New fimbrial antigenic type (E8775) that may represent a colonization factor in enterotoxigenic Escherichia coli in humans.

An enterotoxigenic strain of Escherichia coli O25:H42 (strain E8775), isolated from a patient in Bangladesh with diarrhea, caused mannose-resistant hemagglutination (MRHA) of human and bovine erythrocytes. The strain did not show slide agglutination or immunodiffusion precipitin lines with antiserum specific for the colonization factor antigen CFA/I or CFA/II. A variant E. coli strain, E8775-B, did not cause MRHA or produce enterotoxin. Electron microscopy revealed the presence of fimbriae on the surface of strain E8775 but not strain E8775-B. When strain E8775 was grown at 22 degrees C, it became MRHA negative and fimbriae were absent. An antiserum prepared against strain E8775 was absorbed with strain E8775-B to make an antiserum specific for the fimbrial antigen. Using this absorbed antiserum, we found the fimbrial antigen in 48 of 742 enterotoxigenic E. coli strains. The 48 strains belonged to serogroups O25, O115, and O167. It is suggested by analogy to the properties of previously described colonization factors that these fimbriae may play a part in the colonization of the intestinal epithelium.     

Hemagglutination by Escherichia coli in septicemia and urinary tract infections.

The agglutination of erythrocytes from various animal species by Escherichia coli was studied. The 405 strains of E. coli were isolated from urine in patients with urinary tract infections, from blood in septicemic patients, or from feces in persons without intestinal or urinary disorders. In urinary tract infections, d-mannose-resistant agglutination (MRHA) of human erythrocytes was the most common finding (23% of the strains). The highest frequency of mannose-sensitive hemagglutination (MSHA) attributed to type I (common type) pili occurred with guinea pig erythrocytes (11.5%). Of the 78 E. coli strains isolated from blood cultures, 11 (14%) produced MRHA of human erythrocytes and only one gave MSHA. In the stool cultures, only 1 of 170 E. coli strains was MSHA reacting, whereas 28 strains (16.5%) showed MRHA of human erythrocytes. No MRHA strain reacted with antiserum against colonization factor antigen (CFA)/I of pilus nature in enterotoxigenic human E. coli strains (O78:H12). MRHA of bovine erythrocytes, reputedly typical of enterotoxigenic E. coli of serogroups O6 and O8, was shown by only two strains, neither of which agglutinated with CFA/II antiserum. The most common hemagglutinating pattern of E. coli from urine and blood thus was MRHA for human erythrocytes. This agglutination may have been caused by pili or other surface properties of one or more serotypes. These may represent a new class of colonization-promoting antigens (adhesins).     

Hemagglutinating ability and fimbrial antigens of Escherichia coli strains isolated from urine

The close connection between mannose-resistant hemagglutination (MRHA) and adhesion to uroepithelial cells of urinary E. coli with regard to the pathogenesis of urinary tract infection (UTI) prompted us to examine the hemagglutinating ability of 1499 E. coli strains from urine using human blood group OP1 erythrocytes. In 317 strains (21.2%), an MRHA was found. There were no significant differences in the prevalence of MRHA related to the isolation time and admitting hospital. A correlation was found between MRHA and the presence of P fimbriae in the strains investigated. Another association appears to exist between certain O:K:H serovars and distinct fimbrial antigens which had been serologically identified. The F11 antigen was detected most frequently and proved to be present in strains of serovars O1:K1:H-, O1::K1:H7, O2:K1:H-, O2:K1:H4, O2:K1:H7, and O15:K1:H7. The F8 antigen was strongly associated with serovar O18:K5:H-. O18:K5:H1 and O6:K5:H1 were apparently related to cross-reacting F14 antigens.     

Virulence properties of enterotoxigenic Escherichia coli O8: KX105 strains isolated from diarrheic piglets

Twenty-two enterotoxigenic Escherichia coli (ETEC) O8:KX105 strains isolated from 1- to 7-week-old diarrheic piglets were examined for virulence properties. Thirteen strains caused acute watery diarrhea in orally infected, colostrum-deprived newborn piglets, whereas the remaining nine did not. The enteropathogenic strains colonized the small intestine, albeit with lower intensity than classical porcine ETEC. They produced the heat-stable STb and heat-labile LT enterotoxins, whereas the nonenteropathogenic strains produced the STb enterotoxin alone. None of the E. coli O8:KX105 strains exhibited mannose-resistant hemagglutination with erythrocytes from 12 species. Ten of the enteropathogenic and two of the nonenteropathogenic strains were positive for mannose-sensitive hemagglutination. These strains produced rodlike fimbriae 3 to 5 nm in diameter, whereas no fimbriae were detected on the other strains. None of the 22 strains produced the fimbrial antigens F4, F5, F41, F2, F3, FY(Att 25), and F165. Of the 13 enteropathogenic strains, 10 expressed the F6 antigen in the intestines of infected piglets but not in cultures. The other three enteropathogenic strains apparently lacked all of the known fimbrial antigens from porcine ETEC.     

Hemagglutinating and hemolytic activities of Enterococcus faecalis strains isolated from different human clinical sources

A total of 95 Enterococcus faecalis strains isolated from different human clinical sources were investigated for hemagglutinating activities and hemolysin (Hly) production in the presence of erythrocytes from a wide range of species. MRHA (mannose-resistant hemagglutination) activity was found in all clinical strains tested in this study. MRHA of E. faecalis strains isolated from different sources was most frequently observed with human (both group O and A) and guinea pig erythrocytes. None of the strains agglutinated horse erythrocytes in the presence of 1% alpha-D-mannose. It should be emphasized that our data indicate the absence of a relationship between sources and MRHA. In contrast, all 95 strains investigated in this report were negative for MSHA (mannose-sensitive hemagglutination) activity. Regarding hemolysin production, it was seen that E. faecalis, and particularly urinary strains, preferably lysed horse erythrocytes. On the other hand, none of the 95 clinical strains tested in this study showed hemolytic activity against bovine and sheep erythrocytes. In general, these results show that E. faecalis strains isolated from different clinical sources possessed a diversity of hemagglutinins and a limited repertoire of hemolysin activities.     

Molecular structure of the Dr adhesin: nucleotide sequence and mapping of receptor-binding domain by use of fusion constructs.

The Dr hemagglutinin of uropathogenic Escherichia coli mediates adherence to the upper urinary tract. E. coli strains which express this adhesin bind to the Dr blood group antigen and mediate mannose-resistant hemagglutination (MRHA). Chloramphenicol inhibits MRHA produced by the Dr hemagglutinin and may act as an analog for the tissue receptor at the adhesin-binding site. The nucleotide sequence of the Dr hemagglutinin fimbrial subunit was determined and found to have significant homology with that of F1845, a fimbrial adhesin associated with diarrhea, and with the afimbrial adhesin AFA-I of uropathogenic E. coli. Chimeric adhesin determinants consisting of the Dr structural subunit and F1845 accessory genes or of the F1845 structural subunit and Dr accessory genes were constructed. The Dr and F1845 determinants were shown to have a close structural relationship, with functional differences concentrated in the fimbrial subunit. Oligonucleotide-directed site-specific mutagenesis was used to facilitate construction of a hybrid adhesin subunit gene containing the amino terminus of F1845 fused to the carboxy terminus of the Dr structural gene. The resulting construct confers chloramphenicol-resistant hemagglutination when introduced into an E. coli strain expressing the cloned Dr hemagglutinin. The chloramphenicol sensitivity or resistant phenotype of MRHA produced by this family of adhesins is determined solely by the fimbrial subunit gene. Domains responsible for the chloramphenicol sensitivity of Dr-mediated MRHA reside within the amino-terminal portion of the fimbrial subunit.     

Identification of plasmid-encoded mannose-resistant hemagglutinin and HEp-2 and HeLa cell adherence factors of two diarrheagenic Escherichia coli strains belonging to an enteropathogenic serogroup.

Two Escherichia coli strains (B/M 369 and C-35) belonging to enteropathogenic serogroup O86 were isolated from patients with infantile diarrhea and studied with respect to their cellular adherence properties. Both strains exhibited adherence (Ad+) to HEp-2 and HeLa cell monolayers in vitro and expressed mannose-resistant hemagglutinating (MRHA+) activity towards human, chicken, and sheep (but not mouse, rabbit, or guinea pig) erythrocytes. Cellular adherence properties of both strains could be substantially reduced by pronase treatment and by heat treatment (100 degrees C for 5 min) of bacteria. Electron microscopic examination failed to reveal fimbria- or pilus-like structures on the bacterial cell surface. Conjugation experiments conducted with these strains suggested that both MRHA and HEp-2 and HeLa cell adherence factors were encoded by the same plasmid, with a size of 55 to 57 megadaltons (MDa). Further biochemical studies indicated that the cellular adherence factors were associated with cell surface structures of bacteria that were proteinaceous in nature. An antiserum, rendered specific for the 57-MDa plasmid (pRP201) products of B/M 369 by adsorption, reacted with both MRHA+ Ad+ strains, B/M 369 and C-35, but not with their 57- or 55-MDa plasmidless MRHA- Ad- transconjugants or with other MRHA- Ad- E. coli strains. Immunological studies showed that the absorbed antiserum recognized two proteins with subunit molecular sizes of 18 and 14.5 kDa that were present on the cell surfaces of both strains. Furthermore, the absorbed antiserum at subagglutinating dilutions did inhibit, although only partially, the MRHA and HEp-2 and HeLa cell adherence activities of both E. coli strains. All these results would indicate that some of the E. coli strains belonging to enteropathogenic serogroups express their adherence potential through factors that were hitherto unrecognized.     

Hemagglutination patterns of enterotoxigenic and enteropathogenic Escherichia coli determined with human, bovine, chicken, and guinea pig erythrocytes in the presence and absence of mannose.

A hemagglutination (HA)-typing system has been developed for the presumptive identification of enterotoxigenic Escherichia coli (ETEC) possessing the colonization factor antigens (CFA) CFA/I or CFA/II. E. coli isolates are grown on CFA agar and tested for mannose-sensitive (MS) or mannose-resistant (MR) HA of human, bovine, chicken, and guinea pig erythrocytes. CFA/I-positive ETEC exhibit MRHA with human, bovine, and chicken erythrocytes, but no HA with guinea pig erythrocytes. CFA/II-positive ETEC produce HA (MRHA) only with bovine and chicken erythrocytes. Common pili appear to be the primary MS-hemagglutinin of E. coli because the prototype strain K-12 exhibits HA (MSHA) with all but bovine erythrocytes. However, only 6.6% (23 of 351) of E. coli belonging to the classical enteropathogenic E. coli serogroups (EPEC) possessed the same HA pattern as strain K-12; 42% of the EPEC cultures (146 of 351) were similar to K-12 in producing MSHA with chicken and guinea pig erythrocytes and no HA with bovine erythrocytes, but different in that these produced either no HA or MRHA with human erythrocytes. These EPEC-associated HA patterns were assigned to a separate category, termed HA type III. Non-EPEC serogroups associated with sporadic diarrhea (i.e., the facultatively enteropathogenic E. coli, or FEEC) and 41% (19 of 46) of available Salmonella isolates also produced HA type III patterns. This observation is of considerable interest because many FEEC possess somatic antigens cross-reactive with Salmonella. Although the biochemical basis for this result has not been established, the data reported herein suggest a relationship between the HA type III phenotype and virulence (enteropathogenicity) in both the EPEC and FEEC serogroups. We propose that HA typing be used in conjunction with serotyping of E. coli to determine the degree of association of HA type III E. coli with sporadic diarrhea in infants and young children.     

The role of fimbriae of uropathogenic Escherichia coli as carriers of the adhesin involved in mannose-resistant hemagglutination

The gene clusters encoding various P-fimbriae (F7(1), F7(2), F9 and F11) were compared. Deletion plasmids that lack the gene encoding the fimbrillin were derived from these gene clusters. Introduction of these deletion plasmids into an E. coli K12 strain resulted in non-fimbriated cells that still showed mannose-resistant hemagglutination (MRHA). However when introduced into wild type E. coli strains no MRHA was observed. Derivatives of the wild type E. coli strains with reduced amounts of O-antigen on the other hand showed MRHA when harbouring these plasmids. These results indicate that adhesion and presence of fimbriae are not necessarily linked. P-fimbriae could function as a carrier for the adhesin and thus endow adhesive capacity to cells with a complete O-antigen.     

Cloning of genes determining the production of mannose-resistant fimbriae in a uropathogenic strain of Escherichia coli belonging to serogroup O6.

Chromosomal DNA from a uropathogenic strain of Escherichia coli was partially digested with the restriction enzyme EcoRI. The partial digests were ligated into a cosmid containing an ampicillin-resistant determinant and packaged into lambda phage particles. An ampicillin-resistant transductant of E. coli HB101 was found to possess mannose-resistant hemagglutinating activity associated with a 50-kilobase-pair plasmid. Subcloning of the mannose-resistant fimbrial genes revealed that the genetic determinants were encoded by a 6.9-kilobase-pair DNA fragment of a recombinant plasmid. Chimeric plasmids smaller in size were unable to transform E. coli to fimbrial production. Physical maps of the recombinant plasmids were prepared showing restriction endonuclease sites within the inserted DNA fragments. The hemagglutinating activities of the wild-type strain and of the recombinant derivative were compared. Both strains agglutinated human erythrocytes in the presence of D-mannose to the same degree and also failed to produce fimbriae after incubation at 18 degrees C. Also, both strains were agglutinated by antifimbrial serum at a high titer, whereas no such activity was observed when a strain of E. coli which did not possess a plasmid was used.     

Characterization of a polysaccharide capsular antigen of septicemic Escherichia coli O115:K "V165" :F165 and evaluation of its role in pathogenicity.

Escherichia coli strains of serogroup O115:K(-):F165 have been associated with septicemia in calves and piglets. These strains express a capsular antigen referred to as K"V165" which inhibits agglutination of the O antigen by anti-O115 serum. We used hybrid transposon TnphoA mutants M48, 18b, and 2, and a spontaneous O-agglutinable mutant, 5131a, to evaluate the role of K"V165" in the pathogenicity of E. coli O115. Mutant M48 was as resistant to 90% rabbit serum and as virulent in day-old chickens as the parent strain 5131, mutants 18b and 5131a were less resistant to serum and less virulent in chickens, and mutant 2 was serum sensitive and avirulent. Analysis of outer membrane protein and lipopolysaccharide profiles failed to show any difference between the transposon mutants and the parent strain. In contrast, the spontaneous O-agglutinable mutant showed additional bands in the 16-kDa region of the polysaccharide ladder-like pattern. Mutants 2 and 5131a produced significantly less K"V165" capsular antigen than the parent strain, as demonstrated by a competitive enzyme-linked immunosorbent assay with adsorbed anti-K"V165" serum. In addition, electron microscopic analysis revealed that mutants 2 and 5131a had lost the capsular layer observed in the parent strain after fixation with glutaraldehyde-lysine. This capsule contained carbohydrate compounds and resembled an O-antigen capsule since it prevented O-antigen agglutination before the bacteria were heated at 100 degrees C and induced bacterial serum resistance. The capsule-defective mutants colonized the intestinal epithelium of experimentally infected gnotobiotic pigs but failed to induce clinical signs of septicemia. We concluded that E. coli strains of serogroup O115 expressed a polysaccharide capsular antigen which induced serum resistance and consequently contributed to the pathogenicity of the bacteria.     

O:K:H:F serotypes of fimbriated Escherichia coli strains isolated from infants with diarrhea.

Bacterial agglutination and crossed immunoelectrophoresis were compared as techniques for the subdivision of mannose-resistant hemagglutinating Escherichia coli fimbrial antigens. A total of 22 fimbrial strains, 15 of which had earlier been grouped into two fimbrial agglutination groups, were examined for the presence of fimbrial antigens F7 go F12 by crossed immunoelectrophoresis. Most of the strains were isolated from infants with diarrhea; they were neither enteropathogenic nor enterotoxigenic serotypes. Of the 10 strains in agglutination group 1, 4 had fimbrial antigens F7 and 1C, 4 had antigens F8 and 1C, and in 1 strain, only antigen 1C was demonstrated. The tenth strain did not, by the crossed immunoelectrophoresis test, fit into agglutination group 1. Agglutination group 2 comprised five strains. Four of these had antigens in common with the still unnumbered fimbrial antigens of an O4:K12:H5 strain. In the fifth strain, no known F antigens were demonstrated. The previously found correlation between some O:K:H serotypes and fimbrial antigens in strains from urinary tract infections was confirmed in this study in strains from diarrhea cases. We concluded that, although the agglutination test can indicate the presence of certain fimbriae, it cannot be used presently for an exact demonstration of these antigens because each strain often produces several different fimbriae.     

Cloning and expression of an afimbrial adhesin (AFA-I) responsible for P blood group-independent, mannose-resistant hemagglutination from a pyelonephritic Escherichia coli strain

The uropathogenic Escherichia coli KS52 strain expresses a mannose-resistant hemagglutinin involving an erythrocyte recognition site distinct from the alpha-digalactoside glycosphingolipid receptor identified for the uropathogenic E. coli strains specifying a P adhesin. The KS52 strain showed three major properties. (i) It agglutinated human erythrocytes of all tested blood groups. (ii) Hemagglutinin activity was found both in the supernatant fluid L-broth cultures and in cells grown on L-agar plates. (iii) No fimbriae in organisms grown on L-agar plates were detected by electron microscopy. Whole-cell DNA from the KS52 strain was size fractionated and cloned into the pHC79 cosmid vector. Three recombinant cosmids expressing a mannose-resistant hemagglutination (MRHA) phenotype were characterized and used to subclone the smallest DNA fragment able to confer the same MRHA properties as the parent strain. A 6.7-kilobase chromosomal DNA fragment cloned in pBR322 (pIL14) was shown to be necessary for host-cell MRHA expression and uroepithelial cell adherence. The insert encoded the production of a 16,000-dalton hemagglutinin. This polypeptide could be detected in culture supernatant fluids, in E. coli minicells harboring the pIL14 plasmid, and, by immunoblotting, in the KS52 strain and E. coli whole cells harboring the pIL14 plasmid. No homology was detected by Southern hybridization between the cloned insert and the DNA of the operon responsible for MRHA in the P-specifying, fimbriate strains (pap operon).     

Adhesive fimbriae associated with porcine enterotoxigenic Escherichia coli of the O141 serotype.

Enterotoxigenic Escherichia coli of the O141 serotype, isolated from piglets with postweaning coliform enteritis but producing none of the characterized adhesive fimbriae, was examined for fimbrial production by transmission electron microscopy. Two strains that produced numerous fimbriae were chosen for further characterization. The fimbriae were isolated and purified and had a subunit molecular weight of 17,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Using antiserum raised against this protein, we have shown it to be specific for the 17,000-molecular-weight band by immunoblotting and to be directed against the fimbriae by immunoelectron microscopy. These fimbriae were not produced when the bacteria were grown at 18 degrees C and did not show any mannose-resistant hemagglutination of the erythrocytes tested. We propose that these are a new type of adhesive fimbriae associated with porcine enterotoxigenic E. coli of the O141 serotype.     

F7 and type 1-like fimbriae from three Escherichia coli strains isolated from urinary tract infections: protein chemical and immunological aspects.

Fimbriae from three Escherichia coli strains, C1212, C1214, and C1023, isolated from urinary tract infections, have been purified and characterized by determination of the N-terminal sequences, amino acid composition, and molecular weights of their respective subunits. Furthermore, their immunological interrelationships have been investigated. The three strains all harbored more than one fimbrial species each. Immunologically different type 1-like fimbriae, termed 1A, 1B, and 1C, with highly homologous N-terminal sequences were isolated, of which strain C1212 possessed 1A and 1C, strain C1214 possessed 1A and 1B, and strain C1023 possessed 1A and 1C. Type 1A is known to cause a mannose-sensitive hemagglutination similar to that described for type 1 fimbriae, whereas the functions of types 1B and 1C are not yet known. Strain C1212, in addition, harbored the F7 fimbrial antigen which causes mannose-resistant hemagglutination and adherence to urinary epithelial cells. The N-terminal structure of this antigen seems to indicate a possible evolutionary kinship to the type 1-like fimbriae, although they are immunologically unrelated. Our results indicate that fimbriation of pathogenic wild-type strains can be of an intricate variety.     

Pilus Production, Hemagglutination, and Adhesion by Porcine Strains of Enterotoxigenic Escherichia coli Lacking K88, K99, and 987P Antigens

Three strains of enterotoxigenic Escherichia coli which adhered, colonized intensively, and caused disease in pig intestine, but which did not produce pili of the K88, K99, or 987P antigen types were designated 3P(-) ETEC. The 3P(-) ETEC caused mannose-resistant hemagglutination, adhered to porcine intestinal epithelial cells in vitro, and produced pili. However, most bacteria taken directly from the intestine of pigs infected with 3P(-) ETEC appeared to be nonpiliated. Two preparations were isolated from the 3P(-) ETEC. One (material A) contained pili, caused mannose-sensitive hemagglutination, and did not inhibit adhesion of whole bacteria to epithelial cells in vitro. The other (material B) had no demonstrable pili, caused mannose-resistant hemagglutination, and blocked ahesion of bacteria to epithelial cells in vitro. Antiserum against an acapsular mutant (K(-)) of one 3P(-) ETEC strain was absorbed to remove antibodies directed against somatic (O) antigen. The absorbed antiserum agglutinated all three 3P(-) ETEC strains grown in the K(-) form at 37 degrees C, but not when they were grown at 18 degrees C. The absorbed antiserum blocked the hemagglutinating activity of material B, but not of material A. It also reacted (via indirect immunofluorescence) with all of the 3P(-) ETEC when they were grown in pig intestine. The results were interpreted to indicate that: (i) the epithelial adhesive and mannose-resistant hemagglutinating activities of the 3P(-) ETEC strains may be mediated by an antigen contained in material B; (ii) this antigen either is not pilus associated or is associated with pili that are not demonstrable by the methods used here; (iii) the 3P(-) ETEC strains produce type 1 pili which do not mediate their adhesion to intestinal epithelium of pigs.     

Effects of global regulatory proteins and environmental conditions on fimbrial gene expression of F165(1) and F165(2) produced by Escherichia coli causing septicaemia in pigs

Escherichia coli O115:F165 strains are associated with septicaemia in young pigs and possess at least two types of fimbriae. F165(1) fimbriae belong to the P fimbrial family and F165(2) fimbriae belong to the S fimbrial family. Regulatory regions of foo (F165(1)) and fot (F165(2)) fimbrial gene clusters from wild-type strain 4787 were sequenced and characterised. Expression of F165(1) and F165(2) fimbrial genes was analysed by using lacZ and/or luxAB as reporter genes under the control of the native fimbrial promoters. Differential expression of fimbrial genes was observed. Global regulatory mechanisms such as catabolite repression, leucine-responsive regulatory protein (Lrp), methylation and DNA supercoiling were demonstrated to influence foo and fot expression. foo and fot expression was optimal at 37 degrees C and under aerobic conditions. Expression of foo was higher on minimal medium, whereas fot expression was higher on complex Luria-Bertani medium. This could reflect an in vivo differential expression.     

Haemagglutination and siderophore production as the urovirulence markers of uropathogenic Escherichia coli

A total of 160 strains of Escherichia coli isolated from urine of patients with clinically diagnosed urinary tract infection were included in the study and 50 faecal isolates of E. coli were studied. They were studied for virulence factors, namely mannose-resistant and mannose-sensitive haemagglutination (MRHA, MSHA) and siderophore production. Among 160 urinary isolates of E. coli , 40 (25%) showed MRHA, siderophore production was seen in 156 (97.5%). In 50 faecal isolates, two (4%) were MRHA, four (8%) MSHA and siderophore production in two (4%). The results suggest that MRHA and siderophore production positive strains can be considered as UPEC.     

Comparison of methods for detection of colonization factor antigens on enterotoxigenic Escherichia coli.

Fecal Escherichia coli isolates from 196 patients with watery diarrhea and 68 healthy individuals (controls) were analyzed in Bangladesh immediately after isolation for the presence of colonization factor antigen (CFA) I or II (CFA/I or CFA/II, respectively) by a mannose-resistant hemagglutination (MRHA) test with six species of erythrocytes and by a slide agglutination test with absorbed CFA/I or CFA/II antisera. The presence of CFAs was confirmed by immunodiffusion analyses done in Sweden. By these methods, it was found that 49 of 69 enterotoxin-producing E. coli strains isolated from patients carried CFA/I or CFA/II, whereas none of the nonenterotoxigenic E. coli isolates or the three toxin-positive strains isolated from healthy individuals carried these adhesins. All E. coli strains retained their MRHA ability after transportation to Sweden followed by one subculture and after storage at -70 degrees C (but not at room temperature) for 1 to 2 years without further subculturing. After 5 to 10 subcultures of the fresh isolates, however, 70% of the initially CFA/I- and 80% of the initially CFA/II-carrying strains analyzed did not hemagglutinate. The efficacy of different methods for detecting CFAs on the fresh isolates was compared with that of immunodiffusion. The sensitivity of MRHA with human blood group A erythrocytes for the detection of CFA/I was high (97%), but the specificity was only 69%. The sensitivity of MRHA with bovine erythrocytes for the detection of CFA/II in Bangladesh was very low but increased considerably when chicken erythrocytes were also used. Whereas both false-positive and false-negative reactions were obtained when absorbed CFA antisera were used for agglutination, antisera against purified CFAs were equally effective as immunodiffusion in identifying CFA/I and CFA/II-carrying strains.     

Mannose-Sensitive and Mannose-Resistant Adherence to Human Uroepithelial Cells and Urinary Virulence of Escherichia coli

The adherence to human uroepithelial cells of 23 Escherichia coli strains belonging to three groups with different levels of virulence was investigated, and the mechanism of adherence was studied. It was found that strains belonging to the most virulent group adhered better to human uroepithelial cells than did avirulent strains. Adherence of loss virulent but supposedly nephropathogenic strains was more variable. These results suggest that adherence is an important virulence factor, especially in the group of strains with the highest but a more general virulence. Piliated strains adhered better than did nonpiliated strains. We found strong evidence for the existence of at least two different mechanisms of adherence: (i) mannose-sensitive adherence by piliated strains, very likely mediated by type I pili because this mannose-sensitive adherence was associated with mannose-sensitive hemagglutination of guinea pig erythrocytes by broth cultures of the strains; (ii) mannose-resistant adherence by piliated strains, very likely mediated by non-type I pili because this mannose-resistant adherence was invariably associated with mannose-resistant hemagglutination of human group A erythrocytes by the strains, whether grown in broth or on plates. Additionally, one strain without pili and without hemagglutinating activity adhered well. Thus in most cases adherence seemed to be mediated by bacterial pili, although different types might be involved.