Methicillin-Resistant Staphylococcus aureus Colonization at Different Body Sites: a Prospective, Quantitative Analysis

Mermel, Leonard A.; Cartony, Jennifer M.; Covington, Pauline; Maxey, Gail E.; Morse, Dan J.

doi:10.1128/jcm.02601-10

Cited by 74 publications

(57 citation statements)

References 22 publications

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“…A high concentration of MRSA on chromogenic media most certainly represents a true transmission concern and needs to be immediately reported to infection control. Several factors may contribute to the recovery of MRSA, such as interfering substances (e.g., nasal sprays), patient age and immunosuppression, body site, and proper specimen collection, However, Mermel et al (11) showed that the quantity of MRSA in the nares correlated inversely with the likelihood of MRSA infection.…”

Section: Discussionmentioning

confidence: 99%

Three-Way Comparison of BBL CHROMagar MRSA II, MRSA Select , and Spectra MRSA for Detection of Methicillin-Resistant Staphylococcus aureus Isolates in Nasal Surveillance Cultures

et al. 2013

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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. Methicillin-resistant Staphylococcus aureus (MRSA) is the most common cause of hospital-associated infections. To control the transmission of MRSA in health care facilities, targeted active surveillance cultures and an active infection control program to eliminate or control the spread of MRSA in hospitals are recommended (1, 2). The introduction of molecular methods (e.g., PCR) for the detection of MRSA in nasal specimens has improved the reporting time of MRSA and utilization of infection control resources (3-5). However, not all laboratories can justify the added expense of molecular methods. An alternative, costeffective approach is the use of chromogenic media for screening nasal specimens for MRSA carriage. BBL CHROMagar MRSA II (CMRSA II, BD), MRSASelect (Bio-Rad), and Spectra MRSA (Remel) are selective and differential chromogenic media for the qualitative detection of MRSA from nasal surveillance specimens. Each contains specific chromogenic substrates, antimicrobials, and selective agents for the suppression of Gram-negative organisms, yeasts, and other Gram-positive cocci. Identification of MRSA from the primary culture is based on the cleavage of chromogenic substrate by a specific enzymatic activity of S. aureus, leading to coloration of colonies. A three-way comparison study was conducted to determine the performance characteristics of these commercially av...

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Section: Discussionmentioning

confidence: 99%

Three-Way Comparison of BBL CHROMagar MRSA II, MRSA Select , and Spectra MRSA for Detection of Methicillin-Resistant Staphylococcus aureus Isolates in Nasal Surveillance Cultures

et al. 2013

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“…3 A 2010 survey 4 of 590 US health care facilities indicated that the overall prevalence of MRSA in these institutions was 66.4 per 1000 inpatients. The prevalence of colonization was 41.1 per 1000 inpatients, and the infection rate was 25.3 per 1000 inpatients.…”

Section: Outcomes and Data Collectedmentioning

confidence: 99%

Nasal Colonization and Lower Respiratory Tract Infections with Methicillin-Resistant Staphylococcus aureus

Tilahun

Faust

McCorstin

et al. 2014

American Journal of Critical Care

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Background Methicillin-resistant Staphylococcus aureus is a cause of lower respiratory tract infections, particularly health care-and ventilator-associated pneumonia. Although many health systems use nasal screening for this microorganism for infection control, correlation between nasal carriage of the organism and development of infections due to it is not clear. Methods Records of patients admitted to medical intensive care between January 1, 2011, and December 31, 2012, were reviewed retrospectively. Patients' data were included if the patients were 18 years or older, satisfied clinical criteria for pneumonia, and had both nasal swabbing and culturing of respiratory specimens within 24 hours of admission. Results A total of 165 patients met the inclusion criteria. Most had either community-acquired or health care-associated pneumonia. Of the 28 patients with a nasal swab positive for methicillinresistant S aureus, 8 (4.8%) also had respiratory tract cultures positive for the microorganism. Among the 165 patients, 2 (1.2%) had negative nasal swabs but positive respiratory cultures. Sensitivity and specificity of nasal colonization with methicillinresistant S aureus for subsequent infection with the pathogen were 80% and 87.1%, respectively; positive and negative predictive values were 28.6% and 98.5%, respectively. Conclusions Nasal screening for methicillin-resistant S aureus may be a valuable tool for de-escalation of empiric therapy targeted to the organism, especially in patients admitted for severe community-acquired or health care-associated pneumonia. The high negative predictive value suggests that patients with a negative nasal swab most likely do not have a lower respiratory tract infection caused by the organism.

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“…Serial dilutions of the broth were spiral plated onto Spectra MRSA agar; colonies were counted at 24 h and converted to log 10 CFU/ml (12). Using this method, 73/76 PCR-positive partner swabs grew MRSA.…”

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confidence: 99%

“…An additional advantage of PCR-based tests is an easily obtained measure of quantification in the C T . Quantification of nasal S. aureus colonization was described over 50 years ago and has been linked to the persistently colonized state (14,20), an increased risk of contamination of the environment (5,17), an increased risk of infection (10,19), and a higher likelihood that other body sites (besides the nares) are colonized (12). In those studies, S. aureus carriage was quantified by labor-and time-intensive techniques not easily implemented in a clinical practice.…”

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confidence: 99%

Cepheid Xpert MRSA Cycle Threshold in Discordant Colonization Results and as a Quantitative Measure of Nasal Colonization Burden

et al. 2012

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We analyzed the cycle threshold (C T ) of PCR surveillance MRSA swabs obtained from veterans. Lower C T on admission was associated with a positive culture from nasal swabs at discharge. Compared to PCR, direct plating of nasal swabs performed poorly, especially for patients with an elevated C T . The C T is strongly correlated with quantitative nasal cultures. Clinical and infection control applications of the C T have yet to be defined and warrant further evaluation.

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Methicillin-Resistant Staphylococcus aureus Colonization at Different Body Sites: a Prospective, Quantitative Analysis

Cited by 74 publications

References 22 publications

Three-Way Comparison of BBL CHROMagar MRSA II, MRSA Select , and Spectra MRSA for Detection of Methicillin-Resistant Staphylococcus aureus Isolates in Nasal Surveillance Cultures

Three-Way Comparison of BBL CHROMagar MRSA II, MRSA Select , and Spectra MRSA for Detection of Methicillin-Resistant Staphylococcus aureus Isolates in Nasal Surveillance Cultures

Nasal Colonization and Lower Respiratory Tract Infections with Methicillin-Resistant Staphylococcus aureus

Cepheid Xpert MRSA Cycle Threshold in Discordant Colonization Results and as a Quantitative Measure of Nasal Colonization Burden

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