Time to negative throat culture following initiation of antibiotics for pharyngeal group A Streptococcus: a systematic review and meta-analysis up to October 2021 to inform public health control measures

Abstract

BackgroundPublic health guidance recommending isolation of individuals with group A streptococcal (GAS) infection or carriage for 12-24 h from antibiotic initiation to prevent onward transmission requires a strong evidence base.AimTo estimate the pooled proportion of individuals who remain GAS culture-positive at set intervals after initiation of antibiotics through a systematic literature review (PROSPERO CRD42021290364) and meta-analysis.MethodsWe searched Ovid MEDLINE (1946-), EMBASE (1974-) and Cochrane library. We included interventional or observational studies with ≥ 10 participants reporting rates of GAS throat culture positivity during antibiotic treatment for culture-confirmed GAS pharyngitis, scarlet fever and asymptomatic pharyngeal GAS carriage. We did not apply age, language or geographical restrictions.ResultsOf 5,058 unique records, 43 were included (37 randomised controlled studies, three non-randomised controlled trials and three before-and-after studies). The proportion of individuals remaining culture-positive on day 1, day 2 and days 3-9 were 6.9% (95% CI: 2.7-16.8%), 5.4% (95% CI: 2.1-13.3%) and 2.6% (95% CI: 1.6-4.2%). For penicillins and cephalosporins, day 1 positivity was 6.5% (95% CI: 2.5-16.1%) and 1.6% (95% CI: 0.04-42.9%), respectively. Overall, for 9.1% (95% CI: 7.3-11.3), throat swabs collected after completion of therapy were GAS culture-positive. Only six studies had low risk of bias.ConclusionsOur review provides evidence that antibiotics for pharyngeal GAS achieve a high rate of culture conversion within 24 h but highlights the need for further research given methodological limitations of published studies and imprecision of pooled estimates. Further evidence is needed for non-beta-lactam antibiotics and asymptomatic individuals.

Keywords: Disease Transmission; Group A Strep Infection; Infectious; Infectious Disease Outbreaks; Streptococcal; Streptococcus pyogenes.

Figure 1

PRISMA flow diagram for strategy of identification, screening and inclusion of studies reporting group A Streptococcus culture positivity following initiation of antibiotics for pharyngeal group A Streptococcus, up to October 2021

Figure 2

Proportion of patients with culture-confirmed group A streptococcal throat infection or carriage at day 1, day 2 and days 3–9 after treatment initiation with all antibiotic types, up to October 2021 (n = 42 studies)

Figure 3

Proportion of patients with culture-confirmed group A streptococcal (GAS) throat infection or carriage at day 1, day 2 and days 3–9 after treatment initiation with penicillin, up to October 2021 (n = 34 studies)

Figure 4

Proportion of patients with culture-confirmed group A streptococcal (GAS) throat infection or carriage at day 1, day 2 and days 3–9 after treatment initiation with cephalosporin, up to October 2021 (n = 14 studies)

Figure 5

Proportion of patients with culture-confirmed group A streptococcal (GAS) throat carriage^a after completion of antibiotic therapy by antibiotic class, where typing was reported, up to October 2021 (n = 13 studies)