Antimicrobial Resistance Hidden within Multiserovar Salmonella Populations

Area of Science:

• Food safety
• Microbiology
• Veterinary science

Background:

• Salmonella enterica exists as multiserovar populations in food animals.
• Different serovars possess varied antimicrobial resistance (AMR) profiles.
• Conventional Salmonella isolation methods may miss low-abundance serovars and their AMR traits.

Purpose of the Study:

• To investigate the presence of multiserovar Salmonella populations in cattle.
• To identify AMR profiles within these diverse Salmonella populations.
• To highlight the limitations of culture-based methods in detecting AMR in low-abundance serovars.

Main Methods:

• CRISPR-SeroSeq profiling was employed to analyze Salmonella serovars in cattle fecal samples.
• Culture-based Salmonella isolation was used as a comparative method.
• In vitro challenge experiments were conducted to assess AMR phenotypes.

Main Results:

• Multiserovar Salmonella populations were detected in 60% of cattle fecal samples.
• Salmonella serovar Reading, a tetracycline-resistant serovar, was found in 11% of samples, often at low levels missed by culture.
• More abundant Salmonella serovars in the same samples were susceptible to tetracycline.

Conclusions:

• CRISPR-SeroSeq is crucial for comprehensive AMR surveillance in multiserovar Salmonella populations.
• Undetected, resistant serovars represent a significant reservoir for AMR expansion in food animals.
• Advanced surveillance methods are essential to fully understand and manage AMR risks in livestock.