Spatiotemporal diversity and community structure of cyanobacteria and associated bacteria in the large shallow subtropical Lake Okeechobee (Florida, United States)

Lake Okeechobee is a large eutrophic, shallow, subtropical lake in south Florida, United States. Due to decades of nutrient loading and phosphorus rich sediments, the lake is eutrophic and frequently experiences cyanobacterial harmful algal blooms (cyanoHABs). In the past, surveys of the phytoplankton community structure in the lake have been conducted by morphological studies, whereas molecular based studies have been seldom employed. With increased frequency of cyanoHABs in Lake Okeechobee (e.g., 2016 and 2018 Microcystis-dominated blooms), it is imperative to determine the diversity of cyanobacterial taxa that exist within the lake and the limnological parameters that drive bloom-forming genera. A spatiotemporal study of the lake was conducted over the course of 1 year to characterize the (cyano)bacterial community structure, using 16S rRNA metabarcoding, with coincident collection of limnological parameters (e.g., nutrients, water temperature, major ions), and cyanotoxins. The objectives of this study were to elucidate spatiotemporal trends of community structure, identify drivers of community structure, and examine cyanobacteria-bacterial relationships within the lake. Results indicated that cyanobacterial communities within the lake were significantly different between the wet and dry season, but not between periods of nitrogen limitation and co-nutrient limitation. Throughout the year, the lake was primarily dominated by the picocyanobacterium Cyanobium. The bloom-forming genera Cuspidothrix, Dolichospermum, Microcystis, and Raphidiopsis were highly abundant throughout the lake and had disparate nutrient requirements and niches within the lake. Anatoxin-a, microcystins, and nodularins were detected throughout the lake across both seasons. There were no correlated (cyano)bacteria shared between the common bloom-forming cyanobacteria Dolichospermum, Microcystis, and Raphidiopsis. This study is the first of its kind to use molecular based methods to assess the cyanobacterial community structure within the lake. These data greatly improve our understanding of the cyanobacterial community structure within the lake and the physiochemical parameters which may drive the bloom-forming taxa within Lake Okeechobee.

Wind induced algal migration manipulates sediment denitrification N-loss patterns in shallow Taihu Lake, China

Driven by winds, the distribution of algae is often noticeably patchy at kilometer scales in shallow lakes. The decomposition of the settled algal biomass may affect nitrogen (N) biogeochemical cycles and thereby N loss in sediments. In this study, we investigated sediment denitrification N-loss patterns along algal migration pathway in Taihu Lake, a shallow and eutrophic lake in China, and found that wind-induced algal migration in the overlying water manipulated the temporal and spatial patterns of denitrification N-loss in sediments. A N loss hotspot in sediments was created in the algae concentrated zone, where N loss was, however, temporarily inhibited during algal bloom seasons and generally exhibited a negative relationship with algal biomass. In the zone where algae have left, sediment N loss rate was relatively low and positively correlated with algal biomass. The decay of algal biomass generated organic carbon and created anoxia, favoring denitrification, while excessive algal biomass could deplete oxygen and inhibit nitrification, causing nitrate limitation for denitrification. Piecewise linear regression analysis indicated that algal biomass of Chl-a > 73.0 μg/L in the overlying water could inhibit denitrification N-loss in sediments. This study adds to our understanding of N biogeochemical cycles in shallow eutrophic lakes.

Calcification-driven CO2 emissions exceed "Blue Carbon" sequestration in a carbonate seagrass meadow

Long-term “Blue Carbon” burial in seagrass meadows is complicated by other carbon and alkalinity exchanges that shape net carbon sequestration. We measured a suite of such processes, including denitrification, sulfur, and inorganic carbon cycling, and assessed their impact on air-water CO₂ exchange in a typical seagrass meadow underlain by carbonate sediments. Eddy covariance measurements reveal a consistent source of CO₂ to the atmosphere at an average rate of 610 ± 990 μmol m⁻² hour⁻¹ during our study and 700 ± 660 μmol m⁻² hour⁻¹ (6.1 mol m⁻² year⁻¹) over an annual cycle. Net alkalinity consumption by ecosystem calcification explains >95% of the observed CO₂ emissions, far exceeding organic carbon burial and anaerobic alkalinity generation. We argue that the net carbon sequestration potential of seagrass meadows may be overestimated if calcification-induced CO₂ emissions are not accounted for, especially in regions where calcification rates exceed net primary production and burial.

Variation in benthic metabolism and nitrogen cycling across clam aquaculture sites

As bivalve aquaculture expands globally, an understanding of how it alters nitrogen is important to minimize impacts. This study investigated nitrogen cycling associated with clam aquaculture in the Sacca di Goro, Italy (Ruditapes philipinarum) and the Eastern Shore, USA (Mercenaria mercenaria). Ammonium and dissolved oxygen fluxes were positively correlated with clam biomass; R. philippinarum consumed ~6 times more oxygen and excreted ~5 times more NH₄⁺ than M. mercenaria. There was no direct effect of clams on denitrification or dissimilatory nitrate reduction to ammonium (DNRA); rather, nitrate availability controlled the competition between these microbial pathways. Highest denitrification rates were measured at sites where both water column nitrate and nitrification were elevated due to high densities of a burrowing amphipod (Corophium sp.). DNRA exceeded denitrification where water column nitrate was low and nitrification was suppressed in highly reduced sediment, potentially due to low hydrologic flow and high clam densities.

The pharmacokinetics and toxicity of morning vs. evening tobramycin dosing for pulmonary exacerbations of cystic fibrosis: A randomised comparison

Background

Circadian variation in renal toxicity of aminoglycosides has been demonstrated in animal and human studies. People with CF are frequently prescribed aminoglycosides. Altered pharmacokinetics of aminoglycosides are predictive of toxicity.

Aim

To investigate whether the time of day of aminoglycoside administration modulates renal excretion of tobramycin and toxicity in children with CF. To determine whether circadian rhythms are disrupted in children with CF during hospital admission.

Methods

Children (age 5–18 years) with CF scheduled for tobramycin therapy were randomly allocated to receive tobramycin at 0800 or 2000 h. Serum tobramycin levels were drawn at 1 h and between 3.5 and 5 h post-infusion between days 5 and 9 of therapy. Melatonin levels were measured serially at intervals from 1800 h in the evening until 1200 h on the next day. Circadian rhythm was categorised as normal when dim light melatonin onset was demonstrated between 1800 and 2200 h and/or peak melatonin levels were observed during the night. Weight and spirometry were measured at the start and end of the therapy. Urinary biomarkers of kidney toxicity (KIM1, NAG, NGAL, IL-18 and CysC) were assayed at the start and end of the course of tobramycin.

Results

Eighteen children were recruited to the study. There were no differences in renal clearance between the morning and evening groups. The increase in urinary KIM-1 was greater in the evening dosage group compared to the morning group (mean difference, 0.73 ng/mg; 95% CI, 0.14 to 1.32; p = 0.018). There were no differences in the other urinary biomarkers. There was normal circadian rhythm in 7/11 participants (64%).

Conclusions

Renal elimination of tobramycin was not affected by the time of day of administration. Urinary KIM-1 raises the possibility of greater nephrotoxicity with evening administration. Four children showed disturbed circadian rhythm and high melatonin levels (ClinicalTrials.gov NCT01207245).

Delayed publication of clinical trials in cystic fibrosis

BACKGROUND

When the publication of important trial data is delayed, or data are never published, this will prevent the proper practice of evidence based medicine through robust systematic reviews. Clinical trial registries allow researchers to interrogate the trial protocol and afford the opportunity to identify studies that have been completed and so determine the time lag between completion and publication.

METHODS

We searched ClinicalTrials.gov with the keywords 'cystic fibrosis'. Intervention trials which had completed 1st Jan 1998-31st Dec 2010 were selected. Time to publication in a peer-reviewed journal was calculated. Survival analyses using the log rank test were undertaken.

RESULTS

We identified 142 records. Of these, 62 had full paper publications. The median time to publication was 3.25 years. Phase of study (phase one studies more delayed, p=0.024) but not source of funding (p=0.34) was associated with time to publication.

CONCLUSIONS

Clinical trials in cystic fibrosis take a considerable amount of time to report their findings. More importantly, a large number of trials fail to report at all.

Guideline on the design and conduct of cystic fibrosis clinical trials: the European Cystic Fibrosis Society-Clinical Trials Network (ECFS-CTN)

We describe the rationale for disease specific research networks in general as well as the aims and function of the European Cystic Fibrosis Society-Clinical Trials Network (ECFS-CTN) specifically. The ECFS-CTN was founded in 2009 with the aim of improving the quality and quantity of clinical research in the area of cystic fibrosis (CF) in Europe. A network of 18 clinical trial sites in 8 European countries was established according to uniform state-of-the-art quality criteria. To support the ECFS-CTN in the acquisition, planning and conduct of clinical trials, the network is equipped with a coordinating centre, steering and executive committees, and committees for protocol review, standardization, training and networking as well as a data safety monitoring board. A strong partnership with European CF patient parent organizations aims to increase awareness of the need for efficient clinical research and the participation of patients in clinical trials.

Respiratory medicines for children: current evidence, unlicensed use and research priorities

This European Respiratory Society task force has reviewed the evidence for paediatric medicines in respiratory disease occurring in adults and children. We describe off-licence use, research priorities and ongoing studies. Off-licence and off-label prescribing in children is widespread and potentially harmful. Research areas in asthma include novel formulations and regimens, and individualised prescribing. In cystic fibrosis, future studies will focus on screened infants and robust outcome measures are needed. Other areas include new enzyme and antibiotic formulations and the basic defect. Research into pneumonia should include evaluation of new antibacterials and regimens, rapid diagnostic tests and, in pleural infection, antibiotic penetration, fibrinolytics and surveillance. In uncommon conditions, such as primary ciliary dyskinesia, congenital pulmonary abnormalities or neuromuscular disorders, drugs indicated for other conditions (e.g. dornase alfa) are commonly used and trials are needed. In neuromuscular disorders, the beta-agonists may enhance muscle strength and are in need of evaluation. Studies of antibiotic prophylaxis, immunoglobulin and antifungal drugs are needed in immune deficiency. We hope that this summary of the evidence for respiratory medicines in children, highlighting gaps and research priorities, will be useful for the pharmaceutical industry, the paediatric committee of the European Medicines Agency, academic investigators and the lay public.

Once-daily versus multiple-daily dosing with intravenous aminoglycosides for cystic fibrosis

BACKGROUND

People with cystic fibrosis, who are chronically colonised with the organism Pseudomonas aeruginosa, often require multiple courses of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations. The properties of aminoglycosides suggest that they could be given in higher doses less often.

OBJECTIVES

To assess the effectiveness and safety of once-daily versus multiple-daily dosing of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations in cystic fibrosis.

SEARCH STRATEGY

We searched the Cystic Fibrosis Specialist Register held at the Cochrane Cystic Fibrosis and Genetic Disorders Group's editorial base, comprising references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings.Date of the most recent search: August 2005.

SELECTION CRITERIA

All randomised controlled trials, whether published or unpublished, in which once-daily dosing of aminoglycosides has been compared with multiple-daily dosing in terms of efficacy and/or toxicity, in people with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

The two authors independently selected the studies to be included in the review and assessed methodological quality of each study. Data were independently extracted by each author. Authors of the included studies were contacted for further information. As yet unpublished data were obtained for one of the included studies.

MAIN RESULTS

Eleven studies were identified for possible inclusion in the review. Four studies reporting results from a total of 328 participants were included in this review. All studies compared once-daily dosing with thrice-daily dosing. There was no significant difference between treatment groups in: forced expiratory volume at one second, weighted mean difference (WMD) 0.33 (95% confidence interval (CI) -2.81 to 3.48); forced vital capacity, WMD 0.29 (95% CI -6.58 to 7.16); % weight for height, WMD -0.82 (95% CI -3.77 to 2.13); body mass index, WMD 0.00 (95% CI -0.42 to 0.42); or in the incidence of ototoxicity, relative risk 0.56 (95% CI 0.04 to 7.96). The percentage change in creatinine significantly favoured once-daily treatment in children, WMD -8.20 (95% CI -15.32 to -1.08), but showed no difference in adults, WMD 3.25 (95% CI -1.82 to 8.33).

AUTHORS' CONCLUSIONS

Once and three times daily aminoglycoside antibiotics appear to be equally effective in the treatment of pulmonary exacerbations of cystic fibrosis. There is evidence of less nephrotoxicity in children.

Antibiotic strategies for eradicating Pseudomonas aeruginosa in people with cystic fibrosis

BACKGROUND

Lower respiratory tract infection with Pseudomonas aeruginosa (P. aeruginosa) occurs in most people with cystic fibrosis. Once chronic infection is established, P. aeruginosa is virtually impossible to eradicate and is associated with increased mortality and morbidity. Early infection may be easier to eradicate.

OBJECTIVES

To determine whether antibiotic treatment of early P. aeruginosa infection in children and adults with cystic fibrosis eradicates the organism and improves clinical and microbiological outcome.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register which comprises of references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. Date of most recent search: May 2004

SELECTION CRITERIA

We included randomised controlled trials of people with cystic fibrosis, in whom P. aeruginosa had recently been isolated from respiratory secretions. We compared combinations of inhaled, oral or intravenous antibiotics with placebo or usual treatment (or both) or other combinations of inhaled, oral or intravenous antibiotics. We excluded non-randomised trials, cross-over trials, and those utilising historical controls.

DATA COLLECTION AND ANALYSIS

Both authors independently assessed selected trials, assessed methodological quality and extracted data.

MAIN RESULTS

The search identified 15 trials. Three trials (69 participants) were eligible for inclusion. There is evidence from two randomised controlled trials, of questionable methodological quality, that treatment of early P. aeruginosa infection with inhaled tobramycin results in microbiological eradication of the organism from respiratory secretions more often than placebo and that this effect may persist for up to 12 months, however incomplete data from one of the trials precludes an accurate analysis. One randomised controlled trial of oral ciprofloxacin and nebulised colisitin versus usual treatment was identified. This trial was of poor methodological quality. The results suggested treatment of early infection results in microbiological eradication of P. aeruginosa more often than usual treatment, after two years, RR 0.24 (95% CI 0.06 to 0.96). There is insufficient evidence to determine whether antibiotic strategies for the eradication of early P. aeruginosa decrease mortality or morbidity, improve quality of life, or are associated with adverse effects compared to placebo or standard treatment.

AUTHORS' CONCLUSIONS

From the three trials included in this review, there is some evidence that antibiotic treatment of early P. aeruginosa results in short-term eradication but it remains uncertain whether there is clinical benefit to people with cystic fibrosis.

Parental attitudes: antenatal diagnosis of cystic fibrosis

In order to understand attitudes to antenatal diagnosis of cystic fibrosis (CF), we interviewed parents from 19 families, who already had one child with CF. Nine women had chorion villus sampling in a subsequent pregnancy and 6/19 said they would consider termination of pregnancy if the result confirmed CF. These results differ from the results of antenatal screening studies of previously unaffected families, where most couples opt for termination.

Paradoxical embolism in a boy with cystic fibrosis and a stroke

An 11 year old boy with cystic fibrosis suffered a stroke, producing right sided weakness. Four years previously a totally implantable venous access device (Port-a-Cath) had been inserted. Magnetic resonance angiography revealed a filling defect in the left middle cerebral artery. Transoesophageal echocardiography demonstrated a thrombus attached to the tip of the Port-a-Cath and also the presence of a patent foramen ovale. After an initial period of anticoagulation the defect was closed using a septal occlusion device introduced via a cardiac catheter. The boy's neurological signs completely resolved and he remains free from further thromboembolic episodes. Whilst pulmonary embolism has been described before in relation to a totally implantable venous access device, this is believed to be the first description of a paradoxical embolism in relation to such a device.

The laryngeal mask airway in fibreoptic bronchoscopy

A large series of patients is reported in whom the laryngeal mask airway was used to perform fibreoptic bronchoscopy. It allows direct visualisation of the airways during spontaneous respiration. It has enabled bronchoalveolar lavage and bronchography to be performed in children as young as 6 months and transbronchial biopsies in children as young as 4 years.

Effect of respiratory virus infections including rhinovirus on clinical status in cystic fibrosis

One hundred and eight patients with cystic fibrosis were investigated over one year to determine whether an association existed between rhinovirus or other respiratory virus infection and clinical status. Forced expiratory volume in one second (FEV1), forced vital capacity (FVC), Shwachman score, Chrispin-Norman chest radiograph score, and percentage weight for height were recorded at the beginning and end of the study; days of intravenous antibiotics were noted. Nasopharyngeal aspirates were taken for viral studies during respiratory exacerbations. Serum was collected at enrollment and 2-6 weeks after each respiratory exacerbation. One hundred and fifty seven exacerbations occurred in 76 patients. Respiratory virus infection was detected in 44 exacerbations and rhinovirus was present in 16% (25/157) of exacerbations. Patients with one or more respiratory virus infections were compared with those who had none. When all respiratory virus infections were considered, patients had a significantly greater deterioration in Shwachman score and received significantly more days of intravenous antibiotics. When rhinovirus was considered separately, patients received significantly more days of intravenous antibiotics, but showed no deterioration in clinical status. However, patients infected with another respiratory virus had a significant decline in FEV1, with trends towards significance for decline in FVC and Shwachman score.

Strictures of ascending colon in cystic fibrosis and high-strength pancreatic enzymes

We have observed five children with cystic fibrosis, who presented over 2 months, with meconium ileus equivalent that failed to respond to medical management. At surgery, four had a stricture in the ascending colon, and all had histopathological changes of post-ischaemic ulceration repair, with mucosal and submucosal fibrosis. The only common change in the management of these children was a switch from conventional enteric-coated pancreatic enzymes to high-strength products 12-15 months before presentation.

Ureaplasma urealyticum and chronic lung disease

Neonatal lower respiratory tract colonisation with mycoplasma organisms was examined for an association with chronic lung disease. Ureaplasma urealyticum colonised 9/70 (13%) infants less than 1500 g. Seven (78%) colonised and 33 (54%) non-colonised infants developed chronic lung disease. Logistic regression analyses revealed early gestation, but not mycoplasma colonisation, was independently associated with chronic lung disease.

Compliance with antibiotic prophylaxis in urinary tract infection

Compliance with antibiotic prophylaxis after urinary tract infection was assessed in 32 children, using a parent questionnaire, and a urine test for antibacterial substances. In 31 (97%) cases, parents reported giving the antibiotics every day but only 22 (69%) of urine tests were positive. Failure to understand the reasons for prophylaxis and non-compliance were significantly associated.