AMR in focus: Deep dive into the association between colonization and infection with multi-drug resistant bacteria

Antimicrobial resistance is well-recognized to be a major threat to the continuation of modern medicine because of difficult-to-treat infections due to multiple resistant bacteria, notably gram-negative bacteria (GNB) and vancomycin-resistant enterococci (VRE), especially in high-risk settings and vulnerable patients where morbidity and mortality from such infections are high [i, ii]. Infection prevention and control programs aim to prevent transmission and colonization through approaches such as screening high-risk admissions and isolation or cohorting of individuals known to be colonized. However, the actual risk of colonized patients going on to develop infections has been difficult to quantify, limiting a full understanding of the benefits of screening programs and of prophylactic or pre-emptive treatments for colonized patients.

A very detailed systematic review and meta-analysis [iii] covering 44 cohort studies across 14 countries aimed to provide the best estimate of the risks of infection to patients with gastro-intestinal carriage of multi-drug resistant GNB or VRE, calculated as a cumulative incidence or incidence density of infection, taking into consideration well-defined time frames. In summary, the authors showed that the risk of infection is highest for those patients colonized with gram-negative bacteria resistant to carbapenem antibiotics (approximately 4 per 1000 patient days) and that this risk is nearly five times higher than the risk for patients colonized with VRE.

The authors acknowledge some limitations with this study, particularly around the fact that analysis was limited by regional differences in the number of data sources and incidence data available. Nevertheless, this type of data will become increasingly relevant as healthcare institutions make difficult decisions regarding prioritizing active surveillance programs and considering which patients would benefit the most from planned prophylactic or preemptive antibiotic treatment regimens. Learn more here.

Author: Dr. Beryl Oppenheim

Dr. Beryl Oppenheim is a Senior Director, Medical Affairs at Cepheid.

Beryl is a medically qualified microbiologist who has worked in the

National Health Service in England for many years, leading

laboratories and infection control teams. Dr. Oppenheim has published

widely with more than 100 peer-reviewed publications, and her main research

interests include healthcare-associated infections (HAIs), antimicrobial resistance, and infections in the critically ill and immunocompromised host. 

i. Budhram DR, Mac S, Bielecki JM, Patel SN, Sander B. Health outcomes attributable to carbapenemase-producing Enterobacteriaceae infections: A systematic review and meta-analysis. Infect Control Hosp Epidemiol. 2020 Jan;41(1):37-43

ii. Zhou R, Fang X, Zhang J, Zheng X, Shangguan S, Chen S, Shen Y, Liu Z, Li J, Zhang R, Shen J, Walsh TR, Wang Y. Impact of carbapenem resistance on mortality in patients infected with Enterobacteriaceae: a systematic review and meta-analysis. BMJ Open. 2021 Dec 14;11(12):e054971

iii. Willems RPJ, van Dijk K, Vehreschild MJGT, Biehl LM, Ket JCF, Remmelzwaal S, Vandenbroucke-Grauls CMJE. Incidence of infection with multidrug-resistant Gram-negative bacteria and vancomycin-resistant enterococci in carriers: a systematic review and meta-regression analysis. Lancet Infect Dis. 2023 Jan 30:S1473-3099(22)00811-8