Rising Threat: Evaluating Salmonella Treatment Options Amid Antimicrobial Resistance

Salmonella causes an estimated 1.35 million infection, 26500 hospitalizations, and 420 deaths in the United States each year, according to the US Centers for Disease Control and Prevention (CDC). Most Salmonella transmissions are foodborne, though it can also be contracted by coming in contact with infected animals, their feces, or their environment.

Rates of antimicrobial resistance have been steadily rising in Salmonella, threatening to limit the treatment options available to combat severe infections. In 2014, Nebraska Medicine's Clinical Microbiology laboratory implemented the FilmArray Gastrointestinal Panel (GIP) for rapid detection of 22 pathogens, including Salmonella, but antibiotic susceptibilities are not routinely available with this method.

One study, presented at the recent 2023 MAD-ID Annual Antimicrobial Stewardship Meeting, aimed to evaluate the appropriateness of treatment recommendations for Salmonella based on local susceptibilities reported by the laboratory.

Specifically, the investigators assessed the appropriateness of recommendations for treating Salmonella with ceftriaxone in severe disease/bacteremia and fluoroquinolones or trimethoprim-sulfamethoxazole for non-severe infection. The research was presented by lead author Catherine Christopherson.

The investigators conducted a retrospective review on all Salmonella isolates received at the regional referral laboratory from January 1, 2020-November 14, 2022. Patient demographics, Salmonella serogroups, culture site, and reported antibiotic susceptibilities were analyzed using descriptive statistics.

Out of 40 unique Salmonella isolates, 21 (52.5%) were sent from external facilities. The majority (70%) of isolates were from female patients with an average age of 54.5 years.

Susceptibility data was available for 36 isolates, with blood cultures comprising the largest subset (52.8%). Serogroup identification was possible for 28 isolates, with Group C being the most common (33.3%).

Susceptibility rates were high for ampicillin (86.1%), ceftriaxone (94.4%), ciprofloxacin (80.6%), and trimethoprim-sulfamethoxazole (91.7%). No isolates showed resistance to all antibiotics, although 1 isolate was only susceptible to ciprofloxacin. Resistance to both ceftriaxone and ciprofloxacin was not observed.

The study authors concluded that empiric therapy with ceftriaxone for severe Salmonella disease/bacteremia remains appropriate based on local data. However, due to increasing fluoroquinolone resistance, trimethoprim-sulfamethoxazole will be recommended as the preferred oral empiric therapy for non-severe disease.

The investigators recommended further research of additional isolates and susceptibility patterns to refine treatment guidelines that utilize molecular testing as the primary method for Salmonella detection.

This study, “Rise of the (Possible) Resistance: A Review of Susceptibility Patterns for Nontyphoidal Salmonella enterica in Nebraska,” was presented as an abstract at the 2023 MAD-ID Annual Antimicrobial Stewardship Meeting.