Heterogeneity in the activity of Mexican Helicobacter pylori strains in gastric epithelial cells and its association with diversity in the cagA gene

Helicobacter pylori CagA is translocated into gastric epithelial cells by a type IV secretion system and interacts with the Src homology 2 phosphatase, altering cell morphology. Multiple EPIYA motifs in CagA are associated with increased activity in cells and with gastric cancer. The aim of this work was to study the heterogeneity in activity in cells of multiple H. pylori single colonies isolated from a single patient and its association with polymorphism in cagA. The presence of cagA, cagE, cagT, and cag10 was studied with 318 H. pylori isolates from the antra and corpora of 18 patients. AGS gastric epithelial cells were infected with 75 isolates, and interleukin-8 (IL-8) secretion, cytoskeletal changes, CagA translocation, and tyrosine phosphorylation were measured. The cagA 3'-variable region was sequenced for 30 isolates to determine the number and types of EPIYA motifs. Isolates from an individual stomach were usually genetically related and had quantitatively similar phenotypic effects on cells (IL-8 induction and cytoskeletal changes). However, strains from different patients with similar CagA EPIYA motif patterns varied widely in these phenotypes. Among isolates with an EPIYA-ABC pattern, the phenotype was variable: IL-8 induction ranged from 200 to 1,200 pg/ml, and morphological changes occurred in 20 to 70% of cells. In several cases, cagA sequence diversity appeared to explain the lack of CagA activity, as isolates with an EPIYA-ACC pattern or a modified B motif had reduced cell activity. cag pathogenicity island-positive H. pylori isolates displayed a high level of heterogeneity in the capacity to induce IL-8 secretion and morphological changes; an absent or modified B motif was associated with low activity.

Phenotypic Characterization ofipaH+ Escherichia coli Strains Associated with Yolk Sac Infection

Seventy-six Escherichia coli serotypes possessing the ipaH gene typical of enteroinvasive E. coli (EIEC) strains were characterized. Biochemical identification of our strains shows positive reactions for lactose fermentation (100% of strains), lysine decarboxylase (98.7% of strains) and motility (67.1% of strains), properties that do not correspond with those described to the EIEC group. The serotypes agree with an initial classification. In this, some common O antigens identified among ipaH+ strains were O2 (n=20), OR (n=11) and non-determined O? (n=10). The O2:NM serotype was the most common. Sixty-six percent (n=50) of the ipaH+ E. coli strains were colicin producers, of them, 26 (34%) produced Col V and other colicins, 13 (17%) produced colicins other than Col V, and 11 (14.5%) produced Col V only. Trimethoprim/Sulfa (72%), ampicillin (64.5%), enrofloxacin (55.3%), and ciprofloxacin (47.4%) were the major antimicrobial resistance frequencies observed. Twenty-five different multiresistance patterns were observed, where sixty-six strains (86.8%) were included. A MIC test showed that most of the strains were sensitive to low gentamicin and kanamycin concentrations, whereas most of the strains were resistant to tetracycline. An invasiveness assay showed that the predominant alterations caused to HEp-2 cells were changes in shape and staining, and in most of the specimens, a partial monolayer detachment was also seen. Fifteen strains invaded more than 30% of the monolayer cells, causing the formation of intercellular bridges or filipoidal-like protrusions. The results suggest the existence of specific clone complexes derived from EIEC strains adapted to the avian host. To our knowledge, this is the first study that demonstrates the presence of extraintestinal invasive E. coli (ExIEC) strains.

Enterohaemorrhagic and enteropathogenic Escherichia coli use a different Tir-based mechanism for pedestal formation

Enterohaemorrhagic Escherichia coli (EHEC) adheres to the host intestinal epithelium, resulting in the formation of actin pedestals beneath adhering bacteria. EHEC and a related pathogen, enteropathogenic E. coli (EPEC), insert a bacterial receptor, Tir, into the host plasma membrane, which is required for pedestal formation. An important difference between EPEC and EHEC Tir is that EPEC but not EHEC Tir is tyrosine phosphorylated once delivered into the host. In this study, we assessed the role of Tir tyrosine phosphorylation in pedestal formation by EPEC and EHEC. In EPEC, pedestal formation is absolutely dependent on Tir tyrosine phosphorylation and is not complemented by EHEC Tir. The protein sequence surrounding EPEC Tir tyrosine 474 is critical for Tir tyrosine phosphorylation and pedestal formation by EPEC. In contrast, Tir tyrosine phosphorylation is not required for pedestal formation by EHEC. EHEC forms pedestals with both wild-type EPEC Tir and the non-tyrosine-phosphorylatable EPEC Tir Y474F. Pedestal formation by EHEC requires the type III delivery of additional EHEC factors into the host cell. These findings highlight differences in the mechanisms of pedestal formation by these closely related pathogens and indicate that EPEC and EHEC modulate different signalling pathways to affect the host actin cytoskeleton.

Transcriptional regulation of the orf19 gene and the tir-cesT-eae operon of enteropathogenic Escherichia coli

To establish an intimate interaction with the host epithelial cell surface, enteropathogenic Escherichia coli (EPEC) produces Tir, a bacterial protein that upon translocation and insertion into the epithelial cell membrane constitutes the receptor for intimin. The tir gene is encoded by the locus for enterocyte effacement (LEE), where it is flanked upstream by orf19 and downstream by the cesT and eae genes. With the use of a series of cat transcriptional fusions and primer extension analysis, we confirmed that tir, cesT, and eae form the LEE5 operon, which is under the control of a promoter located upstream from tir, and found that the orf19 gene is transcribed as a monocistronic unit. We also demonstrated that the LEE-encoded regulator Ler was required for efficient activation of both the tir and the orf19 promoters and that a sequence motif located between positions -204 and -157 was needed for the Ler-dependent activation of the tir operon. Sequence elements located between positions -204 and -97 were determined to be required for the differential negative modulatory effects exerted by unknown regulatory factors under specific growth conditions. Upon deletion of the upstream sequences, the tir promoter was fully active even in the absence of Ler, indicating that tir expression is subject to a repression mechanism that is counteracted by this regulatory protein. However, its full activation was still repressed by growth in rich medium or at 25 degrees C, suggesting that negative regulation also occurs at or downstream of the promoter. Expression of orf19, but not of the tir operon, became Ler independent in an hns mutant strain, suggesting that Ler overcomes the repression exerted by H-NS (histone-like nucleoid structuring protein) on this gene.

Transcriptional regulation of type III secretion genes in enteropathogenic Escherichia coli: Ler antagonizes H-NS-dependent repression

Secretion of effector proteins in enteropathogenic Escherichia coli (EPEC) is mediated by a specialized type III secretion system whose components are encoded in the LEE1, LEE2 and LEE3 operons. Using cat transcriptional fusions and primer extension analysis, we determined that the LEE2 and LEE3 operons are expressed from two overlapping divergent promoters, whose expression is negatively regulated by flanking common upstream and downstream silencing regulatory sequences (SRS1 and SRS2). In the absence of either SRS1 or SRS2, expression of the LEE2 and LEE3 operons became independent of Ler, a positive regulatory protein encoded by the first gene of the LEE1 operon. Similarly, in the absence of the histone-like protein H-NS, expression from both promoters became Ler independent even if both SRSs were present. In addition, the efficient expression of both the LEE2 and the LEE3 promoters required PerC (BfpW), a protein coded by the third gene of the per (bfpTVW) locus, but only in the presence of the EAF plasmid. Our deletion analysis also showed that the negative regulation observed in the presence of ammonium or at temperatures above 37 degrees C (e.g. 40 degrees C) required the SRSs or elements located therein. In contrast, the negative regulation observed in LB or at temperatures below 37 degrees C (e.g. 25 degrees C) was still observed even in the absence of both SRSs and seems to act only on the promoters. Together, these results suggest that Ler acts as an antirepressor protein that overcomes the H-NS-mediated silencing on the LEE2/LEE3 divergent promoter region, which is probably caused by the formation of a repressing H-NS-nucleoprotein complex.

Tumour prothymosin alpha content, a potential prognostic marker for primary breast cancer

In a previous report we suggested that the estimation of prothymosin alpha (PTA) levels in primary breast tumours might be used to identify breast cancer patients at high risk for distant metastasis (Dominguez F et al (1993) Eur J Cancer 29A: 893-897). Here the role of tumour PTA levels as predictor was investigated with respect to both disease-free survival (DFS) and survival. Tumours were obtained from a series of 210 consecutive female patients with ductal carcinoma who underwent surgery at the Hospital Xeral de Galicia (Santiago de Compostela, Spain). Characteristics including PTA tumour levels, number of positive axillary nodes, patient's age at surgery and tumour histological grade were significantly associated with DFS and survival, as determined by univariate analysis. Patients with tumours with low or moderate PTA levels demonstrated a statistically decreased rate of tumour recurrence and a statistically significant increased overall survival in comparison with those whose tumours had high PTA levels. Patient's relative risk of dying was 2.1 times greater for tumours with high PTA levels than for those tumours with low or moderate PTA levels. In conclusion, these data support the hypothesis that tumour high PTA levels is associated with a worse outcome.

Enteropathogenic Escherichia coli translocated intimin receptor, Tir, requires a specific chaperone for stable secretion

Enteropathogenic Escherichia coli (EPEC) secretes several Esps (E. coli-secreted proteins) that are required for full virulence. Insertion of the bacterial protein Tir into the host epithelial cell membrane is facilitated by a type III secretion apparatus, and at least EspA and EspB are required for Tir translocation. An EPEC outer membrane protein, intimin, interacts with Tir on the host membrane to establish intimate attachment and formation of a pedestal-like structure. In this study, we identified a Tir chaperone, CesT, whose gene is located between tir and eae (which encodes intimin). A mutation in cesT abolished Tir secretion into culture supernatants and significantly decreased the amount of Tir in the bacterial cytoplasm. In contrast, this mutation did not affect the secretion of the Esp proteins. The level of tir mRNA was not affected by the cesT mutation, indicating that CesT acts at the post-transcriptional level. The cesT mutant could not induce host cytoskeletal rearrangements, and displayed the same phenotype as the tir mutant. Gel overlay and GST pulldown assays demonstrated that CesT specifically interacts with Tir, but not with other Esp proteins. Furthermore, by using a series of Tir deletion derivatives, we determined that the CesT binding domain is located within the first 100 amino-terminal residues of Tir, and that the pool of Tir in the bacterial cytoplasm was greatly reduced when this domain was disrupted. Interestingly, this domain was not sufficient for Tir secretion, and at least the first 200 residues of Tir were required for efficient secretion. Gel filtration studies showed that Tir-CesT forms a large multimeric complex. Collectively, these results indicate that CesT is a Tir chaperone that may act as an anti-degradation factor by specifically binding to its amino-terminus, forming a multimeric stabilized complex.

Autoactivation and environmental regulation of bfpT expression, the gene coding for the transcriptional activator of bfpA in enteropathogenic Escherichia coli

Expression of bfpA, the gene coding for the structural subunit of the bundle-forming pili (BFP) in enteropathogenic Escherichia coli (EPEC), requires the product of bfpT (also called perA), a member of the AraC family of transcriptional regulators. Here, we show that bfpT-cat fusions were not expressed in a bfpT - or in a non-EPEC strain, unless a functional bfpT was present, indicating that an autoregulatory mechanism is involved in expression. Further experiments with bfpT-cat fusions and primer extension analysis showed that bfpT is transcribed from a conventional sigma-70 promoter and that it is expressed throughout the growth curve. It is regulated in response to the ammonium concentration, temperature and growth media, in the same proportions as those described previously for bfpA. In addition, bfpT and bfpA expression was also modulated by osmolarity, but was not affected by pH, iron excess or limitation. Deletion analysis of the bfpT upstream region revealed that a DNA segment of 81 bp, extending upstream from the transcriptional start site, contained all the sequence elements required for maximal expression of bfpT. Furthermore, it shares significant homology with a bfpA upstream AT-rich region, which has been shown to be involved in the BfpT-dependent regulation of bfpA. Interestingly, ammonium repression was observed only when bfpT-cat or bfpA-cat expression was complemented in an EPEC background, whereas low-temperature regulation was observed in both EPEC and non-EPEC strains. This suggests that specific regulatory elements are present in EPEC, while others are shared with non-pathogenic E. coli.

Negative and positive regulation of the non-osmoregulated ompS1 porin gene in Salmonella typhi: a novel regulatory mechanism that involves OmpR

The Salmonella typhi ompS1 gene codes for an outer membrane protein of the OmpC/OmpF porin family. It is expressed at very low levels, relative to the major porins. However, deletion analysis of the 5' regulatory region showed that the gradual removal of nucleotides -310 to -88, upstream from the P1 major transcriptional start-point, resulted in a stepwise increase in expression, reaching levels 10-fold above those for the ompC major porin gene. Hence, this 222 bp segment contains cis-acting regulatory elements involved in negative control. Primer extension analysis revealed the presence of three promoters: P1 activity was OmpR dependent; P2 was expressed at a lower level in the absence of OmpR; and P3 had a minor constitutive activity. OmpR bound preferentially to box II, an 18 bp F1/C1 canonical site, the removal (-88 to -66) of which resulted in a decrease in expression thus supporting its role in positive control. Expression of ompS1 was not induced by a set of stress conditions, including a shift in osmolarity, nor was the IHF regulator involved in negative control. An ompS1 homologue was found in E. coli K-12, which contains a nonsense codon and a shift in the reading frame, whereas Salmonella typhimurium contains an open reading frame in this region. Thus, S. typhi ompS1 provides novel features in OmpR regulation.

The ompB operon partially determines differential expression of OmpC in Salmonella typhi and Escherichia coli

Expression of the Escherichia coli OmpC and OmpF outer membrane proteins is regulated by the osmolarity of the culture media. In contrast, expression of OmpC in Salmonella typhi is not influenced by osmolarity, while OmpF is regulated as in E. coli. To better understand the lack of osmoregulation of OmpC expression in S. typhi, we compared the expression of the ompC gene in S. typhi and E. coli, using ompC-lacZ fusions and outer membrane protein (OMP) electrophoretic profiles. S. typhi ompC expression levels in S. typhi were similar at low and high osmolarity along the growth curve, whereas osmoregulation of E. coli ompC in E. coli was observed during the exponential phase. Both genes were highly expressed at high and low osmolarity when present in S. typhi, while expression of both was regulated by osmolarity in E. coli. Complementation experiments with either the S. typhi or E. coli ompB operon in an S. typhi DeltaompB strain carrying the ompC-lacZ fusions showed that both S. typhi and E. coli ompC were not regulated by osmolarity when they were under the control of S. typhi ompB. Interestingly, in the same strain, both genes were osmoregulated under E. coli ompB. Surprisingly, in E. coli DeltaompB, they were both osmoregulated under S. typhi or E. coli ompB. Thus, the lack of osmoregulation of OmpC expression in S. typhi is determined in part by the ompB operon, as well as by other unknown trans-acting elements present in S. typhi.

Fimbrial expression in enteric bacteria: a critical step in intestinal pathogenesis

The ability of species of enteric bacteria to recognize and colonize unique niches along the intestine is mainly based on receptor distribution and interpretation of a combination of environmental signals leading to the expression of specific adherence factors. Such elaborate orchestration of events is critical during the initial steps of pathogenesis.

Analysis of cis-acting elements required for bfpA expression in enteropathogenic Escherichia coli

bfpA expression in enteropathogenic Escherichia coli is regulated by growth medium, temperature, and ammonium concentration and requires the BfpT protein (also called PerA), a member of the AraC family of transcriptional activators. Site-directed and PCR random mutagenesis, as well as deletion analysis of the bfpA upstream regulatory region, supported assignment of the promoter elements and demonstrated that the cis-acting elements that mediate BfpT-dependent regulation of bfpA are located between positions -85 and -46. Interestingly, this region shares 73% identity with a 40-bp-long AT-rich tract located upstream of the bfpT gene, which is essential for bfpT autoregulation.

Distinctive IS200 insertion between gyrA and rcsC genes in Salmonella typhi

While probing the vicinity of ompC, a copy of the IS200 insertion element was found between the gyrA and rcsC genes of Salmonella typhi, the causal agent of typhoid fever. This distinctive feature was conserved throughout 63 S. typhi isolates of different geographical origins and was absent from 46 other Salmonella serotypes, including those most associated with human infections, as well as from 19 other enteric bacteria. Furthermore, the location of this IS200 copy corresponds to a constant band, present throughout the 14 PstI S. typhi IS200 fingerprints, encompassing several Vi phage types. Interestingly, an apparently unrelated serotype not frequently associated with human disease, Salmonella weltevreden, contained an IS200 copy at the same position, although it was accompanied by an additional segment of cryptic DNA. On the basis of these findings, PCR assays were designed for molecular typing of S. typhi, and these are potentially useful in studying the epidemiology of typhoid fever.

Development of ELISA to estimate thymosin alpha1, the N terminus of prothymosin alpha, in human tumors

We reported that tumor content of prothymosin alpha (ProT alpha) is a proliferation index of human breast tumors that might be used to identify patients at high risk for distant metastasis (Dominguez et al., Eur J Cancer 1993; 29A:893-7). In that study ProT alpha concentrations were measured by a RIA; here we present an alternative nonisotopic assay that could be used in a standard clinical laboratory. Main features of the ELISA are: (a) A recombinant fusion protein glutathione S-transferase (GST)-human ProT alpha was used to coat the microtiter plates; (b) we used a polyclonal antiserum raised in rabbits that detects thymosin alpha1, the NH2-terminal fragment of ProT alpha; (c) it is as sensitive as the RIA; (d) it is faster than the RIA. ProT alpha concentrations in various human tumors (skin, esophagus, colorectal, and breast) as assessed by ELISA were comparable with, although twofold greater than, the values previously estimated by RIA.

Cloning and characterization of bfpTVW, genes required for the transcriptional activation of bfpA in enteropathogenic Escherichia coli

Expression of the bundle-forming pilus (BFP) of enteropathogenic Escherichia coli (EPEC) is regulated at the transcriptional level by growth phase, temperature, calcium and ammonium. Genes required for the transcriptional activation of bfpA were localized to a 1.8 kb fragment of the enteroadherent factor (EAF) plasmid of EPEC that is separated from the bfp operon by 6 kb. Within this fragment three identically oriented and closely spaced open reading frames (ORFs) were identified and designated bfpT, bfpV and bfpW. bfpT is predicted to encode a 31.8 kDa protein that shares homology with the AraC family of transcriptional regulators, including the presence of a conserved C-terminal DNA-binding helix-turn-helix motif. Insertional inactivation of bfpT led to the loss of bfpA transcription, BfpA protein production and the localized adherence (LA) phenotype; this mutant phenotype could be complemented by introduction of bfpTVW and, on separate plasmids, bfpT + bfpW. However, introduction of bfpT + bfpV, bfpV alone, bfpW alone, or bfpV + bfpW did not enable recovery of the wild-type phenotype. Maximal efficiency of bfpA transcription required all three genes, but bfpV and bfpW each enhanced transcription providing bfpT was also present. A series of deletions of the bfpA upstream promoter region was prepared; with respect to the bfpA transcription start site, sequence between nucleotides -94 and -55 was found to bind bfpT. BfpT also bound a DNA fragment containing the eaeA promoter region on the EPEC chromosome. From these results we conclude that bfpTV W causes transcriptional activation of bfpA, and possibly eaeA, by a trans-acting mechanism that may co-ordinately regulate the expression of EPEC virulence determinants.

Enteropathogenic Escherichia coli: identification of a gene cluster coding for bundle-forming pilus morphogenesis

Sequence flanking the bfpA locus on the enteroadherent factor plasmid of the enteropathogenic Escherichia coli (EPEC) strain B171-8 (O111:NM) was obtained to identify genes that might be required for bundle-forming pilus (BFP) biosynthesis. Deletion experiments led to the identification of a contiguous cluster of at least 12 open reading frames, including bfpA, that could direct the synthesis of a morphologically normal BFP filament. Within the bfp gene cluster, we identified open reading frames that share homology with other type IV pilus accessory genes and with genes required for transformation competence and protein secretion. Immediately upstream of the bfp gene cluster, we identified a potential replication origin including genes that are predicted to encode proteins homologous with replicase and resolvase. Restriction fragment length polymorphism analysis of DNA from six additional EPEC serotypes showed that the organization of the bfp gene cluster and its juxtaposition with a potential plasmid origin of replication are highly conserved features of the EPEC biotype.

The bundle-forming pili of enteropathogenic Escherichia coli: transcriptional regulation by environmental signals

The bundle-forming pili (BFP) of enteropathogenic Escherichia coil (EPEC) are required for the development of circumscribed colonies of bacteria attached to the surfaces of cultured epithelial cells, a process termed the localized adherence (LA) phenotype. Similar lesions are evident in jejunal biopsies from EPEC-infected children. BFP production is not constitutive, but instead occurs upon transfer of bacteria from nutrient broth to tissue culture media, indicating that the expression of BFP may be environmentally regulated. To learn more about how BFP protein expression is induced during epithelial-cell adherence, bfpA-cat transcriptional fusions and northern blot analyses were employed to monitor bfpA expression as a function of environmental signals and growth kinetics. bfpA expression was found to be regulated at the transcriptional level, and to require a separate locus on the EPEC adherence factor (EAF) plasmid. Expression occurred selectively during exponential-growth phase and was greatest between 35 and 37 degrees C, and in the presence of calcium. Ammonium (20 mM) significantly reduced bfpA mRNA and protein expression and the development of the LA phenotype. Analysis of the bfpA upstream sequence and identification of the transcription initiation site revealed a conventional sigma (70)-dependent promoter and an AT-rich tract that might affect promoter activity. Taken together, these findings further support the pathogenic role of BFP by explaining how BFP production would commence in the small intestine and terminate in the colon and in external habitats.

Identification of Campylobacter jejuni and C. coli using the rpoB gene and a cryptic DNA fragment from C. jejuni

Campylobacter jejuni (Cj) and C. coli (Cc) clinical isolates, obtained from three different sources, were characterized using two Cj DNA probes, CJ01 and CJ02. These probes were selected at random by virtue of their stability in Escherichia coli (Ec). CJ01 hybridized specifically with DNA from Cj reference strains, but not with DNA from Cc, C. lari (Cl) nor C. fetus (Cf) reference strains. Using clinical isolates characterized by genome-genome hybridization and biotype, CJ01 hybridized with DNA derived from all Cj strains. However, DNA from four out of ten Cc strains, from three different sources, also hybridized with CJ01, suggestive of this region being heterogeneous between clinical isolates of both species. The nucleotide sequence analysis of CJ01 reveals two incomplete open reading frames (ORFs) that did not show significant homology with any other known sequences. CJ02 hybridized specifically with DNA from Cj and Cc reference strains, but not with DNA from Cl and Cf reference strains. The specificity and sensitivity were maintained upon hybridization with DNA from 31 clinical isolates. CJ02 has an uninterrupted ORF whose deduced amino-acid sequence showed extensive homology with the central region of the Ec and Salmonella typhimurium (St) RNA polymerase beta subunits (52 and 66% similarity, respectively). The most conserved segments correspond to putative functional domains.

Isolation and characterization of ompS1, a novel Salmonella typhi outer membrane protein-encoding gene

We have isolated a novel outer membrane protein (OMP)-encoding gene from Salmonella typhi (St), termed ompS1, using the ompF gene of Escherichia coli (Ec) as a heterologous probe. The structural ompS1 gene codes for an OmpS1 polypeptide that consists of 373 amino acids (aa) in the mature product, with a putative 21-aa leader sequence, containing highly conserved aa residues that have been implicated in pore formation. Mature OmpS1 (41 kDa) is larger than the OmpC, OmpF and PhoE St and Ec porins. In contrast to the major porins, it is undetectable in Coomassie-stained OMP preparations; although, when ompS1 was cloned into a high-copy-number plasmid under the control of the inducible tac promoter, it was detectable along with major OMPs. The 5' regulatory region of ompS1 has five putative binding sites for OmpR, a positive transcriptional regulator. The ompS1 gene shows restriction-fragment length polymorphism (RFLP) among Salmonellae.

The Salmonella ompC gene: structure and use as a carrier for heterologous sequences

The Salmonella typhi (St) ompC gene codes for a major outer membrane protein (OMP) that is highly expressed in both low and high osmolarity. By hybridization studies with the entire gene or with segments thereof, ompC was found to be highly conserved within 11 different Salmonella serotypes, with the exception of S. arizonae. The study included several St isolates from Mexico and Indonesia. Variation was only detected in two (e and f) of the seven regions previously found to vary between St and E. coli ompC. Chimeric OmpC proteins, carrying a rotavirus VP4 capsid protein epitope, are well recognized by a specific monoclonal antibody (mAb) against this epitope, either in OMP preparations (by enzyme-linked immunosorbent assay; ELISA) or intact cells (by ELISA and immunogold-labelling), indicating that regions c and f are oriented towards the cell surface and are probably exposed. As has been shown before for other regulated OMP, this experimental approach could be useful for the presentation of heterologous epitopes in order to gain knowledge about porin topology, for testing the effect of altered porin surface epitopes on bacterial physiology, or else, in the development of multivalent vaccines.

Antisense overlapping open reading frames in genes from bacteria to humans

Long Open Reading Frames (ORFs) in antisense DNA strands have been reported in the literature as being rare events. However, an extensive analysis of the GenBank database revealed that a substantial number of genes from several species contain an in-phase ORF in the antisense strand, that overlaps entirely the coding sequence of the sense strand, or even extends beyond. The findings described in this paper show that this is a frequent, non-random phenomenon, which is primarily dependent on codon usage, and to a lesser extent on gene size and GC content. Examination of the sequence database for several prokaryotic and eukaryotic organisms, demonstrates that coding sequences with in-phase, 100% overlapping antisense ORFs are present in every genome studied so far.

Early diagnosis of typhoid fever by an enzyme immunoassay using Salmonella typhi outer membrane protein preparations

An enzyme immunoassay (EIA) for detection of serum antibodies in patients with typhoid fever was developed using Salmonella typhi outer membrane protein (OMP) preparations as antigen. Acute phase (first week) sera from adult typhoid fever patients were tested as well as sera from the following control groups: adult travellers with diarrhea caused by enterotoxigenic Escherichia coli, children infected with Campylobacter jejuni, healthy Mexican adult blood donors, and adults with septicemia caused by other organisms. At a 1:3,125 serum dilution, the mean absorbance values were 1.41 in the typhoid fever patients, and 0.57, 0.55, 0.51 and 0.52 in the respective control groups. Inhibition EIA studies using OMP preparations or lipopolysaccharide (LPS) as free antigen indicated that proteins can play an important role in the detection of antibodies in early typhoid fever. This EIA may be useful for the diagnosis of typhoid fever since results were obtained within about five hours and in an endemic area antibodies against Salmonella typhi OMP preparations appear early in the course of the disease.

Cloning and characterization of the bundle-forming pilin gene of enteropathogenic Escherichia coli and its distribution in Salmonella serotypes

bfp, the structural gene of the major repeating bundle-forming pilus (BFP) subunit, was cloned from the enteroadherent factor (EAF) plasmid of enteropathogenic Escherichia coli (EPEC) strain B171 (O111:NM). The bfp open reading frame encoded a 193-amino-acid protein; comparison of this sequence with the biochemically determined N-terminal amino acid sequence showed that the mature pilin protein is comprised of 180 amino acids, that this sequence is similar to other members of the type IV pilin family, and that it is preceded by a 13-amino-acid signal peptide. Expression of the cloned bfp structural gene in an EPEC strain that had been cured of the EAF plasmid yielded a 21,000 dalton protein that co-migrated with the BFP precursor protein. Thus, other genes, probably carried by the EAF plasmid, are required for the maturation of the bfp product and for the production of extracellular pilus filaments. Use of bfp as a hybridization probe showed that homologous sequences are present in all tested EPEC strains and in 13 of 16 tested Salmonella serotypes. Fifty per cent of these bfp probe-sensitive salmonellae exhibited the localized-adherence (LA) phenotype when incubated with tissue culture cell monolayers, a trait previously associated with EAF plasmid-containing EPEC strains. Scanning electron micrographs of a bfp probe-sensitive, LA-positive Salmonella dublin strain showed that it grows as adherent colonies on infected monolayers and that within these colonies, BFP-like fibres form inter-bacterial linkages. For EAF plasmid-containing EPEC strains and for several Salmonella serotypes, BFP expression may lead to the development of adherent colonies on epithelial surfaces early in the infective process.

Hyperbilirubinemia, jaundice and anergy

A prospective study of delayed hypersensitivity response was carried out in jaundiced patients. One hundred and seventy-seven subjects were studied. Fifty-nine were controls and one hundred and eighteen were patients with hepato-pancreato-biliary pathology and biliary tract obstruction. A multitest technique was used to evaluate the delayed hypersensitivity response, classifying the subjects into one of three groups: immunocompetent, relatively anergic and anergic. In the control group 76.3 per cent of the subjects were immunocompetent as opposed to 16.1 per cent of the patients (p less than 0.0001). Twenty-four per cent of the control subjects and eighty-four per cent of the patients presented anergy or relative anergy (p less than 0.0001). Among the patients no difference could be found in the index of anergy between malignant and benign pathology. We have found, moreover, that patients with a mean bilirubin level of 12 mg/dl showed a change in the delayed hypersensitivity response, with development of anergy or relative anergy.

Expression of Salmonella typhi and Escherichia coli OmpC is influenced differently by medium osmolarity; dependence on Escherichia coli OmpR

OmpC, a major outer-membrane protein, is highly expressed when Salmonella typhi is grown in nutrient broth (NB) of either low (NB + 0% sucrose) or high (NB + 20% sucrose) osmolarity. This contrasts with the expression of Escherichia coli OmpC, which is inhibited in low osmolarity and enhanced in high osmolarity, as has been described previously (van Alphen and Lugtenberg, 1977; Verhoef et al., 1979; Kawaji et al., 1979). Nevertheless, expression of S. typhi OmpC is dependent on the E. coli OmpR transcriptional activator. These findings suggest differences between the mechanisms of osmoregulation of gene expression in both bacteria, although common effectors appear to be shared.

Variations in sensitivity after sectioning the intercostobrachial nerve

The authors present a prospective study of the variations in sensitivity that appear in the armpit and arm after the intercostobrachial nerve has been sectioned in a modified radical mastectomy. Of a total of 208 patients studied between 1978 and 1987, the intercostobrachial nerve was sectioned in 139 patients, whereas in 30 it remained intact; in 39 patients only peripheral branches of the nerve were sectioned. The patients were examined at regular postoperative intervals in order to evaluate their sensitivity both to touch and to pain in the axilla and arm. Four hundred thirty-three examinations were carried out and the 3 operative groups were assessed accordingly. After the nerve was sectioned, there was increasing anesthesia in the armpit and hypoesthesia on the posterointernal face of the arm, while for the patients in whom the intercostobrachial nerve remained intact, these alterations were less intense and long-lasting. Significant statistical differences between the two groups also exist. In the absence of axillary lymphatic ganglia infiltrated by the tumor, the conservation of the intercostobrachial nerve is recommended.

Comparative analysis of the Salmonella typhi and Escherichia coli ompC genes

The nucleotide (nt) sequence of the gene encoding the Salmonella typhi OmpC outer membrane protein, and its deduced amino acid (aa) sequence are presented here. The S. typhi ompC gene consists of an open reading frame of 1134 nt, corresponding to a protein of 378 aa; with a 21-aa signal peptide. This protein is 11 aa longer than Escherichia coli OmpC, but it has an identical leader peptide. The mature OmpC sequence shows 79% similarity for both bacteria at the aa level, and 77% similarity at the nt level. Seven main variable regions in the OmpC protein were identified. Five of them correspond to hydrophilic regions and contain aa observed most frequently in turn configurations in soluble proteins. This suggests that these aa stretches could be located on the exterior of the outer membrane. To probe into the genus and species specificity of the main variable regions, we have constructed complementary oligodeoxyribonucleotides. The use of one of them with a small number of DNA samples is illustrated here; no restriction fragment length polymorphism or nt sequence heterogeneity could be found between S. typhi and Salmonella typhimurium.

[Secondary and residual choledocholithiasis. Our experience]

A retrospective study was made of 780 patients who underwent surgery of the biliary tract for lithiasis between 1973 and 1984; of them, 110 (14.1%) presented secondary choledocholithiasis and 14, residual choledocholithiasis. The decade of highest incidence of choledocholithiasis was 60 to 70 years; the proportion of women-men was 2:1. The predominant symptom was biliary colic, which occurred in 99% of patients; jaundice appeared in 65% of cases. In 5.6% of patients choledocholithiasis was complicated with suppurative cholangitis. The operation most frequently practiced was choledochotomy with extraction of calculi and closure on a Kehr tube, performed in 50% of patients, followed by transduodenal sphincteropapillotomy in 31% of patients. In 32 patients complications occurred during the immediate postoperative period, representing a morbidity of 22.5% and a mortality of 3.2%. The most frequent complications were of infectious nature.

Anergy in patients with gastric cancer

A prospective study of delayed hypersensitivity was carried out in gastric cancer patients. One hundred and fifty-six subjects were studied. Fifty-nine were controls and ninety-nine patients with gastric neoplasm. A multitest technique was used to evaluate the delayed hypersensitivity response, classifying the subjects into one of three groups: immunocompetent, relatively anergic, and anergic. In the control group, 76% per cent of the subjects were immunocompetent; of the patients, only 43% showed an adequate cell-mediated immune response (p less than 0.001). Fourteen control subjects (24%) and 54 patients (56%) presented with either anergy or relative anergy (p less than 0.001). Of the ninety-four patients that underwent surgery, five (11.9%) of the immunocompetent group developed major postoperative septic complications, as did seven (22%) of the relative anergic and seven (35%) of the anergic patients (immunocompetent vs. anergic, p less than 0.05). Our study indicates a relationship between anergy and postoperative septic complications.

Anergy in patients with biliary lithiasis

A prospective study was carried out in 428 subjects (212 controls and 216 patients) to evaluate the delayed cell-mediated immune response preoperatively in patients with biliary lithiasis. The delayed hypersensitivity response was assessed by a Multitest and subjects were classified as immunocompetent, relatively anergic or anergic. Significant differences were found between control subjects and patients with cholelithiasis compared with those with acute cholecystitis (P less than 0.01), non-icteric choledocholithiasis (P less than 0.01) and choledocholithiasis with jaundice (P less than 0.05). There were also differences between patients with icteric and non-icteric choledocholithiasis (P less than 0.02). Seven possible causative factors for anergy were evaluated: a haemoglobin concentration of less than or equal to 12 g/l and a haematocrit of less than or equal to 35 per cent were related to the appearance of anergy and relative anergy in patients with acute cholecystitis. Bilirubin levels greater than or equal to 34 mumol/l were found in 60 per cent of patients with choledocholithiasis and relative anergy and in 80 per cent of those who were anergic (P less than 0.001). These results show a high incidence of failure of the cell-mediated immune response in patients with acute cholecystitis (71 per cent) and icteric choledocholithiasis (82 per cent). In the latter, jaundice appears to be associated with this failure. A close correlation between relatively anergic and anergic state and the development of postoperative septic complications was found.

[Cancer of the gallbladder]

A retrospective study was made of cancer of the gallbladder over a 10-year period, during which 874 operations of the biliary tract were performed, 26 for gallbladder neoplasm (2.97%). Of the 26 patients studied, 22 (84.6%) were women, mean age at appearance of the tumor being 63.9 years. In 77% of the patients the time of evolution of the symptoms was less than a year, a men of 3.6 months. The principal symptom was abdominal pain, encountered in 96% of patients, followed by nausea and vomiting (65.4%). Fifty-eight percent of patients had gallstones and 46% had metastases at the time of operation. In 23% of the patients only laparotomy and biopsy could be performed, 42% underwent cholecystectomy and 34% cholecystectomy and drainage of the biliary tract. Of the 26 patients in our study, 24 (92%) had adenocarcinoma.

Anergy in jaundiced patients

A prospective study of delayed hypersensitivity was carried out in jaundiced patients. One hundred and nineteen subjects were studied. Fifty-nine were controls and sixty were patients with pancreatobiliary pathology and biliary tract obstruction. A Multitest technique was used to evaluate the delayed hypersensitivity response, classifying the subject into one of three groups: immunocompetent, relatively anergic and anergic. In the control group, 76 per cent of the subjects were immunocompetent as opposed to 17 per cent of the patients (P less than 0.001). Ten per cent of the control subjects and fifty-five per cent of the patients presented anergy (P less than 0.001). Amongst the patients no difference could be found in the index of anergy between malignant or benign pathology. A greater incidence of postoperative septic complications in anergic and relatively anergic patients was found. Our study indicates a relationship between jaundice and anergy.

Isolation of an ompC-like outer membrane protein gene from Salmonella typhi

We have isolated the structural gene for an outer membrane protein of Salmonella typhi, from a genomic library constructed in bacteriophage lambda 1059, using the Escherichia coli ompC gene as a heterologous probe. E. coli ompC codes for an outer membrane pore protein (porin) that is induced preferentially at high osmolarity and high temperature. The S. typhi ompC-like gene was subcloned in pBR322 and introduced into E. coli HB101 and into P678-54, a minicell-producing strain. In both strains it expressed a 38.5-kDa protein, which was incorporated into the outer membrane envelope and comigrated with an S. typhi outer membrane protein which was expressed both at low and high osmolarity in vivo.

Prospective randomized controlled study of prophylaxis with cefamandole in high risk patients undergoing operations upon the biliary tract

In this study, 52 high risk patients who underwent operations upon the biliary tract were assigned to receive either antibiotic prophylaxis or no treatment with antibiotics. Twenty-seven patients were given 2 grams of cefamandole intramuscularly 30 minutes before operation and 2 grams every eight hours for two days postoperatively. The remaining patients were in the control group and did not receive antibiotics. Surgical wounds were inspected daily by a surgeon while the patients were in the hospital and a follow-up revision was done four weeks after discharge from the hospital. Samples of exudate or pus were taken when the wound appeared infected and cultures of aerobic and anaerobic organism done. Chi-square affinity test with Yate's correction was used for statistical results; only p values more than or equal to 0.5 were considered significant. Seven patients (28 per cent) in the control group had complications develop postoperatively; seven surgical wound infections, one of which included a subphrenic abscess. Postoperatively, there were no septic complications in the group who received cefamandole as a prophylaxis. The incidence of infection was higher for females than males. The organisms most frequently isolated were Escherichia coli and Klebsiella; only in one instance was Clostridum sporogenes found. Polymicrobial infections accounted for 42.8 per cent of the infections. No incidences were reported with the use of cefamandole in those patients who were treated prophylactically. In view of these results, we believe that cefamandole is an ideal antibiotic to be used in the prophylactic treatment of infections of high risk patients who undergo operations upon the biliary tract.