scholarly journals Susceptibility Testing of Anaerobic Bacteria: Evaluation of the Redesigned (Version 96) bioMérieux ATB ANA Device

1999 ◽  
Vol 37 (6) ◽  
pp. 1824-1828 ◽  
Author(s):  
L. Dubreuil ◽  
I. Houcke ◽  
E. Singer
Keyword(s):  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Anaerobic Bacteria ◽  
Reference Method ◽  
National Committee ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
French Society ◽  
Antibiotic Susceptibilities ◽  
Agar Dilution

We compared the susceptibility results for 200 clinical anaerobes with nine antibiotics obtained by using a new ATB ANA (bioMérieux) device against those obtained by the National Committee for Clinical Laboratory Standards (NCCLS) standard agar dilution method. For better evaluation of the device, we added some resistant Bacteroides fragilis group strains from our own collection: 3, 6, and 12 strains that were resistant to imipenem, ticarcillin plus clavulanic acid, and co-amoxiclav, respectively, and 2 other strains with decreased susceptibility to metronidazole. For some strains that did not grow on ATB S medium, tests were performed by using West-Wilkins medium supplemented with 1.5% agar. The new ATB ANA device made clinical categorization of the investigated strains possible, according to French (Committee of the Antibiogram of the French Society of Microbiology) or U.S. (NCCLS) breakpoints, with the following respective results: category agreement, 94.3 and 94.9%; minor errors, 4.8 and 3.8%; major errors, 0.4 and 0.8%; and very major errors 4.6 and 4.2%. The ATB ANA device was able to detect low-level metronidazole-resistant B. fragilis strains according to the French breakpoints but not the NCCLS ones. For B. fragilis and β-lactamase-positive Prevotellastrains, the clustering effect of amoxicillin MICs around the French breakpoints led to more frequent minor errors. ATB ANA is a very convenient method to determine the antibiotic susceptibilities of anaerobes. Results obtained by ATB ANA correlated well with those obtained by the reference method.

Fluoroquinolone E-Testing against Pseudomonas Aeruginosa and Streptococcus Pneumoniae

2002 ◽  
Vol 18 (5) ◽  
pp. 241-247
Author(s):  
Eric G Sahloff ◽  
Benjamin P Smith ◽  
Steven J Martin
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Streptococcus Pneumoniae ◽  
Clinical Laboratory ◽  
Reference Method ◽  
Test Methods ◽  
National Committee ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Drug Activity ◽  
Agar Dilution

Objectives and Design: The use of fluoroquinolones has increased against antibiotic-resistant pathogens such as Streptococcus pneumoniae and Pseudomonas aeruginosa. The E-test (AB Biodisk, Solna, Sweden) is now commonly used for susceptibility testing of fluoroquinolones against these organisms. The purpose of the present study was to evaluate the accuracy and correlation of minimum inhibitory concentrations (MICs) determined by E-testing with a National Committee for Clinical Laboratory Standards reference standard, agar-dilution MIC testing. E-test and agar dilution MICs were compared for ciprofloxacin, levofloxacin, gatifloxacin, and moxifloxacin against clinical isolates of S. pneumoniae (n = 53) and P. aeruginosa (n = 62). Main Outcome Measures: MICs were determined by use of agar dilution and E-test methods. Essential agreement was defined as MICs from both methods within ± 1 log2 dilution. Categorical agreement compared MIC interpretations: susceptible, intermediate, or resistant. Categorical disagreement between methods was reported as very major, major, or minor errors. Results: E-tests produced lower MICs than the reference method for ciprofloxacin, gatifloxacin, and moxifloxacin versus P. aeruginosa. For S. pneumoniae, E-test MICs tended to be higher for all fluoroquinolones. The best correlation between testing methods was seen with levofloxacin. Essential agreement occurred more frequently with P. aeruginosa in the lower range of MICs and with S. pneumoniae in the higher range of MICs. Categorical agreement was greater than 90% for the 460 comparisons. Two very major errors (false-susceptible) occurred for gatifloxacin versus P. aeruginosa. Conclusions: For the determination of fluoroquinolone susceptibility against S. pneumoniae and P. aeruginosa, E-testing is a simple tool for clinical use, and few very major or major errors in susceptibility interpretation occur for either organism. For determining fluoroquinolone MICs, E-testing may overestimate drug activity against P. aeruginosa and underestimate drug activity versus S. pneumoniae compared with the agar dilution method. These differences could affect appropriate antimicrobial selection, leading to suboptimal outcomes.

scholarly journals Comparison of Three Methods for Testing Azole Susceptibilities of Candida albicans Strains Isolated Sequentially from Oral Cavities of AIDS Patients

1998 ◽  
Vol 36 (6) ◽  
pp. 1578-1583 ◽  
Author(s):  
Anna Maria Tortorano ◽  
Maria Anna Viviani ◽  
Francesco Barchiesi ◽  
Daniela Arzeni ◽  
Anna Lisa Rigoni ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Clinical Laboratory ◽  
Reference Method ◽  
National Committee ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Aids Patients ◽  
Testing Procedures ◽  
Broth Microdilution Method ◽  
Mean Differences

Three susceptibility testing procedures were compared to determine fluconazole, itraconazole, and ketoconazole MICs against 47Candida albicans strains isolated sequentially from the oral cavities of five AIDS patients undergoing azole therapy. They included the broth microdilution method (BM), performed according to the National Committee for Clinical Laboratory Standards’ tentative standard, the agar dilution method (AD), and the Etest; the latter two tests were performed both in Casitone agar (AD-Cas and Etest-Cas) and in RPMI (AD-RPMI and Etest-RPMI). Twenty-four- and 48-h MICs obtained by AD and Etest were compared with 48-h MICs obtained by BM. The MICs of all the azoles determined by BM were usually lower than those obtained by the other methods, mainly due to different reading criteria. In order to assess the most appropriate way of evaluating the agreement of MICs obtained by different methods with those produced by the proposed reference method (BM), we used the mean differences calculated according to Bland and Altman’s method. Comparison of fluconazole MICs obtained by BM and AD-Cas yielded a mean difference of 3, and the percentages of agreement within ±2 dilutions were 98 and 100% at 24 and 48 h, respectively. For ketoconazole and itraconazole MICs, lower mean differences were noted, and agreement ranged from 96 to 100%. Agreement between the AD-RPMI and BM results was poor for all azoles, and an increase in MICs was always observed between the 1st- and 2nd-day readings. Similarly, Etest-Cas gave better agreement with BM than did Etest-RPMI for all the azoles. BM, AD-Cas, and Etest-Cas each demonstrated a progressive increase in fluconazole MICs against strains isolated sequentially from a given patient, in accordance with the decreased clinical response to fluconazole.

scholarly journals Broth Microdilution and Gradient Diffusion Strips vs. Reference Agar Dilution Method: First Evaluation for Clostridiales Species Antimicrobial Susceptibility Testing

Antibiotics ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 975
Author(s):  
Florian Baquer ◽  
Asma Ali Sawan ◽  
Michel Auzou ◽  
Antoine Grillon ◽  
Benoît Jaulhac ◽  
...  
Keyword(s):  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Reference Method ◽  
Antimicrobial Susceptibility Testing ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Broth Microdilution ◽  
Multicenter Studies ◽  
Gradient Diffusion ◽  
Agar Dilution

Antimicrobial susceptibility testing of anaerobes is challenging. Because MIC determination is recommended by both CLSI and EUCAST, commercial broth microdilution and diffusion strip tests have been developed. The reliability of broth microdilution methods has not been assessed yet using the agar dilution reference method. In this work, we evaluated two broth microdilution kits (MICRONAUT-S Anaerobes® MIC and Sensititre Anaerobe MIC®) and one gradient diffusion strip method (Liofilchem®) for antimicrobial susceptibility testing of 47 Clostridiales isolates (Clostridium, Clostridioides and Hungatella species) using the agar dilution method as a reference. The evaluation focused on comparing six antimicrobial molecules available in both microdilution kits. Analytical performances were evaluated according to the Food and Drug Administration (FDA) recommendations. Essential agreements (EA) and categorical agreements (CA) varied greatly according to the molecule and the evaluated method. Vancomycin had values of essential and categorical agreements above 90% for the three methods. The CA fulfilled the FDA criteria for three major molecules in the treatment of Gram-positive anaerobic infections (metronidazole, piperacillin/tazobactam and vancomycin). The highest rate of error was observed for clindamycin. Multicenter studies are needed to further validate these results.

scholarly journals Correlation of Oxacillin MIC with mecAGene Carriage in Coagulase-Negative Staphylococci

2000 ◽  
Vol 38 (2) ◽  
pp. 752-754 ◽  
Author(s):  
Zafar Hussain ◽  
Luba Stoakes ◽  
Viki Massey ◽  
Deb Diagre ◽  
Viivi Fitzgerald ◽  
...  
Keyword(s):  
Staphylococcus Epidermidis ◽  
Clinical Laboratory ◽  
National Committee ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Coagulase Negative Staphylococci ◽  
Methicillin Resistant ◽  
Mueller Hinton ◽  
Mueller Hinton Agar ◽  
Agar Dilution

The National Committee for Clinical Laboratory Standards has recently changed the oxacillin breakpoint from ≥4 mg/liter to ≥0.5 mg/liter to detect methicillin-resistant coagulase-negative staphylococci (CoNS) because the previous breakpoint lacked sensitivity. To determine the correlation between the new oxacillin breakpoint and the presence of themecA gene, 493 CoNS of 11 species were tested. The presence of the mecA gene was determined by PCR, and oxacillin susceptibility was determined by the agar dilution method with Mueller-Hinton agar containing 2% NaCl and oxacillin (0.125 to 4.0 mg/liter). The new breakpoint correctly classified all CoNS strains with mecA as methicillin resistant and strains ofStaphylococcus epidermidis, S. haemolyticus, and S. hominiswithout mecA as methicillin susceptible. The breakpoint of ≥0.5 mg/liter was not specific for S. cohnii, S. lugdunensis, S. saprophyticus, S. warneri, and S. xylosus, in that it categorized 70 of 74 strains of these species withoutmecA (94.6%) as methicillin resistant. The results of this study indicate that the new oxacillin breakpoint accurately identifies strains of CoNS with mecAbut is not specific for strains of certain species of CoNS withoutmecA.

scholarly journals Cefotetan Susceptibility Testing Against Anaerobic Bacteria From Obstetrical and Gynecologic Sources: Comparison of Five Different Methods

1993 ◽  
Vol 1 (1) ◽  
pp. 23-26
Author(s):  
Maurizio Maccato ◽  
Gerald Riddle ◽  
Sebastian Faro
Keyword(s):  
Susceptibility Testing ◽  
Anaerobic Bacteria ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Gradient System ◽  
Minimal Inhibitory Concentrations ◽  
Gradient Technique ◽  
Doubling Dilution ◽  
Agar Dilution ◽  
Elution Method

Five different antibiotic susceptibility methods were utilized to test the effectiveness of cefotetan against 200 anaerobic bacteria recovered from patients with obstetrical or gynecological infections. The object of this study was to determine if a more economical and rapid method for anaerobic susceptibility testing was as acceptable as the reference agar dilution method. The five methods were: 1) broth disk elution, 2) microbroth technique, 3) a commercially available microbroth technique, 4) a commercially available spiral gradient technique, and 5) reference agar dilution. The minimal inhibitory concentrations (MICs) calculated from the spiral gradient technique were equal to or within one doubling dilution of the reference system in 99.5% of cases, while the percentage for the commercially available microbroth system was 96.8%, very similar to the microbroth technique used in our laboratory that yielded a percentage of 96.3. The disk elution method correlated to the reference agar dilution method in 95.3% cases. While the overall agreement between these techniques is good, especially for the spiral gradient system, clustering of certain organisms near the breakpoint of the antibiotic tested results in variability in the labeling of these organisms as susceptible or resistant. This problem appears to be particularly significant for the disk elution method. Therefore, further refinements in these methods of suscleptibility testing are needed in order to provide a more clinically useful assessment of the susceptibility or resistance of certain bacterial isolates.

scholarly journals Modified agar dilution susceptibility testing method for determining in vitro activities of antifungal agents, including azole compounds.

1997 ◽  
Vol 41 (6) ◽  
pp. 1349-1351 ◽  
Author(s):  
T Yoshida ◽  
K Jono ◽  
K Okonogi
Keyword(s):  
Antifungal Agents ◽  
Clinical Laboratory ◽  
National Committee ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Agar Dilution ◽  
Weak Growth ◽  
High Concentrations ◽  
Broth Dilution

In vitro activities of antifungal agents, including azole compounds, against yeasts were easily determined by using RPMI-1640 agar medium and by incubating the plates in the presence of 20% CO2. The end point of inhibition was clear by this method, even in the case of azole compounds, because of the almost complete inhibition of yeast growth at high concentrations which permitted weak growth of some Candida strains by traditional methods. MICs obtained by the agar dilution method were similar to those obtained by the broth dilution method proposed by the National Committee for Clinical Laboratory Standards.

scholarly journals Multilaboratory Comparison of Proficiencies in Susceptibility Testing of Helicobacter pylori and Correlation between Agar Dilution and E Test Methods

2003 ◽  
Vol 47 (10) ◽  
pp. 3138-3144 ◽  
Author(s):  
L. M. Best ◽  
D. J. M. Haldane ◽  
M. Keelan ◽  
D. E. Taylor ◽  
A. B. R. Thomson ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Reference Method ◽  
Test Methods ◽  
Culture Collection ◽  
Test Method ◽  
National Committee ◽  
Reference Laboratory ◽  
Agar Dilution

ABSTRACT Susceptibility testing was performed at seven Canadian microbiology laboratories and the Helicobacter Reference Laboratory, Halifax, Nova Scotia, Canada, to assess susceptibility testing proficiency and the reproducibility of the results for clarithromycin and metronidazole and to compare the Epsilometer test (E test) method to the agar dilution reference method. Control strain Helicobacter pylori ATCC 43504 (American Type Culture Collection) and 13 clinical isolates (plus duplicates of four of these strains including ATCC 43504) were tested blindly. The National Committee for Clinical Laboratory Standards (NCCLS) guidelines for agar dilution testing were followed, and the same suspension of organisms was used for agar dilution and E test. Antimicrobials and E test strips were provided to the investigators. Methods were provided on a website (www.Helicobactercanada.org ). Each center reported MICs within the stated range for strain ATCC 43504. Compared to the average MICs, interlaboratory agreements within 2 log2 dilutions were 90% (range, 69 to 100%) for clarithromycin by agar dilution, with seven very major errors [VMEs], and 85% (range, 65 to 100%) by E test, with three VMEs. Interlaboratory agreements within 2 log2 dilutions were 83% (range, 50 to 100%) for metronidazole by agar dilution, with six VMEs and eight major errors (MEs), and 75% (range, 50 to 94%) by E test, with four VMEs and four MEs. At lower and higher concentrations of antibiotic, E test MICs were slightly different from agar dilution MICs, but these differences did not result in errors. When a standardized protocol based on NCCLS guidelines was used, most participants in this study correctly identified clarithromycin- and metronidazole-susceptible and -resistant strains of H. pylori 93% of the time by either the agar dilution or E test method, and the numbers of errors were relatively equivalent by both methods.

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