Detection of diarrheagenic Escherichia coli using a two-system multiplex-PCR protocol

BACKGROUND

Diarrheagenic Escherichia coli (DEC) strains are important causes of diarrhea. However, they cannot be distinguished from E. coli of the intestinal microbiota by conventional microbiological tests.

METHODS

This work presents a two-system multiplex PCR for detection of DEC. Primers for 16S rRNA gene were added as internal amplification control to validate negative reactions. The multiplex-PCR system 1 contains primers for detection of Shiga toxin producing E. coli (STEC; stx1, stx2), enteropathogenic E. coli (EPEC; eae, bfpA), atypical enteropathogenic E. coli (aEPEc; eae), enteroinvasive E. coli (ETEC; lt, st), enteroinvasive E. coli (EIEC; ial), and the internal amplification control 16S rRNA. The system 2 contains primers for EIEC (ipaH), enteroaggregative E. coli (CVD432), diffusely adherent E. coli (daaE), and 16S rRNA. The protocol was tested with E. coli reference strains, and also with cultures of fecal specimens of people with diarrhea and healthy controls.

RESULTS

The protocol correctly identified the DEC reference strains. No DEC marker was amplified for negative controls; these results were validated by the amplification of a fragment of the 16S rRNA gene. The frequency of DEC was 7.6% for both patients and healthy controls; two Shigella sonnei strains were detected in the group with diarrhea. The identity of the amplicons was confirmed by DNA sequencing.

CONCLUSION

The protocol is specific for DEC Shigella and is suitable for clinical laboratories.

Structural Changes in the Subcutaneous Compartment in Morbid Obesity

Most of the excess fat that accumulates in the morbidly obese is accommodated in the subcutaneous compartment (SCC), specifically in the adipose tissue lobules of the panniculus adiposus which enlarge and expand the SCC. However, the fibroelastic septa that are attached to the skin on one side of the SCC and to the deep fascia on the other invest each lobule and thereby offer resistance to the enlarging lobules. We report observations made during pathologic examinations of the abdominal wall SCC that were surgically excised by abdominal dermo-panniculectomy from 48 morbidly obese subjects after gastroplasty and weight loss. Lobules were large but varied notably upwards in size and, to some extent, shape. Simultaneously upon incision of the SCC, the lobules bulged above and the septa retracted below the same cut surfaces. Light microscopy revealed disruptions of septal elastic fibers, calcification of septa and septal arteries and necrosis of adipocytes, all sparsely distributed. Certain questions and facts emerge from these observations. Are the variations in lobule sizes normal, or do they reflect uneven fat deposition or mobilization during weight gain or loss respectively? Is there any correlation between lobule and adipocyte sizes? The tightly coupled phenomena of lobule-bulging and septal-retraction indicate that the lobules and septa are subjected to compressional and tensile stresses respectively in the intact, non-incised SCC. The histologic changes might be consequences of these stresses. Studies of the variations in body fat distribution and in adipocyte size have contributed to an understanding of obesity pathogenesis. The relevance of the present findings is unknown at this time, but these appear to have potential implications for studies of the morphogenesis of obesity. Confirmation of these findings, particularly the lobule variations, is required so that these can be compared with those in never-obese subjects and in morbidly obese subjects without prior weight loss.

Epigenetic changes of CXCR4 and its ligand CXCL12 as prognostic factors for sporadic breast cancer

Chemokines and their receptors are involved in the development and cancer progression. The chemokine CXCL12 interacts with its receptor, CXCR4, to promote cellular adhesion, survival, proliferation and migration. The CXCR4 gene is upregulated in several types of cancers, including skin, lung, pancreas, brain and breast tumors. In pancreatic cancer and melanoma, CXCR4 expression is regulated by DNA methylation within its promoter region. In this study we examined the role of cytosine methylation in the regulation of CXCR4 expression in breast cancer cell lines and also correlated the methylation pattern with the clinicopathological aspects of sixty-nine primary breast tumors from a cohort of Brazilian women. RT-PCR showed that the PMC-42, MCF7 and MDA-MB-436 breast tumor cell lines expressed high levels of CXCR4. Conversely, the MDA-MB-435 cell line only expressed CXCR4 after treatment with 5-Aza-CdR, which suggests that CXCR4 expression is regulated by DNA methylation. To confirm this hypothesis, a 184 bp fragment of the CXCR4 gene promoter region was cloned after sodium bisulfite DNA treatment. Sequencing data showed that cell lines that expressed CXCR4 had only 15% of methylated CpG dinucleotides, while the cell line that not have CXCR4 expression, had a high density of methylation (91%). Loss of DNA methylation in the CXCR4 promoter was detected in 67% of the breast cancer analyzed. The absence of CXCR4 methylation was associated with the tumor stage, size, histological grade, lymph node status, ESR1 methylation and CXCL12 methylation, metastasis and patient death. Kaplan-Meier curves demonstrated that patients with an unmethylated CXCR4 promoter had a poorer overall survival and disease-free survival. Furthermore, patients with both CXCL12 methylation and unmethylated CXCR4 had a shorter overall survival and disease-free survival. These findings suggest that the DNA methylation status of both CXCR4 and CXCL12 genes could be used as a biomarker for prognosis in breast cancer.

Biochemical properties, enterohaemolysin production and plasmid carriage of Shiga toxin-producing Escherichia coli strains

Thirty-eight strains of Shiga toxin-producing Escherichia coli (STEC) were characterised in terms of biochemical properties, enterohaemolysin production and plasmid carriage. A wide variation in the biochemical properties was observed among the STEC, with 14 distinct biotypes identified. Biotype 1 was the most common, found in 29% of the strains. Enterohaemolysin production was detected in 29% of the strains. Most of the bacterial strains (95%) carried one or more plasmids and considerable heterogeneity in size and combinations was observed. Seven distinct plasmid profiles were identified. The most common profile, characterised by the presence of a single plasmid of ~90 kb, was found in 50% of these strains. These data indicate extensive diversity among STEC strains. No correlation was found among biotype, serotype, enterohaemolysin production and plasmid profile.

The involvement of the nif-associated ferredoxin-like genes fdxA and fdxN of Herbaspirillum seropedicae in nitrogen fixation

The pathway of electron transport to nitrogenase in the endophytic beta-Proteobacterium Herbaspirillum seropedicae has not been characterized. We have generated mutants in two nif-associated genes encoding putative ferredoxins, fdxA and fdxN. The fdxA gene is part of the operon nifHDKENXorf1orf2fdxAnifQmodABC and is transcribed from the nifH promoter, as revealed by lacZ gene fusion. The fdxN gene is probably cotranscribed with the nifB gene. Mutational analysis suggests that the FdxA protein is essential for maximum nitrogenase activity, since the nitrogenase activity of the fdxA mutant strain was reduced to about 30% of that of the wild-type strain. In addition, the fdxA mutation had no effect on the nitrogenase switch-off in response to ammonium. Nitrogenase activity of a mutant strain lacking the fdxN gene was completely abolished. This phenotype was reverted by complementation with fdxN expressed under lacZ promoter control. The results suggest that the products of both the fdxA and fdxN genes are probably involved in electron transfer during nitrogen fixation.

ADAM33 gene silencing by promoter hypermethylation as a molecular marker in breast invasive lobular carcinoma

Background

ADAM33 protein is a member of the family of transmembrane glycoproteins composed of multidomains. ADAM family members have different activities, such as proteolysis and adhesion, making them good candidates to mediate the extracellular matrix remodelling and changes in cellular adhesion that characterise certain pathologies and cancer development. It was reported that one family member, ADAM23, is down-regulated by promoter hypermethylation. This seems to correlate with tumour progression and metastasis in breast cancer. In this study, we explored the involvement of ADAM33, another ADAM family member, in breast cancer.

Methods

First, we analysed ADAM33 expression in breast tumour cell lines by RT-PCR and western blotting. We also used 5-aza-2'-deoxycytidine (5azadCR) treatment and DNA bisulphite sequencing to study the promoter methylation of ADAM33 in breast tumour cell lines. We evaluated ADAM33 methylation in primary tumour samples by methylation specific PCR (MSP). Finally, ADAM33 promoter hypermethylation was correlated with clinicopathological data using the chi-square test and Fisher's exact test.

Results

The expression analysis of ADAM33 in breast tumour cell lines by RT-PCR revealed gene silencing in 65% of tumour cell lines. The corresponding lack of ADAM33 protein was confirmed by western blotting. We also used 5-aza-2'-deoxycytidine (5-aza-dCR) demethylation and bisulphite sequencing methodologies to confirm that gene silencing is due to ADAM33 promoter hypermethylation. Using MSP, we detected ADAM33 promoter hypermethylation in 40% of primary breast tumour samples. The correlation between methylation pattern and patient's clinicopathological data was not significantly associated with histological grade; tumour stage (TNM); tumour size; ER, PR or ERBB2 status; lymph node status; metastasis or recurrence. Methylation frequency in invasive lobular carcinoma (ILC) was 76.2% compared with 25.5% in invasive ductal carcinoma (IDC), and this difference was statistically significant (p = 0.0002).

Conclusion

ADAM33 gene silencing may be related to the discohesive histological appearance of ILCs. We suggest that ADAM33 promoter methylation may be a useful molecular marker for differentiating ILC and IDC.

A prospective study on Shiga toxin-producing Escherichia coli in children with diarrhea in Paraná State, Brazil

AIMS

To examine stool specimens from children with diarrhea from Paraná State, southern Brazil, for presence of STEC.

METHODS AND RESULTS

A PCR screening assay for stx genes was used to examine a loopful of confluent colonies of 306 stool samples cultures. In six (1.96%) of them, DNA fragments of the expected size were observed, and the presence of stx was confirmed by DNA sequencing. Then up to 100 single colonies from each of the six stool cultures were analyzed using the same PCR protocol. However, stx-positive colonies were found only in two of the cultures. The E. coli strains belonged to serotypes O69:H11 and O178:H19, and presented genotypes stx(1)eae ehxA and stx(1) respectively. Shiga toxin production was confirmed using the VTEC Screen Seiken. Except ampicillin, they were susceptible to all the antimicrobials tested.

CONCLUSIONS

These results show that STEC may be an important cause of diarrhea in children of Paraná State, and that they are present in low numbers in stools. The strains belonged to serotypes not commonly found associated with STEC and probably present low virulence.

SIGNIFICANCE AND IMPACT OF STUDY

These results indicate that molecular methods are required to diagnosis of STEC infections.

Effect of anntrCmutation on amino acid or urea utilization and on nitrogenase switch-off inHerbaspirillum seropedicae

Herbaspirillum seropedicae is a nitrogen-fixing bacterium that grows well with ammonium chloride or sodium nitrate as alternative single nitrogen sources but that grows more slowly with l-alanine, l-serine, l-proline, or urea. The ntrC mutant strain DCP286A was able to utilize only ammonium or urea of these nitrogen sources. The addition of 1 mmol·L–1ammonium chloride to the nitrogen-fixing wild-type strain inhibited nitrogenase activity rapidly and completely. Urea was a less effective inhibitor; approximately 20% of nitrogenase activity remained 40 min after the addition of 1 mmol·L–1urea. The effect of the ntrC mutation on nitrogenase inhibition (switch-off) was studied in strain DCP286A containing the constitutively expressed gene nifA of H. seropedicae. In this strain, nitrogenase inhibition by ammonium was completely abolished, but the addition of urea produced a reduction in nitrogenase activity similar to that of the wild-type strain. The results suggest that the NtrC protein is required for assimilation of nitrate and the tested amino acids by H. seropedicae. Furthermore, NtrC is also necessary for ammonium-induced switch-off of nitrogenase but is not involved in the mechanism of nitrogenase switch-off by urea.

Nitrogenase switch-off by ammonium ions in Azospirillum brasilense requires the GlnB nitrogen signal-transducing protein

Nitrogenase activity in several diazotrophs is switched off by ammonium and reactivated after consumption. The signaling pathway to this system in Azospirillum brasilense is not understood. We show that ammonium-dependent switch-off through ADP-ribosylation of Fe protein was partial in a glnB mutant of A. brasilense but absent in a glnB glnZ double mutant. Triggering of inactivation by anaerobic conditions was not affected in either mutant. The results suggest that glnB is necessary for full ammonium-dependent nitrogenase switch-off in A. brasilense.

Nitrogenase activity of Herbaspirillum seropedicae grown under low iron levels requires the products of nifXorf1 genes

Herbaspirillum seropedicae strains mutated in the nifX or orf1 genes showed 90% or 50% reduction in nitrogenase activity under low levels of iron or molybdenum respectively. Mutations in nifX or orf1 genes did not affect nif gene expression since a nifH::lacZ fusion was fully active in both mutants. nifX and the contiguous gene orf1 are essential for maximum nitrogen fixation under iron limitation and are probably involved in synthesis of nitrogenase iron or iron-molybdenum clusters.

Control of nitrogenase reactivation by the GlnZ protein in Azospirillum brasilense

The glnZ mutant of Azospirillum brasilense (strain 7611) showed only partial recovery (20 to 40%) after 80 min of ammonia-induced nitrogenase switch-off, whereas the wild type recovered totally within 10 min. In contrast, the two strains showed identical anoxic-induced switch-on/switch-off, indicating no cross talk between the two reactivation mechanisms.

Recent developments in the structural organization and regulation of nitrogen fixation genes in Herbaspirillum seropedicae

Herbaspirillum seropedicae is a nitrogen-fixing bacterium found in association with economically important gramineae. Regulation of nitrogen fixation involves the transcriptional activator NifA protein. The regulation of NifA protein and its truncated mutant proteins is described and compared with that of other nitrogen fixation bacteria. Nitrogen fixation control in H. seropedicae, of the beta-subgroup of Proteobacteria, has regulatory features in common with Klebsiella pneumoniae, of the gamma-subgroup, at the level of nifA expression and with rhizobia and Azospirillum brasilense, of the alpha-subgroup, at the level of control of NifA by oxygen.

Small bowel obstruction from internal hernia as a complication of colonoscopy

After colonoscopy with polypectomy, a patient developed a surgically acute abdomen. Although abdominal radiology did not show free air, a presumptive diagnosis of bowel perforation was made and laparotomy performed. At the time of surgery the colon was normal, and there was no peritoneal contamination. A loop of ileum was discovered incarcerated into an internal paracecal hernia. The bowel was freed, and the operation was completed without need for resection. Several cases of incarcerated inguinal hernia resulting from endoscopy are described in the medical literature; this is the first reported case of an incarcerated internal hernia as a complication of colonoscopy.

Sequencing and functional analysis of the nifENXorf1orf2 gene cluster of Herbaspirillum seropedicae

A 5.1-kb DNA fragment from the nifHDK region of H. seropedicae was isolated and sequenced. Sequence analysis showed the presence of nifENXorf1orf2 but nifTY were not present. No nif or consensus promoter was identified. Furthermore, orf1 expression occurred only under nitrogen-fixing conditions and no promoter activity was detected between nifK and nifE, suggesting that these genes are expressed from the upstream nifH promoter and are parts of a unique nif operon. Mutagenesis studies indicate that nifN was essential for nitrogenase activity whereas nifXorf1orf2 were not. High homology between the C-terminal region of the NifX and NifB proteins from H. seropedicae was observed. Since the NifX and NifY proteins are important for FeMo cofactor (FeMoco) synthesis, we propose that alternative proteins with similar activities exist in H. seropedicae.

Outcomes of coronary artery bypass surgery in elderly people

OBJECTIVES

To document the impact of coronary artery bypass (CABG) surgery on quality of life in elderly people three months after surgery; to compare quality of life measures; to examine predictors of poor quality of life; and to assess the predictive validity of global clinical rating scales.

STUDY DESIGN

Prospective cohort study with postoperative, three-month and one-year follow-up.

SETTING

A 700-bed tertiary care teaching hospital in Halifax, Nova Scotia.

PATIENTS

One hundred of 200 consecutive patients, 75 years and older, undergoing CABG.

MEASURES

Demographic information, clinical data and global clinical ratings were collected at baseline to assess risk for adverse outcome (death, stroke, functional impairment) at each follow-up. Quality of life three months post-CABG was documented using the RAND 36-Item Health Survey and the Seattle Angina Questionnaire.

MAIN RESULTS

Perioperative deaths occurred in four patients, disabling strokes in six and postoperative complications in seven. Three additional deaths occurred by the three-month follow-up and nine more by one year. On average, important improvements in quality of life were observed at three months' follow-up, using both assessments of quality of life.

CONCLUSIONS

Many elderly patients do well after CABG surgery, but a higher proportion than is seen in younger patients have complications leading to death and disability. A global clinical measure by the attending cardiologist at baseline did not identify patients at a higher risk. Follow-up studies are needed to assess long term outcomes of older patients at higher risk of death or a poor quality of life after CABG surgery.

Effect of nitrogen compounds on nitrogenase activity inHerbaspirillum seropedicaeSMR1

The effect of nitrogen compounds on growth and nitrogenase activity of Herbaspirillum seropedicae SMR1 was determined. L-Glutamate or L-glutamine as sole nitrogen sources supported growth, and nitrogenase activity was observed only after exhaustion of L-glutamate or L-glutamine from the culture medium. L-Serine, L-alanine, or ammonium chloride supported growth but not acetylene reduction activity. No growth was observed with L-histidine, L-lysine, L-arginine, or with the amines methylammonium chloride, tetramethylammonium chloride, or ethylenediamine chloride. All the compounds promoted the switch off of nitrogenase activity except L-histidine, L-lysine, or L-arginine, which were not taken up. The results showed that H. seropedicae cannot utilize exogenously added L-histidine, L-arginine, L-lysine, methylammonium chloride, tetramethylammonium chloride, or ethylediamine as the sole N source for growth. The inability of the positively charged amino acids to promote nitrogenase switch off might be a result of the lack of transport systems and the eventual further metabolism of these compounds.Key words: Herbaspirillum seropedicae, nitrogenase inactivation, amino compounds uptake.

Stress, coping, and social support as psychosocial factors in readmissions for ischaemic heart disease

This exploratory investigation aimed to identify psychological and social factors associated with early (4 months postdischarge) readmission to hospital of persons with ischaemic heart disease (IHD). Data on stress (Stress Appraisal Scale), coping strategies (Ways of Coping Questionnaire), and social network/social support (Norbeck Social Support Questionnaire) were collected from 100 persons with the primary diagnosis of IHD prior to discharge from hospital. Twenty-four persons were readmitted during the 4-month study period. The sample was divided into two groups for analysis: (1) persons with a first admission for IHD, and (2) persons with a prior history of admission for IHD. In comparison to persons with multiple admissions for cardiac illness, first time admissions appraised their IHD as less central and threatening, perceived less affective and affirmational support from health professionals, and identified health professionals less and neighbours more as sources of support. Greater use of the coping strategy 'seeking social support' was associated with the readmission of persons who had had their first admission for IHD. Less use of the coping strategy 'accepting responsibility' was associated with the readmission of persons who had a history of prior admission for IHD.

Cross-national interrater agreement on the clinical diagnostic criteria for dementia. WHO-PRA Age-Associated Dementia Working Group, WHO-Program for Research on Aging, Health of Elderly Program

We assessed the interobserver agreement on the clinical diagnosis of dementia syndrome and dementia subtypes as part of a cross-national project on the prevalence of dementia. Fourteen clinicians from the participating countries (Canada, Chile, Malta, Nigeria, Spain, and the United States) independently assessed the diagnosis of 51 patients whose clinical information was in standard records written in English. We used the DSM-III-R and ICD-10 criteria for dementia syndrome, the NINCDS-ADRDA criteria for Alzheimer's disease (AD), and the ICD-10 criteria for other dementing diseases, and measured interobserver agreement. We found comparable levels of agreement on the diagnosis of dementia using the DSM-III-R (kappa = 0.67) as well as the ICD-10 criteria (kappa = 0.69). Cognitive impairment without dementia was a major source of disagreement (kappa = 0.10). The kappa values were 0.58 for probable AD, 0.12 for possible AD, and rose to 0.72 when the two categories were merged. The interrater reproducibility of the diagnosis of vascular dementia was 0.66 in terms of kappa index; the diagnoses of other dementing disorders as a whole reached a kappa value of 0.40. This study suggests that clinicians from different cultures and medical traditions can use the DSM-III-R and the ICD-10 criteria for dementia effectively and thus reliably identify dementia cases in cross-national research. The interrater agreement on the diagnosis of dementia might be improved if clear-cut guidelines in the definition of cognitive impairment are provided. To improve the reliability of AD diagnosis in epidemiologic studies, we suggest that the NINCDS-ADRDA "probable" and "possible" categories be merged.

Characterization of the ribosomal DNA from Trichinella spiralis

Ribosomal DNA (rDNA) from three isolates of Trichinella was cloned into phage and sublcloned into the plasmid pBR322. The basic repeat unit of rDNA was variable in size, with the mapped clones ranging from 10-12 kb. There were differences in restriction sites within the genic region among the three isolates which were due to variations in the internal transcribed region (ITS) and the intergenic spacer (IGS). Three RsaI sites were mapped to the IGS repeat unit of the isolate AF1, and one RsaI site was mapped to the IGS repeat unit of Trichinella spiralis pseudospiralis (isolate Tp). The number of repetitive units in the IGS region varied markedly within and between the isolates. It was estimated that the basic repeat unit for the rDNA of isolate P1 was 10.6-28 kb, for AF1 10.7-37 kb, and for Tp it was 11-14.9 kb. There appeared to be a greater frequency of some sizes of the basic repeat unit in each of the populations, based on the relative intensity with which certain bands hybridize to the probe.

The effects of partial chronic denervation on forearm metabolism

Effects of chronic denervation upon in vivo forearm metabolism were studied in six patients and six controls. The diagnosis was amyotrophic lateral sclerosis in four patients, the neuronal form of Charcot-Marie Tooth disease in one patient, and an unclassified chronic disease of the lower motor neurons in one patient. In all cases the forearm muscles showed clinical weakness and electrical evidence of denervation, while muscle biopsy from a proximal muscle of the upper limb showed typical denervation atrophy. At rest there was increased oxygen utilization and lactate output as well as a tendency for increased uptake of glucose and long chain fatty acids from arterial blood per 100 ml of forearm tissue. During exercise the abnormally high lactate output increased further. An increased arterial lactate concentration was present during rest and exercise. Oxidation of fatty acids was not impaired. It is suggested that these abnormalities are consistent with an augmented utilization of blood borne fuels at rest by denervated muscles. A concurrent regional ischemia of muscles during rest and exercise, possibly due to defective autoregulation of skeletal muscle blood flow, may explain the abnormally high lactate generation.

Methadone-induced pulmonary edema

A patient with methadone-induced pulmonary edema had increased extravascular water in the lungs and a reduced total vascular albumin space. Diuresis resulted in hypotension. These observations suggest that the appropriate treatment of this condition should be ventilatory support and restoration of plasma oncotic pressure with albumin. Diuretic therapy should be used with caution.

The syndrome of systemic carnitine deficiency. Clinical, morphologic, biochemical, and pathophysiologic features

An 11-year old boy had had recurrent episodes of hepatic and cerebral dysfunction and underdeveloped musculature. Overt weakness developed at age 10. Lipid excess, especially in type I fibers, was found in muscle. Hypertrophied smooth endoplasmic reticulum and excessive microbodies were present in liver. Marked carnitine deficiency was shown in skeletal muscle, plasma, and liver. Ketogenesis was impaired on a high fat diet, but omega oxidation of fatty acids was enhanced. There was excessive glucose uptake and essentially no oxidation of labeled long-chain fatty acids by perfused forearm muscles in vivo. Oral replacement therapy restored plasma carnitine levels to normal, but not liver or muscle carnitine levels, and was accompanied by clinical improvement.