There is controversy about the convenience of performing a bacteriological peritoneal culture in pediatric appendicitis. We performed a sero-epidemiological survey of the bacteria found in peritoneal swabs from pediatric appendicitis operated in our hospital.Ambispective study. Retrospective revision of the bacteriological results from peritoneal swabs performed in pediatric appendicitis from january 2009 to december 2010 (2 years) and prospective study of peritoneal swabs collected between january 2011 and december 2011 (one year).We found 728 pediatric patients (mean age 7.1, range: 2-11 years). Among these, 108 were5 years. Cultures were performed in 328 (45.1%). A positive result was found in 155 swabs, (47.3%). Positive cultures were more frequent in patients5 years (69.2% vs 40.4%, p0.001). The most frequent pathogens were E. coli: 122 specimens, Streptococcus spp (50 swabs), P. aeruginosa: (45) and B.fragilis: (35) Younger age was strongly associated with P. aeruginosa: (30.8% vs 8.4%, p0.001. OR: 4.8. IC 95%: 2.3-9.8). So was the detection of E. coli (50% vs 33.2% p = 0.01). 21.3% (26 swabs) of E. coli were resistant to amoxicillin-clavulanic acid. There were 15 (12.3%) multiresistant (ESBL) E. coli. Among the Streptococcus, 32% (16 out of 50) were resistant to clindamicin, and so were 28.6% of the B. fragilis (10 out of 35).. The most frequent pathogens were E. coli, Streptococcus spp and P. aeruginosa. P. aeruginosa is five times more frequent in patients5 years. Resistance of E. coli to amoxiclavulanate was high: 21.3% of the specimens. We found that 12.3% of the E. coli produced ESBL.