Frequencies of Lipopolysaccharide Core Types among Clinical Isolates of Escherichia coli Defined with Monoclonal Antibodies

Abstract

Mouse monoclonal antibodies (MAbs) specific for the lipopolysaccharide (LPS) core types R1, R2, and R3 of Escherichia coliand a cross-reactive MAb that binds to the LPS core of almost all E. coli were used in ELISA to determine the frequency of cores resembling R1, R2, and R3 in strains of E. coli isolated from clinical samples (blood and urine specimens) and from the feces of asymptomatic individuals. Of the 180 wild-type isolates, 123 were assigned to R1 core type, 14 to R2, and 18 to R3. Twenty-five wild-type E. coliisolates could not be assigned to a particular core type and may have either an R4 or K12 core or a previously unrecognized core type. R1 core type was associated with 0 types 1,4,6,8, and 18 and with K1 or K5 capsules. R3 was associated with 015. 075 isolates could be of either R1 or R2 core type.The lipopolysaccharide (LPS) core region of Escherichia coli has a conserved overall structure, with an inner 2-keto-3-deoxy-octonate-heptose region and an outer hexose region. Most of the variation that does occur is in the outer part of the core, furthest from lipid A. In wild-type smooth E. coli. the core region can occur in at least four different forms, known as R 1, R2, R3, and R4 [1][2][3]. The naturally rough strain Kl2 has a different core region [4].The 0 antigen of smooth LPS may mask some of the epitopes and phage attachment sites in the core region. The chemical, serologic, and phage typing methods that have been used to define the different core types of E. coli are therefore not directly applicable to wild-type smooth strains. The frequency with which these different core types occur in wild-type E. coli is therefore not known.Little is known about the association between core types and 0 serotypes ofE. coli. except that the original R 1 and R2 rough mutants were both derived from 08 strains [I] and that the original R3 mutant was derived from an 0 III strain [2]. There is no published evidence on the relationship of LPS core types to capsular types or to virulence. Information about the distribution of 0 and K antigens has proved to be useful, for example in identifying and understanding enteropathogenic strains [5] and in suggesting novel therapeutic approaches to bacteremia [6]. Information about core types might be equally interesting.We therefore set out to produce a panel ofmouse monoclo- Materials and MethodsBacteria and bacteriophages. E. coli RI (F470), R2 (F576), R3 (F653), R4 (2513) and KI2 (2131) and rough-specific phages FO, BrIO, C21, 6SR, and T4 were obtained from G. Schmidt (Forschunginstitut, Borstel, Germany). E. coli 0 I, 02, 04, 06, 012, 015, 018, and 075 were obtained from A. S. Cross (Walter Reed Army Institute, Washington, DC). Phages specific for E. coli capsular types KI (<f>KIGS) and K5 (<f>K5DG) were obtained from A. P. Roberts (Charing Cross and Westminster Medical School, London). Blood culture and urine isolates were obtained from the Clinical Bacteriology Laboratory, Department of Medical Microbiology, Edinburgh University, from routine clinical specimens. ...

Mucosal and systemic antibody responses to the lipopolysaccharide of Escherichia coli O157 in health and disease*

“…The core oligosaccharide that links the lipid A to the O-polysaccharide can be of ®ve types, denoted R1±R4 and K12. In several surveys, R1 has been shown to be the most common core type in the LPS of E. coli strains, with the R3 type being uncommon [8,9]. Although not based upon an exhaustive study, our experience indicates that the R3 core is more common in the LPS of diarrhoeagenic strains of E. coli, including many enterotoxigenic and enteropathogenic E. coli (ETEC and EPEC) strains and some shigellae, than in normal faecal isolates of E. coli.…”

“…This core is common to many of the E. coli and Shigella spp. that cause GI pathology [8], including the great majority of EHEC strains [10,11]. An increased level of IgA antibodies to this core type has been demonstrated in the WGLF from healthy volunteers from Bangladesh who are likely to be exposed regularly to E. coli and Shigella spp.…”

“…Within core oligosaccharides there are epitopes shared between all other E. coli core types and the similar cores in the LPS of Salmonella and Shigella spp. [8], but we consider the terminal sugar residues in the unsubstituted form to be immunodominant. The response to the R3 core LPS generally paralleled the O157 response, but with no marked increase during convalescence.…”

“…Although not based upon an exhaustive study, our experience indicates that the R3 core is more common in the LPS of diarrhoeagenic strains of E. coli, including many enterotoxigenic and enteropathogenic E. coli (ETEC and EPEC) strains and some shigellae, than in normal faecal isolates of E. coli. In a study of normal faeces, only two of 21 faecal isolates examined had the R3 core [8]. However, a further study showed that the core type of all 28 EHEC strains of O157 and non-O157 serotypes were of the R3 chemotype [10].…”

The distribution of, and antibody response to, the core lipopolysaccharide region of Escherichia coli isolated from the faeces of healthy humans and cattle

“…These include O1, O2, O4, O6, O7, O8, O15, O18 and O75 which are most often associated with blood-borne and urinary tract infection. Other types are more often associated with diseases of the gastrointestinal tract and include O15, O26, O55, O86, O91, O111 and O157 (Ørskov & Ørskov, 1974;Gibb et al, 1992). The core types associated with the former group are R1 and R2, while those with the R3 core are usually associated with the GI pathogens (Gibb et al 1992;Currie & Poxton, 1999;Amor et al, 2000 and I. R. Poxton, unpublished data).…”