The selection of effective antibiotics is critical for the treatment of invasive Salmonella infections. However, some bacteria have been able to survive or grow despite the use of an antibiotic that previously was able to stop them. These bacteria are said to be antibiotic-resistant. Antibiotic use in the animal industry is thought to contribute greatly to the prevalence of antibiotic-resistant infections in humans. Antibiotic-resistant salmonellae have been isolated from various food products and have been the causative agent in several foodborne disease outbreaks in the United States.
Antibiotic-resistant nontyphoidal Salmonella infections are on the rise. The CDC estimates that there are 212,500 drug-resistant nontyphoidal infections and 70 deaths per year. According to the CDC National Antimicrobial Resistance Monitoring System (NARMS), resistance to ciprofloxacin approached 10% in 2017. In 2018, an antibiotic-resistant strain of Salmonella Infantis accounted for 25% of infections in people in the U.S. Most of these infected people had recently eaten chicken.
Over the past decades, several types of Salmonella Typhi have become resistant to multiple antibiotics. The percent of Salmonella Typhi infections nonsusceptible to ciprofloxacin reached 74% in 2017, severely limiting treatment options for this potentially life-threatening disease.