A recent meta-analysis indicates that trophic cascades (indirect effects of predators on plants via herbivores) are weak in marine plankton in striking contrast to freshwater plankton (Shurin et al. 2002, Ecol. Lett., 5, 785-791). Here we show that in a marine plankton community consisting of jellyfish, calanoid copepods and algae, jellyfish predation consistently reduced copepods but produced two distinct, opposite responses of algal biomass. Calanoid copepods act as a switch between alternative trophic cascades along food chains of different length and with counteracting effects on algal biomass. Copepods reduced large algae but simultaneously promoted small algae by feeding on ciliates. The net effect of jellyfish on total algal biomass was positive when large algae were initially abundant in the phytoplankton, negative when small algae were dominant, but zero when experiments were analysed in combination. In contrast to marine systems, major pathways of energy flow in Daphnia-dominated freshwater systems are of similar chain length. Thus, differences in the length of alternative, parallel food chains may explain the apparent discrepancy in trophic cascade strength between freshwater and marine planktonic systems.

Background: The previous epidemiological study of paediatric nephrolithiasis in Britain was conducted more than 30 years ago. Aims: To examine the presenting features, predisposing factors, and treatment strategies used in paediatric stones presenting to a British centre over the past five years. Methods: A total of 121 children presented with a urinary tract renal stone, to one adult and one paediatric centre, over a five year period (1997)(1998)(1999)(2000)(2001). All children were reviewed in a dedicated stone clinic and had a full infective and metabolic stone investigative work up. Treatment was assessed by retrospective hospital note review. Results: A metabolic abnormality was found in 44% of children, 30% were classified as infective, and 26% idiopathic. Bilateral stones on presentation occurred in 26% of the metabolic group compared to 12% in the infective/idiopathic group (odds ratio 2.7, 95% CI 1.03 to 7.02). Coexisting urinary tract infection was common (49%) in the metabolic group. Surgically, minimally invasive techniques (lithotripsy, percutaneous nephrolithotomy, and endoscopy) were used in 68% of patients. Conclusions: There has been a shift in the epidemiology of paediatric renal stone disease in the UK over the past 30 years. Underlying metabolic causes are now the most common but can be masked by coexisting urinary tract infection. Treatment has progressed, especially surgically, with sophisticated minimally invasive techniques now employed. All children with renal stones should have a metabolic screen.

BackgroundDuring the past two decades, methicillin-resistant Staphylococcus aureus (MRSA) has become increasingly common as a source of nosocomial infections. Most studies of MRSA surveillance were performed during outbreaks, so that results are not applicable to settings in which MRSA is endemic. This paper gives an overview of MRSA prevalence in hospitals and other healthcare institutions in non-outbreak situations in Western Europe.MethodsA keyword search was conducted in the Medline database (2000 through June 2010). Titles and abstracts were screened to identify studies on MRSA prevalence in patients in non-outbreak situations in European healthcare facilities. Each study was assessed using seven quality criteria (outcome definition, time unit, target population, participants, observer bias, screening procedure, swabbing sites) and categorized as 'good', 'fair', or 'poor'.Results31 observational studies were included in the review. Four of the studies were of good quality. Surveillance screening of MRSA was performed in long-term care (11 studies) and acute care (20 studies). Prevalence rates varied over a wide range, from less than 1% to greater than 20%. Prevalence in the acute care and long-term care settings was comparable. The prevalence of MRSA was expressed in various ways - the percentage of MRSA among patients (range between 1% and 24%), the percentage of MRSA among S. aureus isolates (range between 5% and 54%), and as the prevalence density (range between 0.4 and 4 MRSA cases per 1,000 patient days). The screening policy differed with respect to time points (on admission or during hospital stay), selection criteria (all admissions or patients at high risk for MRSA) and anatomical sampling sites.ConclusionsThis review underlines the methodological differences between studies of MRSA surveillance. For comparisons between different healthcare settings, surveillance methods and outcome calculations should be standardized.

AbstarctBackgroundA recent review estimated prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in healthcare workers (HCWs) to be 4.6%. However, MRSA carriage in HCWs in non-outbreak settings is thought to be higher than in an outbreak situation, due to increased hygiene awareness in outbreaks, but valid data are missing. The goals of this paper are to summarise the prevalence of MRSA carriage amongst HCWs in non-outbreak situations and to identify occupational groups in healthcare services associated with a higher risk of MRSA colonisation.MethodsA systematic search for literature was conducted in the MEDLINE and EMBASE databases. The methodological quality of the studies was assessed using seven criteria. Pooled prevalence rates were calculated. Pooled effect estimates were identified in a meta-analysis.Results31 studies were included in this review. The pooled MRSA colonisation rate was 1.8% (95% confidence interval [CI], 1.34%-2.50%). The rate increased to 4.4% (95% CI, 3.98%-4.88%) when one study from the Netherlands was excluded. The pooled MRSA rate was highest in nursing staff (6.9%). Nursing staff had an odds ratio of 1.72 (95% CI, 1.07-2.77) when compared with medical staff and an odds ratio of 2.58 (95%, 1.83-3.66) when compared with other healthcare staff. Seven studies were assessed as being of high quality. The pooled MRSA prevalence in high quality studies was 1.1% or 5.4% if the one large study from the Netherlands is not considered. The pooled prevalence in studies of moderate quality was 4.0%.ConclusionsMRSA prevalence among HCWs in non-outbreak settings was no higher than carriage rates estimated for outbreaks. Our estimate is in the lower half of the range of the published MRSA rates in the endemic setting. Our findings demonstrate that nursing staff have an increased risk for MRSA colonisation. In order to confirm this finding, more studies are needed, including healthcare professionals with varying degrees of exposure to MRSA. In order to reduce misclassification bias, standardisation of HCWs screening is warranted.

ObjectivesIn this study, the frequency and consequences of aggressive assaults on employees in the German healthcare and welfare system were investigated.DesignA retrospective cross-sectional study.SettingEmployees in the German healthcare system and their experiences of violence and aggression were examined in this study.ParticipantsThe sample consisted of 1973 employees from 39 facilities (6 facilities for the disabled, 6 hospitals and 27 outpatient and inpatient geriatric care facilities) who have regular contact with patients or clients.Main outcome measuresThe frequency of physical and verbal violence towards employees and the consequences of aggressive assaults were analysed.Results56% of respondents had experienced physical violence and 78% verbal aggression. The highest frequency of physical violence was in inpatient geriatric care (63%) (p=0.000). Younger workers run a higher risk of being affected by physical violence than older colleagues (OR 1.8, 95% CI 1.3 to 2.4). There is also an increased risk of experiencing physical violence in inpatient geriatric care (OR 1.6, 95% CI 1.2 to 2.0). Around a third of workers feel seriously stressed by the violence experienced. The better the facility trained employees for dealing with aggressive and violent clients, the less risk employees ran of experiencing either verbal aggression (OR 0.5, 95% CI 0.4 to 0.7) or physical violence (OR 0.7, 95% CI 0.6 to 0.9). Training by the facility has a positive effect on experienced stress (OR 0.6, 95% CI 0.4 to 0.8).ConclusionsViolence towards nursing and healthcare personnel occurs frequently. Every third respondent feels severely stressed by violence and aggression. Occupational support provisions to prevent and provide aftercare for cases of violence and aggression reduce the risk of incidents and of perceived stress. Research is needed on occupational support provisions that reduce the risk of staff experiencing verbal and physical violence and the stress that is associated with it.

The aim of this study was to estimate the prevalence of viral hepatitis C (HCV) infection among healthcare workers (HCWs) compared to the general population. A systematic search for the years 1989–2014 was conducted in the Medline, Embase and Cochrane databases. Studies on hepatitis C in HCWs were included if they incorporated either a control group or reference data for the general population. The study quality was classified as high, moderate or low. Pooled effect estimates were calculated to determine the odds of occupational infection. Heterogeneity between studies was analysed using the χ2 test (p<0.10) and quantified using the I2 test. 57 studies met our criteria for inclusion and 44 were included in the meta-analysis. Analysis of high and moderate quality studies showed a significantly increased OR for HCV infection in HCWs relative to control populations, with a value of 1.6 (95% CI 1.03 to 2.42). Stratification by study region gave an OR of 2.1 in low prevalence countries; while stratification by occupational groups gave an increased prevalence for medical (OR 2.2) and for laboratory staff (OR 2.2). The OR for professionals at high risk of blood contact was 2.7. The pooled analysis indicates that the prevalence of infection is significantly higher in HCWs than in the general population. The highest prevalence was observed among medical and laboratory staff. Prospective studies that focus on HCW-specific activity and personal risk factors for HCV infection are needed.

IntroductionHealthcare workers (HCWs) in low incidence countries with contact to patients with tuberculosis (TB) are considered a high-risk group for latent TB infection (LTBI) and therefore are routinely screened for LTBI. The German Occupational TB Network data is analyzed in order to estimate the prevalence and incidence of LTBI and to evaluate putative risk factors for a positive IGRA and the performance of IGRA in serial testing.Methods3,823 HCWs were screened with the Quantiferon Gold in Tube (QFT) at least once; a second QFT was performed on 817 HCWs either in the course of contact tracing or serial examination. Risk factors for a positive QFT were assessed by a questionnaire.ResultsWe observed a prevalence of LTBI of 8.3%. Putative risk factors for a positive QFT result were age >55 years (OR 6.89), foreign country of birth (OR 2.39), personal history of TB (OR 6.23) and workplace, e.g. internal medicine (OR 1.40), infection ward (OR 1.8) or geriatric care (OR 1.8). Of those repeatedly tested, 88.2% (721/817) tested consistently QFT-negative and 47 were consistently QFT-positive (5.8%). A conversion was observed in 2.8% (n = 21 of 742 with a negative first QFT) and a reversion occurred in 37.3% (n = 28 of 75 with a positive first QFT). Defining a conversion as an increase of the specific interferon concentration from <0.2 to >0.7 IU/ml, the conversion rate decreased to 1.2% (n = 8). Analogous to this, the reversion rate decreased to 18.8% (n = 9).DiscussionIn countries with a low incidence of TB and high hygiene standards, the LTBI infection risk for HCWs seems low. Introducing a borderline zone from 0.2 to ≤0.7 IU/ml may help to avoid unnecessary X-rays and preventive chemotherapy. No case of active TB was detected. Therefore, it might be reasonable to further restrict TB screening to HCWs who had unprotected contact with infectious patients or materials.

Species conservation depends on robust population assessment. Data on population abundance, distribution, and connectivity are critical for effective management, especially as baseline information for newly documented populations. We describe a pygmy blue whale Balaenoptera musculus brevicauda population in New Zealand waters with year-round presence that overlaps with industrial activities. This population was investigated using a multidisciplinary approach, including analysis of survey data, sighting records, acoustic data, identification photographs, and genetic samples. Blue whales were reported during every month of the year in the New Zealand Exclusive Economic Zone, with reports concentrated in the South Taranaki Bight (STB) region, where foraging behavior was frequently observed. Five hydrophones in the STB recorded the New Zealand blue whale call type on 99.7% of recording days (January to December 2016). A total of 151 individuals were photo-identified between 2004 and 2017. Nine individuals were resighted across multiple years. No matches were made to individuals identified in Australian or Antarctic waters. Mitochondrial DNA haplotype frequencies differed significantly between New Zealand (n = 53 individuals) and all other Southern Hemisphere blue whale populations, and haplotype diversity was significantly lower than all other populations. These results suggest a high degree of isolation of this New Zealand population. Using a closed capturerecapture population model, our conservative abundance estimate of blue whales in New Zealand is 718 (SD = 433, 95% CI = 279−1926). Our results fill critical knowledge gaps to improve management of blue whale populations in New Zealand and surrounding regions.