Prevalence and Genetic Relatedness of Methicillin-Susceptible Staphylococcus aureus Isolates Detected by the Xpert MRSA Nasal Assay

Arbefeville, Sophie; Zhang, Kunyan; Kroeger, J.; Howard, Wanita J.; Diekema, Daniel J.; Richter, Sandra

doi:10.1128/jcm.00046-11

Cited by 32 publications

(29 citation statements)

References 21 publications

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“…In contrast, the first-generation BD Max MRSA assay was not able to correctly identify the mecA empty cassette or the MRSA strains with mecC and missed 3 of the 11 MRSA MREJ type strains. These results corroborate evidence about wrong identification or misidentification of MRSA described by some colleagues (16)(17)(18)(19)(20)33) and demonstrate an improvement of the new-generation BD Max MRSAXT and BD Max StaphSR assays to correctly identify or exclude these strains. A recent study from Europe reports the performance of the Xpert MRSA Gen3 assay, which also detects mecA/mecC and the SCCmec/orfX junction for MRSA (34).…”

Section: Discussionsupporting

confidence: 89%

Evaluation of BD Max StaphSR and BD Max MRSA XT Assays Using ESwab-Collected Specimens

et al. 2015

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The BD Max MRSAXT and the BD Max StaphSR assays were validated for the detection of methicillin-resistant Staphylococcus aureus (MRSA) in ESwab samples. In addition, the BD Max StaphSR assay was evaluated for its ability to detect and differentiate S. aureus and MRSA in the same sample. A total of 255 ESwab samples collected from the anterior nares of patients were tested by each of three BD Max assays, including the BD Max MRSA first-generation assay. The results were compared to those of direct and enrichment culture. Additionally, a challenge panel comprising 14 control strains was evaluated to determine the ability of these assays to correctly identify MRSA and also appropriately differentiate S. Staphylococcus aureus is a leading cause of health care-associated infections. Infection due to S. aureus imposes a high and increasing burden on health care resources and increases morbidity and mortality. Nasal carriage of S. aureus has been identified as a risk factor for the development of infections in various settings. This has been studied extensively in surgical patients (general, orthopedic, and thoracic surgery), patients on hemodialysis, patients on continuous ambulatory peritoneal dialysis (CAPD), HIV-infected patients, and patients in intensive care units (1, 2). Methicillin-resistant S. aureus (MRSA) is an important cause of community-acquired and hospital-acquired infections (3, 4). MRSA can colonize the nares, skin, and other body sites, serving as a reservoir for infection and transmission in health care environments (5-7). Screening for MRSA colonization in order to help identify patients at greater risk for MRSA infection and to allow for the initiation of isolation precautions has become standard practice in many institutions (5,6,(8)(9)(10).MRSA screening using molecular amplification methods provides faster results than culture and has been demonstrated to be more sensitive (11-15). However, most of the molecular commercially available rapid tests are based on the detection of a sequence indicating the integration of the staphylococcal cassette chromosome mec element (SCCmec) within the chromosome and do not specifically target the methicillin resistance gene mecA (16). S. aureus isolates with an SCCmec lacking the mecA gene have been described and can be incorrectly identified as MRSA by assays that do not specifically target the mecA gene (17). False-positive results can lead to unnecessary and expensive isolation and treatment of patients. In addition, MRSA strains with the newly discovered methicillin resistance gene mecC account for 3 to 4% of all new MRSA cases in Denmark (18) and cannot be detected by assays that do not detect the mecC gene (19). These false-negative results can lead to uncontrolled transmission of undetected MRSA strains.The BD Max StaphSR and the BD Max MRSAXT assays (BD Diagnostics, Québec, Canada) performed on the BD Max system (BD Diagnostics, Sparks, MD) are next-generation automated qualitative in vitro diagnostic tests able to detect MRSA strains harboring the m...

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Section: Discussionsupporting

confidence: 89%

Evaluation of BD Max StaphSR and BD Max MRSA XT Assays Using ESwab-Collected Specimens

et al. 2015

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“…The mechanism for the false-positive detection appears to be related to loss of part of the mecA gene (2). A previous study found that 7.7% of 248 S. aureus isolates from an academic hospital were mecA dropouts, similar to what we identified in our population (1). Other studies have reported rates as high as 25% (2,6).…”

Section: Discussionsupporting

confidence: 85%

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Isolates from Patients Newly Identified as Nasal Carriers

Weir¹,

Fram²,

Berg³

et al. 2012

J Clin Microbiol

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We aimed to determine whether additional molecular and microbiological evaluations of methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients newly identified as nasal carriers were useful for control strategies and whether longitudinal testing during the same or repeat hospitalization changed MRSA status. Nasal swabs from patients positive by Xpert MRSA PCR and not known to be colonized in the previous year were cultured for S. aureus. Isolates were tested for resistance to a variety of antibiotics, including high-level mupirocin resistance (HLMR) and low-level mupirocin resistance (LLMR) and the presence of genes mecA and mupA and those for Panton-Valentine leukocidin (PVL), USA300, and USA400. Repeat nasal screens during the 6-month study were tested for continued presence of MRSA. Among 130 patients, cultures revealed MRSA in 85 (65.4%), methicillin-susceptible S. aureus in 19 (14.6%), and no growth in 26 (20%). MRSA isolates were USA300 positive in 13/85 (15.3%) and LLMR in 8/85 (9.4%) patients. No isolates were HLMR or mupA positive. mecA dropout was detected in 9/130 (6.9%) patients. The rate of subsequent MRSA infections in USA300-positive versus -negative patients was not different. MRSA nasal status remained concordant in 69/70 (98.6%) patients who had follow-up testing. The findings do not support expanding MRSA surveillance to include routine detection of genes for USA300, PVL, or mupA, all of which were either of low frequency or not significantly associated with MRSA infection risk in our population of newly identified nasal carriers. Repeat nasal screening for MRSA during the same or subsequent hospitalizations over 6 months could also be deferred, reducing costs associated with screening.

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“…Work to further characterize the genomic relationships and multiple antibiotic resistance of isolated strains is currently underway in our laboratory. This will be achieved using various recently developed methods of analysis including the Xpert MRSA assay 21 and PFGE analysis 22,23 .…”

Section: Resultsmentioning

confidence: 99%

Untitled

Intrakamhaeng¹,

Komutarin²

2012

ScienceAsia

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Methicillin resistant Staphylococcus aureus (MRSA) strains are a global health concern in both human and veterinary medicine. In addition to β-lactam resistance, MRSA can carry resistance to other commonly used antibiotics. The present study sought to determine the antibiotic susceptibility profile and genetic relatedness of strains emerging in Thailand. A total of 229 isolates of S. aureus obtained from 598 mastitis cases were investigated for their susceptibility to several antibiotics. Among 229 isolates of S. aureus, 27 were found to be methicillin resistant and multidrug resistant. Multidrug resistant MRSA infection was detected in 4 provinces including Lopburi, Udon Thani, Khon Kaen and Saraburi. Multidrug resistant strains exhibited several antibiogram patterns (antibiotypes I to XII). The most frequent pattern was antibiotype VII, i.e., resistance to most commonly used antibiotics. Based on random amplification of polymorphic DNA (RAPD) technique and a combined amplicon-profile obtained with three primers, all isolates were grouped according to genetic similarity. Five different RAPD patterns (types I to V) were identified with 90% genetic similarity. The close genetic relatedness within RAPD type I was interesting because most RAPD type I isolates had antibiogram pattern III or VII. In addition, some isolates from different regions were identical in both antibiogram pattern and RAPD type. This revealed that some of the antibiotic-resistant isolates in our study were epidemic strains.

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Prevalence and Genetic Relatedness of Methicillin-Susceptible Staphylococcus aureus Isolates Detected by the Xpert MRSA Nasal Assay

Cited by 32 publications

References 21 publications

Evaluation of BD Max StaphSR and BD Max MRSA XT Assays Using ESwab-Collected Specimens

Evaluation of BD Max StaphSR and BD Max MRSA XT Assays Using ESwab-Collected Specimens

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Isolates from Patients Newly Identified as Nasal Carriers

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