Contributions of Composition and Interactions to Bacterial Respiration Are Reliant on the Phylogenetic Similarity of the Measured Community.

Bacterial diversity underpins many ecosystem functions; however, the impact of within-species variation on the relationship between diversity and function remains unclear. Processes involving strain differentiation, such as niche radiation, are often overlooked in studies that focus on phylogenetic variation. This study used bacterial isolates assembled in two comparable microcosm experiments to test how species variation affected ecosystem function. We compared the relationship between diversity and activity (CO2 production) in increasingly diverse multispecies microcosms and with multiple ecotypes of a single species. The bacteria used were isolated from a low-diversity environment and are species of potential clinical significance such as Pseudomonas aeruginosa. All isolates were profiled for single carbon source utilisation. These data showed an increased breadth of resource use in the multiple ecotypes when compared to the mixed-species. The study observed significantly increasing respiration in more complex mixed-species assemblages, which was not observed when ecotypes of a single species were combined. We further demonstrate that the variation observed in the bacterial activity was due to the roles of each of the constituent isolates; between different species, the interactions between the isolates drove the variation in activity, whilst in single species, assemblage variation was due to which isolates were present. We conclude that both between- and within-species variations play different roles in community function, although through different mechanisms, and should be included in models of changing diversity and ecosystem functioning.

Ciprofloxacin during upper respiratory tract infections to reduce Pseudomonas aeruginosa infection in paediatric cystic fibrosis: a pilot study.

OBJECTIVES: Acute viral respiratory illnesses are associated with acquisition of Pseudomonas aeruginosa infection in cystic fibrosis (CF) patients. This study aimed to pilot a protocol for a randomized controlled trial to determine whether oral antipseudomonal antibiotics used at the onset of such episodes might delay onset of infection with this organism. METHODS: A total of 41 children with CF aged 2-14 years, without chronic Pseudomonas infection, were randomized to receive ciprofloxacin (n = 28) or placebo (n = 13) at the onset of acute viral respiratory infections on an intention to treat basis, during a study period of up to 32 months. RESULTS: There were no unexpected adverse events believed related to the use of the study medication. The rate of withdrawal from the study was low (approximately 7%) and did not differ between groups. Randomization was effective and acceptable to participants. Primary and secondary outcome measures all favoured active treatment, but there were no significant between group differences. The median rate of Pseudomonas isolates was 0/patient/year (interquartile range 0-0.38) in both the active and placebo groups. Kaplan-Meier survival curves showed no significant difference in time to first Pseudomonas isolate between groups. CONCLUSIONS: This study demonstrated the clinical feasibility of using oral ciprofloxacin in CF patients at times of viral infection. Within this sample size, no significant association was found between active treatment and decreased growth of Pseudomonas in follow-up microbiological samples. A definitive study would require at least 320 children to demonstrate significant differences in the rate of pseudomonal isolates.

15-minute consultation: a structured approach to the assessment of chest pain in a child.

This article aims to provide a concise, structured approach to the child with chest pain. Chest pain is a common presenting symptom in children but, unlike in adults, the cause is rarely cardiac. We review the main causes of chest pain in children and discuss the important features that may alert those assessing paediatric chest pain to serious underlying pathology. In the vast majority of cases, reassurance is all that is required and a thorough initial consultation can exclude rare, serious disease and provide vital reassurance to children and families.

A quantitative analysis of Ureaplasma urealyticum and Ureaplasma parvum compared with host immune response in preterm neonates at risk of developing bronchopulmonary dysplasia.

Multiplex, real-time PCR for the identification of Ureaplasma urealyticum and Ureaplasma parvum was performed on nucleic acids extracted from sequential endotracheal aspirates obtained from preterm neonates born at <29 weeks of gestation and ventilated for more than 48 h admitted to two level 3 neonatal intensive care units. Specimens were obtained shortly after birth and sequentially up until extubation. One hundred fifty-two specimens (93.8%) contained material suitable for analysis. Ureaplasma spp. were identified in 5 of 13 neonates studied. In most cases, the DNA load of the detected Ureaplasma species was low and decreased over time. In addition, changes in detectable Ureaplasma species DNA did not relate to changes in the inflammatory marker C-reactive protein (CRP) or respiratory status. All but two blood samples obtained at times of suspected sepsis were culture positive for other microorganisms; the species cultured were typically coagulase-negative staphylococci and were associated with increased levels of CRP (>10 mg/liter). This study was limited by the small number of patients examined and does not have the power to support or contradict the hypothesis that postnatal lung infection with Ureaplasma parvum is causally related to bronchopulmonary dysplasia (BPD) or adverse respiratory outcomes after preterm birth. However, in this study, increases in CRP levels were not associated with patients in whom Ureaplasma parvum was detected, in contrast to the detection of other bacterial species.

Molecular microbiological characterization of preterm neonates at risk of bronchopulmonary dysplasia.

The role of infection in bronchopulmonary dysplasia (BPD) is unknown. We present an observational study of 55 premature infants born weighing less than 1.3 kg within two level III neonatal intensive care units. Endotracheal aspirates (ETA) and nasogastric aspirates (NGA) were studied with denaturing gradient gel electrophoresis (DGGE) profiling to elucidate the total bacterial community, and species-specific PCR was used to detect the presence of Mycoplasma hominis, Ureaplasma urealyticum, and Ureaplasma parvum. DGGE identified bacterial species in 59% of NGA and ETA samples combined. A diverse range of species were identified including several implicated in preterm labor. Species-specific PCR identified M. hominis in 25% of NGA and 11% of ETA samples. Among the 48 infants surviving up to 36 wk-postconceptual age, ordinal logistic regression showed the odds ratio for BPD or death where Ureaplasma was present/absent as 4.80 (95% CI 1.15-20.13). After adjusting for number of days ventilated, this was reduced to 2.04 (0.41-10.25). These data demonstrate how the combined use of DGGE and species-specific PCR identifies a high exposure in utero and around the time of birth to bacteria that might be causally related to preterm delivery and subsequent lung injury.

Frequency of detection of picornaviruses and seven other respiratory pathogens in infants.

BACKGROUND: Previous studies in which molecular-based techniques have been used to identify the causative pathogens of respiratory tract infection have investigated hospitalized children only. We report a prospective study designed to determine the frequency and clinical presentation of community-acquired respiratory illness in infancy associated with 8 common respiratory pathogens. METHODS: Eighty-eight infants were monitored through their first winter. With each respiratory illness, infants were examined, and a nasal lavage specimen was collected. Individual reverse transcription-polymerase chain reactions were performed to detect infection with picornaviruses (rhinoviruses and enteroviruses), coronaviruses (serotypes OC43 and 229E), adenoviruses, parainfluenza viruses 1-3, influenza viruses (types A and B), respiratory syncytial virus (RSV), Chlamydia pneumoniae and Mycoplasma pneumoniae. RESULTS: Picornaviruses were the most frequently detected pathogen identified in 46% (56 of 123) of episodes, followed by RSV (27%), parainfluenza viruses (13%) and coronaviruses (9%). Dual pathogen infections were identified in 20% of episodes, predominantly caused by picornaviruses together with either RSV or parainfluenza viruses. RSV infection was significantly associated with a diagnosis of bronchiolitis. No other associations were found between pathogen and clinical diagnosis. Dual infection did not predispose infants to a more severe clinical course. CONCLUSIONS: Picornaviruses are the predominant cause of community-acquired respiratory tract infection in the first year of life. Large prospective community-based studies will be needed to fully evaluate the contribution of picornaviruses, both in isolation and in combination with other respiratory pathogens, to the various clinical syndromes of respiratory infection observed during infancy.

Type 1 and type 2 cytokine imbalance in acute respiratory syncytial virus bronchiolitis.

We examined the in vivo immune response of infants to natural respiratory syncytial virus (RSV) infection through analysis of cytokine levels in nasal lavage fluid and stimulated peripheral blood mononuclear cells. Eighty-eight babies with at least one parent with atopy and asthma were prospectively studied through their first winter. Twenty-eight infants had an upper respiratory tract infection where RSV was detected, of whom nine developed signs of acute bronchiolitis. Nasal lavage specimens were assayed for interferon-gamma, interleukin (IL)-4, IL-10, and IL-12 and the RSV load determined by quantitative polymerase chain reaction. Messenger RNA (mRNA) was extracted from stimulated peripheral blood mononuclear cells and interferon-gamma, IL-4, IL-12, and IL-18 mRNA levels determined by polymerase chain reaction. Cytokine profiles were analyzed in relation to clinical outcome. The IL-4/interferon-gamma ratio for infants with acute bronchiolitis was elevated in nasal lavage fluid on both Days 1-2 (p = 0.014) and Days 5-7 (p = 0.001) of the illness compared with infants with upper respiratory tract infection alone. Those with acute bronchiolitis demonstrated a higher IL-10/IL-12 ratio (p = 0.0015) on Days 1-2. IL-18 mRNA levels were reduced (p = 0.019) and the IL-4/interferon-gamma ratio elevated (p = 0.01) in stimulated peripheral blood mononuclear cells from infants with acute bronchiolitis. There was no difference in initial RSV load. These data strongly implicate excess type 2 and/or deficient type 1 immune responses in the pathogenesis of RSV bronchiolitis.