LAC DPH Health Advisory

First mcr-1 Producing Bacteria Identified in

a Los Angeles County Resident

January 31, 2017 




This message is intended for all health care providers, particularly hospital-based providers.

Please distribute as appropriate.


Key Message

  • An mcr-1 producing bacterial isolate has been identified in a Los Angeles County (LAC) resident, the first reported case in California. The mcr-1 gene confers resistance to the antibiotic colistin, one of few “last resort” antibiotics used to treat infections caused by certain multi-drug resistant organisms.

  • Hospital-based providers should follow LAC Department of Public Health (DPH) recommendations regarding infection control, testing, and reporting for patients with suspected and confirmed mcr-1 organisms.



Los Angeles County has identified the first patient in California with an mcr-1 producing bacterial isolate. The E. coli infection was most likely acquired during international travel and no evidence of spread in the local health care community has been identified.  Mcr-1 producing bacteria were first identified in the United States in a Pennsylvania patient in May 2016; since then, the mcr-1 gene has been reported in human specimens from five additional states and in animal specimens from two states.  The appearance of mcr-1 in Los Angeles serves as a reminder of the importance of infection control measures and antibiotic stewardship. 


Actions Requested of Providers

√ Infection Prevention: Healthcare providers should follow Standard and Contact Precautions for any patient who is suspected to be colonized or infected with mcr-1 positive organisms based on colistin resistance, pending mcr-1 confirmation, OR any patient confirmed to be colonized or infected with mcr-1 positive organisms

Laboratory Testing: Isolates with a minimum inhibitory concentration (MIC) to colistin of 4 µg/ml or higher should be tested for the presence of mcr-1. If hospital mcr-1 confirmatory testing cannot be performed, contact LAC DPH Acute Communicable Disease Control (ACDC) at 213-240-7941 to arrange for the isolates to be tested at the LAC Public Health Laboratory.

√ Reporting: All mcr-1 positive isolates identified in LAC residents and at LAC health care facilities must be reported within one working day by calling ACDC at 213-240-7941. 


For Questions and Reporting:

Los Angeles County DPH Acute Communicable Disease Control Program:
•Weekdays 8:30am-5pm: call 213-240-7941 
•After hours: call 213-974-1234 and ask for the physician on call.
For Residents of Long Beach and Pasadena:

Long Beach Health and Human Services:
•Weekdays 8am-5pm: call 562-570-4302
•After hours: call 562-435-6711 and ask for Communicable Disease Officer.

Pasadena Public Health Department: 
•Weekdays: call the Communicable Disease Control Program 626-744-6089
•After hours: call 626-744-6043.




This Health Advisory was sent by Dr. Benjamin Schwartz, Interim Director, Acute Communicable Disease Control Program, Los Angeles County Department of Public Health.




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