Investigation of a Pan-Resistant Verona Integron-Encoded Metallo-Beta-Lactamase-Producing Klebsiella pneumoniae

Background: Metallo-beta-lactamases (MBL) have emerged as an important cause of carbapenem resistance.  Although well recognized among non-lactose-fermenting organisms, the Verona integron-encoded MBL (VIM) has been reported rarely among Enterobacteriaceae in the United States.  In July, 2010, the Washington State Department of Health identified a pan-resistant Klebsiella pneumoniae from a patient transferred to a U.S. hospital from Greece.   

Objective: Define the epidemiology and evaluate potential transmission of the organism.

Methods: Hospital laboratory records from the previous year were reviewed to identify additional carbapenem-resistant organisms.  Information on the patient’s history and hospital course was obtained through chart review and interviews with the patient and her family.  Using hospital census data, patients hospitalized on the same unit were identified.  Surveillance cultures were obtained from epidemiologically-linked patients still hospitalized at the facility or at a nearby long-term care facility.   

Results: The patient was a 76 year old woman admitted to two different hospitals in Greece with a diagnosis of sepsis and Clostridium difficile infection after becoming ill on a Mediterranean cruise.  After 12 days, the patient was transferred to a U.S. hospital where she was placed in Contact Precautions.  A blood culture obtained at the time of admission to the U.S. hospital from a central venous catheter placed in Greece grew pan-resistant K. pneumoniae.  This isolate demonstrated production of an MBL, which was characterized by polymerase chain reaction as a VIM-1-type.  DNA sequence analysis confirmed the resistance mechanism as VIM, but it was not identical to any of the >20 established VIM alleles, suggesting that this may be a novel VIM allele.

Three additional carbapenem-resistant organisms were identified during microbiological record review; all were identified as Acinetobacter baumannii with no evidence of MBL activity.  Of 88 patient contacts, 30 were available for evaluation, and 22 (73%) consented to a culture.  Cultures were also obtained from two family members with close contact with the patient during her hospitalization.  Carbapenem-resistant Enterobacteriaceae (CRE) were not detected from any of the contacts.  Of the four specimens obtained from the patient, three cultures (obtained from the peri-rectal area, sacral wound, and abdominal wound) were positive for MBL-producing K. pneumoniae.

Conclusions: Enterobacteriaceae producing a VIM-type metallo-beta-lactamase are now being identified in the United States.  Introduction of this new mechanism of carbapenem resistance in the United States has the potential to contribute to the resistance burden caused by other carbapenemases and reinforces the need for strict adherence to infection control practices to prevent CRE transmission.