scholarly journals Comparative Evaluation of National Committee for Clinical Laboratory Standards Broth Macrodilution and Agar Dilution Screening Methods for Testing Fluconazole Susceptibility ofCryptococcus neoformans

1998 ◽  
Vol 36 (5) ◽  
pp. 1330-1332 ◽  
Author(s):  
William R. Kirkpatrick ◽  
Robert K. McAtee ◽  
Sanjay G. Revankar ◽  
Annette W. Fothergill ◽  
Dora I. McCarthy ◽  
...  
Keyword(s):  
Comparative Evaluation ◽  
Clinical Laboratory ◽  
Screening Method ◽  
National Committee ◽  
Screening Methods ◽  
Free Medium ◽  
Fluconazole Resistance ◽  
Agar Dilution ◽  
Broth Macrodilution ◽  
Simple Screening

A simple screening method for fluconazole susceptibility ofCryptococcus neoformans using 2% dextrose Sabouraud dextrose agar (SabDex) with fluconazole was compared to the National Committee for Clinical Laboratory Standards (NCCLS) broth macrodilution method. By this method, fluconazole-susceptible C. neoformans isolates are significantly smaller on medium with fluconazole than on fluconazole-free medium. Isolates with decreased susceptibility have normal-size colonies on medium containing fluconazole. The 48-h NCCLS broth macrodilution MICs (NCCLS MICs) for isolates with normal-size colonies on 8- or 16-μg/ml fluconazole plates were predicted to be ≥8 or ≥16 μg/ml, respectively. On medium with 16 μg of fluconazole per ml, all strains (84 of 84) for which the NCCLS MICs were <16 μg/ml were correctly predicted, as were all isolates (7 of 7) for which the MICs were ≥16 μg/ml. Agar dilution appears to be an effective screening method for fluconazole resistance in C. neoformans.

scholarly journals In vitro activities of trovafloxacin against 557 strains of anaerobic bacteria.

1996 ◽  
Vol 40 (9) ◽  
pp. 2232-2235 ◽  
Author(s):  
H M Wexler ◽  
E Molitoris ◽  
D Molitoris ◽  
S M Finegold
Keyword(s):  
Antimicrobial Activity ◽  
Clinical Laboratory ◽  
Anaerobic Bacteria ◽  
Bacteroides Fragilis ◽  
National Committee ◽  
Dilution Technique ◽  
Agar Dilution ◽  
Group Species ◽  
Clostridium Spp

The antimicrobial activity of trovafloxacin for 557 strains of anaerobic bacteria was determined by the National Committee for Clinical Laboratory Standards-approved Wadsworth agar dilution technique. The species tested included Bacteroides fragilis (n = 91), other members of the B. fragilis group (n = 130), Campylobacter gracilis (n = 15), other Bacteroides spp. (n = 16), Prevotella spp. (n = 49), Porphyromonas spp. (n = 15), Fusobacterium spp. (n = 62), Bilophila wadsworthia (n = 24), Sutterella wadsworthensis (n = 21), Clostridium spp. (n = 61), Peptostreptococcus spp. (n = 38), and gram-positive non-spore-forming rods (n = 35). Trovafloxacin inhibited all strains of B. fragilis at < or = 0.5 microgram/ml, 99% of other B. fragilis group species at < or = 2 micrograms/ml, and 96% of all anaerobes tested at < or = 2 micrograms/ml.

scholarly journals Reappraisal of the antimicrobial susceptibilities of Chryseobacterium and Flavobacterium species and methods for reliable susceptibility testing.

1997 ◽  
Vol 41 (12) ◽  
pp. 2738-2741 ◽  
Author(s):  
S L Fraser ◽  
J H Jorgensen
Keyword(s):  
Susceptibility Testing ◽  
Opportunistic Infections ◽  
Clinical Laboratory ◽  
Error Rates ◽  
National Committee ◽  
Broth Microdilution ◽  
Gram Positive Bacteria ◽  
Serious Infections ◽  
Agar Dilution ◽  
Investigational Agents

Several Flavobacterium species, comprising a heterogeneous group of gram-negative bacilli that are capable of causing opportunistic infections in humans, have recently been reclassified as Chryseobacterium or Myroides species. Intrinsically resistant to a number of antibiotics, these organisms have been reported to be susceptible to vancomycin and certain other drugs that are normally active against gram-positive bacteria. By using the National Committee for Clinical Laboratory Standards (NCCLS) broth microdilution procedure, 58 clinical isolates of former flavobacteria (36 Chryseobacterium meningosepticum isolates, 11 C. indologenes isolates, 3 C. gleum isolates, 4 unspeciated former members of Flavobacterium group IIb, and 4 Myroides odoratum isolates) were tested with 23 antibiotics, including conventional and investigational agents. In addition, the broth microdilution results were compared to those generated by agar dilution, E-test, and disk diffusion for vancomycin and piperacillin-tazobactam. Compared to the NCCLS microdilution results, there were 7.1 and 17.9% very major errors with piperacillin-tazobactam by agar dilution and E-test, respectively. In addition, there were from 12.1 to 48.3% minor errors with both procedures with vancomycin and piperacillin-tazobactam. The very major and minor error rates were unacceptably high with disk testing of piperacillin-tazobactam; the use of enterococcal vancomycin disk breakpoints (zone diameter of > or =17 mm = susceptible) resulted in >20% minor errors but only one very major error. All of the isolates were susceptible to minocycline; over 90% were susceptible to sparfloxacin, levofloxacin, and clinafloxacin; and 88% were susceptible to rifampin. None was susceptible to vancomycin. When Chryseobacterium or Myroides species are isolated from serious infections, susceptibility testing by broth microdilution should be performed and therapy should be guided by those results.

scholarly journals In Vitro Activities of Free and Lipid Formulations of Amphotericin B and Nystatin against Clinical Isolates of Coccidioides immitis at Various Saprobic Stages

2002 ◽  
Vol 46 (5) ◽  
pp. 1583-1585 ◽  
Author(s):  
Gloria M. González ◽  
Rolando Tijerina ◽  
Deanna A. Sutton ◽  
John R. Graybill ◽  
Michael G. Rinaldi
Keyword(s):  
Amphotericin B ◽  
Clinical Laboratory ◽  
National Committee ◽  
Growth Stages ◽  
Coccidioides Immitis ◽  
In Vitro Susceptibility ◽  
Broth Macrodilution ◽  
Lipid Formulations ◽  
Different Growth Stages

ABSTRACT We investigated the susceptibilities of hyphal, mixed hyphal, ungerminated arthroconidial, and germinated arthroconidial populations of Coccidioides immitis to lipid formulations of amphotericin B and nystatin and their conventional preparations, utilizing the National Committee for Clinical Laboratory Standards M38-P broth macrodilution method. The differences in effects of the three different growth stages of the saprobic phase of C. immitis on the MIC/minimum lethal concentration (MLC) ratio were not statistically significant for any of the antifungal agents tested. These results suggest that either inocula could be used for in vitro susceptibility studies with C. immitis.

scholarly journals Interpretation of Trailing Endpoints in Antifungal Susceptibility Testing by the National Committee for Clinical Laboratory Standards Method

1998 ◽  
Vol 36 (1) ◽  
pp. 153-156 ◽  
Author(s):  
Sanjay G. Revankar ◽  
William R. Kirkpatrick ◽  
Robert K. McAtee ◽  
Annette W. Fothergill ◽  
Spencer W. Redding ◽  
...  
Keyword(s):  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Antifungal Susceptibility ◽  
Antifungal Susceptibility Testing ◽  
National Committee ◽  
Oropharyngeal Candidiasis ◽  
Length Polymorphisms ◽  
Immunodeficiency Virus ◽  
Agar Dilution ◽  
Different Strains

Trailing endpoints remain a problem in antifungal susceptibility testing using the National Committee for Clinical Laboratory Standards (NCCLS) method. For isolates for which trailing endpoints are found, MICs of ≤1 μg/ml at 24 h and of >64 μg/ml at 48 h are usually observed. In a study of human immunodeficiency virus (HIV)-infected patients with oropharyngeal candidiasis, we identified three patients with multiple serial isolates for which trailing endpoints were observed with fluconazole. At 24 h, MICs were generally ≤1 μg/ml by both broth macro- and microdilution methods. However, at 48 h, MICs were >64 μg/ml, while the organism remained susceptible by agar dilution testing with fluconazole. Most episodes of oropharyngeal candidiasis with trailing-endpoint isolates responded to doses of fluconazole as low as 100 mg/day. Two patients had both susceptible and trailing-endpoint isolates by NCCLS broth macro- and microdilution testing; these isolates were found to be the same strain by pulsed-field gel electrophoresis using restriction fragment length polymorphisms. Another patient had two different strains, one for which trailing endpoints were observed and one which was susceptible at 48 h. Trailing endpoints may be seen with selected isolates of a strain or may be a characteristic finding for most or all isolates of a strain. In addition, with isolates for which trailing endpoints are observed, reading the endpoint for the NCCLS method at 24 h may be more appropriate.

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.

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