Antimicrobial Susceptibility Testing and Successful Treatment of Hospitalised Patients with Extensively Drug-Resistant Campylobacter Jejuni Infections Linked to a Pet Store Puppy Outbreak.

Objectives: Most patients with Campylobacter infection do not require antibiotics; however, they are indicated in severe cases. Clinical breakpoints for many antibiotics are not yet established by the CLSI, making antibiotic selection for resistant infections challenging. During an outbreak of pet store puppy-associated XDR Campylobacter jejuni infections resistant to seven antibiotic classes, several patients required antibiotics. This study aimed to determine MICs of the outbreak strain for various antibiotics and describes the successful treatment of two patients using imipenem/cilastatin, a drug not traditionally used for Campylobacter infections. Methods: We used whole-genome multilocus sequence typing (wgMLST) to determine the genetic relatedness of Campylobacter isolates collected from two human patients' stool samples with the outbreak strain. We performed extended antimicrobial susceptibility testing on 14 outbreak isolates and 6 control strains to determine MICs for 30 antibiotics (14 classes). Results: Isolates from both patients were highly related to the outbreak strain by wgMLST. MICs indicated resistance of the outbreak strain to most antibiotic classes, except phenicols, glycylcyclines and carbapenems. Due to potential side effects of phenicols and safety issues precluding use of glycylcyclines such as tigecycline when alternatives agents are available, we used carbapenems to treat patients who were severely ill from the outbreak strain infections. Conclusion: Stewardship and clinical vigilance are warranted when deciding whether and how to treat patients with suspected C. jejuni diarrhoea with antibiotics. Clinicians should maintain a high index of suspicion for XDR Campylobacter when patients fail to improve and consider the use of carbapenems in such settings. (c) 2021 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )