Relation Of Pili To Other Virulence Factors
Cholera has become the prototype for a group of intestinal infections called enterotoxic enteropathies. The mechanism of action of cholera toxin has been studied in great detail and encouraged a search for toxins in other intestinal infections. Surveys in Brazil and Ethiopia and on Cyprus showed that other enterobacteria such as klebsiella and enterobacter species produce enterotoxin(s). The discovery of human enterotoxigenic E. coli (ETEC) strains stimulated many studies on possible roles of heat labile (LT) and heat stable enterotoxins in the so-called enteropathogenic E. coli serotypes of E. coli. Successful recent development of LT toxoid as well as pili vaccines for prevention of ETEC infections in animals have confirmed that enterotoxins as well as pili are key virulence factors in enterotoxic enteropathies caused by ETEC. A classical electron microscopy study on vibrio and aeromonas strains showed that both these organisms can possess surface appendages of pili-like nature.