Antibiotic-ResistantSalmonella typhiFrom Two Outbreaks: Few Ribotypes and IS200Types Harbor Inc HI1 Plasmids

Abstract

To investigate factors that could be involved in the emergence of antibiotic resistant S. typhi, we characterized R plasmids and antibiotic resistant S. typhi strains from two outbreaks of typhoid in Peru and Chile. Differences in the Inc HI1 plasmids of Peruvian and Chilean strains were identified by conjugation and incompatibility studies and plasmid DNA characterization. Antibiotic-resistant S. typhi harboring Inc HI1 plasmids belonged to a reduced number of Pst1 and Cla1 ribotypes and IS200 types, in contrast to the high genetic diversity found among epidemic antibiotic-susceptible S. typhi. The low diversity of antibiotic-resistant S. typhi suggests that they may express properties that are related to both their ability to harbor Inc HI1 R plasmids and to disseminate.

Analysis of Salmonella enterica Serotype Typhi Pulsed-Field Gel Electrophoresis Patterns Associated with International Travel

“…Another study found similarities in PFGE patterns and plasmid profiles of MDRST isolates from Tajikistan and the Indian subcontinent, suggesting that the ciprofloxacin-resistant strains isolated in Tajikistan originated from the Indian subcontinent (7). Several studies have associated large conjugative plasmids with the presence of the MDR phenotype (2,5,9,13,14,26). Our data and those of others thus support the suggestion that multiple-drug resistance in S. enterica serotype Typhi is largely due to the clonal expansion of a limited number of strains that have acquired (presumably) plasmid-mediated drug resistance genes.…”

“…The lack of diversity among MDRST strains suggests that the MDR phenotype may provide a selective advantage that has allowed these strains to spread relatively unchanged. Alternatively, the lack of diversity may indicate that relatively few strains of S. enterica serotype Typhi are capable of receiving and maintaining conjugative resistance plasmids (5). Continued monitoring of MDRST PFGE patterns for the divergence of existing patterns and the emergence of new patterns many help clarify this issue.…”

The Hha protein facilitates incorporation of horizontally acquired DNA in enteric bacteria

“…Although the Enterobacteriaceae are the potential host range of IncHI1 plasmids, most of them have been isolated solely from the genus Salmonella (Suzuki et al, 2010). In fact, IncHI plasmids account for a significant percentage of the multiple antibiotic resistance phenotypes in this genus (Fica et al, 1997). Plasmid R27 confers to its host resistance to tetracycline.…”

Temperature-Dependent Conjugative Transfer of R27: Role of Chromosome- and Plasmid-Encoded Hha and H-NS Proteins

“…1). IncHI plasmids are low-copy-number conjugative plasmids that encode multiple-antibiotic resistance in S. enterica serovar Typhi (14). Plasmids belonging to the IncHI group have been considered to play a relevant role in the persistence and reemergence of this pathogen (20).…”