Group Milleri Streptococci in perianal infections

Background Anal abscesses are commonly associated with fistulas-in-ano and are usually polymicrobial in nature, with gram-negative rods and anaerobes being the most prevalent isolates. Group Milleri Streptococci (GMS) comprise a heterogeneous group of cocci, which are capable of causing severe purulent infection with a high recurrence rate. Method All anorectal infections caused by GMS, which were identified at our centre during a 4-year period were retrospectively analysed. The 18 patients with GMS-positive anorectal abscesses were matched with 36 GMS-negative anorectal abscesses to identify outcome characteristics of this clinical entity. Results During the study period, 358 patients underwent surgical treatment for anal infections; GMS were isolated in 46 individuals (13%) including 18 perianal abscesses, 11 pilonidal sinuses, eight fistulae in and nine miscellaneous infections. Seventy-two per cent of perianal GMS infections were polymicrobial with E. coli and Bacteroides fragilis being the predominant second bacteria. Nine patients (20%) developed recurrent abscesses and fistulae-in-ano and underwent additional surgical interventions with resolution at follow-up. Additional antibiotic treatment was administered in 10 patients with complex anal infections. Matched pair analysis revealed that GMS-positive perianal abscesses were more commonly polymicrobial, and that the recurrence rate was higher (55.6% GMS-positive and 22.2% GMS-negative patients, P = 0.017). Conclusions Our data confirm the propensity of GMS to form deep and recurrent abscesses with a higher recurrence rate than non-GMS infections. First-line treatment includes surgical drainage, and antibiotic treatment may be useful in selected patients.