Examination of Antibiotic Resistant Gene Suggests Low Risk of Transmission

Transmission risk of a urinary tract infection caused by drug resistant, mcr-1-positive Escherichia coli seems to be low.

The risk of transmission of the mcr1 antibiotic-resistant gene from bacteria is relatively low, according to a report published in the Center for Disease Control and Prevention’s (CDC) Morbidity and Mortality Weekly Report.1

Kelly E. Kline, MPH of the Pennsylvania Department of Health and colleagues from the CDC examined the contacts of a Pennsylvania woman who was diagnosed in May 2016 with a urinary tract infection caused by the mcr1 gene Escherichia coli that showed colistin resistance. Researchers were unsure of the origin of the infection, since the woman had not traveled internationally for 1 year, had no exposure to farm animals and minimal exposure to high risk food products from a grocery store. Ms Kline and colleagues noted that the woman did have multiple admissions to 4 medical facilities in 2016.

Researchers reported that the CDC and the Pennsylvania Department of Health tracked the woman’s contacts and tested them using a perirectal swab screening.

“Twenty persons at higher risk included the patient’s medical facility roommate, household contacts, home health personnel, friends who assisted with activities of daily living such as cleaning, bathing, rotating, ambulating and toileting, and a patient who developed an E coli infection after receiving direct care from a caregiver who also assisted the index patient. Persons at lower risk included 98 health care personnel from the two high-risk facilities who directly assisted with activities of daily living while generally adhering to contact precautions. All 20 higher-risk contacts completed screening; among the 98 lower-risk contacts, 78 agreed to testing,” researchers reported.

In addition, to see if the bacteria was being transmitted among patients, state health officials offered testing at 2 high risk facilities, researchers said. One refused, and the other offered 18 patients testing where the woman had stayed in the same unit. Seven patients there accepted the screening.

Ms Kline and colleagues reported that none of the 105 people screened had the mcr1 gene bacteria. Researchers also reported that they found no evidence of colistin-resistant bacteria.

“These findings suggest that the risk for transmission from a colonized patient to otherwise healthy persons, including persons with substantial exposure to the patient, might be relatively low,” researchers said.

In an interview with Infectious Disease Advisor, Alexander Kallen, MD, MPH, co-author of the report, medical officer and team lead for antimicrobial resistance and emerging pathogens at the CDC explained that, “Although there is no immediate threat to the public, the discovery of mcr1 vividly illustrates the many domestic and global challenges facing us as we work to slow the spread of antibiotic resistance and improve antibiotic use.”

“New resistant bacteria continue to emerge with the potential to severely impact our ability to provide effective medical treatment,” he continued. “It is critical for clinicians to implement strong infection prevention measures and work to stop the spread of infection across healthcare settings and the community,” Dr Kallen said during the interview. He added “These discoveries emphasize the importance of a coordinated public health response, not only to detect new threats like mcr1, but also to track, slow, and respond to the emergence of antibiotic resistance. CDC is working with federal partners to continue searching for the mcr1 gene using sophisticated laboratory methods, such as whole genome sequencing, for some isolates.”

“Beginning in fall 2016, CDC’s Antibiotic Resistance Laboratory Network will expand nationwide capabilities to combat antibiotic resistance with a network of seven regional labs fully equipped to detect resistance in human samples,” said Dr Kallen and noted that the labs will have the ability to detect and report new forms of antibiotic resistance to the CDC.

Dr Kallen concluded by explaining that the “CDC and FDA have put together a panel, ‘Isolates with New or Novel Antibiotic Resistance,’ which includes two mcr1 isolates for the AR Isolate Bank. These isolates can be used for development of new diagnostics and therapeutics that can rapidly detect and treat infections caused by resistant bacteria.”

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  1. Kline KE, Shover J, Kallen AJ, et al. Investigation of first identified mcr-1 gene in an isolate from a U.S. patient — Pennsylvania, 2016. MMWR. 2016; 65(36):977-978.