Antibiotics as a silent driver of climate change? A case study investigating methane production in freshwater sediments.

Methane (CH4) is the second most important greenhouse gas after carbon dioxide (CO2) and is inter alia produced in natural freshwater ecosystems. Given the rise in CH4 emissions from natural sources, researchers are investigating environmental factors and climate change feedbacks to explain this increment. Despite being omnipresent in freshwaters, knowledge on the influence of chemical stressors of anthropogenic origin (e.g., antibiotics) on methanogenesis is lacking. To address this knowledge gap, we incubated freshwater sediment under anaerobic conditions with a mixture of five antibiotics at four levels (from 0 to 5000 µg/L) for 42 days. Weekly measurements of CH4 and CO2 in the headspace, as well as their compound-specific δ13C, showed that the CH4 production rate was increased by up to 94% at 5000 µg/L and up to 29% at field-relevant concentrations (i.e., 50 µg/L). Metabarcoding of the archaeal and eubacterial 16S rRNA gene showed that effects of antibiotics on bacterial community level (i.e., species composition) may partially explain the observed differences in CH4 production rates. Despite the complications of transferring experimental CH4 production rates to realistic field conditions, the study indicated that chemical stressors contribute to the emissions of greenhouse gases by affecting the methanogenesis in freshwaters.

A comparison of the reproducibility of two cine-derived strain software programmes in disease states.

BACKGROUND: Systolic strain and peak-early diastolic strain rate (PEDSR) measure subclinical cardiac dysfunction. These parameters can be derived from cardiovascular magnetic resonance (CMR) cine images using new software packages, but the comparative test-retest reproducibility of these software in disease states is unknown. This study compared the test-retest reproducibility of strain measures derived from two software packages (feature-tracking software (FT) and tissue-tracking (TT)) in disease populations with preserved ejection fractions. METHODS: This was a prospective study of 10 patients with aortic stenosis (AS), 10 haemodialysis patients and 10 diabetic patients at 1.5 and 3-Tesla. 30 subjects underwent test-retest reproducibility scans of global circumferential strain (GCS), global longitudinal strain (GLS), circumferential-PEDSR and longitudinal-PEDSR calculated using TT and FT software. RESULTS: Test-retest reproducibility of GCS and GLS were similar for FT and TT across patient groups. Coefficient of variability (CoV) for FT-derived GCS 8.1%, 5% and 7.9% for AS, diabetic and haemodialysis patients, compared to 3.3%, 9.2% and 5.4% for TT-derived GCS, with CoV for FT-derived GLS 8%, 6.4% and 8.2% for AS, diabetic and haemodialysis patients, compared to 5.3%, 4.8% and 7% for TT-derived GLS). Reproducibility of FT-derived circumferential and longitudinal-PEDSR was worse than TT-derived circumferential and longitudinal-PEDSR (CoV for FT-derived circumferential-PEDSR 18.2%, 18% and 17.4% for AS, diabetic and haemodialysis patients, compared to 6.1%, 11.7% and 11% for TT-derived circumferential-PEDSR with CoV for FT-derived longitudinal PEDSR 18.2%, 18.9%, 18.3% for AS, diabetic and haemodialysis patients, compared to 8.9%, 9.1% and 11.4% for TT-derived longitudinal-PEDSR). Bland-Altman analysis revealed no systematic bias with tighter limits of agreement for TT-derived strain measures. CONCLUSIONS: Reproducibility of GCS and GLS are excellent with FT and TT software across diseases. TT had superior test-retest reproducibility for quantification of longitudinal and circumferential-PEDSR than FT-derived PEDSR across diseases.

Prevalence of antibodies against measles, mumps and rubella in the childhood population in Singapore, 2008-2010.

We undertook a national paediatric seroprevalence survey of measles, mumps and rubella (MMR) in Singapore to assess the impact of the national childhood immunization programme against these three diseases after introduction of the trivalent MMR vaccine in 1990. The survey involved 1200 residual sera of Singapore residents aged 1-17 years collected from two hospitals between 2008 and 2010. The overall prevalence of antibodies against measles, mumps and rubella was 83∙1% [95% confidence interval (CI) 80∙9-85∙1], 71.8% (95% CI 69∙1-74∙2) and 88∙5% (95% CI 86∙6-90∙2), respectively. For all three diseases, the lowest prevalence was in children aged 1 year (47∙8-62∙3%). The seroprevalence of the vaccinated children declined over time. The national MMR immunization programme is effective in raising the herd immunity of the childhood population, although certain age groups are more susceptible to infection, in particular, those who are not eligible for vaccination at age <15 months.

Comparative seroepidemiology of pertussis, diphtheria and poliovirus antibodies in Singapore: waning pertussis immunity in a highly immunized population and the need for adolescent booster doses.

BACKGROUND: We assessed the seroepidemiology of pertussis, diphtheria and poliovirus antibodies in a cohort of highly immunized children, together with the burden of these diseases in Singapore. METHODS: Hospital residual sera collected between August 2008 and July 2010 from 1200 children aged 1-17 years were tested for the prevalence of IgG antibodies against Bordetella pertussis, diphtheria toxoid, and all three poliovirus types by enzyme-linked immunosorbent assays. RESULTS: We found an overall seroprevalence of 99.4% (95% CI 98.8-99.7%) for diphtheria, and 92.3% (95% CI 90.6-93.6%) for poliomyelitis, along with no indigenous cases of these diseases since 1993. However, the seroprevalence for pertussis was 60.8% (95% CI 58.0-63.5%) only. Among the subjects who had completed three doses of pertussis vaccination by the age of 2 years (n=1092), the pertussis seroprevalence was 85.0% (95% CI 79.7-89.2%) in those who received the last vaccination within a year before the study, and it decreased to 75.0% (95% CI 64.5-83.2%) and 63.1% (95% CI 50.9-73.8%) in those who had the last vaccination 1 year and 2 years before the study, respectively. The seroprevalence remained at about 50% for those whose last pertussis vaccination was administered 4 years and longer before the study. CONCLUSIONS: The high seroprevalence for poliomyelitis and diphtheria confer solid herd immunity to eliminate these diseases in Singapore. In contrast, immunity against pertussis waned considerably over time, and routine boosters should be given to adolescents to ensure sustained immunity against pertussis.

Correlations between clinical illness, respiratory virus infections and climate factors in a tropical paediatric population.

Weekly (August 2003-December 2008) numbers of five common paediatric diseases and the incidence of respiratory viruses were obtained from a children's hospital in Singapore and correlated with climate data using multivariate time-series techniques. Upper respiratory tract infections were positively correlated with the incidences of influenza A, B, respiratory syncytial virus (RSV) and parainfluenza viruses (types 1-3 combined). Lower respiratory tract infections were positively correlated with only the incidence of RSV. Both upper and lower respiratory tract infections were negatively correlated with relative humidity. Asthma admissions were negatively correlated with maximum temperature and positively correlated with the incidence of influenza B and increasing hours of sunshine. Although sporadic cases of adenovirus infection were identified, not enough cases were available for a more detailed analysis. Gastroenteritis and urinary tract infections, included as control diseases, were not correlated significantly with any climate parameters. These correlations are compatible with current understanding of respiratory virus survival under certain climate conditions and may assist the prediction of disease burdens and hospital resource planning in such tropical environments.

Incidence of common respiratory viral infections related to climate factors in hospitalized children in Hong Kong.

Hong Kong has a subtropical climate and an influenza seasonality lying approximately mid-way (March-June) between those of the Northern (November-March) and Southern (June-September) hemispheres. Respiratory syncytial virus (RSV) shares a similar seasonality to that of influenza in Hong Kong and is another important respiratory infection of childhood. Daily virus incidence data from public hospitals in Hong Kong's New Territory East Cluster, together with Hong Kong climate data were obtained for 2000-2007. Statistical time-series analysis using monthly time windows showed that influenza A and RSV incidence increased with higher environmental relative humidity, whereas influenza B incidence decreased with higher environmental temperatures. The other climate variables (including vapour pressure as a measure of absolute humidity) were not significantly related to the incidence of these respiratory viruses. Data from this study further reinforces the concept that the relationship between climate factors and respiratory virus incidence differ between subtropical/tropical and temperate countries.

Construction of a broad-host-range promoter-probing vector and cloning of promoter fragments of Xanthomonas campestris.

A broad-host-range promoter-probing vector, pMY3 (8.0 kb), was constructed for cloning of DNA fragments containing promoter sequences of Xanthomonas campestris pv. campestris. This vector (pMY3) consists of the RK2 replicon, promoterless luxAB genes, the thr attenuator to block the transcription of RNA into the luxAB region, and multiple cloning sites for cloning of the fragment carrying promoter sequences. The feasibility of using pMY3 as a promoter-probing vector in both E. coli and Xc17 was demonstrated by using the lac promoter of E. coli, and the amy promoter of X. campestris in Xc17. Among the 63 promoter-containing fragments cloned from Xc17, only 9 were able to express in E. coli. It appears that X. campestris can recognize most E. coli type promoters, but, E. coli can recognize only a small portion of the X. campestris type promoters.