Association between Streptococcus milleri and abscess formation after appendicitis

Abscesses after appendicitis occur in some patients despite timely surgery and antibiotics. The Streptococcus milleri group of bacteria are commonly associated with gastrointestinal abscesses. This study investigated the relationship between S. milleri and abscess formation after appendicectomy a total of 301 patients (172 males, 129 females, median age 22 years) with appendicitis were identified retrospectively from the hospital PAS computer system who had an appendicectomy and peritoneal bacteriology swabs taken. All but one patient had prophylactic antibiotics. Patients were divided into three groups according to peritoneal bacteriology: group 1 (S. milleri +/- mixed faecal organisms, n = 61); group 2 (mixed faecal organisms, n = 126); and group 3 (sterile, n = 114). The chi squared and Student t-tests were used for statistical analysis. Thirteen (21%) of group 1 patients developed an intra-abdominal abscess compared with 4 (3%) in group 2 and 2 (1.7%) in group 3 (P < 0.0001). There was no difference in the prevalence of gangrenous or perforated appendicitis between groups 1 and 2 (56% versus 52%) but these worse forms of appendicitis were less common in group 3 (22%). Group 1 patients had a mean total hospital stay of 10 days versus 6 days for group 2 and 4 days for group 3 (P < 0.001). S. milleri was associated with a 7-fold increase in abscess formation after appendicectomy and a longer hospital stay. Antibiotic prophylaxis did not prevent this complication.