Escherichia coli and Appendicitis: Phenotypic Characteristics of E. coli Isolates from Inflamed and Noninflamed Appendices

Two hundred four appendiceal isolates of Escherichia coli from 146 patients with either inflamed appendices (IA) (110 patients) or noninflamed appendices (NA) (36 patients) were characterized. Strains with P fimbriae were detected in 27 % of IA and 31 % of NA whereas type 1C—fimbriated strains were found only in IA (13%). Four serotypes, three with K5 antigens (018:K5, 025:K5:H1, and 075:K5:H-) and one with K1 antigen (075:K1:H7), were isolated only from IA (20 [18%] of 110); 025:K5:H1 was the most common serotype (isolated from 11 IA [10%]). Fecal isolates from the patients with IA resembled their corresponding appendiceal isolates rather than fecal isolates from patients with NA; this finding suggests that colonization of the gut by virulent E. coli-such as a hemolysin-producing, type 1C—fimbriated, P-fimbriated 025:K5:H1 serotype—may be a prerequisite for the development of appendicitis. During recent years, our understanding of the pathogenesis of infections caused by Escherichia coli has substantially in-creased [1]. Various virulence factors and serotypes of E. coli are clearly associated with certain infections, such as pyelone-phritis and neonatal meningitis [2-4]. In cases of acute appen