JAC Advance Access originally published online on March 5, 2008
Journal of Antimicrobial Chemotherapy 2008 61(4):967-968; doi:10.1093/jac/dkn095
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Letters to the Editor |
Community-associated MRSA (CA-MRSA): an emerging pathogen in infective endocarditis—authors' response
1 Northern Ireland Public Health Laboratory, Department of Bacteriology, Belfast City Hospital, Lisburn Road, Belfast BT9 7AD, Northern Ireland, UK 2 Department of Cardiology, John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK
* Corresponding author. Tel: +44-28-9026-3554; Fax: +44-28-9026-3991; E-mail: jemoore{at}niphl.dnet.co.uk
Keywords: Staphylococcus aureus , CDC criteria , hospital-acquired MRSA
We read with interest the comments made by Tsai et al.,1 in response to our recently published Leading article.2 These comments primarily serve to reiterate the importance of definitions for community-associated MRSA (CA-MRSA), regardless of whether such infections have been acquired in the community or healthcare setting. Such definitions are applicable to all CA-MRSA infections, not only those resulting in infective endocarditis (IE). Indeed, the comments made by these authors do not directly address any issues per se relating to IE, but how CA-MRSA is defined within the 23 reviewed cases of IE.
As reiterated by Tsai et al., there is no unique characteristic (for example, SCCmec type IV) that is attributed to all CA-MRSA isolates, and in order to help define CA-MRSA, we have previously proposed definitions based on a combination of characteristics.3 Furthermore, there appears to be confusion with regard to the terminologies ‘associated’ and ‘acquired’. These terms are not synonymous or interchangeable. ‘Associated’ represents where the isolate originated, whereas ‘acquired’ identifies where the patient acquired the isolate.
CA-MRSA is predominately acquired within the community setting; however, there are increasing reports of CA-MRSA infections acquired within the healthcare setting,4–6 whereby a community strain has entered into the healthcare environment and has subsequently been transmitted nosocomially, similar to the transmission of healthcare-associated MRSA (HA-MRSA). As such, in Table 3 of our article,2 although the isolates had characteristics of CA-MRSA, in four cases, the infection was acquired within a healthcare setting.
Haque et al.7 described two of their seven cases of IE, due to USA300 MRSA, as healthcare-associated; however, they did not clarify how they defined community-associated. It may be presumed that, due to the fact that these two patients had a prior hospital admission, the authors deemed the MRSA to be hospital-acquired as per the CDC criteria (http://www.cdc.gov/ncidod/dhqp/ar_mrsa_ca_clinicians.html#4). This further highlights the inadequacies of the CDC criteria, which do not take into account the microbiological characteristics of the isolates but focus largely on the epidemiological characteristics of the patient.
Overall, the emergence of CA-MRSA over the last decade and its relative difference from HA-MRSA in terms of its epidemiology, microbiology and treatment now require proper categorization so that authors and readers are clear as to the nature of the MRSA isolate being described. Therefore, when MRSA isolates are being reported, further microbiological work should be undertaken to ensure that a correct classification of the isolate as CA-MRSA/HA-MRSA is given.
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1 Tsai H-C, Chen Y-S, Lee SS-J, et al. Comment on: Community-associated MRSA (CA-MRSA): an emerging pathogen in infective endocarditis. J Antimicrob Chemother (2008) 61:966–7.
2
Millar BC, Prendergast BD, Moore JE. Community-associated MRSA (CA-MRSA): an emerging pathogen in infective endocarditis. J Antimicrob Chemother (2008) 61:1–7.
3 Millar BC, Loughrey A, Elborn JS, et al. Proposed definitions of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). J Hosp Infect (2007) 67:109–13.[CrossRef][Medline]
4 Maree CL, Daum RS, Boyle-Vavra S, et al. Community-associated methicillin-resistant Staphylococcus aureus isolates causing healthcare-associated infections. Emerg Infect Dis (2007) 13:236–42.[Web of Science][Medline]
5 David MD, Kearns AM, Gossain S, et al. Community-associated methicillin-resistant Staphylococcus aureus: nosocomial transmission in a neonatal unit. J Hosp Infect (2006) 64:244–50.[CrossRef][Web of Science][Medline]
6 Gonzalez BE, Rueda AM, Shelburne SA, et al. Community-associated strains of methicillin-resistant Staphylococcus aureus as the cause of healthcare-associated infection. Infect Control Hosp Epidemiol (2006) 27:1051–6.[CrossRef][Web of Science][Medline]
7 Haque NZ, Davis SL, Manierski CL, et al. Infective endocarditis caused by USA300 methicillin-resistant Staphylococcus aureus (MRSA). Int J Antimicrob Agents (2007) 30:72–7.[CrossRef][Web of Science][Medline]
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