity . Effect of heat . Produced by
. Converted to toxoid . Mode of release from bacteria
released on bacterial death