Salmonella enterica serovar Typhi has a 4.1 kb genetic Island inserted within the sapABCDF operon that causes loss of resistance to the antimicrobial peptide protamine

Abstract

Objectives: To investigate the association between the presence of a genetic island inserted within the sapABCDF operon of Salmonella Typhi and the susceptibility to antimicrobial peptides. Methods: Genetics and bioinformatics approaches were used to study the genomic organization of the sap operon of Salmonella Typhi and several serovars of Salmonella enterica. PCR was used to confirm the information obtained from these analyses. Deletion of the entire genetic island of Salmonella Typhi was achieved by the red swap method. RT-PCR amplification and antimicrobial peptide susceptibility tests were used to evaluate expression of the sap genes and bacterial resistance to protamine. Results: Inspection of the genomes of Salmonella Typhi and 10 serovars of Salmonella enterica showed an insertion of a genetic island located between the sapB and sapC genes of the sap operon. This genetic element was referred to as GICT18/1. Unlike Salmonella Typhimurium, the bacterial susceptibility to protami