Many cohorted patients acquire secondary strains of multidrug-resistant organisms
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Researchers detected secondary multidrug-resistant isolates with distinct resistance genes in nearly half of cohorted patients in a long-term acute-care hospital, suggesting cross-transmission, according to study findings.
“A commonly employed approach to reduce the spread of high-priority pathogens in health care settings is to place carrier patients together in a physically separated space away from noncarriers,” Evan Snitkin, PhD, assistant professor of microbiology and immunology at the University of Michigan Medical School, told Healio. “An underlying assumption of cohorting positive patients together is that they pose no additional risk to one another. However, health care pathogens of a given species are often genetically diverse and differ in clinically important characteristics, such as their antibiotic resistance arsenal.”
Snitkin and colleagues “set out to understand whether patients identified as carriers of carbapenem-resistant Klebsiella pneumoniae who were placed together in a cohort location showed evidence of transmitting their strains to one another and whether newly acquired strains harbored antibiotic resistance determinants that their initial strain did not,” he explained.
From 2011 to 2013 at a high-prevalence long-term acute-care hospital in Chicago, Snitkin and colleagues conducted a bundled intervention that included cohorting patients with K. pneumoniae carbapenemase and K. pneumoniae (KPC-Kp)-positive patients. According to the study, the researchers analyzed whole-genome sequencing and location data to identify potential cases of cross-transmission among the cohorted patients.
Snitkin explained that the study revealed that most patients showed evidence of acquiring a secondary strain in the facility, which differed from the strain identified before they entered the cohort location.
Data from the study showed that secondary KPC-Kp isolates from 19 of 28 patients who were positive upon admission were more closely related to another patient’s isolate than to their own admission isolate. According to the study, of these 19 cases, 14 showed strong genomic evidence for cross-transmission, with most of these patients occupying shared cohort floors (12 patients) or rooms (four patients).
“In many of these cases, we found strong genomic and epidemiological support for these secondary strains having been acquired from another patient with whom they were cohorted,” Snitkin said. “Importantly, these secondary strains often carried distinct antibiotic resistance determinants, which could potentially lead to more difficult treatment.”
According to the study, of the 14 patients with strong genomic evidence of acquisition, 12 had antibiotic resistance genes not found in their primary isolates.
“Our results highlight the importance of effective infection prevention practices, even when dealing with patients who are already known carriers of the same organism,” Snitkin concluded.
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