Escherichia coli K5 antigen in relation to various infections and in healthy individuals

Abstract

A phage specific for Escherichia coli K5 antigen was used to determine the frequency of K5 in strains of E. coli isolated from cases of sepsis, meningitis, and urinary tract infection (pyelonephritis, cystitis, and asymptomatic bacteriuria), as well as from fecal samples of healthy subjects. Although entirely absent from meningitic strains, K5 was found to be one of the most common E. coli capsular antigens, especially in strains causing sepsis. K5 was less common in the fecal strains of healthy subjects than in strains causing various urinary tract infections, between which there was no significant difference in its frequency. Thus, even if K5 is a less important antigen than Ki in the etiology of acute pyelonephritis or acute meningitis, as the fifth most commonly occurring K antigen in E. coli strains causing urinary tract infection it should be included as a component in any K antigen-based vaccine against acute pyelonephritis. In meningococci, Haemophilus influenza, pneumococci, and Escherichia coli the capsular antigens are important factors affecting bacterial virulence, and their significance in E. coli has been studied in conjunction with urinary tract infections (6, 8, 11-13). A limited number of the K antigens

Virulence of Escherichia coli in relation to host factors in women with symptomatic urinary tract infection

“…In childhood UTI, 39% of pyelonephritogenic E. coli strains were found to contain Ki (13), compared with 37% of the strains in this study. The frequency of K5 (15%) is the highest reported so far (14). The capsular antigens have been proposed to increase virulence by several mechanisms.…”

Escherichia coli K5 capsule expression enhances colonization of the large intestine in the gnotobiotic rat

“…K5 was identified by using a K5-specific bacteriophage (15), which only infects K5 ϩ isolates of E. coli. The analyses were performed as previously described (19). Each of the colonies selected was spread onto an agar plate containing 1% nutrient agar and 1% glucose.…”

“…Capsules increase bacterial virulence by inhibiting the opsonizing activities of complement, thereby decreasing the elimination by phagocytes, or escape the immune response by mimicking host molecules (3,6,9). The Escherichia coli K1 and K5 capsules are frequently found among isolates causing extraintestinal infections, K1 being more commonly associated with neonatal septicemia and K5 being more frequently associated with sepsis and urinary tract infection (9,19,34,35). E. coli strains causing extraintestinal disease derive from the normal intestinal microbiota (29,35).…”

Masquerading microbial pathogens: capsular polysaccharides mimic host-tissue molecules

“…As traditional CPS typing relied on antigenicity, the capsule of E. coli K5 was originally classified as K-nontypeable (Jann & Jann, 1987). In part due to the difficulty of identifying the K5 antigen and the frequency or extent in different infections, more effective methods of typing were developed, including one by Gupta et al that utilized a specific phage to type K5 in various infections (Kaijser & Jodal, 1984).…”