Investigation of inducible clindamycin and telithromycin resistance in isolates of beta-hemolytic streptococci.
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.
Division of Healthcare Quality Promotion, Centers of Disease Control and Prevention, Atlanta, GA 30333, USA.
Patti M
PM
Raney
Fred C
FC
Tenover
Roberta B
RB
Carey
John E
JE
McGowan
Jean B
JB
Patel
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002981:Clindamycin / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D006460:Hemolysin Proteins; D006801:Humans; D048628:Ketolides / Q000494:pharmacology; D018942:Macrolides / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics*; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests / Q000379:methods; D013291:Streptococcus / Q000187:drug effects / Q000235:genetics*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D006460:Hemolysin Proteins; D048628:Ketolides; D018942:Macrolides; C117866:MefA protein, Streptococcus; D008565:Membrane Proteins; C071495:streptococcal group B hemolysin; D002981:Clindamycin; D008780:Methyltransferases; C431709:ErmA protein, Bacteria; C106791:telithromycin