Effect of a Widespread Reduction in Treatment Duration for Group A Streptococcal Pharyngitis on Outcomes Including Household Transmission

Abstract

Background: Shorter-course treatment for group A streptococcal (GAS) pharyngitis may be equivalent to 10 days for clinical cure but effectiveness for pharyngeal GAS eradication is uncertain. The effect on household transmission has not been examined directly. In 2022, a laboratory antimicrobial stewardship initiative drove an abrupt reduction in treatment durations for GAS pharyngitis locally. This study aimed to assess whether this had any negative effect on key treatment outcomes: clinical failure, microbiological failure, immune sequelae, and household GAS transmission.

Methods: Positive throat swab cultures for GAS 2 years prechange until 25 months postchange were matched to antibiotic dispensing data. Logistic models were fitted to examine associations between treatment duration and 30-day repeat antibiotic treatment, repeat GAS-positive throat swab cultures, hospitalization, incident household cases, and 90-day incidence of rheumatic fever.

Results: A total of 851 patients prechange and 1746 postchange were included; 31.3% prechange received ≤7 days' treatment versus 59.0% postchange (P < .01). There were no significant differences across any outcome measure between periods. When the postchange period was examined specifically, no significant increases occurred for any outcome measure for patients receiving 0, 5, or 7 days of antibiotics versus 10 days, except higher 30-day antibiotic treatment in those initially receiving no antibiotics (15.6% vs 11.4%, P < .01).

Conclusions: Shorter-course treatment had no detectable negative effect on GAS pharyngitis outcomes in this population, including patients receiving no antibiotics. Short-course therapy for GAS pharyngitis has been associated with lower pharyngeal eradication; this did not translate to a detectable increase in household transmission in this real-world setting, which to our knowledge is a novel finding.

Keywords: antibiotics; diagnostic stewardship; duration(s); pharyngitis; streptococcus pyogenes.

Figure 1.

Formation of the analysis and comparator cohorts for ^aprechange period and ^bpostchange. ^aRepeat positive throat swab cultures from the same patient within 30 d were excluded from the analysis. ^bIn New Zealand, these are Māori or Pacific ethnicity and aged 3–35 y. ARF, acute rheumatic fever; GAS, group A Streptococcus; TSC, throat swab culture.

Figure 2.

Percentage of patients in the analysis cohort receiving a given antibiotic course duration following positive throat swab culture for group A Streptococcus in the pre- and postchange periods.