Refine
Has Fulltext
- yes (20)
Is part of the Bibliography
- yes (20)
Document Type
- Journal article (20)
Language
- English (20)
Keywords
- Infektionsbiologie (16)
- Escherichia coli (4)
- gene cloning (2)
- (Nucleotide sequence (1)
- E. coli hemolysin (1)
- E. coli virulence (1)
- F8 fimbriae (1)
- Fimbria (1)
- Haemolysin (1)
- P-fimbriae (1)
Institute
The haemolysin (hly) determinant of the plasmid pHly152 contains an IS2 element at 469 bp upstream of the hlyC gene. The sequence at the other (right-hand) end (RS) also shows multiple hybridization with the plasmid pHly152 and the chromosome of some Escherichia coli strains but the nucleotide sequence of this region does not reveal the typical properties of an IS element. Similar arrangements in the regions flanking the hly determinant are also found on various Hly plasmids from uropathogenic E. coli strains. Chromosomal hly determinants Iack both flanking sequences (IS2 and RS) in the immediate vicinity of the hly genes. The sequences immediately upstream of the hlyC gene have been determined from several chromosomal hly determinants and compared with the corresponding sequence of the hly determinant of the plasmid pHly152. We show that these sequences, which contain one promoter (left promoter, phlyL) in all hly determinants tested, vary considerably although common sequence elements can still be identified. In contrast, only relatively few nucleotide exchanges have been detected in the adjacent structural hlyC genes. The A + T content of the 200 bp sequence upstream of hlyC is very high (72 mol% A + T) but even the structural hly genes show a considerably higher A + T content (about 60 mol%) than the E. coli chromosome on average (50 mol% A+T) suggesting that the hly determinant may not have originated in E. coli.
The genetic determinant coding for the Pspecific F8 fimbriae was cloned from · the chromosome of the Escherichia coli wild-type strain 2980 (018: K5: H5: FlC, F8). The F8 determinant was further subcloned into the Pstl site of pBR322 and a restriction map was established. In a Southern hybridization experiment identity between the chromosomally encoded F8 determinant of 2980 and its cloned Counterpart was demonstrated. The cloned F8 fimbriäe and those of the wild type strain consist of a protein subunit of nearly 20 kDa. F8 fimbriated strains were agglutinated by an F8 polyclonal antiserum, caused mannose-resistant hemagglutination and attached to human uroepi thellal cells. The cloned F8 determinant was weil expressed in a variety of host strains.
The hemolytic, uropathogenic Escherichia coli 536 (06:K15:H31) contains two inserts in its chromosome (insert I and insert II), both of which carried hly genes, were rather unstable, and were deleted spontaneously with a frequen~y of 10-3 to 10-4• These inserts were not found in the chromosome of two nonhemolytic E. coli strains, whereas the chromosomal ~equences adjacent to these inserts appeared tobe again homologous in the uropathogenic and two other E. coü strains. Insert I was 75 kilobases in size and was ftanked at both ends by 16 base pairs (bp) (TTCGACTCCTGTGATC) which were arranged in direct orientation. For insert I it was demonstrated that deletion occurred by recombination between the two 16-bp ftanking sequences, since mutants lacking this insert still carried a single copy of the 16-bp sequence in the chromosome. 8oth inserts contained a functional hemolysin determinant. However, the loss of the inserts not only atfected the hemolytic phenotype bot led to a considerable reduction in serum resistance and the loss of mannose-resistant hemagglutination, caused by the presence of S-type funbriae (sja). lt is shown that the Sfa-negative phenotype is due to a block in transcription of the sfa genes. Mutants of strain 536 which lacked both inserts were entirely avirulent when tested in several animal model systems.
The virulence of the uropathogenic E. coli strain 536 (06: K 1 5: H31) which produces the S-fimbrial adhesin (Sfa•), is serum-resistant (Sre+) and hemolytic (Hiy+) and its derivatives were assessed in five different animal models. Cloned hemolysin (h/y) determinants from the Chromosomes of 06,018 and 075 E. colistrains and from the plasmid pHiy152 were introduced into the spontaneaus Sfa-, Sre-, Hly- mutant 536-21 and its Sfa+, Sre+, Hly- variant 536-31. As already demonstrated for the 536-21 strains {lnfect. Immun. 42: 57-63) the 018-hly determinant but not the plasmid-encoded hly determinant of pHiy 1 52 transformed into 536-31 contribute to lethality in a mouse peritonitis modal. Similar results were obtained with both Hlyhost strains and their Hly+ transformants in a chicken embryo test and in a mouse nephropathogenicity assay in which the renal bacterial counts were measured 1 5 min to 8 hours after i.v. infection. S-fimbriae and serum resistance had only a marginal influence in these three in vivo systems. ln centrast all three factors, S-fimbriae, serum resistance and hemolysin, were necessary for full virulence in a respiratory mouse infection assay. ln a subcutaneously-induced sepsis model in the mouse restoration of S-fimbriae and serum resistance and separately chromosomally-encoded hemolysis increased virulence to a Ievel comparable to that of the parental 536 strain.
Recently we have described the molecular cloning of the genetic determinant coding for the S-fimbrial adhesin (Sfa), a sialic acid-recognizing pilus frequently found among extraintestinal Eschenchili coli isolates. Fimbriae from the resulting Sfa + E. coli K-12 clone were isolated, and an Sfa-specific antiserum was prepared. Western blots indicate that S fimbriae isolated from different uropathogenic and meningitis-associated E. coli strains, including 083:Kl isolates, were serologically related. The Sfa-specific antibodies did not cross-react with P fimbriae, but did cross-react with FlC fimbriae. Furthermore the sja+ recombinant DNAs and some cloned s/a-flanking regions were used as probes in Southem experiments. Chromosomal DNAs isolated from 018:Kl and 083:Kl meningitis strains with and without S fimbriae and from uropathogenic 06:K + strains were hybridized against these sfa-specific probes. Only one copy of the sfa determinant was identified on the chromosome of these strains. No sfa-specific sequences were observed on the chromosome of E. coli K-12 strains and an 07:Kl isolate. With the exception of small alterations in the sfa-coding region the genetic determinants for S fimbriae were identical in uropathogenic 06:K + and meningitis 018:Kl and 083:Kl strains. The sfa determinant was also detected on the chromosome of Kl isolates with an Sfa-negative phenotype, and specific cross-hybridization signals were visible after blotting against FlC-specific DNA. In addition homology among the different strains was observed in the sfa-flanking regions.
Escherichia coli 536 (06:K15:H31), which was isolated from a case of urinary tract infection, determines high nephropathogenicity in a rat pyelonephritis system as measured by renal bacterial counts 7 days after infection. The loss of S fimbrial adhesin formation (Sfa-) (mannose-resistant hemagglutination [Mrh-] and fimbria production [Fim-]), serum resistance (Sre-), and hemolysin production (Hly-) in the mutaßt 536-21 led to a dramatic reduction of bacterial counts from almost tOS to only 40 cells per g of kidney. The reintroduction of the cloned S fimbrial adhesin determinant (sfa) increases the virulence of the avirulent mutant strain by a factor of 20; almost the same eß'ect was observed after restoration of serum resistance by Integration of an sja+ recombinant cosmid into the chromosome. Additional reintroduction of the my+ phenotype by Iransformation of two hly determinants increased the virulence of the strains. Demolysin production determined increased renal elimination of leukocytes and erythrocytes. Thus all three determinants investigated, S fimbriae, serum resistance, and hemolysin, contribute to the multifactorial phenomenon of E. coli nephropathogenicity.
We investigated the role of bacterial mannose-resistant fimbriation of S fimbriae (Firn), mannose-resistant hemagglutination (S-Mrh), and hemolysin (Hiy) production by an Escherichitl coli parent and genetically cloned strains as regards (i) their eß'ect on histamine release from rat mast ceUs and (ii) generation of the chemiluminescence response, leukotriene, and enzyme release from human polymorphonuclear granulocytes. These mediators are involved in the induction of inftammatory disease processes and Iead, e.g., to the enhancement of vascular permeability, chemotaxis, aggregation of granulocytes (leukotriene 8 4), lysosomal enzyme release, and smooth-muscle contraction (leukotrienes C4, D4, and E4). The content of azurophilic and specific granules in polymorphonuclear granulocytes consists of highly reactive enzymes which amplify inflammatory reactions. Washed bacteria (E. coli 764 my:t:, E. coli 21085 Hly:t:, E. coli 536 Hly:t: Firn:~: Mrh:t:), as weil as their culture supernatants, were analyzed at various times during their growth cycle. No differences exist between parent and cloned or mutant strains with respect to their outer . membrane proteins and lipopolysaccharide pattern. Washed bacteria [E. coli 764 and 21085(pANN202-312)] which produced hemolysin, unlike my- strains, induced high Ievels of histamine release from rat mast ceUs and led to a significant chemiluminescence response and enzyme and leukotriene release from human polymorphonuclear granulocytes. Bacterial culture supernatants from Hly+ and secreting strains showed similar results with the exception of E. coli 21085(pANN202-312), which is a hemolysin-producing bot not a secretory strain. Our data soggest a potent role for hernolysin as a stimulus for noncytotoxic mediator release from various cells. Furthermore, we showed that the presence of Firn and S Mrh potentiales mediator release. The simultaneous presence of Mrh and Firn [E. coli 535/2l(pANN801-4)] increased mediator release compared with Mrh+ Firn- strains [E. coli 536/21(pANN801-1)]. E. coli 536/21 (Msh- Mrh- Firn- Hly-) did not induce mediator release. Escherichia coli alpha-hemolysin is a protein that causes in vitro Iysis of erythrocytes from several species of animals (6, 12, 1~18, 23). Hemolysin-producing E. coli strains occur only infrequently in the normal fecal ftora of humans but are often isolated from patients with extraintestinal infections such as urinary tract infections, bacteremia, and septicemia (13, 22, 25, 36-38, 46-48). The high percentage of Hly+ E. coli strains among isolates from patients with urinary tract infections suggested that hemolysin contributes to the virulence of E. coli strains. The role of hemolysin as a virulence factor has been recently demonstrated by using various animal models and cell cultures. Alpha-hemolysin is one of the very few proteins produced by members of the family Enterobacteriaceae that is released extracellulary. The genetic control of alpha-hemolysin production, transport, and release from cells is complex (24, 26, 30). At least four genes located on the bacterial chromosome or on ]arge transmissible plasmids are required to elicit a cell-free hemolytic phenotype. Bobach and Snyder (6) suggested that the existence of alpha-hemolysin complexed with lipopolysaccharide may have important implications in the understanding of its biological effects. In addition to hemolysin production, a variety of factors, e.g., fimbriae, expression of specific hemagglutination, and • Corresponding author. 886 0 and K antigens, may contribute to the vi
The hemolytic Escherichia coli strain 536 (06) propagates spontaneous hemolysin- negative mutants at relatively high rates (10-3 to 10-4 ). One type of mutant (type I) lacks both secreted (external) and periplasmic (internal) hemolysin activity (HlYex - IHlYin -) and in addition shows no mannose-resistant hemagglutination (Mrh -), whereas the other type (type II) is HlYex -IHIYin + and Mrh +. The genetic determinants for hemolysin production (hly) and for mannose-resistant hemagglutination (mrh) of this strain are located on the chromosome. Hybridization experiments with DNA probes specific for various parts of the hly determinant reveal that mutants of type I have lost the total hly determinant, whereas those of type 11 lack only part of the hlyB that is essential for transport of hemolysin across the outer membrane. Using a probe that contains the end sequence of the plasmid pHly152-encoded hly determinant (adjacent to hlyB), we determined that a related sequence flanks also the hlyB-distal end of the chromosomal hly determinant of E. coli 536. In addition several other similar or even identical sequences are found in the vicinity of the hlyC- and the hlyB-distal ends of both the chromosomal and the plasmid hly determinants.
Like all other Salmonella typhimurium strains examined, the smooth variants SF1397 (L T2) and 1366 and also their semi-rough and rough derivatives are non-haemolytic. Nevertheless, two haemolysin (Hly) plasmids of E. coli belonging to the inc groups incFllI,lv (pSU316) and incIz (pHly152) were able to be introduced into these strains by conjugation and stably maintained. A considerable percentage of the Hly+ transconjugants obtained had lost parts of their O-side chains, a result of selection for the better recipient capability of « semi-rough» variants rather than the direct influence of the Hly+ plasmids themselves. In contrast to the incF1lI1V plasmid pSU316, which exhibited higher conjugation rates with rough recipients, the incIz plasmid pHly152 was accepted best by smooth strains. Transformation with cloned E. coli haemolysin (hly) determinant was inefficient ( <10-8) for smooth strains, but 102-103 times higher for rough recipients, and was increased by the use of Salmonella-modified DNA. The transform ants and transconjugants were relatively stable and showed the same haemolytic activity as the E. coli donor strains. The virulence of the Hly+ smooth, semi-rough and rough S. typhimurium strains was tested in two mouse models, and neither the mortality rate nor the ability to multiply within the mouse spleen was influenced by the hly determinants.