Prophylaxis regimens for iGAS infection

Antibiotic prophylaxis may be required for close contacts of patients with probable or confirmed invasive group A streptococcal (iGAS) infection – see Indications for iGAS antibiotic prophylaxis.

Close contacts are at the highest risk of infection within 48 hours of iGAS diagnosis in the index case. However, secondary cases can occur up to 10 days after index case diagnosis. If prophylactic antibiotics are given to close contacts, this should be done as soon as possible (ideally within 24 hours but not more than 10 days after iGAS diagnosis in the index case)UK Health Security Agency, 2023 Centre for Disease Control, 2022.

The optimal antibiotic prophylaxis regimen for iGAS infection has not been determined – suitable regimens includeCentre for Disease Control, 2022 UK Health Security Agency, 2023:

1benzathine benzylpenicillin intramuscularly, as a single dose¹ ² benzathine benzylpenicillin benzathine benzylpenicillin benzathine benzylpenicillin

adult: 1.2 million units (2.3 mL)

child less than 10 kg: 0.45 million units (0.9 mL)

child 10 kg to less than 20 kg: 0.6 million units (1.2 mL)

child 20 kg or more: 1.2 million units (2.3 mL)

1cefalexin 1 g (neonate and child: 25 mg/kg up to 1 g) orally, 12-hourly for 10 days. For dosage adjustment in adults with kidney impairment, see cefalexin dosage adjustment. cefalexin cefalexin cefalexin

Benzathine benzylpenicillin is long acting; do not confuse benzathine benzylpenicillin with benzylpenicillin, which is short acting.

For patients who prefer oral therapy and in whom the risk of poor adherence to cefalexin is likely to outweigh the risk of macrolide resistance, azithromycin may be a suitable alternative. UseCentre for Disease Control, 2022:

azithromycin 500 mg (child: 12 mg/kg up to 500 mg) orally, daily for 5 days. azithromycin azithromycin azithromycin

For close contacts who have had a nonsevere (immediate or delayed) hypersensitivity reaction to a penicillin³, cefalexin or azithromycin (at the dosages above) can be used.

For close contacts who have had a severe (immediate or delayed)⁴ hypersensitivity reaction to a penicillin, use azithromycin at the dosage above.

¹ The ventrogluteal site is preferred for administration of intramuscular benzathine benzylpenicillin because of reduced pain and risk of nerve injury. For instructions on intramuscular injection at the ventrogluteal site, see Instructions for intramuscular injection at the ventrogluteal site.Return

² It is unclear if eradication of pharyngeal group A streptococcus carriage is required to prevent secondary casesDeMuri 2014. Limited evidence suggest the addition of rifampicin to benzathine benzylpenicillin increases the rate of pharyngeal carriage eradication. However, the role of rifampicin in the prevention of secondary invasive group A streptococcal infection is uncertain and routine combination prophylaxis is not recommendedChaudhary 1985 Tanz 1985.Return

³ Cefalexin may be used in patients who have had a nonsevere (immediate or delayed) reaction to amoxicillin or ampicillin. However, because cross-reactivity between these drugs is possible, consideration should be given to the extent of the reaction, patient acceptability, and the suitability of non–beta-lactam options.Return

⁴ Severe immediate hypersensitivity reactions include anaphylaxis, compromised airway, airway angioedema, hypotension and collapse. Severe delayed hypersensitivity reactions include cutaneous adverse drug reactions (eg drug rash with eosinophilia and systemic symptoms [DRESS], Stevens–Johnson syndrome/toxic epidermal necrolysis [SJS/TEN], severe blistering or desquamative rash), and significant internal organ involvement (eg acute interstitial nephritis).Return