Bacteria can damage cells at all around the invasions site directly; most of this damage occurs as a result of natural bacterial life processes such as movement, metabolism and reproduction.
For example simply by penetrating the plasma membrane of a host cell or by secreting enzymes a bacterium can damage the cell; more over when too many bacteria infect the cell either of by invasion or reproduction within the cell the host cell may be lysed.
Compared with direct actions; the production of toxins is more efficient pathogenic mechanism; released toxins can travel via the bloodstream and damaged tissues far from the original invasion site; most toxins cause damaged by damaging host cell membranes or by inhibiting protein synthesis within the cell; there are two types of bacterial toxins exotoxin and endotoxin.
Exotoxins in general are produced by gram positive species; exotoxins may be released into the body of a host by bacteria that have invaded and colonized in it; alternatively a host may eat a contaminated piece of rot beef that already contains the exotoxins.
exotoxins travel through the bloodstream and active at specific sites to produce characteristic diseases; for example the exotoxins produced by Corynebacterium diphtheriae causes diphtheria a disease that affects the respiratory membranes; the exotoxins produced by Clostridium tetani causes tetanus a disease that affects muscle contraction.
In contrast Endotoxins are substances that generally produced by gram negative bacteria; in particular lipopolysaccharides are released from the cell walls of gram negative bacteria; unlike exotoxins which produce specific diseases at specific sites in the body lipopolysaccharides produce the same general effects throughout the body; fever, weakness, aching regardless of the bacteria that produce them; typhoid fever and meningitis are among the disease caused by endotoxins.
