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One patient responsible for K. pneumoniae outbreak in 2011
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Whole-genome sequencing traced an outbreak of carbapenem-resistant Klebsiella pneumoniae to a single patient who was responsible for three separate transmissions, NIH researchers reported.
“In recent years, the threat posed by K. pneumoniae has markedly increased with the emergence of strains resistant to carbapenem antibiotics and their worldwide dissemination,” the researchers wrote. “Infections caused by carbapenem-resistant strains have few treatment options and are associated with mortality rates upwards of 50%.”
The outbreak affected 18 patients, of whom 11 died. The researchers performed whole-genome sequencing on K. pneumoniae isolates to determine why the outbreak happened despite infection control procedures. The index patient was transferred to the ICU at the NIH on June 13, 2011, and was placed in isolation. Another incidence of K. pneumoniae was observed on Aug. 5. An average of one new case per week was detected subsequently, with 17 total cases by Jan. 1, 2012.
The researchers performed whole-genome sequencing on the isolates from the index patient, revealing seven single nucleotide variants. Whole-genome sequencing was then performed on single K. pneumoniae isolates from each of the 18 patients, which revealed 41 single nucleotide variants.
The isolates were grouped according to shared patterns and grouped into three clusters. Variants common among the clusters showed that clusters one and three share three variants from the index patient’s groin and bronchoalveolar lavage isolates. The isolates in cluster two share three variants from the index patient’s throat isolate. This suggested that the index patient was responsible for three separate transmission events.
“Our results point to ways in which carbapenem-resistant K. pneumoniae outbreaks may be controlled more effectively in the future,” the researchers wrote. “Although additional sequencing studies capturing the genetic diversity of clinical strains of K. pneumoniae will be necessary to verify that this outbreak did not stem from multiple introductions, the genetic diversity that accumulated just during the course of the outbreak suggests that a monoclonal outbreak is most likely.”
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Keith Kaye, MD, MPH
CRE are one of the biggest emerging threats in hospital-based infectious diseases. These organisms are extremely virulent and can spread rapidly, usually from patient to patient or from the environment to the patient via the hands or equipment of healthcare workers. Advanced genotypic methods can help to demonstrate the spread of a single common bacterial strain which can help to effectively guide infection control interventions.
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