Pathogenicity islands (PAIs): Properties and Types

Last updated on May 13th, 2021

 Pathogenicity islands (PAIs) are large groups of mobile genetic elements that are associated with pathogenicity and are located on the bacterial chromosome. The concept of PAI was founded in the late 1980s by Jörg Hacker and colleagues.

The presence of pathogenicity islands (PAIs) in the genomes of bacterial pathogens is one of the main features that differentiate them from closely related nonpathogenic strains or species.

The major properties of PAIs are as follows:

  1. PAIs have one or more virulence genes
  2. PAIs are present in the genome of the pathogenic member of a species but absent in the nonpathogenic members
  3. PAIs are large organized group of genes, usually 100 to 200 kb in size.
  4. PAIs are found with parts of the genome associated with mobile genetic elements;
  5. PAIs often have genetic instability
  6. PAIs typically have different guanine plus cytosine content than the rest of the bacterial genome. 

Few examples of the very large number of pathogenicity islands of human pathogens are:

Genus/SpeciesPAI NameVirulence Characteristics
Escherichia  coliPAI I536Alpha hemolysin, fimbriae, adhesions, in urinary tract infections.
Escherichia coliPAI Ij96Alpha hemolysin, P-pilus in urinary tract infections
Escherichia coli (EHEC)01#7Macrophage toxin of enterohaemorrhagic Escherichia coli
Salmonella typhimuriumSPI-1Invasion and damage of host cells, diarrhea
Yersinia pestisHPI/pgmGene that enhance iron uptake
Vibrio cholerae EL tor O1VPI-1Neuraminidase, utilization of amino sugars
Staphylococcus aureusSCC mecMethicillin and other antibiotic resistance
Staphylococcus aureusSaPI1Toxic shock syndrome toxin-1, enterotoxin
Enterococcus faecalisNPmCytolysin, biofilm formation

 Source: LANGE Medical Microbiology/PubMed Central

About Acharya Tankeshwar 468 Articles
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