Background: Antimicrobial resistance in foodborne pathogens, including nontyphoidal Salmonella (NTS), is a public health concern. Pennsylvania conducts integrated surveillance for antimicrobial resistance in NTS from human and animal sources.
Methods: During 2015-2017, clinical laboratories submitted 4478 NTS isolates from humans and 96 isolates were found in 2520 retail meat samples. One hundred nine clinical isolates that shared pulsed-field gel electrophoresis patterns with meat isolates and all strains from meat samples were tested for susceptibility to antimicrobial agents. Six clinical and 96 NTS isolates from meat sources (total 102) were analyzed by whole-genome sequencing (WGS).
Results: Twenty-eight (25.7%) of the 109 clinical NTS and 21 (21.9%) of strains from meat sources had resistance to ≥3 antimicrobial drug classes (multidrug resistance). Sixteen of the 102 (15.7%) isolates analyzed by WGS had resistance mechanisms that confer resistance to expanded-spectrum cephalosporins, such as ceftriaxone. We identified bla CTX-M-65 in 2 S. Infantis isolates from clinical and 3 S. Infantis isolates from meat sources. These 5 bla CTX-M-65-positive S. Infantis strains carried ≥5 additional resistance genes plus a D87Y mutation in gyrA that encodes fluoroquinolone resistance. WGS showed that isolates from patients and meat samples were within ≤10 and ≤5 alleles for S. Infantis and S. Reading, respectively.
Conclusions: A significant proportion of NTS isolates from human and animal sources were multidrug resistant and 16% had genetic mechanisms that confer resistant to ceftriaxone. These results emphasize need for integrated surveillance in healthcare and agricultural settings.
Keywords: CTX-M-65; ESBL; Salmonella; antibacterial agents; antimicrobial resistance; blaCMY; ceftriaxone susceptibility; extended-spectrum β-lactamase; foodborne pathogens; microbial quality; multidrug resistant; producing.
© The Author(s) 2021. Published by Oxford University Press on behalf of Infectious Diseases Society of America.