Escherichia coli bacteraemia in patients with and without haematological malignancies: a study of strain characters and recurrent episodes.

We compared serotypes, virulence factors and susceptibility to antibiotics of Escherichia coli strains isolated from 282 patients with bacteraemia. Thirty-five of these were neutropenic patients with haematological malignancy and 247 were patients with a normal or raised total white blood cell count and no haematological malignancy. Strains isolated from recurrent bacteraemia were also bio- and ribotyped. Overall, no significant difference was found between O serogroups, K antigens, serum sensitivity, production of haemolysin, expression of P-fimbriae and patterns of antibiotic susceptibility in the two groups of strains. The haematological patients more often than the non-haematological patients had an unknown focus of infection, recurrent bacteraemia, shorter intervals between recurrences and recurrences caused by identical strains. Despite a well-defined focus, six of eight non-haematological patients had recurrences with a strain different from the strain isolated in a previous episode. A possible connection between shorter intervals and recurrence with identical strains is discussed. We suggest that strains from recurrent E. coli bacteraemia are sent to a reference laboratory for serotyping and possibly ribotyping.

A comparative study of nosocomial and community-acquired strains of Escherichia coli causing bacteraemia in a Danish University Hospital.

In a previous study we found a considerably higher mortality rate in patients with nosocomial (NO) compared with community-acquired (CA) Escherichia coli bacteraemia. To establish whether this was due to host differences or to differences in the infecting bacteria, we compared 205 NO with 172 CA bacteraemic isolates of E. coli with respect to serotype, virulence factors and antimicrobial susceptibility. Overall the six most frequent O antigens were O18ac, O6, O1, O2, O15 and O75, respectively. The six most frequent capsular antigens were K1, K5, K52, K2, K7 and K34, respectively. No major differences were found regarding O-antigens, capsular antigens, production of haemolysin, P-fimbriation, serum sensitivity or antimicrobial susceptibility. Surprisingly we found 17 strains of serotype O15:K52:[H1] of both NO (eight) and CA (nine) origin with similar phenotypic characteristics to a strain causing a CA outbreak in London 1986-1987. Possibly the Danish and the English strains belong to the same clone. Our findings argue against the existence of a distinct NO flora. NO E. coli bacteraemia strains seem to originate primarily from the patients' own flora.

Bacteraemia due to Escherichia coli in a Danish university hospital, 1986-1990.

433 episodes of E. coli bactereaemia over a 5-year period in a Danish university hospital were studied with special emphasis on possible differences between nosocomial (NO) and community-acquired (CA) cases. Data from 186 males and 247 females with ages ranging from 9 days to 94 years were recorded. The average incidence of E. coli bacteraemia was 24.4 episodes/10,000 admissions/year. Older females accounted for the largest number of cases, which reflected the composition of the background population. The highest risk of infection was in males 80-89 years of age. The highest frequency of NO infections was in the departments of Intensive Care (90%) Orthopaedic Surgery (87%) and Haematology (80%). The most common focus was the urinary tract, with 72% of the episodes with a known focus, while the biliary tract was the focus in 14%. NO bacteraemia was independently related to immunosuppressive therapy, presence of predisposing factors, polymicrobial bacteraemia and presence of a non-urinary tract focus. A urinary tract focus was associated with CA bacteraemia, monomicrobial infection, female sex and a normal or elevated total white blood cell count. Patients with NO bacteraemia had predisposing factors more often than had CA patients, especially haematological malignancies and immunosuppressive therapy. Lack of a known bacterial focus was more common in NO than CA episodes, particularly among patients with haematologic malignancies. The overall mortality was 21%. Increased mortality was independently related to leukopenia (45%), immunosuppressive therapy and NO bacteraemia.

Clonal relationships among Escherichia coli serogroup O78 isolates from human and animal infections.

We investigated the clonal relationships among 63 Escherichia coli strains of antigen serogroup O78 isolated from infections in humans, cattle, sheep, pigs, and chickens. Both septicemic and enterotoxigenic isolates were included in the study. A main group of 55 E. coli strains consisting of 52 septicemic isolates and 3 human enterotoxigenic E. coli isolates were clustered in related clones. The remaining eight strains, four human and four animal isolates, were clonally heterogeneous. The main group of 55 clonally related strains included isolates from human and animal infections. This result indicates that animals are a possible source of serogroup O78 septicemic E. coli infections in humans.

Cluster of multiresistant Escherichia coli O78:H10 in Greater Copenhagen.

A multiresistant, lactose-negative Escherichia coli O78:H10 was isolated from 19 patients in Greater Copenhagen over a period of 8 months. At least 14 cases were community-acquired. 18 isolates originated from urine cultures and 1 from a faecal sample. 13 patients were predisposed to urinary tract infection (UTI) and 11 patients showed clinical signs of UTI. This is the first report of E. coli O78:H10 causing human disease. The cluster was probably food-borne, but the source was not identified. This cluster of identical disease associated E. coli was only uncovered because of its multiresistance and lactose-negative phenotype.

O, K, and H antigens predict virulence factors, carboxylesterase B pattern, antimicrobial resistance, and host compromise among Escherichia coli strains causing urosepsis.

The O:K:H serotypes of 75 Escherichia coli blood isolates from patients with urosepsis were compared for the presence and expression of determinants for P fimbriae, hemolysin, and aerobactin; antimicrobial resistance; the carboxylesterase B phenotype; and associated compromising host conditions. O groups, K types, and O:K:H serotypes previously associated with urovirulence accounted for 69%, 60%, and 31% of the population, respectively. Chromosomal determinants for P fimbriae, hemolysin, and aerobactin were present in combination more commonly among strains belonging to urovirulence-associated O groups, K types, and O:K:H serotypes. Similarly, antimicrobial resistance was strikingly less prevalent, the B2 carboxylesterase phenotype more common, and associated host compromise less common among such strains. These data demonstrate that the O groups, K types, and O:K:H serotypes traditionally associated with urovirulence are prominent among E. coli strains causing urosepsis, in which they are associated with presence and expression of multiple chromosomal virulence factor determinants, susceptibility to antimicrobial agents, the B2 carboxylesterase phenotype, and noncompromised hosts.

Clonal relationships among Escherichia coli strains that cause hemorrhagic colitis and infantile diarrhea.

The genetic relationships among 1,300 isolates of Escherichia coli representing 16 serotypes associated with enteric disease, including O157:H7 strains recovered from patients with hemorrhagic colitis and hemolytic uremic syndrome and O26:H11, O55:H6, O55:H7, O111:H2, and O128:H2 strains, many of which were isolated originally from infants with diarrhea, were estimated from allelic variation among 20 enzyme-encoding genes detected by multilocus enzyme electrophoresis. Multiple electrophoretic types were observed among isolates of each serotype, with isolates of the same O serogroup differing on average at 28% of the enzyme loci. Comparisons of the multilocus enzyme profiles revealed that 72% of the isolates belong to 15 major electrophoretic types, each of which corresponds to a bacterial clone with a wide geographic distribution. Genetically, the O157:H7 clone is most closely related to a clone of O55:H7 strains that has long been associated with worldwide outbreaks of infantile diarrhea. We propose that the new pathogen emerged when an O55:H7-like progenitor, already possessing a mechanism for adherence to intestinal cells, acquired secondary virulence factors (Shiga-like cytotoxins and plasmid-encoded adhesins) via horizontal transfer and recombination.

Clonal differentiation of uropathogenic Escherichia coli isolates of serotype O6:K5 by fimbrial antigen typing and DNA long-range mapping techniques.

Escherichia coli isolates of serotype O6:K5 are the most common causative agents of cystitis and pyelonephritis in adults. To answer the question, as to whether strains of this particular serotype represent one special clonal group, out of a collection of 34 serotype O6:K5 isolates [Zingler et al. (1990) Zentralbl. Bakteriol Mikrobiol Hyg [A] 274:372-381] 15 strains were selected and analyzed in detail. The flagellar (H) antigen and the outer membrane protein (OMP) pattern were determined. Further serum resistance properties and the genetic presence and expression of other virulence factors, including hemolysin, aerobactin, P fimbriae, S/F1C fimbriae and type 1 fimbriae was evaluated. In addition the XbaI-macrorestriction pattern of ten representative isolates was elaborated and the fimbrial (F) antigen type of the P fimbriae was determined, to obtain the complete O:K:H:F pattern. These analyses could clearly show that the O6:K5 isolates do not represent one clonal group. The XbaI-macrorestriction profiles were heterogeneous and marked differences in the hybridization patterns, using virulence-associated gene probes in Southern hybridization of long-range-separated genomic DNA, were observed among the strains. However, some of strains showed similarities in the genomic profiles, arguing for clonal groupings among the O6:K5 isolates. Interestingly the strains grouped together exhibited the same fimbrial F type that many indicate a coincidence of this phenotypic trait with clonality.

Occurrence and phenotypic properties of verotoxin producing Escherichia coli in sporadic cases of gastroenteritis.

Five verotoxin producing Escherichia coli strains were detected in 405 patients with infectious gastroenteritis and 3 such strains were detected in 11 patients with the hemolytic uremic syndrome in Switzerland. Production of verotoxin 2 was associated with the latter three strains. Four strains reacted with the probe for the virulence plasmid of Escherichia coli O157:H7, and six reacted with a recently described probe for the eae gene of enteropathogenic Escherichia coli. None of the strains was of serotype O157:H7. The methods available at present for detecting toxins or toxin genes will reliably detect all such verotoxin producing strains.

Escherichia coli serotyping and disease in man and animals.

Serotyping of Escherichia coli is useful, but complex, with 173 O antigens, 80 K antigens, and 56 H antigens, which can all be subdivided into partial antigens. The O, K, and H antigens can be found in nature in many of the possible combinations. The final number of E. coli serotypes is very high, 50,000-100,000 or more. The number of frequent pathogenic serotypes is, however, limited. Two main groups of such frequent serotypes are (i) serotypes from diarrhoeal disease and (ii) serotypes from extraintestinal disease. Serotypes from diarrhoeal diseases are mostly species specific, and could at present be used as epidemiological markers for bacterial clones equipped with special virulence markers, such as toxins and adhesins. Their O-antigen lipopolysaccharides may be regarded as virulence factors. These strains are not inhabitants of the normal intestine. Serotypes from extraintestinal diseases constitute a different set of clones, which are good colonizers of the intestinal tract, that under certain conditions succeed in invading host tissues. They are characterized by virulence factors different from those found in strains from diarrhoeal disease. Thus, the two groups of pathogenic E. coli are both composed of a limited number of clones for which the O:K:H serotypes are excellent, although not faultless, markers.

The importance of P and type 1 fimbriae for the persistence of Escherichia coli in the human gut.

The faecal Escherichia coli flora was studied in 89 infants. Each infant was followed with a mean of 12 faecal samples (range 5-21) between 0 and 18 months of age. All isolates were assayed for P fimbriae and biochemically phenotyped and the persistence of each strain (phenotype) in the infant's gut was determined. In a subset of strains the occurrence of type 1 fimbriae and adherence to HeLa cells was studied. Thirty-one per cent of isolates belonging to strains colonizing for longer than 6 months expressed P fimbriae compared to 19% of the isolates from strains colonizing 1-6 months or transient strains colonizing less than 1 month. Type 1 fimbriae and adherence to HeLa cells occurred similarly often in all groups of strains. We conclude that P fimbriae, but not type 1 fimbriae or HeLa cell adherence seemed to contribute to the ability of the E. coli strain to colonize the human intestine.

Fimbriation, capsulation, and iron-scavenging systems of Klebsiella strains associated with human urinary tract infection.

Thirty-two strains of Klebsiella pneumoniae and seven strains of Klebsiella oxytoca isolated from urinary tract infections in elderly adults were analyzed for capsular antigens, iron-scavenging systems, and fimbriation. All strains were capsulated. Twenty-seven different K antigens were identified among the strains, with no particular antigen dominating. All strains produced the iron-scavenging system enterochelin as analyzed by bioassay and DNA hybridization. In contrast, the aerobactin iron-sequestering system was not detected in any of the strains. All strains caused hemagglutination of tannin-treated human erythrocytes and reacted with an anti-type 3 fimbriae antiserum as well as in DNA hybridization with a type 3 fimbria-specific probe, indicating that the Klebsiella strains possessed this fimbrial type. Possession of type 1 fimbriae was analyzed by agglutination tests and by hybridization with DNA probes from two distinct Klebsiella type 1 fimbria gene clusters. Phenotypic expression of the type 1 fimbriae was found in 29 of 32 K. pneumoniae strains, whereas 30 strains reacted with either of the two type 1 fimbrial cluster DNA probes. In K. oxytoca, however, only three of seven strains expressed type 1 fimbriae and reacted with the DNA probes. The type 3 fimbriae were found to bind to a fraction of epithelial cells exfoliated in normal human urine, whereas the type 1 fimbriae bound strongly to urinary slime. No inhibitors of type 3 fimbrial binding were detected in human urine.

Tissue culture-adherent Escherichia coli in infantile diarrhea.

To determine the association of tissue culture-adherent Escherichia coli with diarrhea, serotyped E. coli strains isolated in a yearlong case-control study of infantile diarrhea in Bangkok, Thailand, were examined for adherence to HeLa cells and for hybridization with the enteropathogenic E. coli adherence factor, the F1845, and the enteroaggregative E. coli (EAggEC) DNA probes. E. coli that adhered to HeLa cells in a localized adherence (LA) pattern (LA E. coli) was isolated from 26 of 509 infants with diarrhea (cases) and 9 of 509 age-matched controls (P = .006); E. coli with diffuse or aggregative adherence (DA or AA) to HeLa cells or that hybridized with the F1845 or EAggEC probes was not associated with infantile diarrhea. LA E. coli of classical enteropathogenic E. coli (EPEC) serotypes was isolated from 11 cases and 1 control (P = .003). EPEC O44:H18 that adhered to HeLa cells in a DA pattern and hybridized with the F1845 DNA probe was the predominant E. coli (five of five colonies tested) isolated from a 5-month-old girl with diarrhea in whom no other enteric infections were identified. Although LA E. coli was highly associated with infantile diarrhea, the role of DA and AA E. coli was uncertain in this setting.

Colonization factors of enterotoxigenic Escherichia coli isolated from children with diarrhea in Argentina.

A prospective study was performed to evaluate the presence of colonization factor antigens (CFAs) in enterotoxigenic Escherichia coli (ETEC) strains isolated from 1,211 children with diarrhea in Argentina. One hundred nine ETEC strains that were isolated from seven different laboratories in various regions of the country were tested for CFAs by using monoclonal antibodies against CFA/I and E. coli surface antigens CS1, CS2, and CS3 of CFA/II and CS4 and CS5 of CFA/IV; a polyclonal antiserum against CS6 was used. The CFAs searched for were found in 52% of the ETEC strains: 23% of the strains carried CFA/I, 17% carried CFA/IV, and 12% carried CFA/II. All of the CFA/I strains produced heat-stable enterotoxin, and several of them were of the prevalent serotypes O153:H45 and O78:H12. Among the 19 strains expressing CFA/IV, 16 expressed CS5 and CS6 and produced the heat-stable enterotoxin and most were of serotype O128:H21; the remaining 3 strains produced CS6 only. No ETEC strains expressing CS4 were found. Most (11 of 13) of the CFA/II-carrying ETEC strains expressed CS1 and CS3, and 10 of them were of the O6:K15:H16 serotype and produced both heat-labile and heat-stable toxins. As many as 24 of the 109 CFA-negative ETEC strains gave mannose-resistant hemagglutination with erythrocytes from different species; 4 strains had high surface hydrophobicity, suggesting the presence of additional, as yet undefined, colonization factors in up to 25% of the ETEC isolates.

Attaching and effacing enteropathogenic Escherichia coli as a cause of infantile diarrhea in Bangkok.

To identify Escherichia coli that cause infantile diarrhea in Bangkok, Thailand, E. coli isolated in a year-long study of infantile diarrhea were examined for O and H serotypes and virulence determinants. Classic enteropathogenic E. coli (EPEC) were isolated from 28 of 509 infants with diarrhea (cases) and 11 of 509 age-matched controls (P = .009; odds ratio [OR], 2.64). Most of this difference was attributable to EPEC adherence factor (EAF)-positive EPEC that produced an attachment and effacement lesion, as identified in the fluorescence actin staining assay, isolated from 13 cases and 1 control (P = .003; OR, 13.3). EAF-EPEC was isolated from 15 cases and 10 controls (P = .418; OR, 1.52) and EAF+ non-EPEC from 17 cases and 10 controls (P = .242; OR, 1.72). EAF+EPEC that caused an attachment and effacement lesion was found in 3% of children less than 6 months old with diarrhea who were studied in an outpatient clinic in Bangkok in 1988.

Complex formation between Escherichia coli lipopolysaccharide O antigen and capsular K antigen as detected by immunoelectrophoresis.

Many Escherichia coli of serotypes commonly found in the normal intestine and in extraintestinal diseases, and having capsular antigens of the low molecular group called group II, will, in simple saline extracts, produce complexes between some or all of the lipopolysaccharide molecules and some of the polysaccharide K molecules. Non-complex-forming and complex-forming strains with the same O and K can be found. The complexes are thermostable but are disrupted by some detergents. O-K complex formation may lead to misinterpretation of immunoprecipitation results; one example is the counter current technique used for K determination of E. coli. In this technique O antigen lipopolysaccharide may, when complexed to K polysaccharide, mimic a K antigen. The possible implications of O-K complex formation during the infection process, especially for antibody formation need to be examined.

Clonal relationships among Escherichia coli serogroup 06 isolates from human and animal infections.

The clonal relationship of thirty E. coli strains of 0 antigen serotype 06 isolated from human, dog, pig or cow infections were investigated. Two main clones with serotypes 06 : H1 or 06 : H31, H- were identified. Isolates from humans, dogs, pigs and cows were found in both clones, indicating that animals are a possible source for human extraintestinal Escherichia coli strains. Two human ETEC (06 : H16) and two pig isolates (06 : H10) were not related to the 06 : H1 or 06 : H31, H- E. coli clones.

Antibodies against core and O antigen epitopes of Escherichia coli O83 in rabbit antisera and in commercial human immunoglobulin.

An unexpected serological cross-reaction was detected between two common Escherichia coli O antigens: O83 and O6. It was found that the cross-reacting antibodies were induced by common core epitopes not exposed in naturally occurring smooth strains. Smooth O6 strains would, however, after prolonged immunization of rabbits provoke production of precipitating antibodies against this common core epitope. Routine rabbit O antisera of smooth test strains O1 to O171 did not contain antibodies to the core epitope. Core antisera could readily be produced with an R mutant of the O6 strain. Extracts or Lipopolysaccharides (LPS) of several of the E. coli commonly found in the normal intestine and in extraintestinal diseases would only precipitate in antisera containing anti-core epitope anti-bodies after treatment with deoxycholate or sodium dodecyl sulfate. Other E. coli such as J5 (O111), used extensively for production of antisera intended for protection against endotoxemia, did not react with antibodies against this common core epitope. Another unexpected observation was that normal commercial human immunoglobulin contained precipitating IgG antibodies to the E. coli O83 antigen commonly found in strains from neonatal meningitis and other extraintestinal infections. Significant amounts of precipitating anti-LPS antibodies against other common O antigens (O2, O4, O6, O75 etc.) could not be detected in normal immunoglobulin.

Two new Escherichia coli O groups: O172 from "Shiga-like" toxin II-producing strains (EHEC) and O173 from enteroinvasive E. coli (EIEC).

Two Escherichia coli strains were established as antigenic test strains for two new O groups, O172 and O173. The O172 strain (EHEC) which produces "Shiga-like" toxin II (verocytotoxin 2) was isolated from a case of haemorrhagic colitis while the enteroinvasive O173 strain (EIEC) originated from a child with diarrhoea.

Clonal diversity and virulence factors in strains of Escherichia coli of the classic enteropathogenic serogroup O114.

Eighty-eight Escherichia coli strains of the enteropathogenic (EPEC) group O114 that were isolated from humans and animals in geographically different places and over more than 30 years were examined for virulence markers, O:H serotypes, and for electrophoretic types by multilocus enzyme electrophoresis. Four major genetically tightly related clusters of strains showed close correlation between electrophoretic types and other phenotypic characters. Cluster I contained 35 EPEC class II strains of serotypes O114:H9 and O114:H- and 5 enterotoxigenic E. coli belonging to O114:H21 and O114:H49. Clusters II and III comprised 36 O114:H4, O114:H32, and O114:H- strains; most were of doubtful pathogenicity except one Verotoxin-positive O114:H4 strain isolated from a human with diarrhea. Cluster IV contained 9 classic EPEC strains of serogroup O114:H2 that were characterized by localized adherence to HEp-2 cells and by the EPEC adherence factor.