Clindamycin, Erythromycin Resistance Seen in GBS

OB/GYN News, Oct 15, 1999 by Mitchel L. Zoler

Given to women allergic to penicillin G.

TORONTO - Clindamycin and erythromycin are poor second-line drugs for peripartum prophylaxis against transmission of group B streptococcus.

In a series of 333 isolates of group B streptococcus taken from 287 pregnant women in San Antonio, 3.1% were resistant to clindamycin, and 11.1 % were resistant to erythromycin and azithromycin, Dr. Jeanna M. Piper reported in a poster presentation at the annual meeting of the Infectious Diseases Society for Obstetrics and Gynecology.

Clindamycin and erythromycin have been recommended as second-line drugs for prophylaxis for women who are allergic to the frontline agent, penicillin G. None of the group B streptococci tested in this study showed resistance to penicillin G or to ampicillin or cephalothin.

The isolates were collected from March 1998 through July 1999. The resistance seen in this study was similar to what was described earlier this year in an independent report from researchers in Florida.

"We certainly should not use erythromycin" or azithromycin, said Dr. Piper, an ob.gyn. at the University of Texas in San Antonio.

Although the study showed less resistance to clindamycin, "3% is significant, and so clindamycin may not be the best drug to use," she told this newspaper.

The prime alternative agent is vancomycin; the group B streptococcal isolates tested in this study showed no resistance to vancomycin. But "vancomycin is not an ideal alternative; we would like to save it as a big gun" and use it only when absolutely necessary Dr. Piper said at the meeting, also sponsored by the American College of Obstetricians and Gynecologists.

The ideal approach, she said, is to perform susceptibility testing on all group B streptococcal isolates from pregnant women before starting treatment. If an isolate is clindamycin resistant, consider using vancomycin.

Another strategy is to test the woman to verify that she is truly allergic to penicillin and unable to receive penicillin G, according to Dr. Piper.