scholarly journals Evaluation of cefoxitin disk diffusion breakpoint for detection of methicillin resistance in Staphylococcus pseudintermedius isolates from dogs

2012 ◽  
Vol 24 (5) ◽  
pp. 964-967 ◽  
Author(s):  
David A. Bemis ◽  
Rebekah D. Jones ◽  
Ricardo Videla ◽  
Stephen A. Kania
Keyword(s):  
Methicillin Resistance ◽  
Screening Method ◽  
Inhibition Zone ◽  
Disk Diffusion ◽  
Coagulase Negative Staphylococci ◽  
Staphylococcus Pseudintermedius ◽  
Growth Inhibition Zone ◽  
Disk Method ◽  
Cefoxitin Disk ◽  
Cefoxitin Disk Diffusion

Cefoxitin disk diffusion susceptibility testing is a recommended screening method for the detection of methicillin resistance in human isolates of Staphylococcus aureus and coagulase-negative staphylococci. A retrospective analysis of 1,146 clinical isolates of Staphylococcus pseudintermedius from dogs was conducted to determine if screening by the cefoxitin disk method can be similarly useful with S. pseudintermedius. The distribution of cefoxitin growth inhibition zone diameters within this collection was bimodal and correlated well with the results of methicillin resistance gene ( mecA) detection by polymerase chain reaction. Of the isolates, 5% had discordant results and, when retested, 84% of these were in agreement. While a greater diversity of isolates and interlaboratory comparisons must be tested, the current study suggests that an epidemiological breakpoint (of approximately ≤30 mm = resistant; ≥31 = susceptible) can be established to predict methicillin resistance in S. pseudintermedius.

scholarly journals Evaluation of Clinical Laboratory Standards Institute Interpretive Criteria for Methicillin-Resistant Staphylococcus Pseudintermedius Isolated from Dogs

2009 ◽  
Vol 21 (5) ◽  
pp. 684-688 ◽  
Author(s):  
Jennifer R. Schissler ◽  
Andrew Hillier ◽  
Joshua B. Daniels ◽  
Lynette K. Cole ◽  
Wondwossen A. Gebreyes
Keyword(s):  
Methicillin Resistance ◽  
False Negative ◽  
Meca Gene ◽  
Diagnostic Sensitivity ◽  
Disk Diffusion ◽  
Staphylococcus Pseudintermedius ◽  
Methicillin Resistant ◽  
Interpretive Criterion ◽  
Cefoxitin Disk ◽  
Cefoxitin Disk Diffusion

The Clinical and Laboratory Standards Institute published in 2008 new interpretive criteria for the identification of methicillin resistance in staphylococci isolated from animals. The sensitivity of the 2008 interpretive criteria for mecA gene-positive Staphylococcus pseudintermedius, compared with the previous criteria of 2004, was investigated. Thirty clinical isolates of methicillin-resistant S. pseudintermedius from dogs were used. The presence of the mecA gene was determined by polymerase chain reaction. The minimum inhibitory concentration for oxacillin was determined by broth microdilution. The 2008 breakpoint of 4 μg/ml for methicillin resistance resulted in a diagnostic sensitivity of 73.3% (22/30). The 2004 breakpoint guideline of 0.5 μg/ml resulted in a diagnostic sensitivity of 97% (29/30). For oxacillin disk diffusion, the 2008 interpretive criterion of 10 mm for methicillin resistance resulted in a sensitivity of 70% (21/30). If intermediate isolates (11 or 12 mm) were considered resistant, the sensitivity was 93% (28/30). Application of the 2004 interpretive criterion of 17 mm resulted in a diagnostic sensitivity of 100% (30/30). For cefoxitin disk diffusion, the interpretive criterion of 21 mm for methicillin resistance (as used for Staphylococcus aureus) resulted in a diagnostic sensitivity of 6.7% (2/30). The interpretive criterion of 24 mm (as used for coagulase-negative staphylococci) resulted in a diagnostic sensitivity of 43.3% (13/30). With the use of 2008 interpretive criteria, all 3 tests produced what we consider to be an unacceptable level of false negative results. Our findings also suggest that cefoxitin disk diffusion is an inappropriate screening test for methicillin resistance of canine S. pseudintermedius.

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 Disk Diffusion Testing for Detection of Methicillin-Resistant Staphylococci: Does Moxalactam Improve upon Cefoxitin?

2016 ◽  
Vol 54 (12) ◽  
pp. 2905-2909 ◽  
Author(s):  
Marie Bonjean ◽  
Elisabeth Hodille ◽  
Oana Dumitrescu ◽  
Céline Dupieux ◽  
Christina Nkoud Mongo ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Operating Characteristic ◽  
Methicillin Resistance ◽  
Inhibition Zone ◽  
Disk Diffusion ◽  
Large Collection ◽  
Coagulase Negative Staphylococci ◽  
Content Type ◽  
High Inoculum ◽  
Disk Diffusion Testing

Disk diffusion testing is widely used to detect methicillin resistance in staphylococci, and cefoxitin is currently considered the best marker formecA-mediated methicillin resistance. In low-inoculum diffusion testing (colony suspension at 106CFU/ml), the addition of moxalactam in combination with cefoxitin has been reported to improve on cefoxitin alone for the detection of methicillin-heteroresistant staphylococci. However, moxalactam is absent from EUCAST and CLSI guidelines, which use high-inoculum diffusion testing (colony suspension at 108CFU/ml), calling into question the potential interest of including moxalactam in their recommendations. The inhibition zone diameters of cefoxitin and moxalactam, alone and in combination, were evaluated for concordance withmecAandmecCpositivity in a large collection of clinicalStaphylococcusisolates (611Staphylococcus aureus,Staphylococcuslugdunensis, andStaphylococcus saprophyticusisolates and 307 coagulase-negative staphylococci other thanS. lugdunensisandS. saprophyticusisolates, of which 22% and 53% weremecA-positive, respectively) and in 25mecC-positiveS. aureusisolates using high-inoculum diffusion testing. Receiver operating characteristic, sensitivity, and specificity analyses indicated that the detection ofmecA- andmecC-positive and negative isolates did not improve with moxalactam, either alone or in combination with cefoxitin, compared to cefoxitin alone. These findings were similar in both theS. aureus/S. lugdunensis/S. saprophyticusgroup and in the coagulase-negative staphylococci group. Our results do not support the use of moxalactam as an additional marker of methicillin resistance when testing with high-inoculum disk diffusion.

scholarly journals Bactericides Properties of Chitosan Metal Quantum Dots Microbial Pathogenicity Against E. coli, S. aureus, and S. Typhi

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Galo Cárdenas-Triviño ◽  
María J. Saludes-Betanzo ◽  
Luis Vergara-González
Keyword(s):  
Quantum Dots ◽  
Antibacterial Properties ◽  
Inhibition Zone ◽  
Bactericidal Effect ◽  
Salmonella Typhi ◽  
Disk Diffusion ◽  
Initial Inoculum ◽  
E Coli ◽  
Growth Inhibition Zone ◽  
Average Size

The nanotechnology is considered as a tool to overcome antibiotic-resistant infections. The aim of this study was to investigate the antibacterial properties of quantum dots (QDs) of Au, Ag, and Cu supported in chitosan against Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 29213), and Salmonella Typhi (ATCC 9993) strains. The QDs were synthesized by the method (Chemical Liquid Deposition, CLD) using 2-ethoxyethanol as solvent (1×10−3 M approximate dispersion concentration). Then, NPs supported in chitosan were synthesized by solvated metal atom dispersion (SMAD) in two concentrations, labelled [A] and [B] (0.05 and 0.1 g/L) for each metal with chitosan resulting in an average size of Au 10±2.0, Ag 6±1.3, and Cu 10±2.4 nm, respectively. Several other techniques were performed such as TEM, SEM/EDX, TGA, DSC, and FT-IR for characterizing QDs. The antibacterial assay was performed with 8 agents on cultures of E. coli, S. aureus, and S. Typhi by disk diffusion, broth macrodilution, and determining death curve to the most sensitive pathogen. The antibacterial effect of the nanoparticles was compared using the diameter of growth inhibition zone by agar disk diffusion and through the minimal inhibitory concentration (MIC) and minimal bactericide concentration (MBC) obtained by macrodilution in batch culture with an initial inoculum of 5×105 CFU/mL. The highest bactericidal effect was obtained with nanoparticles of Au, Ag, and Cu (0.1 g/L) with MIC and MBC of 200 and 400 mg/mL, respectively. The greatest bactericidal effect considering the three pathogens turned out to be Ag QDs (0.05 and 0.1 g/L). A bactericidal effect of metal nanoparticles is affected mainly by the electronegativity, the concentration of nanoparticles, and the bacterial age culture.

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