MRSA-Screen Test Research Articles

Evaluation of the methicillin-resistant Staphylococcus aureus (MRSA)-Screen latex agglutination test for detection of MRSA of animal origin.

Methicillin (oxacillin)-resistant staphylococci (MRS) have emerged as major clinical and epidemiological pathogens, and there have been frequent reports of MRS infections in the veterinary field. The MRSA-Screen latex agglutination test (Denka Seiken Co., Ltd., Tokyo, Japan) was compared with an oxacillin agar screen test, MIC determination, and mecA PCR assay, the "gold standard." In an analysis of 15 mecA-positive and 48 mecA-negative S. aureus animal isolates, as well as 9 mecA-positive and 147 mecA-negative, coagulase-negative staphylococcal animal isolates, the latex agglutination test surpassed the widely used oxacillin agar screen method and MIC determination, with a sensitivity and a specificity of 100%. The MRSA-Screen test is a reliable and rapid method of detecting MRS in the veterinary field.

Rapid MRSA detection by a latex kit.

Methicillin resistant strains of Staphylococcus aureus (MRSA) are implicated in serious infections and nosocomial outbreaks, and show resistance to a wide range of antibiotics, thus limiting the treatment options. Therefore, rapid detection is clinically crucial for both treatment and infection control measures. This study assessed the performance of a rapid latex agglutination kit marketed to detect MRSA clinical isolates (MRSA-Screen test Denka Seiken Co Ltd, Tokyo, Japan) based on detecting a specific penicillin binding protein 2a (PBP2a) in comparison to the NCCLS oxacillin salt agar screen plate, the 1 microg oxacillin disk diffusion test, and the oxacillin MIC by E-test. Testing was carried out on 133 isolates consisting of 99 MRSA and 34 methicillin sensitive strains of S. aureus (MSSA). Concordant results were observed between the latex kit and all the other tests for the 99 MRSA isolates. Only 1 of the 34 MSSA isolates gave a positive agglutination reaction in the latex kit. The kit sensitivity and specificity were determined to be 100% and 97%, respectively. This reliable performance indicates that the MRSA-Screen latex test is very useful test for the rapid detection of MRSA isolates in the clinical microbiology laboratory.

Validation of rapid screening tests for the identification of methicillin resistance in staphylococci.

The Velogene Rapid MRSA Identification Assay (Alexon-Trend Inc., Ramsey, MN), a commercially available 90-min genotypic test using a chimeric probe for the cycling-mediated recognition of the mecA gene in staphylococci, was compared with the MRSA-Screen latex agglutination test, a 15-min phenotypic test (Denka Seiken Co., Tokyo, Japan) for the identification of the mecA gene product PBP 2a. The results of both techniques were compared with mecA gene PCR. A total of 210 stock-culture strains were tested, consisting of 108 methicillin-susceptible Staphylococcus aureus (MSSA) strains and 92 methicillin-resistant S. aureus (MRSA) strains. The performance of the assays was good, displaying sensitivities and specificities for Velogene and MRSA Screen of 96.7% and 100% and 96.7% and 100%, respectively. Both Velogene and MRSA Screen could not correctly identify three of the MRSA strains each. Repeat testing with a larger inoculum or exposure of the three distinct strains to methicillin, respectively, resolved these problems. All MSSA strains as well as the other genera were correctly addressed by both techniques. The 10 methicillin-resistant Staphylococcus epidermidis strains were detected by both techniques. Both the Velogene and the MRSA Screen assays accurately identified mecA-positive staphylococcal strains and can be successfully used for routine application in clinical microbiology laboratories.

Methods for identifying methicillin resistancein Staphylococcus aureus

Five methods for the detection of methicillin-resistant Staphylococcus aureus were used to examine a collection of 100 clinical isolates comprising both susceptible and resistant strains. The disc diffusion test with oxacillin had a sensitivity of 93.3% and a specificity of 92.0% whereas mannitol salt agar containing oxacillin had a sensitivity of 100% and specificity 80.6% with high inoculum. With a low inoculum the sensitivity was 90.7% and specificity 96.0%. The MRSA screen test (Denka Seiken Co. Ltd., Japan) and Evigene MRSA Detection Kit (State Serum Institute, Denmark) tests were in complete agreement with results obtained with polymerase chain reaction assays amplifying mecA and nuc gene sequences.

Evaluation of the MRSA-Screen test in detecting oxacillin resistance in community and hospital isolates of Staphylococcus aureus

The MRSA-Screen Test (Denka Seiken Co., Japan), a latex agglutination test to detect penicillin-binding protein 2a, was compared with PCR for the detection of oxacillin resistance in Staphylococcus aureus. A total of 77 oxacillin-sensitive and 269 oxacillin-resistant (ORSA) isolates were evaluated. Of the ORSA isolates, 186 were non-multiresistant (NORSA), defined as being resistant to two or fewer antibiotics other than beta-lactams. Eighty-three were multiresistant ORSA (MORSA) strains. If PCR is considered the gold standard test, then the sensitivity, specificity, positive and negative predictive values of the MRSA-Screen Test were 100, 99, 99 and 100%, respectively. The endpoint was hard to read with NORSA strains that took longer than 60 s to react. MORSA strains took a median 12 s (range 5-60 s) to give a positive reaction with the MRSA-Screen Test, whereas NORSA strains took a median 30 s (range 5-180 s), a difference which was significantly different (P < 0.0001, two-tailed Mann-Whitney unpaired two sample test). NORSA strains had an MIC50 of 128 mg/l and MIC90 of 256mg/l, whereas MORSA strains had an MIC50 and MIC90 of >256mg/l. The time that the MRSA-Screen Test took to agglutinate with ORSA strains correlated weakly with the MIC (r2 = 0.26). Detection of methicillin resistance cost AUD$9 per isolate with the MRSA-Screen Test, compared with AUD$13 per isolate with mecA PCR. The MRSA-Screen Test gave excellent sensitivity and specificity, and was quicker and cheaper than PCR. The full 3 min should be allowed to elapse before calling a test negative. Organisms giving indeterminate reactions should be tested for the mecA gene by PCR.

Rapid detection of methicillin resistance in staphylococci using a slide latex agglutination kit

The slide latex agglutination test, MRSA-Screen, was compared with the mecA polymerase chain reaction (PCR) and traditional susceptibility test methods for the detection of methicillin resistance in Staphylococcus aureus and coagulase-negative staphylococci. The MRSA-Screen test detected the same number of methicillin-resistant S. aureus as the mecA PCR and the traditional susceptibility tests. It correctly identified all 21 methicillin-susceptible S. aureus as being sensitive. It also produced the same result as the mecA PCR in identifying a methicillin-resistant S. aureus among six isolates classified as borderline resistant by traditional susceptibility tests. The MRSA-Screen test and mecA PCR detected methicillin resistance in 10 and 15 of 17 methicillin-resistant coagulase-negative staphylococci, respectively. From these results, it is concluded that the MRSA-Screen is a very accurate, reliable and rapid method of detecting methicillin resistance in S. aureus and is suitable for use in clinical microbiology laboratories. Further study of its use in detecting methicillin resistance in coagulase-negative staphylococci is required.

Rapid slide latex agglutination test for detection of methicillin resistance in Staphylococcus aureus.

The MRSA screen test (Denka Seiken Co., Ltd.), a commercially available, rapid (20-min) slide latex agglutination test for the determination of methicillin resistance by detection of PBP 2a in Staphylococcus aureus, was compared with the oxacillin agar screen test and PCR detection of the mecA gene. A total of 563 S. aureus isolates were tested. Two hundred ninety-six of the isolates were methicillin-susceptible isolates from cultures of blood from consecutive patients. Also, 267 methicillin-resistant isolates that comprised 248 different phage types were tested. Methicillin resistance was defined as the presence of the mecA gene. Of the 267 mecA gene-positive isolates, 263 were positive by the MRSA screen test (sensitivity, 98.5%), and all the mecA-gene negative strains were negative by the MRSA screen test (specificity, 100%). The oxacillin agar screen test detected methicillin resistance in 250 of the mecA gene-positive isolates (sensitivity, 93.6%). The sensitivity of the MRSA screen test was statistically significantly higher than the sensitivity of the oxacillin agar screen test (P < 0. 05). The MRSA screen test is a highly sensitive and specific test for the detection of methicillin resistance. Also, it offers results within half an hour and is easy to perform, which makes this test a valuable tool in the ongoing battle against methicillin-resistant S. aureus.

Evaluation of MRSA-Screen, a simple anti-PBP 2a slide latex agglutination kit, for rapid detection of methicillin resistance in Staphylococcus aureus.

The MRSA-Screen test (Denka Seiken Co., Ltd., Tokyo, Japan), consisting of a slide latex agglutination kit that detects PBP 2a with a monoclonal antibody, was blindly compared to the oxacillin disk diffusion test, the oxacillin-salt agar screen, and PCR of the mecA gene for the detection of methicillin resistance in Staphylococcus aureus. A total of 120 methicillin-susceptible S. aureus (MSSA) and 80 methicillin-resistant S. aureus (MRSA) isolates, defined by the absence or presence of the mecA gene, respectively, were tested. The MRSA-Screen test, the oxacillin disk diffusion test, and the oxacillin-salt agar screening test showed sensitivities of 100, 61.3, and 82.5% and specificities of 99.2, 96.7, and 98.3%, respectively. We conclude that the MRSA-Screen is a very accurate, reliable, and fast test (15 min) for differentiation of MRSA from MSSA colonies on agar plates.

Rapid Detection of Methicillin Resistance in Staphylococcus aureus Isolates by the MRSA-Screen Latex Agglutination Test

The slide agglutination test MRSA-Screen (Denka Seiken Co., Niigata, Japan) was compared with the mecA PCR ("gold standard") for the detection of methicillin resistance in Staphylococcus aureus. The MRSA-Screen test detected the penicillin-binding protein 2a (PBP2a) antigen in 87 of 90 genetically diverse methicillin-resistant S. aureus (MRSA) stock culture strains, leading to a sensitivity of 97%. The three discrepant MRSA strains displayed positive results only after induction of the mecA gene by exposure to methicillin. Both mecA PCR and MRSA-Screen displayed negative results among the methicillin-susceptible S. aureus strains (n = 106), as well as for Micrococcus spp. (n = 10), members of the family Enterobacteriaceae (n = 10), Streptococcus pneumoniae (n = 10), and Enterococcus spp. (n = 10) (specificity = 100%). Producing the same PBP2a antigen, all 10 methicillin-resistant Staphylococcus epidermidis strains score positived in both the latex test and the mecA PCR. Consequently, the MRSA-Screen test should be applied only after identification of the MRSA strain to the species level to rule out coagulase-negative staphylococci. In conclusion, due to excellent specificity and sensitivity the MRSA-Screen latex test has the potential to be successfully used for routine applications in the microbiology laboratory.