What are the possible causes of penicillin treatment failure in streptococcal pharyngitis (strep throat)?

Updated: Sep 07, 2018
  • Author: Zartash Zafar Khan, MD, FACP; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

Even in compliant patients, reports suggest that penicillin fails to eradicate S pyogenes in about 15% of treated patients. Many theories have been proposed to explain these apparent penicillin failures. The presence of beta-lactamase–producing normal flora (particularly organisms such as mouth anaerobes) is proposed as a potential mechanism by which penicillin may become inactivated. However, the clinical significance of this theory has never been conclusively demonstrated.

Many of the failures of penicillin therapy are more likely to occur in studies in which streptococcal pharyngitis has not been defined rigorously enough, and some of the studies' patients may, in fact, be streptococcal carriers who had viral pharyngitis at the onset of these trials.


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