Genomic diversity of class I integrons from antimicrobial resistant strains of Salmonella Typhimurium isolated from livestock, poultry and humans.

Introduction: Multidrug resistance (MDR) is a serious issue prevalent in various agriculture-related foodborne pathogens including Salmonella enterica (S. enterica) Typhimurium. Class I integrons have been detected in Salmonella spp. strains isolated from food producing animals and humans and likely play a critical role in transmitting antimicrobial resistance within and between livestock and human populations.

Objective: The main objective of our study was to characterize class I integron presence to identify possible integron diversity among and between antimicrobial resistant Salmonella Typhimurium isolates from various host species, including humans, cattle, swine, and poultry.

Methods: An association between integron presence with multidrug resistance was evaluated. One hundred and eighty-three S. Typhimurium isolates were tested for antimicrobial resistance (AMR). Class I integrons were detected and sequenced. Similarity of AMR patterns between host species was also studied within each integron type.

Results: One hundred seventy-four (95.1%) of 183 S.Typhimurium isolates were resistant to at least one antimicrobial and 82 (44.8%) were resistant to 5 or more antimicrobials. The majority of isolates resistant to at least one antimicrobial was from humans (45.9%), followed by swine (19.1%) and then bovine (16.9%) isolates; poultry showed the lowest number (13.1%) of resistant isolates. Our study has demonstrated high occurrence of class I integrons in S. Typhimurium across different host species. Only one integron size was detected in poultry isolates. There was a significant association between integron presence of any size and specific multidrug resistance pattern among the isolates from human, bovine and swine.

Conclusions: Our study has demonstrated a high occurrence of class I integrons of different sizes in Salmonella Typhimurium across various host species and their association with multidrug resistance. This demonstration indicates that multidrug resistant Salmonella Typhimurium is of significant public health occurrence and reflects on the importance of judicious use of antimicrobials among livestock and poultry.