|
|
|
|
|
|
Antimicrobial Agents and Chemotherapy, November 2004, p . 4441-4443, Vol . 48, No . 11 Altered Susceptibility of Candida glabrata Bloodstream Isolates to Triazoles at Clinically Relevant pH Values: Comparison of the NCCLS M27-A2, Sensititre YeastOne, and Etest Methods
College of Pharmacy, University of New Mexico, Albuquerque, New Mexico Received 20 April 2004/ Returned for modification 8 June 2004/ Accepted 20 July 2004
(This work was previously presented in part [Abstr . 43rd Intersci . Conf . Antimicrob . Agents Chemother., abstr . 121, 2003].) Fifteen unique clinical C . glabrata bloodstream isolates obtained from TriCore Reference Laboratories (Albuquerque, N.Mex.) and two quality control isolates, ATCC 6258 (C . krusei) and ATCC 22019 (C . parapsilosis), were tested . Fluconazole and itraconazole powder were obtained through Sigma Chemicals (St . Louis, Mo.) . Pfizer, Inc . (New York, N.Y.) donated the voriconazole powder used in this study . Drug stock solutions (100x) were prepared as outlined by the NCCLS M27-A2 document and stored frozen at –80°C until plate preparation . Etest strips of fluconazole, itraconazole, and voriconazole were purchased through AB Biodisk North America (Piscataway, N.J.) . Alamar Blue 100x was purchased through Trek Diagnostics Inc . (Cleveland, Ohio) to perform susceptibility testing by the SYO method . Isolates were tested against all antifungal agents with 0.075 M 3-(N-morpholino)propanesulfonic acid (MOPS)-buffered RPMI 1640 medium supplemented with dextrose to 20 g/liter and adjusted to pHs 7.0, 6.0, and 7.4 . Microplates containing appropriate drug dilutions were sealed, stored frozen at –80°C, and thawed prior to each experiment . MICs were interpreted in duplicate at 24 and 48 h after incubation at 35°C both visually and by the use of a spectrophotometer reading at 490 nm as previously described (7) . Triazole MIC determinations were also performed in duplicate by the SYO method that included incorporation of Alamar Blue 100x to a final concentration of 1% (vol/vol) per well . MICs were interpreted as the lowest antifungal concentration that corresponded to the first purple or blue well after 24 h of incubation at 35°C (1) . The Etest procedure included preparation of agar plates with MOPS-buffered RPMI 1640 medium-2% dextrose adjusted to the specified pH, Bacto Agar (1.5 g/dl), and previously described experimental procedures (2) . Etest triazole results include a wide array of elliptical profiles and trailing growth that required interpretation based on Etest photographically illustrated technical guideline 4 (AB Biodisk NA, Piscataway, N.J.) . Tables 1, 2, and 3 include the specific MICs generated by the NCCLS M27-A2 (48 h), SYO (24 h), and Etest (48 h) methods at the three pH values used against fluconazole, itraconazole, and voriconazole, respectively . In general, the MICs of 2 of the 15 C . glabrata isolates and both ATCC strains were unaffected by the alterations in pH . These two clinical isolates included a highly susceptible strain (Z-zAN) and a highly resistant strain (Z-zAS) that demonstrated essentially identical MIC profiles at the three pH values and by all of the susceptibility test methods used . The two quality control American Type Culture Collection strains were not affected by pH . The MICs were more easily interpretable at pH 6.0 compared to either pH 7.0 or 7.4 . The 48-h MICs generated by the NCCLS M27-A2 method with a spectrophotometric endpoint was identical to the visual endpoint for >90% of the isolates tested at all three pH values . Figure 1 illustrates the optical density profile of a C . glabrata isolate tested by the NCCLS M27-A2 method . The graph demonstrates the higher MIC but sharper and correspondingly easier to visually interpret endpoint seen at pH 6.0 . Assessment of MICs by the Etest method demonstrated reduction in triazole MICs with incremental pH increases (Fig . 2) .
As demonstrated in the present study, the NCCLS M27-A2 method with media buffered to pH 7.0 did not consistently predict the activity of triazoles against C . glabrata at urine and blood pH values . The susceptibility profiles of fluconazole, itraconazole, and voriconazole were markedly improved at pH 7.4 compared to those at pH 7.0 when C . glabrata was tested . The two commercially available susceptibility-testing methods produced similar results . Further investigations assessing the clinical utility of antifungal susceptibility testing should take these findings into consideration .
What Is Protein?,
What Is Prokaryote?,
What Is Cell Biology?,
What Is Water Purification?,
What Is Pcr?,
r,
Microorganisms,
i,
Bacterium,
i,
Microorganism,
i,
Bacteria,
r,
Microbes,
e,
S. cerevisiae,
i,
Listeriosis,
i,
Biodegradation,
o,
Denitrificans,
s,
Bactericidal,
c,
Vibriosis,
o,
Bacteriological,
s,
Escherichia coli,
r,
Pseudomonas aeruginosa,
i,
S. cerevisiae,
i,
Microflora,
a,
Antimicrobials,
i,
Vibriosis,
n,
Bacillus,
s,
Bacteriological,
n,
Microorganisms,
i,
Pasteurella,
a,
Yeasts,
s,
Bacillus,
n,
Pasteurella,
c,
Staphylococcus
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
8 µg/ml) was different: 6.6% at pH 6.0, 40% at pH 7.0, and 66% at pH 7.4