Racial and Gender Differences Noted in Community-Associated Carbapenem-Resistant Enterobacterales Cases

CRE cases are considered a US public health threat, and, concerningly, a small, but notable proportion of CRE cases occur in patients without traditional health care risk factors.

Because carbapenem-resistant Enterobacterales (CREs) are a key component of the multidrug resistant infections in the US, it is considered a US public health threat by the Centers for Disease Control and Prevention (CDC). In a recent study, the investigators found that CRE cases, although traditionally considered a health care-associated infection, a noteworthy percentage were found to be community-associated (CA) and, significantly, in White female patients.

Sandra Bulens, MPH, health scientist, CDC, and lead author of the study published in the American Journal of Infection Control discussed the findings with Infection Control Today® (ICT®).

Infection Control Today® (ICT®): A summary of the key findings and why they are important.

Sandra Bulens, MPH, health scientist, CDC: Through the Centers for Disease Control and Prevention’s (CDC’s) Emerging Infections Program (EIP) we have been conducting active laboratory- and population-based surveillance for carbapenem-resistant Enterobacterales (CRE), and other drug-resistant gram-negative organisms. From 2012 to 2015, we identified a total of 1499 CRE cases, and after extensive medical record review, 10% were determined to have no known prior health care risk factors in the year before culture. Among these community-associated cases (ie, cases without known health care risk factors), 12 isolates underwent whole genome sequencing, and 5 of them were found to harbor a carbapenemase gene.

These findings are important for several reasons:

  • First, we have added to the growing body of literature that is documenting the spread of CRE into the community, which is of concern.

  • Second, although a very small number of isolates underwent whole genome sequencing, the fact that 5 of the 12 isolates harbored a carbapenemase gene introduces new challenges for controlling spread of carbapenemase-producing carbapenem-resistant (CP-CRE). We are working on approaches that will allow us to gather more information about possible health care encounters and community activities and practices that might put people at risk for acquiring these organisms.

  • Third, most CA-CRE cases were E. coli identified from a urine culture and occurred among females, of White race, who had a urinary tract infection. Although these findings are consistent with the literature describing urinary tract infections, it highlights the importance of using local epidemiology and patient characteristics, such as age and sex, when making decisions about testing and treatment.

ICT®: How did the study idea come about?

SB: In some of the earlier work we did to validate data collected through this surveillance activity, we confirmed that a small number of cases did not have health care exposures that could be identified in medical records reviewed by our emerging infections program (EIP) site partners. This analysis is a continuation of that earlier work, recognizing the importance of the finding that there are these highly resistant organisms affecting persons in community settings.

ICT®: What is the practical application for the key findings for infection preventionists from this study?

SB: There are a few important findings for infection preventionists from this study.

  • First, this highlights the potential for CP-CRE to move from a pathogen primarily encountered in healthcare settings into the community. Taking recommended actions to prevent the spread of CP-CRE in health care settings, especially in inpatient and long-term care settings where the risk of transmission is highest, can slow spread into the community, where this can impact more individuals, cause infections that are challenging to treat in the outpatient settings, and multiply the challenges of controlling further spread.

  • Second, this emphasizes that all health care settings, regardless of level of care provided, should make infection prevention a priority, including educating staff on and monitoring adherence to transmission-based precautions, hand hygiene and PPE use, and environmental cleaning.

ICT®: What results surprised you?

SB: The finding that 10% of our cases occurred in patients without identifiable health care risk factors, and that a substantial proportion of sequenced CA-CRE harbored carbapenemase, was surprising since these are typically organisms identified in individuals with extensive healthcare exposure. We were also surprised to identify that a significantly higher proportion of patients with CA-CRE were White individuals compared to those with health care-associated (HCA)-CRE; these apparent racial differences merit further exploration.

ICT®: What, if any, future research will there be related to this one?

SB: There are several activities that we are working on to better understand the occurrence of CA-CRE in our EIP surveillance population.

  • First, there is a plan to assess the data that have been collected since 2016. These data were not included in the current paper because the phenotypic case definition changed, and cases identified in 2016 and more recent years cannot readily be compared to older cases.

  • Second, we are planning to conduct a health interview with our EIP partners that would ask patients who are identified with CP-CRE more about exposures that we do not get information about through this surveillance program. These exposures include household and occupational exposures, travel related exposures, exposures to animals, and prior antibiotic use.

ICT®: Is there anything else that you would like to add?

SB: Thank you for the opportunity to talk with you about our paper.