title: High levels of mecA DNA detected by a quantitative real-time PCR assay are associated with mortality in patients with methicillin-resistant Staphylococcus aureus bacteremia.
abstract: Persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is known to be a poor prognostic factor. While several PCR assays for the detection of MRSA in various clinical samples were recently reported, the possibility that a quantitative PCR assay could be used to quantify and monitor MRSA bacteremia has not been explored. In this study, we established a quantitative real-time PCR assay for the mecA gene using known copy numbers of a plasmid containing mecA DNA as a standard and the previously described mecA-specific primers and probe (P. Francois et al., J. Clin. Microbiol. 41:254-260, 2003). We employed this assay to examine 250 sequential whole-blood samples from 20 adult patients, including 13 survivors and 7 nonsurvivors, with culture-proven MRSA bacteremia at the intensive care units of National Taiwan University Hospital between 1 July 2006 and 31 January 2007. The levels of mecA DNA in the nonsurvivors were significantly higher than those in the survivors during the three periods of bacteremia examined (days 0 to 2, 3 to 5, and 6 to 8) (P = 0.003 by two-tailed Mann-Whitney U test). Moreover, the nonsurvivors had higher mecA DNA levels than the survivors after 3 days and 7 days of anti-MRSA therapy (medians for nonsurvivors and survivors at 3 days, 5.86 and 4.30 log copies/ml, respectively; medians for nonsurvivors and survivors at 7 days, 5.21 and 4.36 log copies/ml, respectively; P = 0.02 and P = 0.04, respectively, by two-tailed Mann-Whitney U test). Together, these findings suggest that the level of mecA DNA in blood could potentially be used to monitor MRSA bacteremia and evaluate responses to therapy.
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, Yun-Lin Branch, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Ya-Chi
authors.initials: YC
authors.lastname: Ho
authors.forename: Shan-Chwen
authors.initials: SC
authors.lastname: Chang
authors.forename: Su-Ru
authors.initials: SR
authors.lastname: Lin
authors.forename: Wei-Kung
authors.initials: WK
authors.lastname: Wang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000188:drug therapy / Q000382:microbiology* / Q000401:mortality; D001426:Bacterial Proteins / Q000235:genetics*; D004269:DNA, Bacterial / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics*; D008875:Middle Aged; D046915:Penicillin-Binding Proteins; D016133:Polymerase Chain Reaction / Q000379:methods*; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology* / Q000401:mortality; D013624:Taiwan; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus