On the Role of Genomic Islands in Bacterial Pathogenicity and Antimicrobial Resistance

The problem of antimicrobials use failure is increasing everyday due to the transfer of virulence and antimicrobial resistance genes among different bacterial species where Genomic Islands (GEIs) have a major role. Virulence and antimicrobial resistance genes are encoded on GEIs where they can excise from a host chromosome, transfer and integrate into a new chromosome. Nonpathogenic strains become pathogenic by horizontal transfer of GEIs which in turn contributes in evolution of bacteria. GEIs was originated for symbiotic purposes then became pathogenic due changes in the environment and genes acquisition and they are useful in bacterial diagnosis as they are species-specific in some strains. The locus of enterocyte effacement (LEE) pathogenicity islands (PAIs) of Enteropathogenic E.coli (EPEC), Staphylococcus PAIs encoding toxic shock syndrome toxin (TSST), Salmonella genomic island 1(SGI1) of S. Typhimurium, the AbaR and Tn6167 GEIs of A. baumannii and the cytotoxin-associated gene (cag) and tfs4 GEIs of H. pylori are well known examples of GEIs. Target DNAs are edited by Clustered regularly interspaced short palindromic repeats (CRISPRs) and their associated (Cas) proteins causing bacterial evolution and pathogenicity. Genomic signature variation is utilized for detection of GEIs in host chromosome.