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Table 2 Clinical samples results of single and double-locus detection assays

From: Evaluation of single and double-locus real-time PCR assays for methicillin-resistant Staphylococcus aureus (MRSA) surveillance

  Real Time PCR results
Conventional
culture
identification
(n = 338)
Huletsky's[8]
single-locus detectiona
Reischl's[5]
double-locus detectionb
Combined resultsc
  SCC:orfX+
(MRSA)
SCC:orfX-
(other)
Sa442+ mec+
(MRSA)
Sa442+ mec-
(MSSA)
Sa442- mec+
(non S.A oxaR)
Sa442- mec-
(other)
MRSAd Not MRSAe
MRSA (n = 219) 203 16 218 1 --- --- 202 17f
MSSA (n = 90) 13 77 (44+2)g 35 --- 9 1h 89i
MR-CoNS (n = 16) --- 16 --- --- 16 ---   16
MS-CoNS (n = 8) --- 8 --- --- --- 8   8
non-Staph. (n = 5) --- 5     5   5
  1. a sensitivity = 92.7%, specificity = 89.1%, Positive predictive value = 93.4%, Negative predicted value = 86.9%,
  2. b sensitivity = 99.5%, specificity = 61.3%, Positive predictive value = 82.6%, Negative predicted value = 98.6%
  3. c sensitivity = 92.2%, specificity = 99.2%, Positive predictive value = 99.5%, Negative predicted value = 87.4%
  4. d MRSA = SCC:orfX positive, Sa442 positive, mec positive
  5. e Not MRSA = all other results.
  6. f 16 SCC:orfX negative, Sa442 positive, mec positive and 1 oxacillin-resistant MSSA (SCC:orfX positive, Sa442 positive mec negative) classified as MRSA by culture methods.
  7. g 44 were MSSA mixed with MR-CoNS, 2 were oxacillin-susceptible MRSA classified as MSSA by culture methods.
  8. h 1 SCC:orfX positive, Sa442 positive, mec positive originated from a mixture of SCC:orfX positive, Sa442 positive, mec negative MSSA and mec positive MR-CoNS
  9. i 9 SCC:orfX negative, Sa442 negative, mec negative; 2 SCC:orfX negative, Sa442 positive, mec positive; 22 SCC:orfX negative, Sa442 positive, mec negative; 13 SCC:orfX positive, Sa442 positive, mec negative MSSA's and 43 SCC:orfX negative, Sa442 positive, mec