3 Common Causes of Drug-Resistant Bacteria Transmission

Researchers in Israel suggest that ventilation, carriage of another multidrug-resistant organism, and duration of contact appear to be risk factors for transmission and acquisition of the extremely drug-resistant bacteria carbapenemase-producing carbapenem-resistant Enterobacteriaceae (CP-CRE) among contacts.

Published online in Infection Control & Hospital Epidemiology, the study findings help explain why some contacts of patients infected with CP-CRE acquire the dangerous bacteria and others do not.

“The spread of CP-CRE is a major public health concern because it is extremely drug resistant; however, the research on these pathogens is very limited, and so is our knowledge of their transmission,” said lead author Vered Schechner, MD, MSc, an infection control physician in the Department of Epidemiology at Tel Aviv Sourasky Medical Center in Israel. “Identifying high-risk groups helps us to avoid excessive screening that can be risky and expensive, and to determine who should be screened and who might be a candidate for pre-emptive isolation or antibiotics.”

With the screening of newly identified CP-CRE patients identified as an important step to limit further transmission, Schechner and colleagues performed a matched case-control study in a tertiary care hospital in Israel. Participants included patients who underwent rectal screening for CP-CRE following close contact with a newly identified CP-CRE index patient. Cases were defined as positive tests for CP-CRE. For each case patient, two matched controls were randomly selected from the pool of contacts who tested negative for CP-CRE following exposure to the same index case. Bivariate and multivariate analyses were conducted using conditional logistic regression. The researchers identified 53 positive contacts in 40 unique investigations (896 tests performed on 735 contacts) between October 6, 2008 and June 7, 2012.

The study investigators found that 96% of patient-to-patient transmissions had at least one identified risk factor:

• Contact for three or more days with the infected individual (odds ratio [OR], 9.8).
• Mechanical ventilation (OR, 4.1).
• Infection with another multidrug-resistant organism (OR, 2.6).

Among patients who received antibiotics, cephalosporins were associated with a lower risk of CP-CRE acquisition when compared with other antibiotics. Although it appears that cephalosporins may reduce one’s risk of acquiring CP-CRE when compared with other drugs, no protective effective was seen in patients who received a cephalosporin when compared with patients who received no antibiotics, leading Schechner and colleagues to conclude that the role of cephalosporins requires further study.