Three-way comparison of BBL CHROMagar MRSA II, MRSASelect, and spectra MRSA for detection of methicillin-resistant Staphylococcus aureus isolates in nasal surveillance cultures

Gerald Denys, Pamela B. Renzi, Kim M. Koch, Carol M. Wissel

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital-acquired and life-threatening infections. Active surveillance programs for MRSA utilize either molecular or culture-based methods. A prospective study was performed to compare the performance of selective and differential chromogenic media, BBL CHROMagar MRSA II (CMRSA II; BD Diagnostics, Sparks, MD), MRSASelect (Bio-Rad Laboratories, Redmond, WA), and Spectra MRSA (Remel, Lenexa, KS), for the detection of MRSA in nasal swab specimens. A total of 515 compliant remnant nasal swab specimens were sequentially used to inoculate BBL Trypticase soy agar with 5% sheep blood (TSA II) and each chromogenic medium. After 24 h of incubation, colony color reactions and morphology on chromogenic media were compared to suspicious colonies on nonselective TSA II. MRSA on TSA II was confirmed by Gram staining, a coagulase test, and a cefoxitin disk test. The overall prevalence of MRSA and methicillin-susceptible S. aureus (MSSA) on TSA II was 12.4% (64/515) and 9.7% (50/515), respectively. When each chromogenic medium was compared to the standard culture method, the sensitivity and specificity, respectively, were as follows: CMRSA II, 87.7% and 98.6%; MRSASelect, 89.0% and 93.4%; and Spectra MRSA, 83.6% and 92.1%. The positive predictive values were highest for CMRSA II (91.4%), followed by MRSASelect (69.1%) and Spectra MRSA (63.5%). False-positive results on chromogenic media were mainly due to color interpretation. The negative predictive values for all three media were greater than 97%. In conclusion, CMRSA II gave the best overall results for detecting MRSA from nasal specimens.

Original languageEnglish (US)
Pages (from-to)202-205
Number of pages4
JournalJournal of clinical microbiology
Volume51
Issue number1
DOIs
StatePublished - Jan 1 2013

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Methicillin-Resistant Staphylococcus aureus
Nose
Color
Cefoxitin
Methicillin
Coagulase
Agar
Staphylococcus aureus
Sheep
Prospective Studies
Staining and Labeling
Sensitivity and Specificity

ASJC Scopus subject areas

  • Microbiology (medical)

Cite this

Three-way comparison of BBL CHROMagar MRSA II, MRSASelect, and spectra MRSA for detection of methicillin-resistant Staphylococcus aureus isolates in nasal surveillance cultures. / Denys, Gerald; Renzi, Pamela B.; Koch, Kim M.; Wissel, Carol M.

In: Journal of clinical microbiology, Vol. 51, No. 1, 01.01.2013, p. 202-205.

Research output: Contribution to journalArticle

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abstract = "Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital-acquired and life-threatening infections. Active surveillance programs for MRSA utilize either molecular or culture-based methods. A prospective study was performed to compare the performance of selective and differential chromogenic media, BBL CHROMagar MRSA II (CMRSA II; BD Diagnostics, Sparks, MD), MRSASelect (Bio-Rad Laboratories, Redmond, WA), and Spectra MRSA (Remel, Lenexa, KS), for the detection of MRSA in nasal swab specimens. A total of 515 compliant remnant nasal swab specimens were sequentially used to inoculate BBL Trypticase soy agar with 5{\%} sheep blood (TSA II) and each chromogenic medium. After 24 h of incubation, colony color reactions and morphology on chromogenic media were compared to suspicious colonies on nonselective TSA II. MRSA on TSA II was confirmed by Gram staining, a coagulase test, and a cefoxitin disk test. The overall prevalence of MRSA and methicillin-susceptible S. aureus (MSSA) on TSA II was 12.4{\%} (64/515) and 9.7{\%} (50/515), respectively. When each chromogenic medium was compared to the standard culture method, the sensitivity and specificity, respectively, were as follows: CMRSA II, 87.7{\%} and 98.6{\%}; MRSASelect, 89.0{\%} and 93.4{\%}; and Spectra MRSA, 83.6{\%} and 92.1{\%}. The positive predictive values were highest for CMRSA II (91.4{\%}), followed by MRSASelect (69.1{\%}) and Spectra MRSA (63.5{\%}). False-positive results on chromogenic media were mainly due to color interpretation. The negative predictive values for all three media were greater than 97{\%}. In conclusion, CMRSA II gave the best overall results for detecting MRSA from nasal specimens.",
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