Biomedical subjects

J M Simpson

Publications and source records attributed to J M Simpson.

At least 37 records · Page 2Linked to original sources

PubMed2003

Review of diagnosis, treatment, and outcome of fetal atrial flutter compared with supraventricular tachycardia.

OBJECTIVE: To review the diagnosis, treatment, and outcome of fetal atrial flutter compared with supraventricular tachycardia. DESIGN: Retrospective review of published reports: 11 papers about fetal tachyarrhythmia published between 1991 and 2002 were selected for review. MAIN OUTCOME MEASURES: All selected studies were analysed for the type of arrhythmia, degree of atrioventricular block in atrial flutter, occurrence of hydrops fetalis, gestational age at diagnosis, first and second line drug treatment, associated cardiac and extracardiac malformations, and mortality of the fetuses. RESULTS: Atrial flutter accounted for 26.2% of all cases of fetal tachyarrhythmias, and supraventricular tachycardia for 73.2%. Hydrops fetalis was reported in 38.6% and 40.5% of fetuses with atrial flutter and supraventricular tachycardia, respectively (NS). Hydropic fetuses with atrial flutter had higher ventricular rates (median 240 beats/min, range 240-300) than non-hydropic fetuses (220 beats/min, range 200-310) (p = 0.02), whereas the atrial rates were not significantly different (median 450 beats/min, range 370-500). Digoxin treatment resulted in a higher conversion rate in non-hydropic fetuses with fetal tachyarrhythmias than in hydropic fetuses (p < 0.001). The overall mortality of atrial flutter was similar to that of supraventricular tachycardia, at 8.0% v 8.9% (p = 0.7). CONCLUSIONS: The prevalence of hydrops fetalis did not differ in fetal atrial flutter and supraventricular tachycardia with 1:1 conduction. There was no difference between the response rate to digoxin in fetus with atrial flutter or supraventricular tachycardia. Mortality was similar in the two types of tachyarrhythmia.

Anti-Arrhythmia Agents↗

PubMed2003

Analysing differences in clinical outcomes between hospitals.

OBJECTIVE: To examine the variation between hospitals in rates of severe intraventricular haemorrhage (IVH) in preterm babies adjusting for case mix and sampling variability. DESIGN: Cross sectional study of pooled data from 1995 to 1997. SETTING: 24 neonatal intensive care units (NICUs) in the Australian and New Zealand Neonatal Network. PARTICIPANTS: 5413 infants of gestational age 24-30 weeks. MAIN OUTCOME MEASURES: Crude rates of severe (grades 3 and 4) IVH and rates adjusted for case mix using logistic regression, and for sampling variability using shrinkage estimators. RESULTS: The overall rate of severe IVH was 6.8%, but crude rates for individual units ranged from 2.9 to 21.4%, with interquartile range (IQR) 5.7-8.1%. Adjusting for the five significant predictor variables--gestational age at birth, 1 minute Apgar score, antenatal corticosteroids, transfer after birth, and sex--actually increased the variability in rates (IQR 5.9-9.7%). Shrinkage estimators, which adjust for differences in unit sizes and outcome rates, reduced the variation in rates (IQR 6.3-7.5%). Adjusting for case mix and using shrinkage estimators showed that one unit had a significantly higher adjusted rate than expected, while another was significantly lower. If all units could achieve an average rate equal to the 20th centile (5.74%), then 60 cases of severe IVH could be prevented in a 3 year period. CONCLUSIONS: The use of shrinkage estimators may have a greater impact on the variation in outcomes between hospitals than adjusting for case mix. Greater reductions in morbidity may be achieved by concentrating on the best rather than the worst performing hospitals.

Australia↗

PubMed2003

Molecular characterization of bacteria inhabiting a water distribution system simulator.

The objective of this study was to monitor the impact of chlorination and chloramination treatments on heterotrophic bacteria (HB) and ammonia-oxidizing bacteria (AOB) inhabiting a water distribution system simulator. HB densities decreased while AOB densities increased when chloramine was added. AOB densities decreased below detection limits after the disinfection treatment was switched back to chlorination. The presence of AOB was confirmed using a group-specific 16S rDNA-PCR method. 16S rDNA sequence analysis showed that most bacterial isolates from feed water, discharge water, and biofilm samples were alpha-Proteobacteria or beta-Proteobacteria. The latter bacterial groups were also numerically dominant among the sequences recovered from water and biofilm 16S rDNA clone libraries. The relative frequency of each culturable bacterial group was different for each sample examined. Denaturing gradient gel electrophoresis analysis of total community 16S rDNA genes showed notable differences between the microbial community structure of biofilm samples and feed water. The results of this study suggest that disinfection treatments could influence the type of bacterial community inhabiting water distribution systems.

Ammonia↗

PubMed2002

Characterization of fecal bacterial populations in canines: effects of age, breed and dietary fiber.

The effects of age, breed, and diet on fecal chemistry, enzyme activity, and bacterial populations of dogs were studied. Eighteen dogs from two age groups (young: 2.5 +/- 0.5 years, old: 10.9 +/-0.7 years) and three different breeds (German shepherds, miniature schnauzers, and English setters) were rotated through a Latin Square design such that every dog was fed each of the diets. The test diets included a low-fiber (control) diet and a 10% fiber diet which contained 5% soybean hulls and 5% beet pulp. Inclusion of 10% fiber in the diet decreased the fecal concentration of ammonia, sulfide, and indole. Fiber inclusion significantly increased acetic, propionic, and butyric acid concentrations, while fecal pH decreased by 0.4 units. Fresh fecal samples were plated on selected aerobic and anaerobic culture media and DNA extracted for denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S ribosomal DNA fragments. Plate counts showed significant effects of breed (p < or = 0.05) and age (p < or = 0.01) on selected aerobic and anaerobic bacterial counts, while no significant effect of diet was found. Analysis of PCR-DGGE banding patterns showed there was a tendency for individual dogs to cluster together according to age (young or old dogs) and also for size (large or small dogs). However, the outstanding conclusion obtained from the DGGE analysis of fecal bacterial profiles was that individual dogs had their own characteristic banding pattern which was unique and stable. The relative stability and individuality of the patterns indicates that each individual harbored a characteristic fecal bacterial community which was independent of diet.

Age Factors↗

PubMed2002

The Aberdeen Trauma Screening Index: an instrument to predict post-accident psychopathology.

BACKGROUND: A key challenge in trauma care is the prevention of psychopathology. However, no definitive method of identifying individuals at risk of developing psychopathology exists. The Aberdeen Trauma Screening Index (ATSI) is a brief screening tool developed for use in a clinical setting by non-mental health professionals to facilitate the early identification of individuals most at risk of psychopathology 3-months post-accident. METHODS: The ATSI derived from a prospective study of a 150 out of an initial pool of 213 consecutive admissions to the Orthopaedic Trauma Unit and the Accident and Emergency Department of Aberdeen Royal Infirmary. Potential predictors were identified by a comprehensive assessment conducted within 1-week post-accident. Outcome at 3-months post-accident was measured using 'caseness' according to the General Health Questionnaire (GHQ-28). RESULTS: The ATSI is based on a final model comprising only seven variables with a sensitivity of 79% and specificity of 65%. A predictive index score (0-100) was produced to ensure the practical utility of the ATSI in a clinical setting. A ROC curve was constructed to illustrate the relationship between sensitivity and the specificity values with their corresponding threshold scores. On the basis of a prevalence rate of 55% 'caseness', as identified in the present study, a cut-off point of 45 provides the optimal outcome with a sensitivity value of 70% and a specificity value of 71%. CONCLUSIONS: The ATSI can accurately identify those most at risk of developing psychopathology 3-months post-accident in a sample of accidentally injured adult subjects recruited as consecutive admissions to an urban hospital in the North East of Scotland. However, to establish the generalizability of these findings, it is important that the ATSI be validated in both similar and diverse populations.

Accidents↗

PubMed2002

Repeatability of echocardiographic measurements in the human fetus.

OBJECTIVES: To determine the repeatability of cross-sectional, M-mode and Doppler echocardiographic measurements in the human fetus. METHODS: This was a prospective echocardiographic study of 10 normal fetuses, involving measurement of 32 different echocardiographic variables in each. The intra- and interobserver error of measurements were quantified. The median (range) gestational age was 23 (17-34) weeks. RESULTS: Cross-sectional echocardiography: for left ventricular end-diastolic volume the intraobserver coefficient of variation was 13% and the interobserver limits of agreement were a ratio of 0.46-2.19. For left ventricular ejection fraction the repeatability was +/- 8.8% and the interobserver limits of agreement were +/- 20%. M-mode echocardiography: the coefficient of variation for left ventricular end-diastolic dimension was 10%, and the interobserver limits of agreement were a ratio of 0.74-1.70. The intraobserver repeatability of left ventricular fractional shortening was +/- 8.8%, and interobserver limits of agreement +/-15%. Limits of agreement for M-mode-derived left ventricular end-diastolic volume were wide, intraobserver coefficient of variation 32% and interobserver limits were a ratio of 0.44-4.36. Doppler echocardiography: the intra- and interobserver errors were high for Doppler variables such as acceleration time, acceleration slope, stroke volume, cardiac output and vessel dimension. There was less error associated with measurements such as maximum Doppler velocity, velocity time integral, ejection time and heart rate. CONCLUSIONS: The repeatability of most echocardiographic measurements in the fetus is poor. This applies particularly to volumetric data such as ventricular volumes and volume flow estimations. Interobserver errors are consistently higher than intraobserver errors, confirming that when sequential measurements are clinically important, the same observer should be used.

Aorta↗

PubMed2002

The comparative sensitivity of mammography and ultrasound in women with breast symptoms: an age-specific analysis.

Despite its importance for clinical policy, there is little research on the age at which ultrasound or mammography is the preferred initial diagnostic test in women with breast symptoms. We analysed data from a series of 3799 consecutively presenting cancers. The overall sensitivity was 77.6% for mammography and 80.5% for ultrasound. Sensitivity increased with age in both mammography and ultrasound, though more steeply for mammography. In the 975 women who had both tests, ultrasound had a higher sensitivity than mammography in women younger than 62 years of age, whereas mammography had a higher sensitivity than ultrasound in women older than 62 years. However, if the test results of the 2393 women who had mammography only are compared with the ultrasound results of the 975 women who had both tests, the 'cross-over' age at which the sensitivity of the two tests is equal occurs at the earlier age of 48 years. The presence of a palpable finding increases the sensitivity of ultrasound but does not influence the sensitivity of mammography.

Journal Article↗

PubMed2002

Paracetamol versus paracetamol-codeine in the treatment of post-operative dental pain: a randomized, double-blind, prospective trial.

BACKGROUND: Codeine is frequently added to paracetamol to treat post-operative dento-alveolar pain; studies have shown effectiveness in relief of post-operative pain at high doses but at the expense of central nervous and gastrointestinal side effects. There has been no trial to compare the efficacy and safety of paracetamol 1000 mg with paracetamol 1000 mg combined with codeine 30 mg. METHOD: A randomized, single centre, double-blind prospective parallel group trial was performed to compare paracetamol 1000 mg with paracetamol 1000 mg with codeine 30 mg for the relief of pain following surgical removal of impacted third molars, and analysed on an intention-to-treat (ITT) basis. Eighty-two patients were assigned randomly to receive either drug for a maximum of three doses. Patients recorded their pain intensity one hour after surgery and hourly thereafter for 12 hours. RESULTS: The average increase in pain intensity over 12 hours was significantly less in patients receiving paracetamol plus codeine than in those receiving paracetamol alone (p=0.03) -1.81 cm/h compared with 0.45 cm/h - a difference of 1.13 cm/h (95 per cent CI: 0.18 to 2.08). Of the patients who received the paracetamol codeine combination, 62 per cent used escape medication compared with 75 per cent of those on paracetamol alone (p=0.20). There was no significant difference between the two groups in the proportion of patients experiencing adverse events (p=0.5). CONCLUSION: A combination of 1000 mg paracetamol and 30 mg codeine was significantly more effective in controlling pain for 12 hours following third molar removal, with no significant difference of side effects during the 12 hour period studied.

Acetaminophen↗

PubMed2002

Perinatal risk factors for major intraventricular haemorrhage in the Australian and New Zealand Neonatal Network, 1995-97.

BACKGROUND: In 1995, large differences were identified in rates of grade 3-4 intraventricular/periventricular haemorrhage (major IVH) among neonatal intensive care units (NICUs) in the Australian and New Zealand Neonatal Network. AIMS: To develop a predictive model for major IVH in order to allow risk adjustment for the variation in rates of major IVH among NICUs. METHODS: Rates of IVH were determined in 5712 infants of 24-30 weeks gestation born from 1995 to 1997. Significant antenatal and perinatal variables for major IVH in 1995 and 1996 were identified by univariate and multivariate analysis. A predictive model was developed and then validated on 1997 data. RESULTS: Rates of all grades of IVH fell from 1995 to 1997 (30.4 to 24.3%) but wide interunit variation remained. Seven antenatal and perinatal characteristics had significant association with major IVH: fetal distress, intrauterine growth restriction (protective), antenatal corticosteroids (protective), gestational age, 1 minute Apgar <4, male gender, and transfer after birth. A predictive model based on the last five of these variables was developed using data from 1995 and 1996 which gave an area under the receiver operator characteristic (ROC) curve of 0.76. This model was then validated on the 1997 dataset where an identical ROC curve resulted. CONCLUSIONS: Antenatal and perinatal factors are important in the pathogenesis of major IVH. The predictive model developed from these factors can be used to adjust for confounders in interunit outcome comparison.

Analysis of Variance↗

PubMed2001

Echocardiographic features and outcome of truncus arteriosus diagnosed during fetal life.

There are few data on the outcome of truncus arteriosus when this diagnosis is made during fetal life. Such prognostic information is important to assist parental counseling during pregnancy. This study aimed to analyze, retrospectively, the echocardiographic features and outcome of fetuses with truncus arteriosus. A database of those presenting to a tertiary center for fetal cardiology between 1990 and 1999 was reviewed. Cases in which truncus arteriosus was identified as a firm or differential diagnosis were selected. Outcome data were derived from clinical records, and fetal echocardiograms were reviewed retrospectively. At presentation, truncus arteriosus was firmly diagnosed in 16 patients and was a differential diagnosis in 12. Fourteen of 16 (87%) of the firm diagnoses were correct. There were 17 confirmed cases of truncus arteriosus. Pregnancy was terminated in 4 patients (24%) and there were 13 live births. One child was not actively treated, 4 (31%) died preoperatively, and 8 (61%) underwent surgery. Thirty-day surgical mortality was 2 of 8 (25%). There was 1 late death after cardiac catheterization, and overall survival on an intention-to-treat basis was 5 of 12 (42%). Five of 6 patients with a prenatal truncal valve Doppler velocity above the normal aortic range were found to have postnatal truncal valve stenosis. Two fetuses with stenotic valves died preoperatively with sudden cardiovascular collapse. Counseling of parents for fetuses with truncus arteriosus should include the relatively high nonsurgical mortality as well as surgical results. Elevated prenatal truncal valve Doppler velocity predicts postnatal truncal valve stenosis. Fetuses with truncal valve stenosis may be at risk of early sudden death.

Female↗

PubMed2001

Cardiac catheterization of low birth weight infants.

The increased survival of low birth weight infants means that more of these infants may be candidates for catheter interventions. There are few data on the results of cardiac catheterization in this group. This study aimed to analyze, retrospectively, cardiac catheterization of infants weighing < or =2.5 kg, with emphasis on the results of interventions. The complication rates of interventional and diagnostic procedures were compared. One hundred eleven catheterizations were performed in 107 patients between 1985 and 1998. Thirty-one procedures were interventional. Balloon atrial septostomy (n = 16), balloon pulmonary valvuloplasty (n = 10), balloon pulmonary angioplasty (n = 1), and coil occlusion of collateral vessels (n = 3) were all performed successfully. One infant (3%) died while undergoing myocardial biopsy. The reintervention rate for isolated pulmonary valve stenosis was 25% (2 of 8) at 1 month, 57% (4 of 7) at 6 months, and 71% (5 of 7) at 1 year. Complications were significantly more frequent during interventional (13 of 31, 42%) than during diagnostic (13 of 80, 16%) procedures. The most common complications during interventions were arrhythmias (3 of 31, 10%) and respiratory deterioration (3 of 31, 10%). Cardiac catheterization was technically feasible in all patients. Balloon pulmonary valvuloplasty and atrial septostomy provided good palliation in this patient group. The mortality of interventional procedures was low. The high incidence of respiratory complications suggests that low birth weight infants should undergo elective ventilation for interventional cardiac catheterization.

Cardiac Catheterization↗

PubMed2001

Visual impairment, age-related cataract, and mortality.

OBJECTIVE: To explore associations between visual impairment, cataract, and mortality in older persons after adjusting for other factors associated with mortality. METHODS: A population cohort of 3654 persons aged 49 years or older (82.4% of eligible residents in the Blue Mountains region, west of Sydney, Australia), were examined at the Blue Mountains Eye Study baseline period (1992-1994) and followed up 5 years later (1997-1999). Australian National Death Index data were used to confirm persons who had died since baseline. Associations between mortality and presence of visual impairment and cataract at baseline were assessed using the Cox proportional hazards regression model, controlling for age, sex, demographic and socioeconomic status, medical history, and health risk behaviors. RESULTS: By June 30, 1999, 604 participants (16.5%) had died. The age- and sex-standardized 7-year cumulative mortality rate was 26% among persons with any visual impairment and 16% in persons without visual impairment. After adjusting for factors found significantly associated with mortality, including age, male sex, low self-rated health, low socioeconomic status, systemic medical conditions, and negative health risk behaviors, the presence at baseline of any visual impairment was independently associated with increased mortality risk (risk ratio [RR], 1.7; 95% confidence interval, 1.2-2.3). The presence of age-related cataract, either nuclear (RR, 1.5), cortical (RR, 1.3), or posterior subcapsular cataract (RR, 1.5), was also significantly associated with increased mortality risk. These associations remained statistically significant when visual impairment and each type of cataract were included simultaneously in the multivariate Cox model. CONCLUSION: Visual impairment and age-related cataract may be independent risk factors for increased mortality in older persons.

Aged↗

PubMed2001

Infant stress and sleep deprivation as an aetiological basis for the sudden infant death syndrome.

SIDS is almost invariably sleep-related. Viable syndrome aetiology must be compatible with its many epidemiologically diverse risk factors, each of which directly or indirectly associates with the creation of psychological and/or physiological infant stress, and the subsequent disruption of normal, contented sleep. During essential deep 'rebound' recovery sleep, arousal ability and upper airway muscle tone decrease further to that in normal sleep, with subsequent upper airway obstruction. When stress impact causes sufficient sleep disruption and physiological fatigue, a failure to arouse and so restore sufficient tone to overcome such obstruction results in sudden, unexpected death. SIDS has therefore many causes which share a final lethal mechanical pathway. Evidence is presented for obstructive apnoea during sleep as being the primary syndrome death mode, for sleep disruption, reduced arousal ability, and infant stress in SIDS, and for risk factor association with the creation of this stress. Specific infant vulnerability in the first 6 months of life to stress predominantly related to total dependency on a carer for gratification of need, and to obstructive sleep apnoea due to normal anatomical, physical, and respiratory immaturity, including rapid physiological fatigue, and peaks in sleep and thermal stress vulnerability, are discussed. Further reasons for the limited age period of SIDS, and for reduced neonatal risk, are given. Prone sleeping risk can relate to positional airway obstruction during normal sleep without prior infant stress. Much of SIDS aetiology appears to concern factors related to socio-economic deprivation and subsequent sub-optimal infant care.

Airway Obstruction↗

PubMed2001

Detailed three-dimensional fetal echocardiography facilitated by an Internet link.

OBJECTIVES: To assess whether a complete virtual cardiological examination can be achieved in stored three-dimensional volumes of the fetal heart, transmitted to a tertiary fetal cardiology center via the Internet. METHODS: Thirty sequential normal singleton pregnancies were included in the study. Four cardiac volumes were acquired using a three-dimensional ultrasound system. The volumes were sent via the Internet to a tertiary fetal cardiology center, where a detailed fetal cardiac examination was attempted using the three-dimensional volumetric dataset. RESULTS: The median gestational age was 24 (range, 22-28) weeks. A complete heart examination was accomplished in 23 of 30 cases (76.7%; 95% confidence interval, 58-90%). The four-chamber view and the cardiac situs were seen in all cases. The right ventricular outflow tract was seen in 29 (96.7%) cases and the left ventricular outflow tract in 25 (83.3%) cases. The long-axis view of the aortic arch, superior vena cava, inferior vena cava and pulmonary veins were visualized in more than 80% of cases. The mean time of volume acquisition was 9.5 (standard deviation, 2.3) min and the mean examination time by the fetal cardiologist was 17 (standard deviation, 4.8) min. CONCLUSIONS: These preliminary results demonstrate that a three-dimensional virtual examination of the fetal heart is possible. There are limitations such as the lack of flow and functional information but complete ascertainment of the main cardiac connections was possible in the majority of cases. The use of an Internet link has major implications, particularly for situations in which the scanning center is geographically remote from the tertiary referral center.

Adult↗

PubMed2001

Isolated echogenic foci in the fetal heart as marker of chromosomal abnormality.

OBJECTIVE: To assess the effect of echogenic foci in the fetal heart on the risk for Down's syndrome. DESIGN: Prospective evaluation of fetal echocardiograms at a fetal cardiology referral center and systematic postnatal follow-up. A relative risk was calculated from the prevalence of echogenic foci in fetuses subsequently demonstrated to have trisomy 21 divided by that in normal fetuses. For a subgroup of 548 fetuses with echogenic foci but otherwise normal detailed anomaly scans, the expected number of trisomy 21 fetuses calculated from maternal age risks was compared with the observed number to derive a relative risk for isolated echogenic foci. RESULTS: Echogenic foci occurred in 905 of 6904 fetuses scanned, but after excluding those referred specifically because of an echogenic focus and those with heart defects, the incidence was 9.5%. Overall, echogenic foci were more frequent in fetuses with trisomy 21 than those without by a factor of 2.93. For the 548 fetuses with echogenic foci but otherwise normal detailed anomaly scans, the actual number of trisomy 21 fetuses exceeded that expected on the basis of maternal age risks by a factor of 5.54. Combination with data from several previous studies suggests a consensus relative risk of about 3.0. CONCLUSIONS: Echogenic foci are associated with increased risk of trisomy 21 even when present as an isolated finding. Their significance in an individual should be interpreted in the light of prior risk assessment based on maternal age and results of any first-trimester screening tests. We suggest that the prior risk is increased by a factor of 3.0.

Adult↗

PubMed2001

Retrospective prenatal diagnosis of scimitar syndrome aided by three-dimensional power Doppler imaging.

Scimitar syndrome is a rare malformation of the arterial supply and venous drainage of the lung. We report the case of a fetus that presented with cardiac asymmetry and malposition of the fetal heart. Postnatally, scimitar syndrome was confirmed at cardiac catheterization. Retrospective reconstruction of three-dimensional power Doppler volumes, obtained during fetal life, allowed direct visualization of the abnormal aortopulmonary collateral vessel. This had not been seen on conventional scans. This case demonstrates many of the strengths of three-dimensional sonographic techniques for the delineation of complex vascular anatomy. It confirms that a prospective diagnosis of scimitar syndrome should be possible during fetal life.

Collateral Circulation↗

PubMed2001

Comparison of two frequency questionnaires for quantifying fruit and vegetable intake.

OBJECTIVE: The effect on individual rankings and total intakes of nutrients of correcting total fruit and vegetable frequencies from a long food frequency questionnaire (FFQ) using the responses to two summary questions was examined in a group of women. METHODS: The performance of a self-administered FFQ in ranking individual levels of intake and estimating absolute levels of nutrient and energy intake was compared with the performance of the questionnaire when it was corrected for fruit and vegetable intake reported using the Block summary questions. SUBJECTS: The study population included 123 women, aged between 18 and 54 years, who were recruited from the Family Planning Association Colposcopy Clinic in Sydney. RESULTS: Substantial and significant differences (P < 0.001) were found in fruit and vegetable intakes between the FFQ and the summary questions. Intake frequency by the FFQ was more than double that by the summary questions. When the FFQ was corrected for fruit and vegetable intakes using the summary questions, the intakes of beta-carotene, vitamins A and C, and dietary fibre were more than 20% lower (p < 0.001) than the uncorrected results. However, this had little effect on ranking individuals. This study also examined seasonal differences in vegetable intakes and differences in nutrient intakes when either summer or winter vegetable consumption was substituted for seasonal vegetable intake in the FFQ. Although there were seasonal differences for some foods, the substitution had little effect on intake of nutrients. CONCLUSION: These results indicate that important differences in intakes are observed when two methods, which appear to yield the same results, are used. Further work is needed to determine which, if either, of the two methods yields intakes that can be compared quantitatively with national references for assessing the adequacy of population intakes.

Adolescent↗

PubMed2001

Molecular ecological analysis of dietary and antibiotic-induced alterations of the mouse intestinal microbiota.

A cultivation-independent approach, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), was used to characterize changes in fecal bacterial populations resulting from consumption of a low residue diet or oral administration of a broad-spectrum antibiotic. C57BL/6NHsd mice were weaned to either a standard nonpurified diet (LC-diet) or a low residue diet (LR-diet) and at 17 wk of age were randomly assigned to receive drinking water with or without 25 ppm cefoxitin for 14 d. On d 1, 2, 7 and 14, microbial DNA was extracted from feces, and the V3 region of the 16S rDNA gene was amplified by PCR and analyzed by DGGE. The diversity of fecal microbial populations, assessed using Shannon's index (H'), which incorporates species richness (number of species, or in this case, PCR-DGGE bands) and evenness (the relative distribution of species), was not affected by cefoxitin. However, use of Sorenson's pairwise similarity coefficient (C(s)), an index that measures the species in common between different habitats, indicated that the species composition of fecal bacterial communities was altered by cefoxitin in mice fed either diet. Dietary effects on fecal microbial communities were more pronounced, with greater H' values (P < 0.05) in mice fed the LR-diet (1.9 +/- 0.1) compared with the LC-diet (1.6 +/- 0.1). The C(s) values were also greater (P < 0.05) in fecal bacterial populations from mice fed the LR-diet (C(s) = 69.8 +/- 2.0%) compared with mice fed the LC-diet (C(s) = 50.1 +/- 3.8%), indicating greater homogeneity of fecal bacterial communities in mice fed the LR-diet. These results demonstrate the utility of cultivation-independent PCR-DGGE analysis combined with measurements of ecological diversity for monitoring diet- and antibiotic-induced alterations of the complex intestinal microbial ecosystem.

Animals↗