Treatment of Perirectal Streptococcal Infection
Oral penicillin or amoxicillin for 14-21 days is the first-line treatment for perirectal streptococcal dermatitis, with treatment duration dictated by both clinical and microbiological cure. 1, 2
Diagnosis Confirmation
Before initiating treatment, confirm the diagnosis through:
- Perianal swab for bacterial culture with specific request for β-hemolytic streptococci 1, 2
- Rapid streptococcal test as an alternative (positive predictive value 80%, negative predictive value 96%) 3
- Consider throat swab, as 63% of patients have asymptomatic group A streptococcal throat carriage 3
First-Line Antibiotic Therapy
For Group A β-Hemolytic Streptococci (Most Common in Children)
Preferred oral regimens:
- Penicillin V 500 mg four times daily (adults) 4, 5
- Amoxicillin 500 mg every 8 hours or 875 mg every 12 hours (adults) 4, 6
- Pediatric dosing: Amoxicillin 20-40 mg/kg/day divided every 8-12 hours 6, 1
Treatment duration: Minimum 14 days, preferably 21 days 2, 3
For Group B Streptococci (More Common in Adults)
In adults, group B β-hemolytic streptococci are the predominant causative organism 7. Use the same penicillin-based regimens as above, with antibiotic selection guided by sensitivity testing 7.
Alternative Regimens for Penicillin Allergy
For non-immediate hypersensitivity:
- Cephalexin 500 mg every 6 hours orally 4
For immediate-type hypersensitivity:
Adjunctive Measures
- Topical antiseptic or antibiotic ointments may augment systemic therapy 2, 8
- Treat any concomitant anorectal conditions (hemorrhoids, fissures) according to standard guidelines 7
Monitoring and Follow-Up
Post-treatment assessment is mandatory:
- Repeat perianal swab to confirm microbiological cure 2, 8
- Urinalysis to monitor for post-streptococcal glomerulonephritis 2
- Clinical examination to assess resolution of erythema and symptoms 2
In one study, 28 of 33 patients (85%) had negative post-treatment swabs, while 5 showed different streptococcal groups requiring further treatment 7.
Critical Pitfalls to Avoid
Do not stop antibiotics at 10 days despite clinical improvement—this leads to recurrence in approximately 20% of cases within 3.5 months 3. The minimum duration is 14 days, with 21 days preferred for complete eradication 2.
Do not miss the diagnosis in adults—perirectal streptococcal dermatitis occurs more frequently in adults than reported in the literature, with group B streptococci being the predominant pathogen 7. This organism can cause serious systemic infections, especially in elderly patients 7.
Do not overlook throat carriage—consider treating asymptomatic streptococcal throat carriage in patients with recurrent perirectal infection, as digital inoculation from nasopharynx to anus is the hypothesized transmission mechanism 3.
Do not confuse with perirectal abscess—the guidelines for complex perirectal abscesses requiring broad-spectrum coverage for polymicrobial infections (Gram-positive, Gram-negative, and anaerobes) do not apply to perirectal streptococcal dermatitis, which is a superficial infection with a characteristic sharply demarcated bright red rash 9, 1.
Recurrence Management
For the 20% of patients who experience recurrence 3: