Real-time evaluation of an optimized real-time PCR assay versus Brilliance chromogenic MRSA agar for the detection of meticillin-resistant Staphylococcus aureus from clinical specimens
A total of 1204 meticillin-resistant Staphylococcus aureus (MRSA) screens (3340 individual swabs) were tested to evaluate a staphylococcal cassette chromosome mec (SCCmec) real-time PCR. In total, 148 (12.3 %) of the screens were MRSA-positive, where 146 (12.1 %) were MRSA-positive by the SCCmec real-time PCR assay. In contrast, 128 (10.6 %) screens were MRSA-positive by culture. One hundred and twenty-six (10.5 %) of the screens were positive by both culture and PCR. Twenty of the 1204 screens (1.66 %) were negative by culture but positive by PCR; these samples were sequenced. In 14 of the cases, a homology search confirmed the sequence as SCCmec, indicating that these samples could be considered true positives. Two of the 1204 (0.2 %) screens were positive by culture and negative by PCR. The mean turnaround time (TAT) for PCR-negative swabs was 6 h 12 min and for PCR-positive swabs was 6 h 48 min. In comparison, for culture-negative swabs the mean TAT was 29 h 30 min and for culture-positive swabs was 69 h. The cost per swab for routine culture was £0.41 (€0.48) and that of the real-time PCR assay was £2.35 (€2.75). This optimized, in-house, inexpensive, real-time PCR test maintained a very high sensitivity and specificity when evaluated under real-time laboratory conditions. The TAT of this real-time PCR assay was substantially lower than that of chromogenic culture. It was also maintained throughout the entire process, which can be taken as an indirect measure of test performance. This study showed that implementation of a molecular test can be achieved with limited resources in a standard microbiology laboratory.
AldeyabM. A.,
KearneyM. P.,
HughesC. M.,
ScottM. G.,
TunneyM. M.,
GilpinD. F.,
DevineM. J.,
WatsonJ. D.,
GardinerA.other authors2009; Can the use of rapid polymerase chain screening method decrease the incidence of nosocomial methicillin-resistant Staphylococcus aureus ?. J Hosp Infect 71:22–28[CrossRef]
BishopE. J.,
GrabschE. A.,
BallardS. A.,
MayallB.,
XieS.,
MartinR.,
GraysonM. L.2006; Concurrent analysis of nose and groin swab specimens by the IDI-MRSA PCR assay is comparable to analysis by individual-specimen PCR and routine culture assays for detection of colonization by methicillin-resistant Staphylococcus aureus
. J Clin Microbiol 44:2904–2908[CrossRef]
CepedaJ.,
WhitehouseT.,
CooperB.,
HailsJ.,
JonesK.,
KwakuF.,
TaylorL.,
HaymanS.,
CooksonB.,
ShawS.other authors2005; Isolation of patients in single rooms or cohorts to reduce spread of MRSA in intensive-care units: prospective two centre study. Lancet 365:295–304[CrossRef]
ChaixC.,
Durand-ZaleskiI.,
AlbertiC.,
Brun-BuissonC.1999; Control of endemic methicillin-resistant Staphylococcus aureus : a cost–benefit analysis in an intensive care unit. JAMA 282:1745–1751[CrossRef]
CherneskyM.,
CastricianoS.,
JangD.,
SmiejaM.2006; Use of flocked swabs and a universal transport medium to enhance molecular detection of Chlamydia trachomatis and Neisseria gonorrhoeae
. J Clin Microbiol 44:1084–1086[CrossRef]
CoiaJ. E.,
DuckworthG. J.,
EdwardsD. I.,
FarringtonM.,
FryC.,
HumphreysH.,
MallaghanC.,
TuckerD. R. for the Joint Working Party of the British Society of Antimicrobial Chemotherapy, the Hospital Infection Society, and the Infection Control Nurses Association; 2006; Guidelines for the control and prevention of methicillin resistant Staphylococcus aureus (MRSA) in healthcare facilities. J Hosp Infect 63:S1–S44[CrossRef]
CooperB. S.,
MedleyG. F.,
StoneS. P.,
KibblerC. C.,
CooksonB. D.,
RobertsJ. A.,
DuckworthG.,
LaiR.,
EbrahimS.2004; Methicillin-resistant Staphylococcus aureus in hospitals and the community: stealth dynamics and control catastrophes. Proc Natl Acad Sci U S A 101:10223–10228[CrossRef]
CosgroveS. E.,
SakoulasG.,
PerencevichE. N.,
SchwaberM. J.,
KarchmerA. W.,
CarmeliY.2003; Comparison of mortality associated with methicillin-resistant and methicillin-susceptible Staphylococcus aureus bacteremia: a meta-analysis. Clin Infect Dis 36:53–59[CrossRef]
FangH.,
HedinG.2003; Rapid screening and identification of methicillin-resistant Staphylococcus aureus from clinical samples by selective-broth and real-time PCR assay. J Clin Microbiol 41:2894–2899[CrossRef]
FrancoisP.,
PittetD.,
BentoM.,
PepeyB.,
VaudauxP.,
LewD.,
SchrenzelJ.2003; Rapid detection of methicillin-resistant Staphylococcus aureus directly from sterile or nonsterile clinical samples by a new molecular assay. J Clin Microbiol 41:254–260[CrossRef]
GröbnerS.,
DionM.,
PlanteM.,
KempfV. A. J.2009; Evaluation of the BD GeneOhm StaphSR assay for detection of methicillin-resistant and methicillin-susceptible Staphylococcus aureus isolates from spiked positive blood culture bottles. J Clin Microbiol 47:1689–1694[CrossRef]
HarbarthS.,
RutschmannO.,
SudreP.,
PittetD.1998; Impact of methicillin resistance on the outcome of patients with bacteraemia caused by Staphylococcus aureus
. Arch Intern Med 158:182–189[CrossRef]
HuletskyA.,
LebelP.,
PicardF. J.,
BernierM.,
GagnonM.,
BoucherN.,
BergeronM. G.2005; Identification of methicillin-resistant Staphylococcus aureus carriage in less than 1 hour during a hospital surveillance program. Clin Infect Dis 40:976–981[CrossRef]
KalpoeJ. S.,
KroesA. C. M.,
de JongM. D.,
SchinkelJ.,
de BrouwerC. S.,
BeersmaM. F. C.,
ClaasE. C. J.2004; Validation of clinical application of cytomegalovirus plasma DNA load measurement and definition of treatment criteria by analysis of correlation to antigen detection. J Clin Microbiol 42:1498–1504[CrossRef]
KrishnaB. V. S.,
SmithM.,
McIndeorA.,
GibbA. P.,
DaveJ.2008; Evaluation of chromogenic MRSA medium, MRSA Select and oxacillin resistance screening agar for the detection of methicillin-resistant Staphylococcus aureus
. J Clin Pathol 61:841–843[CrossRef]
RenwickL.,
HardieA.,
GirvanE. K.,
SmithM.,
LeadbetterG.,
ClaasE.,
MorrisonD.,
GibbA. P.,
DaveJ.,
TempletonK. E.2008; Detection of meticillin-resistant Staphylococcus aureus and Panton–Valentine leukocidin directly from clinical samples and the development of a multiplex assay using real-time polymerase chain reaction. Eur J Clin Microbiol Infect Dis 27:791–796[CrossRef]
RobicsekA.,
BeaumontJ. L.,
PauleS. M.,
HacekD. M.,
ThomsonR. B.,
KaulK. L.,
KingP.,
PetersonL. R.2008; Universal surveillance for methicillin-resistant Staphylococcus aureus in 3 affiliated hospitals. Ann Intern Med 148:409–418[CrossRef]
RossneyA. S.,
HerraC. M.,
BrennanG. I.,
MorganP. M.,
O'ConnellB.2008; Evaluation of the Xpert methicillin-resistant Staphylococcus aureus (MRSA) assay using the GeneXpert real-time PCR platform for rapid detection of MRSA from screening specimens. J Clin Microbiol 46:3285–3290[CrossRef]
SalgadoC. D.,
FarrB. M.,
CalfeeD. P.2003; Community-acquired methicillin-resistant Staphylococcus aureus : a meta-analysis of prevalence and risk factors. Clin Infect Dis 36:131–139[CrossRef]
Real-time evaluation of an optimized real-time PCR assay versus Brilliance chromogenic MRSA agar for the detection of meticillin-resistant Staphylococcus aureus from clinical specimens