Determination of Trimethoprim-Sulfamethoxazole Resistance in Streptococcus pneumoniae by Using the E Test with Mueller-Hinton Agar Supplemented with Sheep or Horse Blood May Be Unreliable |
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| Authors: | M. Lovgren, L. Dell&#x Acqua, R. Palacio, G. Ech niz-Aviles, A. Soto-Noguer n, E. Casta eda, C. I. Agudelo, I. Heitmann, M. C. Brandileone, R. C. Zanella, A. Rossi, J. Pace, J. A. Talbot, The Pneumococcal Study Group&#x |
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| Affiliation: | M. Lovgren, L. Dell’Acqua, R. Palacio, G. Echániz-Aviles, A. Soto-Noguerón, E. Castañeda, C. I. Agudelo, I. Heitmann, M. C. Brandileone, R. C. Zanella, A. Rossi, J. Pace, J. A. Talbot, and The Pneumococcal Study Group† |
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| Abstract: | An international, multicenter study compared trimethoprim-sulfamethoxazole MICs for 743 Streptococcus pneumoniae isolates (107 to 244 isolates per country) by E test, using Mueller-Hinton agar supplemented with 5% defibrinated horse blood or 5% defibrinated sheep blood, with MICs determined by the National Committee for Clinical Laboratory Standards broth microdilution reference method. Agreement within 1 log2 dilution and minor error rates were 69.3 and 15.5%, respectively, on sheep blood-supplemented agar and 76.9 and 13.6%, respectively, with horse blood as the supplement. Significant interlaboratory variability was observed. E test may not be a reliable method for determining the resistance of pneumococci to trimethoprim-sulfamethoxazole. |
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