scholarly journals Multicenter Evaluation of a Modified Cefoxitin Disk Diffusion Method and PBP2a Testing To PredictmecA-Mediated Oxacillin Resistance in Atypical Staphylococcus aureus

2016 ◽  
Vol 55 (2) ◽  
pp. 485-494 ◽  
Author(s):  
Shelley A. Miller ◽  
James Karichu ◽  
Peggy Kohner ◽  
Nicolynn Cole ◽  
Janet A. Hindler ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Clinical Laboratory ◽  
Disk Diffusion ◽  
Diffusion Method ◽  
Disk Diffusion Method ◽  
Content Type ◽  
Oxacillin Resistance ◽  
Mueller Hinton ◽  
Cefoxitin Disk ◽  
Cefoxitin Disk Diffusion

ABSTRACTPhenotypic variants ofStaphylococcus aureusthat display small colonies, reduced pigmentation, and decreased hemolysis and/or coagulase activity are periodically isolated by the clinical laboratory. Antimicrobial susceptibility testing (AST) of these isolates is complicated, because many do not grow on routine AST media, including Mueller-Hinton agar (MHA) and cation-adjusted Mueller-Hinton broth. This multicenter study evaluated cefoxitin disk diffusion for 37 atypicalS. aureusisolates (156 readings) with MHA supplemented with 5% sheep's blood (BMHA), usingmecAPCR as the reference standard. The correlation of two commercial PBP2a assays withmecAPCR was also assessed. Ten isolates were negative and 27 positive formecA. No major errors for cefoxitin were observed, but 19.5% very major errors (VMEs) were observed at 24 h of incubation, and 17.2% VMEs were observed at 48 h. The proportions of VMEs ranged from 14.7 to 23.0% at 24 h, and from 13.3 to 17.6% at 48 h, across three testing laboratories. PBP2a tests were performed from growth on BMHA and blood agar plates (BAP), with and without cefoxitin disk induction. The Alere PBP2a SA culture colony test sensitivities formecAwere 90.0% with uninduced growth and 97.4% with induced growth from BMHA. On BAP, sensitivity was 96.0% with induced growth. The sensitivities of the Oxoid PBP2′ latex agglutination test were 85.7% with uninduced growth and 93.9% with induced growth from BMHA and 95.9% with induced growth on BAP. On the basis of these data, we recommend that laboratories perform onlymecAPCR and/or PBP2a tests when requested to perform AST on atypical isolates ofS. aureus.

scholarly journals Evaluation of different phenotypic methods for the detection of methicillin resistant Staphylococcus aureus and antimicrobial susceptibility pattern of MRSA

2017 ◽  
Vol 4 (9) ◽  
pp. 3297 ◽  
Author(s):  
Sheetal Sharma ◽  
Preeti Srivastava ◽  
Anjali Kulshrestha ◽  
Ameer Abbas
Keyword(s):  
Staphylococcus Aureus ◽  
Sensitivity And Specificity ◽  
Antimicrobial Susceptibility ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Disk Diffusion ◽  
Diffusion Method ◽  
Disk Diffusion Method ◽  
Phenotypic Methods ◽  
Cefoxitin Disk ◽  
Cefoxitin Disk Diffusion

Background: Rapid and accurate detection of methicillin resistant Staphylococcus aureus (MRSA) is an important role of clinical microbiology laboratories to avoid treatment failure. The aim of this study was to compare conventional methods against the cefoxitin disc diffusion method to determine the best phenotypic method. Methods: Study was carried out in the Department of Microbiology, National Institute of Medical Sciences & Research, Jaipur (India), between July 2016 – December 2016. The methods included were Oxacillin E-test MIC, Oxacillin screen agar, Oxacillin disk diffusion, Cefoxitin disk diffusion and CHROMagar- MRSA methods. Antimicrobial susceptibility performed as per CLSI guidelines.Results: Out of 142 isolates of S. aureus, fifty three (37.32%) strains of MRSA were isolated from clinical specimen. E-MIC test was selected as gold standard method. The sensitivity and specificity of Oxacillin screen agar and CHROMagar-MRSA were same 98.07% and 97.80%, respectively. The sensitivity and specificity of oxacillin disk diffusion were 94.23% and 98.89%. Fifty three strains of S. aureus were MRSA by cefoxitin disk diffusion method and Oxacillin Ezy MIC test. The sensitivity and specificity of cefoxitin disk diffusion method and Oxacillin Ezy MIC method was 100% and 100% respectively. All isolates including MRSA were susceptible to Vancomycin and Linezolid. Conclusions: All phenotypic methods had high sensitivity and specificity for detection of MRSA. However, cefoxitin disk diffusion method in comparison to other methods had higher sensitivity and specificity. 

scholarly journals Detection of Oxacillin Resistance in Staphylococcus aureus Isolated from the Neonatal and Pediatric Units of a Brazilian Teaching Hospital

2009 ◽  
Vol 3 ◽  
pp. CMPed.S2085 ◽  
Author(s):  
Valéria Cataneli Pereira ◽  
André Martins ◽  
Lígia Maria Suppo de Souza Rugolo ◽  
Maria de Lourdes Ribeiro de Souza da Cunha
Keyword(s):  
Staphylococcus Aureus ◽  
Screening Test ◽  
Blood Cultures ◽  
Neonatal Unit ◽  
Disk Diffusion ◽  
Diffusion Method ◽  
Fluid Sample ◽  
Disk Diffusion Method ◽  
Cefoxitin Disk ◽  
Cefoxitin Disk Diffusion

Objective To determine, by phenotypic and genotypic methods, oxacillin susceptibility in Staphylococcus aureus strains isolated from pediatric and neonatal intensive care unit patients seen at the University Hospital of the Botucatu School of Medicine. Methods A total of 100 S. aureus strains isolated from the following materials were studied: 25 blood cultures, 21 secretions, 12 catheters, 3 cannulae and one chest drain from 62 patients in the neonatal unit, and 36 blood cultures, one pleural fluid sample and one peritoneal fluid sample from 38 patients in the pediatric unit. Resistance of the S. aureus isolates to oxacillin was evaluated by the disk diffusion method with oxacillin (1 μg) and cefoxitin (30 μg), agar screening test using Mueller-Hinton agar supplemented with 6 μg/ml oxacillin and 4% NaCl, and detection of the mecA gene by PCR. In addition, the isolates were tested for β-lactamase production using disks impregnated with Nitrocefin and hyperproduction of β-lactamase using amoxicillin (20 μg) and clavulanic acid (10 μg) disks. Results Among the 100 S. aureus strains included in the study, 18.0% were resistant to oxacillin, with 16.1% MRSA being detected in the neonatal unit and 21.0% in the pediatric unit. The oxacillin (1 μg) and cefoxitin (30 μg) disk diffusion methods presented 94.4% and 100% sensitivity, respectively, and 98.8% specificity. The screening test showed 100% sensitivity and 98.8% specificity. All isolates produced β-lactamase and one of these strains was considered to be a hyperproducer. Conclusions The 30 μg cefoxitin disk diffusion method presented the best result when compared to the 1 μg oxacillin disk. The sensitivity of the agar screening test was similar to that of the cefoxitin disk diffusion method and higher than that of the oxacillin disk diffusion method. We observed variations in the percentage of oxacillin-resistant isolates during the study period, with a decline over the last years which might be related to improved nosocomial infection control and the rational use of antibiotics.

scholarly journals Current status of oxacillin-susceptible mecA-positive Staphylococcus aureus infection in Shanghai, China: A multicenter study

2019 ◽  
Author(s):  
Junlan Liu ◽  
Tianming Li ◽  
Ni Zhong ◽  
Xing Wang ◽  
Jie Jiang ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Multicenter Study ◽  
Multidrug Resistant ◽  
Disk Diffusion ◽  
Current Status ◽  
Oxacillin Resistance ◽  
Important Challenge ◽  
Underlying Mechanisms ◽  
Cefoxitin Disk ◽  
Cefoxitin Disk Diffusion

Abstract The worldwide reported oxacillin-susceptible mecA -positive Staphylococcus aureus (OS-MRSA) represents a distinctly important challenge to detection and treatment of MRSA, but finite data on current status of OS-MRSA infection in Chinese hospitals are available. The present multicenter study carried out a battery of phenotypic susceptibility tests as well as diagnostic tests (PBP2a detection, mecA , and mecC PCR) for a collection of 956 clinical S. aureus isolates from 10 hospitals in Shanghai, molecular typing was performed for all identified OS-MRSA strains. OS-MRSA represented 1.8% (17/956) of total isolates and were commonly borderline oxacillin-susceptible (Oxacillin-MIC of 1 or 2 mg/L). 10 of 17 OS-MRSA were ST59 lineages, followed by ST965 (3/17). Unlike oxacillin-resistant MRSA that commonly exhibit a multidrug resistant (MDR) phenotype, OS-MRSA were less likely to be MDR and displayed MIC pattern remarkably differential from OR-MRSA. OS-MRSA showed oxacillin-inducible oxacillin resistance and the majority of them (15/17) were cefoxitin-resistant by cefoxitin disk diffusion. S. aureus with borderline susceptible oxacillin MICs (1 or 2 mg/L) should be confirmed by cefoxitin disk diffusion in clinical practice, whereas susceptible isolates reclassified by cefoxitin disk diffusion should still be subjected to PBP2a testing and (or) mecA (mecC) PCR. The presented study has characterized phenotypically and molecularly an atypical type of MRSA showing cryptic but inducible resistance to oxacillin, but its underlying mechanisms warrant further elucidation.

scholarly journals Comparison of Different Phenotypic Approaches To Screen and Detect mecC-Harboring Methicillin-Resistant Staphylococcus aureus

2017 ◽  
Vol 56 (1) ◽  
Author(s):  
André Kriegeskorte ◽  
Evgeny A. Idelevich ◽  
Andreas Schlattmann ◽  
Franziska Layer ◽  
Birgit Strommenger ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Susceptibility Testing ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
Disk Diffusion Test ◽  
Methicillin Resistant ◽  
Content Type ◽  
Vitek 2 ◽  
Cefoxitin Disk ◽  
Cefoxitin Disk Diffusion

ABSTRACT Similar to mecA, mecC confers resistance against beta-lactams, leading to the phenotype of methicillin-resistant Staphylococcus aureus (MRSA). However, mecC-harboring MRSA strains pose special difficulties in their detection. The aim of this study was to assess and compare different phenotypic systems for screening, identification, and susceptibility testing of mecC-positive MRSA isolates. A well-characterized collection of mecC-positive S. aureus isolates (n = 111) was used for evaluation. Routinely used approaches were studied to determine their suitability to correctly identify mecC-harboring MRSA, including three (semi)automated antimicrobial susceptibility testing (AST) systems and five selective chromogenic agar plates. Additionally, a cefoxitin disk diffusion test and an oxacillin broth microdilution assay were examined. All mecC-harboring MRSA isolates were able to grow on all chromogenic MRSA screening plates tested. Detection of these isolates in AST systems based on cefoxitin and/or oxacillin testing yielded overall positive agreements with the mecC genotype of 97.3% (MicroScan WalkAway; Siemens), 91.9% (Vitek 2; bioMérieux), and 64.9% (Phoenix, BD). The phenotypic resistance pattern most frequently observed by AST devices was “cefoxitin resistance/oxacillin susceptibility,” ranging from 54.1% (Phoenix) and 83.8% (Vitek 2) to 92.8% (WalkAway). The cefoxitin disk diffusion and oxacillin broth microdilution assays categorized 100% and 61.3% of isolates to be MRSA, respectively. The chromogenic media tested confirmed their suitability to reliably screen for mecC-harboring MRSA. The AST systems showed false-negative results with varying numbers, misidentifying mecC-harboring MRSA as methicillin-susceptible S. aureus. This study underlines cefoxitin's status as the superior surrogate mecC-positive MRSA marker.

scholarly journals Evaluation of Oxacillin and Cefoxitin Disk Diffusion and MIC Breakpoints Established by the Clinical and Laboratory Standards Institute for Detection of mecA-Mediated Oxacillin Resistance in Staphylococcus schleiferi

2017 ◽  
Vol 56 (2) ◽  
Author(s):  
H. K. Huse ◽  
S. A. Miller ◽  
S. Chandrasekaran ◽  
J. A. Hindler ◽  
S. D. Lawhon ◽  
...  
Keyword(s):  
Opportunistic Infections ◽  
Performance Standards ◽  
Inhibition Zone ◽  
Disk Diffusion ◽  
Testing Methods ◽  
Coagulase Negative Staphylococci ◽  
Content Type ◽  
Oxacillin Resistance ◽  
Cefoxitin Disk ◽  
Cefoxitin Disk Diffusion

ABSTRACTStaphylococcus schleiferiis a beta-hemolytic, coagulase-variable colonizer of small animals that can cause opportunistic infections in humans. In veterinary isolates, the rate ofmecA-mediated oxacillin resistance is significant, with reported resistance rates of >39%. The goal of this study was to evaluate oxacillin and cefoxitin disk diffusion (DD) and MIC breakpoints for detection ofmecA-mediated oxacillin resistance in 52 human and 38 veterinary isolates ofS. schleiferi. Isolates were tested on multiple brands of commercial media and according to Clinical and Laboratory Standards Institute (CLSI) methods. Zone diameters and MIC values were interpreted using CLSI breakpoints (CLSI,Performance Standards for Antimicrobial Susceptibility Testing. M100-S27, 2017) forStaphylococcus aureus/Staphylococcus lugdunensis, coagulase-negative staphylococci (CoNS), andStaphylococcus pseudintermedius. Results were compared to those ofmecAPCR. Twenty-nine of 90 (32%) isolates weremecApositive. Oxacillin inhibition zone sizes and MICs interpreted byS. pseudintermediusbreakpoints reliably differentiatedmecA-positive andmecA-negative isolates, with a categorical agreement (CA) of 100% and no very major errors (VMEs) or major errors (MEs) for all media. For cefoxitin DD results interpreted usingS. aureus/S. lugdunensisand CoNS breakpoints, CA values were 85% and 75%, respectively, and there were 72% and 64% VMEs, respectively, and 0 MEs. For cefoxitin MICs interpreted usingS. aureus/S. lugdunensisbreakpoints, CA was 81%, and there were 60% VMEs and no MEs. Our data demonstrate that oxacillin DD or MIC testing methods using the currentS. pseudintermediusbreakpoints reliably identifymecA-mediated oxacillin resistance inS. schleiferi, while cefoxitin DD and MIC testing methods perform poorly.

scholarly journals Performance of a New MicroScan WalkAway PC30 Panel and Disk Diffusion Method for Detection of Oxacillin Resistance in Staphylococcus spp.

2011 ◽  
Vol 49 (6) ◽  
pp. 2269-2271 ◽  
Author(s):  
Olivier Gallon ◽  
Patrick Pina ◽  
Alain Gravet ◽  
Frederic Laurent ◽  
Brigitte Lamy ◽  
...  
Keyword(s):  
Disk Diffusion ◽  
Diffusion Method ◽  
Disk Diffusion Method ◽  
Oxacillin Resistance ◽  
Microscan Walkaway ◽  
Staphylococcus Spp

Evaluation of antibiotic resistance pattern and mecA gene frequency in methicillin-resistant Staphylococcus aureus strains collected from clinical specimens in Marand hospital and treatment centers, Iran

2021 ◽  
Author(s):  
Abolfazl Jafari-Sales ◽  
Zahra Sadeghi Deylamdeh ◽  
Afsoon Shariat
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Meca Gene ◽  
Disk Diffusion ◽  
Diffusion Method ◽  
Disk Diffusion Method ◽  
Methicillin Resistant ◽  
Medical Centers ◽  
Wide Range

Introduction: Staphylococcus aureus causes a wide range of infections and as a multivalent pathogen is one of the causative agents of nosocomial and community infections. Therefore, the aim of this study was to identify and determine the pattern of antibiotic resistance of methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients in hospitals and medical centers in Marand city and also to evaluate the presence of mecA gene. Materials and Methods: In this cross-sectional descriptive study, 385 samples of S. aureus were collected from different clinical samples of patients in hospitals and medical centers of Marand city. S. aureus was identified using standard biochemical methods.  Methicillin resistance was determined by disk diffusion method in the presence of oxacillin and cefoxitin. The pattern of antibiotic resistance of the strains was determined by disk diffusion method and according to CLSI recommendation and also PCR method was used to evaluate the frequency of MecA gene. Results: In the present study, out of 385 samples of S. aureus, 215 (55.84%) samples were methicillin resistant. PCR results for mecA gene showed that 110 samples had mecA gene.  The highest antibiotic resistance was observed against penicillin (100%) and erythromycin (83.63%). Most MRSA were isolated from urine and wound samples. Conclusion: The results of this study indicate the prevalence of methicillin-resistant species and also the increase in antibiotic resistance of MRSA to various antibiotics.  Therefore, in order to prevent increased resistance to other antibiotics, it is recommended to avoid inappropriate use of antibiotics.

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