TY - JOUR
T1 - Is Streptococcus pyogenes Resistant or Susceptible to Trimethoprim- Sulfamethoxazole?
AU - Bowen, Asha
AU - Lilliebridge, Rachael
AU - Tong, Steven
AU - Baird, Robert
AU - Ward, Peter
AU - McDonald, Malcolm
AU - Currie, Bart
AU - Carapetis, Jonathan
PY - 2012/12
Y1 - 2012/12
N2 - Streptococcus pyogenes is commonly believed to be resistant to trimethoprim-sulfamethoxazole (SXT), resulting in reservations about using SXT for skin and soft tissue infections (SSTI) where S. pyogenes is involved. S. pyogenes' in vitro susceptibility to SXT depends on the medium's thymidine content. Thymidine allows S. pyogenes to bypass the sulfur-mediated inhibition of folate metabolism and, historically, has resulted in apparently reduced susceptibility of S. pyogenes to sulfur antibacterials. The low thymidine concentration in Mueller-Hinton agar (MHA) is now regulated. We explored S. pyogenes susceptibility to SXT on various media. Using two sets of 100 clinical S. pyogenes isolates, we tested for susceptibility using SXT Etests on MHA containing defibrinated horse blood and 20 mg/liter ?-NAD (MHF), MHA with sheep blood (MHS), MHA alone, MHA with horse blood (MHBA), and MHA with lysed horse blood (MHLHBA). European Committee on Antibacterial Susceptibility Testing (EUCAST) breakpoints defined susceptibility (MIC, ?1 mg/liter) and resistance (MIC, >2 mg/liter). In study 1, 99% of S. pyogenes isolates were susceptible to SXT on MHA, MHBA, and MHLHBA, with geometric mean MICs of 0.04, 0.04, and 0.05 mg/liter, respectively. In study 2, all 100 S. pyogenes isolates were susceptible to SXT on MHF, MHS, MHA, and MHLHBA with geometric mean MICs of 0.07, 0.16, 0.07, and 0.09 mg/liter, respectively. This study confirms the in vitro susceptibility of S. pyogenes to SXT, providing support for the use of SXT for SSTIs. A clinical trial using SXT for impetigo is ongoing.
AB - Streptococcus pyogenes is commonly believed to be resistant to trimethoprim-sulfamethoxazole (SXT), resulting in reservations about using SXT for skin and soft tissue infections (SSTI) where S. pyogenes is involved. S. pyogenes' in vitro susceptibility to SXT depends on the medium's thymidine content. Thymidine allows S. pyogenes to bypass the sulfur-mediated inhibition of folate metabolism and, historically, has resulted in apparently reduced susceptibility of S. pyogenes to sulfur antibacterials. The low thymidine concentration in Mueller-Hinton agar (MHA) is now regulated. We explored S. pyogenes susceptibility to SXT on various media. Using two sets of 100 clinical S. pyogenes isolates, we tested for susceptibility using SXT Etests on MHA containing defibrinated horse blood and 20 mg/liter ?-NAD (MHF), MHA with sheep blood (MHS), MHA alone, MHA with horse blood (MHBA), and MHA with lysed horse blood (MHLHBA). European Committee on Antibacterial Susceptibility Testing (EUCAST) breakpoints defined susceptibility (MIC, ?1 mg/liter) and resistance (MIC, >2 mg/liter). In study 1, 99% of S. pyogenes isolates were susceptible to SXT on MHA, MHBA, and MHLHBA, with geometric mean MICs of 0.04, 0.04, and 0.05 mg/liter, respectively. In study 2, all 100 S. pyogenes isolates were susceptible to SXT on MHF, MHS, MHA, and MHLHBA with geometric mean MICs of 0.07, 0.16, 0.07, and 0.09 mg/liter, respectively. This study confirms the in vitro susceptibility of S. pyogenes to SXT, providing support for the use of SXT for SSTIs. A clinical trial using SXT for impetigo is ongoing.
KW - benzathine penicillin
KW - cotrimoxazole
KW - adolescent
KW - agar medium
KW - antibiotic resistance
KW - antibiotic sensitivity
KW - article
KW - bacterium isolate
KW - child
KW - clinical article
KW - controlled study
KW - culture medium
KW - epsilometer test
KW - human
KW - human tissue
KW - impetigo
KW - in vitro study
KW - infant
KW - minimum inhibitory concentration
KW - Mueller Hinton agar medium
KW - nonhuman
KW - preschool child
KW - priority journal
KW - randomized controlled trial
KW - school child
KW - Streptococcus pyogenes
KW - Adolescent
KW - Animals
KW - Anti-Bacterial Agents
KW - Child
KW - Child, Preschool
KW - Culture Media
KW - Humans
KW - Infant
KW - Microbial Sensitivity Tests
KW - Streptococcal Infections
KW - Trimethoprim-Sulfamethoxazole Combination
KW - Equidae
KW - Ovis aries
UR - http://www.scopus.com/inward/record.url?scp=84869236202&partnerID=8YFLogxK
U2 - 10.1128/JCM.02195-12
DO - 10.1128/JCM.02195-12
M3 - Article
C2 - PubMed:23052313
VL - 50
SP - 4067
EP - 4072
JO - Journal of Clinical Microbiology
JF - Journal of Clinical Microbiology
SN - 0095-1137
IS - 12
ER -