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Diagn Microbiol Infect Dis. 2006 Jul;55(3):213-8. Epub 2006 Mar 20.

Investigation of inducible clindamycin and telithromycin resistance in isolates of beta-hemolytic streptococci.

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Division of Healthcare Quality Promotion, Centers of Disease Control and Prevention, Atlanta, GA 30333, USA.


We evaluated the accuracy of an erythromycin-clindamycin double-disk test (D-zone test) and an erythromycin-telithromycin D-zone test for detection of inducible resistance in isolates of beta-hemolytic streptococci with erythromycin resistance. The results of these tests were compared to results of a broth microdilution (BMD) induction test using combinations of erythromycin and either clindamycin or telithromycin. Of 29 erythromycin-resistant, clindamycin-susceptible isolates, 16 were positive by the erythromycin-clindamycin D-zone test; all of these demonstrated inducible clindamycin resistance by BMD. Twelve isolates were D-zone test-negative, did not demonstrate inducible resistance by BMD, and were positive for a mef determinant. Of 39 erythromycin-resistant, telithromycin-susceptible isolates, 13 were erythromycin-telithromycin D-zone test-positive, 19 questionably positive (unclear blunting of the zone), and 7 were D-zone test-negative. The erythromycin-telithromycin D-zone test result did not correlate with inducible resistance by BMD or the presence of an erm or mef gene. These results demonstrate that the erythromycin-clindamycin D-zone and BMD induction tests accurately detect inducible clindamycin resistance, but the erythromycin-telithromycin D-zone test is not reliable for detecting inducible telithromycin resistance.

[Indexed for MEDLINE]

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