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Detection of Enterobacteriaceae Isolates Carrying Metallo-Beta-Lactamase --- United States, 2010

During January--June 2010, three Enterobacteriaceae isolates carrying a newly described resistance mechanism, the New Delhi metallo-beta-lactamase (NDM-1) (1), were identified from three U.S. states at the CDC antimicrobial susceptibility laboratory. This is the first report of NDM-1 in the United States, and the first report of metallo-beta-lactamase carriage among Enterobacteriaceae in the United States. These isolates, which include an Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae, carry blaNDM-1, which confers resistance to all beta-lactam agents except aztreonam (a monobactam antimicrobial) (1); all three isolates were aztreonam resistant, presumably by a different mechanism. In the United Kingdom, where these organisms are increasingly common, carriage of Enterobacteriaceae containing blaNDM-1 has been closely linked to receipt of medical care in India and Pakistan (2). All three U.S. isolates were from patients who received recent medical care in India.

Carbapenem resistance and carbapenemase production conferred by blaNDM-1 is detected reliably with phenotypic testing methods currently recommended by the Clinical and Laboratory Standards Institute (3), including disk diffusion testing and the modified Hodge test (4). Carbapenem resistance in all three of these isolates was detected in the course of routine testing. Current CDC infection control guidance for carbapenem-resistant Enterobacteriaceae also is appropriate for NDM-1--producing isolates (5). This includes recognizing carbapenem-resistant Enterobacteriaceae when cultured from clinical specimens, placing patients colonized or infected with these isolates in contact precautions, and in some circumstances, conducting point prevalence surveys or active-surveillance testing among other high-risk patients. Laboratory identification of the carbapenem- resistance mechanism is not necessary to guide treatment or infection control practices but should instead be used for surveillance and epidemiologic purposes.

Clinicians should be aware of the possibility of NDM-1--producing Enterobacteriaceae in patients who have received medical care in India and Pakistan, and should specifically inquire about this risk factor when carbapenem-resistant Enterobacteriaceae are identified. CDC asks that carbapenem-resistant isolates from patients who have received medical care within 6 months in India or Pakistan be forwarded through state public health laboratories to CDC for further characterization. Infection control interventions aimed at preventing transmission, as outlined in current guidance (5), should be implemented when NDM-1--producing isolates are identified, even in areas where other carbapenem-resistance mechanisms are common among Enterobacteriaceae. Additional information is available by contacting Brandi Limbago or Alex Kallen at search@cdc.gov.

References

  1. Yong D, Toleman MA, Giske CG, et al. Characterization of a new metallo-β-lactamase gene, blaNDM-1, and a novel erythromycin esterase gene carried on a unique genetic structure in Klebsiella pneumoniae sequence type 14 from India. Antimicrob Agents Chemother 2009;53:5046--54.
  2. Health Protection Agency. Multi-resistant hospital bacteria linked to India and Pakistan. Health Protection Report 2009;3(26):3--4. Available at http://www.hpa.org.uk/hpr/archives/2009/hpr2609.pdf. Accessed June 18, 2010.
  3. Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing; twentieth informational supplement. Wayne, PA: Clinical and Laboratory Standards Institute; 2010.
  4. Deshpande P, Rodrigues C, Shetty A, Kapadia F, Hedge A, Soman R. New Delhi metallo-β lactamase (NDM-1) in Enterobacteriaceae: treatment options with carbapenems compromised. J Acad Physicians India 2010;58:147--9.
  5. CDC. Guidance for control of infections with carbapenem-resistant or carbapenemase-producing Enterobacteriaceae in acute care facilities. MMWR 2009;58:256--60.

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