Identification of Three Patients with Colistin-resistant Escherichia coli Isolates Containing the mcr-1 (Mobile Colistin Resistance) Gene from a Single Health System in Michigan, USA

• Published in: Open forum infectious diseases Vol. 4; no. suppl_1; p. S149
• Main Authors: Washer, Laraine L, Brennan, Brenda, Mills, John, Dombecki, Carolyn, Valyko, Amanda, Henig, Oryan, Soehnlen, Marty, Jones, Kelly, Kaye, Keith S, Bachman, Michael A
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 01.10.2017
• ISSN: 2328-8957; 2328-8957
• DOI: 10.1093/ofid/ofx163.241

Abstract Background The plasmid encoded mcr-1 gene conferring resistance to colistin was first reported in bacterial isolates from food, animal, and human origin in China in November 2015. As of May 2017, the USA has reported 13 mcr-1 isolates from human cases in 9 states. We describe three patients with mcr-1 E.coli from a single healthcare system in Michigan, USA. Methods In January 2016, the University of Michigan Health System clinical microbiology laboratory began colistin susceptibility testing of Enterobacteriaceae with broth microdilution using minimum inhibitory concentration of ≥ 4 mcg/mL as the epidemiologic cut-off value for resistance. Resistance was confirmed by the Michigan Department of Health and Human Services. Real-time PCR for mcr-1 was performed by the Centers for Disease Control and Prevention. Travel and dietary history was obtained by public health authorities and medical history from the electronic health record. Results Three unique patient isolates with the mcr-1 gene were identified. All were carbapenem susceptible and all had international travel within the prior 6 months. There were no healthcare-associated epidemiologic links identified. Rectal swab and urine cultures did not reveal transmission to household contacts. Patient A Patient B Patient C Age (years) 70 19 22 Gender Female Male Female Culture Source Urine Urine Urine Comorbidities Cirrhosis, diabetes Spina bifida, neurogenic bladder, pressure ulcer None Preceding Hospitalization Yes No No Procedures Liver transplant Urodynamic studies Intrauterine device Subspecialty Clinic Hepatology, gynecology Pediatric specialties Gynecology Prior travel Kenya 7/2016 (17 d) China 10/2016 (13 d) Lebanon 7/2016 (22 d) Mexico 2/2017 (9 d) Diet lyesaCTO-vegetarian dairy, poultry, beef, fish; no pork chicken, seafood, cheese, street vendor Prior antibiotics Yes Yes No Colistin MIC (mcg/mL) 4 4 > 4 ESBL Yes No No Quinolone susceptibility Resistant Resistant Susceptible ESBL, Extended Spectrum Β Lactamase; d, days Conclusion Routine colistin susceptibility testing identified three patients with travel-associated colistin-resistant E.coli due to mcr-1 in a single healthcare system. Increased surveillance is needed to understand the scope and risk factors for mcr-1 mediated resistance. Disclosures K. S. Kaye, Xellia: Consultant, Consulting fee. Merck: Consultant and Grant Investigator, Consulting fee and Research support. The Medicines Company: Consultant and Grant Investigator, Consulting fee and Research support