Microbial communities from different types of natural wastewater treatment systems: vertical and horizontal flow constructed wetlands and biofilters

The prokaryotic microbial communities (Bacteria and Archaea) of three different systems operating in Denmark for the treatment of domestic wastewater (horizontal flow constructed wetlands (HFCW), vertical flow constructed wetlands (VFCW) and biofilters (BF)) was analysed using endpoint PCR followed by Denaturing Gradient Gel Electrophoresis (DGGE). Further sequencing of the most representative bacterial bands revealed that diverse and distinct bacterial communities were found in each system unit, being γ-Proteobacteria and Bacteroidetes present mainly in all of them, while Firmicutes was observed in HFCW and BF. Members of the Actinobacteria group, although found in HFCW and VFCW, seemed to be more abundant in BF units. Finally, some representatives of α, β and δ-Proteobacteria, Acidobacteria and Chloroflexi were also retrieved from some samples. On the other hand, a lower archaeal diversity was found in comparison with the bacterial population. Cluster analysis of the DGGE bacterial band patterns showed that community structure was related to the design of the treatment system and the organic matter load, while no clear relation was established between the microbial assemblage and the wastewater influent.

A new microtitre plate screening method for evaluating the viability of aerobic respiring bacteria in high surface biofilms

AIMS

It is difficult to determine the effects of bactericidal compounds against bacteria in a biofilm because classical procedures for determining cell viability require several working days, multiple complicated steps and are frequently only applicable to cells in suspension. We attempt to develop a compact, inexpensive and versatile system to measure directly the extent of biofilm formation from water systems and to determine the viability of respiring bacteria in high surface biofilms.

METHODS AND RESULTS

It has been reported that the reduction of tetrazolium sodium salts, such as XTT (sodium 3,3'-[1-[(phenylamino)carbonyl]-3,4-tetrazolium]Bis(4-methoxy)-6-nitro)benzene sulfonic acid hydrate), during active bacterial metabolism can be incorporated into a colorimetric method for quantifying cell viability. XTT is reduced to a soluble formazan compound during bacterial aerobic metabolism such that the amount of formazan generated is proportional to the bacterial biomass.

CONCLUSIONS

We show here, for the first time, that this colorimetric approach can be used to determine the metabolic activity of adherent aerobic bacteria in a biofilm as a measure of cell viability. This technique has been used to estimate viability and proliferation of bacteria in suspension, but this is the first application to microbial communities in a real undisturbed biofilm.

SIGNIFICANCE AND IMPACT OF THE STUDY

This simple new system can be used to evaluate the complex biofilm community without separating the bacteria from their support. Thus, the results obtained by this practice may be more representative of the circumstances in a natural system, opening the possibility to multiple potential applications.

[Cardiovascular risk and glucose metabolism: agreements and discrepancies between the WHO-85 and ADA-97 classifications]

AIM. To identify the differences between coronary heart disease risk in patients with altered basal glucemia (ABG), oral glucose intolerance (OGI) and type II diabetes mellitus according to the WHO-85 and ADA-97 diagnostic classifications, in an adult population at high risk for diabetes mellitus.

DESIGN

Descriptive, cross-sectional, multicenter study.Setting. Seven primary health care centers in Spain.Patient. 970 persons considered the population at risk for type II diabetes mellitus.

MEASURES

Participants were classified according to the criteria of the WHO-85 (normal, OGI, diabetes) and the ADA-97 system (normal, ABG, diabetes). The following variables were recorded: age, sex, smoking habit, body mass index, systolic blood pressure, diastolic blood pressure, basal glucemia, glucemia 2 h after an oral glucose tolerance test, HbA1c, microalbmuniuria, total cholesterol, HDL, LDL and triglycerides. Coronary heart disease risk was calculated with the 1998 table developed by Wilson et al. on the basis of the Framingham study.

RESULTS

A total of 970 participants were studied. Mean age was 58.6 #+ 12.4 years; 453 were men (46.7%) and 517 were women (53.3%). Our analysis showed that cardiovascular disease risk factors were less frequent in normal subjects, and that their prevalence was higher in persons with diabetes (according to both WHO and ADA classifications). There were no significant differences in coronary heart disease risk or different risk factors between analogous groups in the two classification systems (normal, OGI/ABG or diabetes). Coronary heart disease risk in persons with different types of alterations in glucose metabolism was 11.3% in normal subjects, 14% in persons with OGI and 27.3% in persons with diabetes according to the WHO-85 system, and 11.4% in normal subjects, 15.7% in persons with ABG and 29.5% in persons with diabetes according to the ADA-97 system.

CONCLUSIONS

The greater the alteration in carbohydrate metabolism, the greater the coexistence of risk factors and the estimated risk of coronary heart disease. There were no significant differences in the presence of cardiovascular risk factors, or in the relationship between carbohydrate metabolism and coronary heart disease risk, between analogous stages identified with one classification system or the other.

[Prevention of thromboembolic disease in patients with heart disease]

OBJECTIVE

To evaluate the adequacy to thromboembolic disease prophylaxis protocol in patients with heart disease.

DESIGN

Cross-sectional study.

SUBJECTS

Patients older than 14 years affected of heart disease in a semi-urban health primary-care clinic with a population of 10,610 persons and 5582 clinical records.

METHODS

Data about age, sex, cardiovascular risk factors, heart disease, prophylactic treatment and its adequacy to the protocol of the "thromboembolic disease commission" of the reference hospital were analysed.

RESULTS

Age 67 +/- 13 years (mean +/- SD). Cardiovascular risk factors: hypertension 40%, diabetes 33%, dyslipemia 15%, smoking 21%. Heart disease: ischemic cardiopathy 48%, atrial fibrillation 15%, valvulopathy 19%, dilated myocardiopathy 4% and other 14%. In 20% of cases had two different affections (80% with atrial fibrillation). Prophylactic therapy: 52% of patients were under prophylactic treatment (35% antiaggregation, 18% anticoagulation). Among antiaggregants, drugs used were acetylsalicylic acid 73.5%, triflusal 14.7%, dipyridamole, 8.8% and ticlopidine 3%. In 53% of people without prophylactic treatment antiaggregation criteria were present. 15% of patient under antiaggregation therapy did not meet antiaggregation criteria, and 6% fulfilled anticoagulation criteria. 67% treatments accorded the reference protocol, without significant differences between kind of heart disease or sex. The only statistically significant difference was found in age: 46% of patients older than 80 year were correctly treated, in front 75% adequacy in younger people.

CONCLUSION

Prophylactic antithrombotic therapy was according the reference protocol in 67% of cases. In older patients, with greater risk of thromboembolic disease, the adequacy is worse.

Impact of the American Diabetes Association diagnosis criteria on high-risk Spanish population. IGT Research Group. Impaired glucose tolerance

To research into the impact of the new American Diabetes Association (ADA) diagnostic criteria on high risk Spanish population, two cross-sectional studies involving seven primary health care centers in Catalonia (Spain) were revised. Individuals aged > 40 years with any major risk factor for diabetes were screened according to the World Health Organization (WHO) rules using a 75 g oral glucose tolerance test to measure fasting plasma glucose (FPG) and 2 h plasma glucose. The changes on diabetes prevalence and on epidemiological characteristics were evaluated applying the ADA criteria on the basis of FPG alone. A total of 970 individuals, 453 males (46.7%), mean age 59 years and mean body mass index (BMI) 30.6 kg/m2 were screened. Among the 459 diabetic subjects according to either the WHO or the ADA criteria, 314 (68.4%) were classified as having diabetes with respect to both sets of criteria (WHO and ADA). The overlap between impaired glucose tolerance (WHO) and impaired fasting glucose (ADA) diagnoses was 20.7%. Using the ADA criteria results in a decrease of the prevalence of diabetes by 1.5% (95% confidence interval (CI) = -2.2 to -0.8%). No changes in the diabetic phenotype (age, sex and BMI) were found. Impaired fasting glucose prevalence was 18.4% (95% CI = 16-21%). Overall concordance in terms of crude and weighted kappa-value was only acceptable (kappa = 0.51 and kappa = 0.61, respectively). To apply the new ADA diagnostic criteria on high risk Spanish population evidenced a decrease on diabetes prevalence. Nevertheless, the change of criteria undervalued the risk of postprandial hyperglycaemia related to impaired glucose tolerance.

Resistance to chlorine of freshwater bacterial strains

The disinfectant properties of chlorine have been known for centuries but in the last few years water chlorination has attracted some criticism due to its secondary effects and the increased resistance of bacterial strains to chlorine inactivation. In this paper the kinetics of inactivation by chlorine of different Gram-positive and Gram-negative bacterial strains isolated from chlorinated water is studied. The Gram-positive strains were more resistant to chlorine and the behaviour of some of them in the presence of chloramphenicol suggests either the synthesis of unique proteins or aggregation of the bacteria as mechanisms of resistance to inactivation. The concept of Ki, the inactivation rate constant, by comparison with Ks in Michaelis-Menten enzyme kinetics (considering enzymic saturation), or with Ks in Monod growth kinetics (considering limiting rates of transport and metabolism of substrates), may be an interesting parameter to define microbial resistance to disinfectants and toxics.