Key Risk Factors for Patient-to-Patient Transmission of Drug-Resistant Bacterium

In a recent study, researchers identified three key factors that increase the risk for patient-to-patient transmission of carbapenemase-producing carbapenem-resistant Enterobacteriaceae (CP-CRE). Anat Schwartz-Neiderman, Tel Aviv Sourasky Medical Center, Israel, and colleagues, published the results of their study online in Infection Control & Hospital Epidemiology.

According to the authors, “[p]atient characteristics (ventilation and carriage of another MDRO [multidrug-resistant organism]), as well as duration of contact, are risk factors for CP-CRE acquisition among contacts.” CP-CRE is a dangerous drug-resistant bacterium that often affects patients in hospitals and nursing homes who are on ventilators, require catheters, or receiving long courses of antibiotics.

“The emergence and spread of carbapenemase-producing carbapenem-resistant Enterobacteriaceae (CP-CRE) harboring the gene for Klebsiella pneumoniae carbapenemase (bla_KPC) is a major public health concern,” the authors write. “Strains of K. pneumoniae and other Enterobacteriaceae harboring bla_KPC are often extremely drug-resistant and pose a significant therapeutic challenge. Infections by these strains have also been associated with poor clinical outcomes.”

However, limited data are available on these pathogens, and therefore, little is known about their transmission. As a consequence, the researchers conducted a study to identify risk factors for acquisition of CP-CRE among individuals exposed to a patient who is colonized or infected with CP-CRE.

They evaluated data from 3,158 adult inpatients who were screened for CP-CRE between October 2008 and June 2012, because they had been in contact with a specific patient who was newly diagnosed with CP-CRE. Among the patients who were screened, 53 tested positive for CP-CRE. The researchers then compared data from these patients with data from 106 who were negative for CP-CRE.

The researchers showed that 96% of cases of patient-to-patient transmission of CP-CRE had at least one of three key risk factors: carriage of, or infection with, another MDRO; mechanical ventilation; and contact period of ≥3 days. They also found that patients who had taken cephalosporin antibiotics were less likely to acquire CP-CRE from another patient than those who had taken other classes of antibiotics. However, when the researchers compared patients who received only cephalosporins with those who received no antibiotics, they found no protective effect of cephalosporins.

To limit the spread of MDROs, clinicians typically isolate patients who carry CP-CRE. Although clinicians use bacterial cultures to identify these individuals, this method detects only a portion of the actual colonized population. As a consequence, active surveillance of high-risk patients is therefore also critical.

The researchers therefore emphasize that identification of these three key predictors of CP-CRE acquisition among individuals who come into contact with infected patients has important implications for clinical practice. “Potentially, such predictors can be used to direct clinical care, for example, the choice of empiric antibiotic therapy for exposed patients with signs of infection while screening results are pending.”

“Repeat studies confirming our findings are needed before such recommendations can be made as a means of promoting antibiotic stewardship,” they conclude.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.