81. Azithromycin-Nonsusceptible Salmonella Newport Infections Associated with Mexican-style Soft Cheese and Beef—the United States, 2018–2019
BACKGROUND: Azithromycin is a recommended oral agent for treating nontyphoidal Salmonella (NTS), when antibiotics are indicated. Azithromycin nonsusceptibility among NTS is <1% in the United States. CDC, FSIS, and state health departments investigated an outbreak of azithromycin-nonsusceptible Salmonella serotype Newport infections to determine sources. METHODS: We classified isolates as the outbreak strain if they were within 11 alleles by core genome multilocus sequence typing. We defined a case as infection with the outbreak strain during June 2018–February 2019. After stratifying by gender and ethnicity, we compared food exposures ≤7 days before illness onset with those reported by healthy persons in the Foodborne Diseases Active Surveillance Network population survey (2006–2007). We used broth microdilution to determine antimicrobial susceptibility. RESULTS: We identified 218 case patients from 31 states; 49 of 176 (28%) were hospitalized and 2 died. Overall, 65% (121/187) were Hispanic, and 41% (70/169) visited Mexico in the 7 days before illness onset. Among travelers to Mexico, 71% (23/32) reported eating Mexican-style soft cheese; 16/23 (70%) recalled obtaining the cheese in Mexico. Among nontravelers, the proportion who ate Mexican-style soft cheese (30%, 18/60) was similar to that reported by healthy persons, whereas the proportion who consumed beef (91%, 60/66) was higher than reported by healthy persons (P = 0.04). The outbreak strain was detected in a sample of soft cheese obtained in Mexico, and in a cecal sample from a steer and a beef sample that was collected at FSIS-regulated establishments in the United States. Isolates were resistant to ampicillin and trimethoprim–sulfamethoxazole, nonsusceptible to azithromycin, and showed decreased susceptibility to ciprofloxacin. CONCLUSION: This is the first documented outbreak of azithromycin-nonsusceptible Salmonella infections in the United States. Two food vehicles—soft cheese obtained in Mexico, and beef obtained in the United States—were ...
