Background

A multistate outbreak of campylobacteriosis linked to pet store puppies (2017-2019) was identified as a strain of Campylobacter jejuni. The strain was resistant to multiple antimicrobial classes, including macrolides and fluoroquinolones, both of which are routinely used for the treatment of Campylobacter infections in humans and animals. The Centers for Disease Control and Prevention (CDC) and the Ohio Department of Health, identified patients who developed a severe illness to a resistant strain of Campylobacter jejuni that was acquired through the handling of puppies purchased from pet stores.

Purpose

The isolated Campylobacter organisms were sent to the Center for Veterinary Medicine/Office of Research, Division of Animal and Food Microbiology, to determine susceptibility patterns to effective antimicrobial agents not traditionally used in the testing of Campylobacter species. Due to the treatment needs of patients infected in this outbreak, time was of the essence in finding a suitable antimicrobial. Agar dilution, the gold standard of antimicrobial susceptibility testing, required time-consuming testing and the availability of antimicrobial powders.

Methodology

Antimicrobial testing methods were designed based on supplies available to both clinical laboratories and the National Antimicrobial Resistance Monitoring System (NARMS). Campylobacter broth microdilution methods approved for use by the Clinical Laboratories Standard Institute (CLSI, M45) were applied to clinical and surveillance antimicrobial susceptibility testing panels (Fisher Scientific, Trek Diagnostics, Cleveland Ohio) in order to measure susceptibility to 14 classes of antibiotics. For method validation, quality control organisms and Campylobacter isolates with known susceptibility patterns were included.

Results

The Campylobacter outbreak strain was susceptible to imipenem/cilastatin, a carbapenem drug seldom used to treat Campylobacter infections in humans. Although clinical interpretive criteria for Campylobacter are only available for fluoroquinolones, macrolides, and tetracyclines, we demonstrated that outbreak isolates had low minimum inhibitory concentrations to carbapenems.

Conclusion

This work highlights an excellent collaboration between government agencies, state agencies and hospital laboratories to effectively treat and improve human and animal health. It also highlights the need for laboratories to be able to identify approved methods that can be used in alternative systems to help aid in defining effective treatment options for clinicians and patients.