Association between specific plasmids and relapse in typhoid fever

Area of Science:

• * Infectious Diseases
• * Microbiology
• * Epidemiology

Background:

• * Typhoid fever, caused by Salmonella typhi, remains a significant public health concern, particularly in endemic regions like Lima, Peru.
• * Clinical relapse after initial treatment for typhoid fever is a recognized complication, impacting patient recovery and disease transmission.
• * Understanding the factors contributing to relapse is crucial for developing effective treatment and prevention strategies.

Purpose of the Study:

• * To investigate the incidence and potential causes of clinical relapse in patients hospitalized with typhoid fever in Lima, Peru.
• * To explore the role of multiple Salmonella typhi strains and plasmid profiles in typhoid fever relapse.
• * To identify potential epidemiologic markers associated with recurrent typhoid fever.

Main Methods:

• * Analysis of Salmonella typhi isolates from 73 hospitalized typhoid fever patients in Lima, Peru.
• * Clinical data collection, including monitoring for fever and positive blood cultures for relapse within 3 months.
• * Plasmid profiling of Salmonella typhi strains to identify epidemiologic markers and assess for multiple strain infections.

Main Results:

• * 15% (11 out of 73) of patients experienced a clinical relapse within 3 months.
• * Three patients who relapsed were initially infected with more than one strain of Salmonella typhi.
• * Isolation of a strain with a 24- or 38-kilobase plasmid at the time of original infection was significantly associated with relapse.

Conclusions:

• * Infection with multiple Salmonella typhi strains is common in this endemic area and may contribute to clinical relapse.
• * The presence of specific plasmids (24- or 38-kilobase) in the infecting strain is linked to an increased risk of relapse.
• * Relapse in typhoid fever may be partly dependent on the specific characteristics of the infecting Salmonella typhi strain(s).