Background-The normal intestinal microflora plays an important role in host metabolism and provides a natural defence mechanism against invading pathogens. Although the microbiota in adults has been extensively studied, little is known of the changes that occur in the microflora with aging. These may have important consequences in elderly people, many of whom are receiving antibiotic therapy and who are most susceptible to intestinal dysbiosis. Aims-To characterise the major groups of faecal bacteria in subjects of diVerent ages using a combination of cultural, molecular, and chemotaxonomic approaches. Methods-Comparative microbiological studies were made on four diVerent subject groups: children (16 months to seven years, n=10), adults (21-34 years, n=7), healthy elderly subjects (67-88 years, n=5), and geriatric patients (68-73 years, n=4) diagnosed with Clostridium diYcile diarrhoea. Selected faecal bacteria were investigated using viable counting procedures, 16S ribosomal RNA (rRNA) abundance measurements, and the occurrence of specific signature fatty acids in whole community fatty acid methyl ester profiles. Results-The principal microbiological diVerence between adults and children was the occurrence of higher numbers of enterobacteria in the latter group, as determined by viable counts (p<0.05) and 16S rRNA (p<0.01) measurements. Moreover, a greater proportion of children's faecal rRNA was hybridised by the three probes (bifidobacteria, enterobacteria, bacteroides-porphyromonasprevotella) used in the study, indicating a less developed gut microbiota. Species diversity was also markedly lower in the Clostridium diYcile associated diarrhoea group, which was characterised by high numbers of facultative anaerobes and low levels of bifidobacteria and bacteroides. Although it was a considerably less sensitive diagnostic tool, cellular fatty acid analysis correlated with viable bacterial counts and 16S rRNA measurements in a number of bacteria, including bacteroides.Conclusions-Polyphasic analysis of faecal bacteria showed that significant structural changes occur in the microbiota with aging, and this was especially evident with respect to putatively protective bifidobacteria. Reductions in these organisms in the large bowel may be related to increased disease risk in elderly people.

The bacterial composition of human faeces can vary greatly with factors such as age and disease, although relatively few studies have monitored these events, particularly at species level. In this investigation, bacteria were isolated from faecal samples from healthy young adults and elderly subjects, and elderly patients with Clostridium difficileassociated diarrhoea (CDAD). The organisms were identified to species level on the basis of their cellular fatty acid profiles with the MIDI system. In some groups of bacteria, species diversity was found to change with age despite the overall numbers of organisms being similar at genus level. Bacteroides thetaiotaomicron, B. ovatus and Prevotella tannerae were common gram-negative anaerobes isolated from young adults. Bacteroides species diversity increased in the faeces of healthy elderly people. Bifidobacterial species diversity decreased with age, with Bifidobacterium adolescentis and Bif. angulatum being the most common isolates. CDAD patients were characterised by greater diversity of facultative species, lactobacilli and clostridia, but greatly reduced numbers of bacteroides, prevotella and bifidobacteria. Such bacterial population changes in the normal microbiota could result in metabolic conditions favourable for the establishment of pathogenic micro-organisms, such as clostridia, and would have considerable effects on the biochemical capacity of the large intestine as a whole. Alterations in the community structure of bifidobacteria and lactobacilli have relevance for dietary and therapeutic interventions such as the use of pre-or probiotics that aim to modify the composition or metabolic activities of the intestinal microflora in a beneficial way, particularly in elderly people or individuals at risk of CDAD.

BackgroundAcute respiratory infection (ARI) is a leading cause of morbidity and mortality in children worldwide. This study aimed to determine the viral and atypical bacterial causes of different severities and clinical manifestations of ARI in preschool children from low-income families in North-East Brazil.MethodsClinical/demographic data and nasopharyngeal aspirates (NPA) were prospectively collected from children <5 years presenting with ARI over one year to a paediatric A&E department. Disease severity was grouped according to presence of lower respiratory tract signs, need for hospital admission and need for oxygen. Clinical manifestation of ARI was based on discharge diagnosis from hospital with four conditions predominating: bronchiolitis, pneumonia, episodic viral wheeze/asthma and upper respiratory tract infection. Multiplex PCR was used to detect 17 common respiratory viral and atypical bacterial pathogens in NPA.Findings407 children with a median age of eight months were recruited. Pathogens were detected in 85·5% samples with co-infection being particularly common (39·5%). Respiratory Syncytial Virus (RSV; 37%), Adenoviruses (AdV; 25%), Rhinoviruses (hRV; 19%), Bocavirus (hBoV; 19%), human Meta-pneumovirus (hMPV; 10%) and Mycoplasma pneumoniae (Mpp; 10%) were most prevalent. Detection and co-infection rates were similar in all severities and clinical manifestations of ARI apart from RSV, which was associated with more severe disease and specifically more severe cases of bronchiolitis, and Mpp, which was associated with more severe cases of pneumonia. Mpp was detected in 17% of children admitted to hospital with pneumonia.InterpretationThis study underlines the importance of viral and atypical bacterial pathogens in ARI in pre-school children and highlights the complex epidemiology of these pathogens in this age group. Generally, viruses and atypical bacteria were detected in all severities and clinical manifestations of ARI but RSV and Mpp were associated with more severe cases of bronchiolitis and pneumonia respectively.

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Objective:To investigate HIV, its treatment, and hypertension as stroke risk factors in Malawian adults.Methods:We performed a case-control study of 222 adults with acute stroke, confirmed by MRI in 86%, and 503 population controls, frequency-matched for age, sex, and place of residence, using Global Positioning System for random selection. Multivariate logistic regression models were used for case-control comparisons.Results:HIV infection (population attributable fraction [PAF] 15%) and hypertension (PAF 46%) were strongly linked to stroke. HIV was the predominant risk factor for young stroke (≤45 years), with a prevalence of 67% and an adjusted odds ratio (aOR) (95% confidence interval) of 5.57 (2.43–12.8) (PAF 42%). There was an increased risk of a stroke in patients with untreated HIV infection (aOR 4.48 [2.44–8.24], p < 0.001), but the highest risk was in the first 6 months after starting antiretroviral therapy (ART) (aOR 15.6 [4.21–46.6], p < 0.001); this group had a lower median CD4+ T-lymphocyte count (92 vs 375 cells/mm3, p = 0.004). In older participants (HIV prevalence 17%), HIV was associated with stroke, but with a lower PAF than hypertension (5% vs 68%). There was no interaction between HIV and hypertension on stroke risk.Conclusions:In a population with high HIV prevalence, where stroke incidence is increasing, we have shown that HIV is an important risk factor. Early ART use in immunosuppressed patients poses an additional and potentially treatable stroke risk. Immune reconstitution inflammatory syndrome may be contributing to the disease mechanisms.