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H R Smith

Publications and source records attributed to H R Smith.

At least 145 records · Page 8Linked to original sources
PubMed1992

Virulence properties of Enterobacteriaceae isolated from the small intestine of children with diarrhea.

Enterobacteriaceae isolated from the duodena of Peruvian children with persistent diarrhea (PD) have been examined for virulence factors and compared with Enterobacteriaceae isolated from children with acute diarrhea, those convalescent from PD and diarrhea-free controls. Escherichia coli were isolated from 42 of 186 (23%) of the aspirates. All 11 children with PD in whom multiple E. coli colonies were examined were colonized by a single serotype. DNA probes identified enterotoxigenic E. coli in 2 of 89 (2.2%) PD aspirates and 2 of 38 (5.3%) acute diarrhea aspirates and enteroaggregative E. coli in one PD and one control aspirate. Strains positive with the enteropathogenic E. coli adherence factor probe were identified from 2 of 89 (2.2%) patients with PD and 1 of 34 (2.9%) controls. A subset of 12 E. coli strains failed to show adhesion to human duodenal enterocytes although 5 of 9 showed sparse but polar attachment to ileal cells from a child with short bowel syndrome and PD. Three of 10 Enterobacteriaceae (two E. coli, one Klebsiella species) caused diarrhea in the reversible ileal tie adult rabbit model. Colonization with virulent Enterobactericeae did not explain the majority of episodes of PD. Examination of these duodenal bacteria in the rabbit model revealed some that caused diarrhea but were not recognized pathogens.

Bacterial Toxins↗
PubMed1991

cDNA cloning of mouse NKR-P1 and genetic linkage with LY-49. Identification of a natural killer cell gene complex on mouse chromosome 6.

NK cells lyse tumor cells and virally infected cells, but the molecular basis for this phenomenon has not been defined. A mAb specific for the rat cell surface molecule, NKR-P1, stimulates rat NK cell lytic activity and is reactive with all rat NK cells, suggesting that this molecule may play a significant role in NK cell function. We have previously described another NK cell-specific Ag, Ly-49, that belongs to a family of cross-hybridizing genes on distal mouse chromosome 6. The rat NKR-P1 Ag shares several features with the mouse Ly-49 Ag, including selective cell surface expression on NK cells, homology to the C-type lectins, expression as a type II integral membrane protein, and disulfide-linked homodimeric structure. To further examine the relationship of NKR-P1 to Ly-49, we have cloned the cDNA encoding a mouse homologue of NKR-P1 (mNKR-P1). The mouse and rat NKR-P1-deduced polypeptide sequences are highly conserved, suggesting a similar tertiary structure. By examination of DNA from informative recombinant inbred mice with Southern blot analysis, we have determined that mNKR-P1 is encoded by a distinct gene that is genetically linked to the Ly-49 locus, lying within 0.5 centi-Morgan (cM) of Ly-49. Although the deduced amino acid sequences of mNKR-P1 and Ly-49 reveal that these proteins are structurally similar, they are only 24% identical at the amino acid level and the cDNA sequences do not demonstrate significant nucleotide homology. Our studies suggest that we have identified a region on mouse chromosome 6 that includes distinct NK-specific genes that encode structurally related proteins (type II integral membrane proteins, C-type lectin super-gene family) but which demonstrate considerable heterogeneity. We have termed this genetic region the NK complex.

Amino Acid Sequence↗
PubMed1991

Cloning of regulator genes controlling fimbrial production by enterotoxigenic Escherichia coli.

Sequences regulating production of fimbriae were cloned from two enterotoxigenic Escherichia coli strains. One cloned region, from E. coli 0.25.H42, controlled expression of coli surface-associated (CS) antigen 4, whereas the function of the other, from E. coli 0167.H5, was unclear. Both regulators were related to the cfaD gene that controls expression of colonization factor antigen I (CFA/I) although low stringency conditions were required to show significant hybridization between cfaD and the regulatory fragment from E. coli 0167. The cloned regulatory genes promoted expression of CFA/I, CS1, CS2 and CS4 antigens but the levels of production in the presence of the 0167 regulator were lower than those promoted by the CS4 regulator or cfaD.

Antigens, Bacterial↗
PubMed1991

Serological identification of Escherichia coli O157:H7 infection in haemolytic uraemic syndrome.

To test the value of serological tests as an adjunct to bacteriological methods and toxin testing in haemolytic uraemic syndrome (HUS), 60 patients with the disorder were examined for evidence of faecal Escherichia coli producing verocytotoxin (VTEC), particularly of serogroup O157. They were also tested for serum antibodies reacting with the lipopolysaccharide of E coli O157 by means of an enzyme-linked immunosorbent assay (ELISA) and immunoblotting; for faecal VTEC by means of DNA probes hybridising with the genes encoding verocytotoxins VT1 and VT2; and for "free" faecal VT. Strains of E coli serotype O157:H7 were isolated from 9 patients, and faecal VT2 was detected in 3 of them. Strains of E coli of serotypes 05:H-, O55:H10, O105ac:H18, and O163:H19 were isolated from 4 patients, but faecal VT was not detected. Faecal VT2 was present in 1 patient from whom VTEC were not isolated. Antibodies to the lipopolysaccharide of E coli O157 were detected in serum samples from 44 patients. The 9 patients with faecal O157:H7 all had high titres of these antibodies, but serum samples from 16 healthy control children were negative. Serological testing of patients with HUS for antibodies to the lipopolysaccharide of E coli O157 provides evidence of infection with E coli O157 when faecal bacteria or VT cannot be detected.

Antibodies, Bacterial↗
PubMed1991

Applications of DNA probes for Vero cytotoxin-producing Escherichia coli.

Vero cytotoxin-producing Escherichia coli (VTEC) are now recognized as important aetiological agents in human disease. The symptoms of VTEC infection range from mild non-bloody diarrhoea to severe conditions such as haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS). Two types of Vero cytotoxin (VT), VT1 and VT2, have been identified. The genes controlling production of VT1 and VT2 are phageencoded in several E. coli strains and DNA probes have been developed from cloned genes derived from these VT phages. Recently, synthetic oligonucleotide probes for VTEC have also been prepared and evaluated. The VT probes have been labelled radioactively and also non-radioactively with digoxigenin and biotin. Present applications of VT probes include detection of VTEC in faecal samples from patients with diarrhoea, HC or HUS and also the examination of different foods for the presence of VTEC. The proportion of VTEC in the faecal flora or foods may be low, often less than 1%. The use of DNA probes allows several hundred colonies from a sample to be examined and by this technique VT genes were detected in 30-40% of faecal specimens from patients with HC or HUS. Use of methods such as the polymerase chain reaction for amplification of the target genes combined with DNA probes should result in an increased sensitivity for the detection of VTEC.

Bacterial Toxins↗
PubMed1991

Non-radioactively labelled polynucleotide and oligonucleotide DNA probes, for selectively detecting Escherichia coli strains producing Vero cytotoxins VT1, VT2 and VT2 variant.

Vero cytotoxin producing Escherichia coli (VTEC) were detected in faecal specimens and bacterial isolates, using non-radioactively labelled polynucleotide and oligonucleotide DNA probes specific for Vero cytotoxin (VT) genes. VT1 and VT2 structural gene sequences, previously cloned and used for radioactive probes, were labelled with digoxigenin or biotin. Oligonucleotide gene sequences coding for the A subunit of VT1, VT2 and VT2 variant were labelled with digoxigenin. The VT1 and VT2 probes were specific for detecting VT1 and VT2 gene sequences and gave very similar results to those obtained using the radioactive label 35S as a standard. The VT2 variant probe hybridized only with the strains of porcine origin. For the range of isolates tested, there was little significant difference in specificity and sensitivity between the digoxigenin-labelled polynucleotide and oligonucleotide probes. The biotin system gave rise to more non-specific effects, particularly with some non-E. coli strains, and was therefore less reliable. All of the digoxigenin-labelled probes gave satisfactory results after several times re-use, which is of importance when considering cost.

Bacterial Toxins↗
PubMed1991

Positive regulation of colonization factor antigen I (CFA/I) production by enterotoxigenic Escherichia coli producing the colonization factors CS5, CS6, CS7, CS17, PCFO9, PCFO159:H4 and PCFO166.

Entertoxigenic Escherichia coli (ETEC) strains of nineteen serogroups which produced colonization factors (coli-surface-associated antigens CS5, CS6, CS7 and CS17, colonization factor antigen CFA/III and putative colonization factors PCFO159:H4, PCFO166 and PCFO9) were tested for hybridization with a DNA probe containing the cfaD sequence that regulates expression of CFA/I. Strong colony hybridization, similar to that with the CFA/I-positive control strain H10407, occurred with ETEC strains of serogroups O27, O159 and O169 which produced CS6 antigen, and with all the strains which produced PCFO166 fimbriae. Weak colony hybridization, compared to the control strain, was found with ETEC producing CS5 fimbriae with CS6 antigen, CFA/III fimbriae with CS6 antigen, CS7 fimbriae or PCFO159:H4 fimbriae. CS6-antigen-positive strains of serogroups O79, O89 and O148 and all the CS17-antigen-positive and PCFO9-fimbriae-positive strains were negative in colony hybridization tests with the cfaD probe. Plasmid DNA of nine ETEC strains and their colonization-factor-negative derivatives was tested for hybridization with the cfaD probe and with ST and LT oligonucleotide probes. The sequences that hybridized with the cfaD probe were on the plasmids which coded for enterotoxin production. Fifteen strains were transformed with NTP513, a recombinant plasmid which contains the CFA/I region 1 fimbrial subunit operon but lacks a functional cfaD sequence, in order to determine whether DNA in any of these strains could substitute for the cfaD sequence in the regulation of production of CFA/I fimbriae.(ABSTRACT TRUNCATED AT 250 WORDS)

Agglutination Tests↗
PubMed1991

Identification of enteropathogenic Escherichia coli isolated in Britain as enteroaggregative or as members of a subclass of attaching-and-effacing E. coli not hybridising with the EPEC adherence-factor probe.

Strains of Escherichia coli from sporadic cases of diarrhoea and belonging to serotypes O44:H18, O55:H7, O111ab:H21, O111ab:H25 or O126:H27 were examined for virulence properties. With the exception of O111ab:H25 these are considered to be classical enteropathogenic E. coli (EPEC) serotypes. The strains had been isolated in Britain from the faeces of children less than 3 years old. Of the serotypes examined, 7 of 13 O44:H18 strains, all of 10 O111ab:H21 strains and 13 of 21 O126:H27 strains belonged to the enteroaggregative class of E. coli (EAggEC) that attached to HEp-2 cells in the characteristic aggregative pattern and hybridised with the EAggEC probe. They also caused mannose-resistant haemagglutination of rat erythrocytes, a property which may be a useful marker for their identification. Strains of O44:H18 with similar properties were also isolated from three small outbreaks in Britain, one of which involved elderly patients. EAggEC have not been considered previously as aetiological agents of diarrhoea in developed countries and have rarely been reported as belonging to EPEC serotypes. All 15 O55:H7 strains and seven of eight O111ab:H25 strains were also considered to be potentially diarrhoeagenic as they gave localised attachment (LA) to HEp-2 cells that resulted in a positive fluorescence actin-staining test. This test is considered to correlate with the attaching-and-effacing virulence mechanisms of EPEC in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Examination of retail chickens and sausages in Britain for vero cytotoxin-producing Escherichia coli.

Samples from chickens and pork sausages were examined for the presence of Vero cytotoxin-producing Escherichia coli by using DNA probes for the Vero cytotoxin genes. Hybridization was detected in 25% of the 184 sausage samples, but none of the chickens was positive. No E. coli O157:H7 strains were isolated, and serotyping showed that the Vero cytotoxin-producing E. coli strains belonged to eight different O serogroups and that six strains had an unidentifiable O antigen.

Animals↗
PubMed1991

Screening for enteropathogenic Escherichia coli in infants with diarrhea by the fluorescent-actin staining test.

The attaching effacing (AE) adherence property is now recognized as an important virulence characteristic of enteropathogenic Escherichia coli (EPEC). The fluorescent-actin staining (FAS) test (S. Knutton, T. Baldwin, P. H. Williams, and A. S. McNeish, Infect. Immun. 57:1290-1298, 1989), which is diagnostic for the AE lesions produced by EPEC (and Vero cytotoxin-producing E. coli), has provided an additional tool with which to investigate this important class of enteric pathogens. In this study, we screened for the AE adherence property in two groups of E. coli isolated from infants with diarrhea by using the FAS test and compared the results with those from O:H serotyping, localized adhesion to HEp-2 cells (LA), and the EPEC adherence factor (EAF) probe. Only 16 of 41 (39%) E. coli strains previously diagnosed as EPEC by O antigen serogrouping were FAS test positive, and of these only 12 belonged to recognized EPEC O:H serotypes; 9 strains which did belong to EPEC O:H serotypes were FAS test negative. Of a second group of 297 untyped E. coli, 7 (2.3%) were FAS test positive, and of these only 2 belonged to EPEC serogroups; 5 belonged to serogroups not regarded as EPEC serogroups or were nontypeable. Of the 23 FAS-test-positive strains identified, 10 were EAF probe positive and showed good LA; 13 were EAF probe negative and showed a quantitatively distinctly poor LA. EAF-positive and EAF-negative strains, however, showed equally good adhesion to human small intestinal mucosa. None of the FAS-test-positive E. coli hybridized with probes for Vero toxins 1 or 2. We conclude that the FAS test is diagnostic not only for classical EPEC and Vero cytotoxin-producing E. coli but also for EPEC strains which are not currently being diagnosed because they belong to serotypes not generally regarded as EPEC serotypes.

Actins↗
PubMed1991

Escherichia coli O128 strains from infants with diarrhea commonly show localized adhesion and positivity in the fluorescent-actin staining test but do not hybridize with an enteropathogenic E. coli adherence factor probe.

Twenty-nine strains of Escherichia coli O128 isolated from infants with diarrhea that did not produce heat-stable enterotoxin, heat-labile enterotoxins, or Vero cytotoxin showed localized attachment to HEp-2 cells (LA). Only four strains hybridized with the enteropathogenic E. coli adherence factor (EAF) probe. One of the 25 LA+ EAF- strains attached to 72% of cells, while a plasmid-negative variant attached to 0.5% of cells. LA+ EAF- and LA+ EAF+ strains gave a positive fluorescent-actin staining test that correlates with the ability to cause attaching and effacing lesions in the intestine. The use of the EAF probe alone to detect LA+ strains is inadequate for epidemiological studies.

Actins↗
PubMed1991

Airways inflammation in nocturnal asthma.

Nocturnal asthma is a frequent problem, but the mechanism is unclear. We investigated the possibility that airways inflammation occurred during the night. Bronchoalveolar lavage fluid was analyzed in asthmatic patients with (n = 7) and without nocturnal asthma (n = 7) at 1600 and 0400 h. The nocturnal asthma group had an increase in the total leukocyte count (24.0 +/- 7.0 to 41.1 +/- 9.9 x 10(4) cells/ml, p less than 0.05), neutrophils (1.1 +/- 0.6 to 3.7 +/- 1.5 x 10(4) cells/ml, p less than 0.05), and eosinophils (0.5 +/- 0.1 to 1.7 +/- 0.7 x 10(4) cells/ml, p less than 0.05) from 1600 to 0400 h. Cellular components for the non-nocturnal asthma group did not change. Between groups, the 1600-h cells were similar. At 0400 h the nocturnal asthma group had significantly higher total leukocyte, neutrophil, eosinophil, lymphocyte, and epithelial cell counts. For all subjects, the overnight fall in peak expiratory flow rates was correlated to the change in neutrophils (r = 0.54, p less than 0.05) and eosinophils (r = 0.77, p less than 0.05). We conclude that the nocturnal worsening of asthma has an associated cellular inflammatory response that is not seen in patients without overnight decrements in lung function. This inflammatory response together with epithelial damage may be important factors in the etiology of nocturnal asthma.

Asthma↗
PubMed1991

Urinary leukotriene E4 in patients with asthma. Effect of airways reactivity and sodium cromoglycate.

A group of 17 patients with allergic asthma was challenged with aerosolized antigen, and the excretion of the peptidoleukotriene metabolite leukotriene (LT) E4 in the urine was determined as an index of leukotriene synthesis. The allergen challenge caused a drop in FEV1 of 25 to 59% within the first 2 h in all patients. This was associated with an increase in urine LTE4 excretion during the subsequent 12 h. The amount of urinary LTE4 excreted increased from a 12-h baseline level of 46 +/- 6.8 ng to a postallergen challenge level of 92 +/- 13 ng. In a similar experimental protocol methacholine challenge alone did not significantly increase urinary LTE4 excretion. In comparing all individuals as a group, there was no significant positive correlation between the magnitude of the drop in FEV1 during the immediate asthmatic response (IAR) and the increased amount of LTE4 excreted in the urine (p = 0.08). These parameters were still not significantly correlated when airways reactivity (log PC20) was also considered (p = 0.057). However, when each individual was compared to self in the presence and absence of cromoglycate, a significant correlation was found to exist between the drop in FEV1 during the IAR, the excretion of urinary LTE4, and the airways reactivity. No correlation was found between the increase in urine LTE4 excreted during the 12 h following allergen challenge and the severity of late (3 to 12 h) responses to allergen, but there was a significant prolonged (12 to 36 h) elevated urine LTE4 excretion in those patients with the most severe late asthmatic response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Palpable purpura and uveitis precipitated by splenectomy in an atypical case of Cogan's syndrome.

A patient with a baffling multisystem illness developed uveitis and palpable purpura shortly after a splenectomy, leading to the diagnosis of vasculitis. Clearance by the mononuclear phagocyte system is a key factor determining the pathogenicity of circulating immune complexes, which are known to be the cause of some forms of vasculitis. The sudden appearance of uveitis and cutaneous vasculitis in an illness of many years' duration was probably a direct result of removal of the spleen.

Hearing Disorders↗
PubMed1990

Structural and regulatory genes for coli surface associated antigen 4 (CS4) are encoded by separate plasmids in enterotoxigenic Escherichia coli strains of serotype 0.25.H42.

Two enterotoxigenic Escherichia coli strains of serotype 0.25.H42 that produced coli surface associated antigens CS4 and CS6 hybridized with a probe containing the cfaD sequence that regulates expression of colonization factor antigen CFA/I. Transformation of a cloned cfaD gene into some derivatives of the strains that were negative for CS4 and CS6 resulted in expression of CS4 but not CS6. By hybridization the sequence that regulated CS4 production in the wild type 025 strains was located on a plasmid that also encoded the CS6 antigen. The structural genes for the CS4 antigen were on a separate plasmid. The 025 strains carried a third plasmid encoding enterotoxin production which was therefore unlinked to regulation sequences or genes encoding CS antigens.

Antigens, Bacterial↗
PubMed1990

A silent regulatory gene cfaD' on region 1 of the CFA/I plasmid NTP 113 of enterotoxigenic Escherichia coli.

A DNA sequence, homologous to the cfaD gene of CFA/I region 2, was identified on CFA/I region 1. This sequence is designated cfaD'. It differs from the cfaD gene in containing two deletions and a stop codon. The cfaD' sequence therefore can only encode a truncated CfaD-like protein. The CfaD protein may be a DNA binding protein and functions as a positive regulator of CFA/I fimbriae expression. A regulatory function for the cfaD' is not likely since deletion of the cfaD' sequence does not affect production of CFA/I fimbriae in E. coli K-12 strains. That the cfaD' sequence is present on CFA/I wild-type plasmids isolated from CFA/I strains of different serotypes, obtained at various geographical locations, suggests, however, that this DNA region is not completely without a function.

Antigens, Bacterial↗
PubMed1990

Plasmid-encoded production of coli surface-associated antigen 1 (CS1) in a strain of Escherichia coli serotype O139.H28.

Production of coli surface-associated antigen 1 (CS1) by Escherichia coli strain E24377 of serotype O139.H28 was controlled by a plasmid that also encoded heat stable and heat labile enterotoxins and CS3. The presence of a regulatory sequence was detected on this plasmid by hybridization with the cfaD gene that regulates expression of colonization factor antigen I fimbriae and is at least 96% homologous with the rns sequence controlling production of CS1 or CS2 fimbriae by strains of serotype O6.H16 of appropriate biotype. A separate plasmid, pDEP20, carrying the structural genes for CS1 synthesis was identified and transformed into E. coli strain HB101 or a derivative of strain E24377 without large plasmids. Transformants carrying pDEP20 did not produce CS1 fimbrial antigen, but antigen expression was obtained when a cloned cfaD gene or a wild-type plasmid carrying the rns sequence was introduced. Transposon mutagenesis with Tn1000 identified a 3.7 kbp region of pDEP20 essential for production of CS1 fimbriae. Genes encoding production of CS1 fimbriae were cloned on a 9.9 kbp BamHI fragment and were expressed in the presence of the cfaD sequence. A strain producing both CS1 and CS2 antigens was constructed by introduction of the cloned cfaD gene into a strain of serotype O6.H16 biotype C carrying plasmid pDEP20.

Antigens, Bacterial↗