Question
Can Bactrim Treat Streptococcus pyogenes?
Answer
Infectious Diseases Society of America guidelines suggest that β-hemolytic Streptococci (e.g., Streptococcus pyogenes) and Staphylococcus aureus are the culprits most often implicated in run-of-the-mill skin and soft tissue infections (SSTI’s). While the presence of purulence suggests Staphylococcus aureus alone, empiric antimicrobial therapy targeting both β-hemolytic Streptococci and Staphylococcus aureus may be utilized for various SSTIs. In the not-so-distant past, a beta-lactam would provide sufficient coverage for both of these gram-positive bacteria, but increasing rates of methicillin resistance in Staphylococcus aureus in the community have largely retired this strategy. This is because we lack a readily available orally administered beta-lactam with activity against methicillin-resistant Staphylococcus aureus (MRSA). In place of a beta-lactam alone, adding coverage for MRSA is now of interest.
Clindamycin has been utilized to provide coverage for both MRSA and MSSA, however rates of resistance in MRSA to clindamycin have increased to a concerning extent. Tetracyclines (e.g., doxycycline) and trimethoprim/sulfamethoxazole (SMX/TMP, Bactrim®, Septra®) can both provide more reliable MRSA coverage than clindamycin, but both have been described as possessing unreliable activity against β-hemolytic Streptococci. For SMX/TMP, prior to 2006 the data describing activity against Streptococci were discordant, likely caused by the high thymidine content within the susceptibility testing media microbiology labs were using at the time. Thymidine is known to inhibit the activity of SMX/TMP, so it could mute the anti-bacterial effects of SMX/TMP. Following strict regulations from CLSI (a major microbiology lab regulator) in 2006, thymidine content was standardized to low levels in the agar used to perform susceptibility testing. In turn, the issue of SMX/TMP effects being impaired by high thymidine levels may no longer be a problem, and SMX/TMP monotherapy may be an option.
A recent study investigated the in vitro activity of SMX/TMP against Streptococci, finding all tested β-hemolytic Streptococcus isolates to be susceptible. In combination with studies such as this randomized, non-inferiority trial, the authors concluded that SMX/TMP is a viable option for treating β-hemolytic Streptococcus spp
Key Takeaway
As called out by McCreary and colleagues, “Bactrim can’t treat GAS” is a myth. In a skin and soft tissue infection where β-hemolytic Streptococcus is expected, it is likely SMX/TMP is active against this organism. It is anticipated the next iteration of the IDSA SSTI guidelines is likely to incorporate SMX/TMP as an option for non-purulent cellulitis. However, respected journals like AJHP are still publishing articles like this one in July 2024 which do not list SMX/TMP as an option for cases of non-purulent skin and soft tissue infections. Time will tell how the leading experts interpret the data into guideline recommendations for widespread use.
ANSWERED BY
Hunter O. Rondeau, Pharm.D., BCIDP & Timothy Gauthier, Pharm.D., BCPS, BCIDP – July 2024
Q&A DISCLAIMER
The ID PharmD Q&A pages attempt to answer common pharmacy questions by providing the perspective and opinion of a trained expert with knowledge relevant to the question. That noted, these answers are not provided as all-inclusive comprehensive responses. This is not provided for direct patient care purposes.
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