An analysis of reported non-typhoidal Salmonella (NTS) infections in the United States suggests international travel is a significant risk factor for antibiotic resistance, US researchers reported today in the Journal of Infectious Diseases.
Although most of the 1.35 million NTS infections that occur each year in the United States don't require antibiotic treatment, antibiotics are needed for more severe invasive infections, and roughly 16% of reported NTS infections are antibiotic resistant. To assess the documented links between international travel and antibiotic-resistant NTS infections, a team led by researchers with the Centers for Disease Control and Prevention analyzed NTS infections reported to the Foodborne Diseases Active Surveillance Network during 2018-2019 that were screened for resistance genes, including those conferring resistance to first-line agents (ciprofloxacin, ceftriaxone, or azithromycin). They used multivariable regression analysis to estimate the contribution of international travel to drug-resistant NTS infections.
Among 9,301 NTS infections with sequenced isolates and known travel status, 1,159 (12%) occurred after recent international travel. Among 1,220 infections with predicted resistance to first-line antibiotics, 30% were among travelers and 19% were estimated to be attributable to international travel during the 7 days before illness began.
Adjusted for age, sex, and season, NTS infections following recent travel were more likely to have predicted resistance for first-line antibiotics compared with non-travelers (adjusted odds ratio [aOR], 3.7; 95% confidence interval [CI], 3.2 to 4.3). The odds of predicted resistance to first-line antibiotics were highest among travelers to Asia (aOR, 7.2; 95% CI, 5.5 to 9.5). The highest incidence of infections resistant to first-line antibiotics was in Latin America and the Caribbean (3 per 100,000 travelers).
The study authors say the association between travel and antibiotic resistance could be related to increased selection pressure for resistance genes in particular regions from use of antibiotics in human medicine but could also be linked to antibiotic use in animals. They also say that use of whole genome sequencing for NTS surveillance can help track resistant strains.
"Understanding risks of resistant infection could help target prevention efforts," they concluded.