Perspectives on greenhouse gas emission estimates based on Australian wastewater treatment plant operating data.

Primary operating data were collected from forty-six wastewater treatment plants (WWTPs) located across three states within Australia. The size range of plants was indicatively from 500 to 900,000 person equivalents. Direct and indirect greenhouse gas emissions were calculated using a mass balance approach and default emission factors, based on Australia's National Greenhouse Energy Reporting (NGER) scheme and IPCC guidelines. A Monte Carlo-type combined uncertainty analysis was applied to the some of the key emission factors in order to study sensitivity. The results suggest that Scope 2 (indirect emissions due to electrical power purchased from the grid) dominate the emissions profile for most of the plants (indicatively half to three quarters of the average estimated total emissions). This is only offset for the relatively small number of plants (in this study) that have significant on-site power generation from biogas, or where the water utility purchases grid electricity generated from renewable sources. For plants with anaerobic digestion, inventory data issues around theoretical biogas generation, capture and measurement were sometimes encountered that can skew reportable emissions using the NGER methodology. Typically, nitrous oxide (N(2)O) emissions dominated the Scope 1 (direct) emissions. However, N(2)O still only accounted for approximately 10 to 37% of total emissions. This conservative estimate is based on the 'default' NGER steady-state emission factor, which amounts to 1% of nitrogen removed through biological nitrification-denitrification processing in the plant (or indicatively 0.7 to 0.8% of plant influent total nitrogen). Current research suggests that true N(2)O emissions may be much lower and certainly not steady-state. The results of this study help to place in context research work that is focused on direct emissions from WWTPs (including N(2)O, methane and carbon dioxide of non-biogenic origin). For example, whereas non-biogenic CO(2) contributions are relatively minor, it appears that opportunities to reduce indirect emissions as a result of modest savings in power consumption are at least in the same order as those from reducing N(2)O emissions. To avoid potentially high reportable emissions under NGER guidelines, particularly for methane, the onus is placed on WWTP managers to ensure that accurate plant monitoring operating records are kept.

Local epidemic history as a predictor of tuberculosis incidence in Saskatchewan Aboriginal communities.

BACKGROUND: Average tuberculosis (TB) incidence rates are high in Canadian Aboriginal communities, but there is significant variability within this group. OBJECTIVE: To determine whether local history of post-contact TB epidemics is predictive of contemporary epidemiology among Aboriginal communities in Saskatchewan, Canada. METHODS: TB incidence, age-specific morbidity patterns and rates of clustering of TB genotypes from 1986 to 2004 were compared between two groups of communities: Group 1, in which post-contact epidemics of TB were established around 1870, and Group 2, in which they were delayed until after 1920. Concomitant effects of socio-economic and geographic variables were explored with multivariate models. RESULTS: Group 2 communities were characterized by higher annual incidence of TB (median 431 per 100,000 population vs. 38/100,000). In multivariate models that included socio-economic and geographic variables, historical grouping remained a significant independent predictor of community incidence of TB. Clustering of TB genotypes was associated with Group 2 (OR 8.7, 95%CI 3.3-22.7) and age 10-34 years (OR 2.5, 95%CI 1.1-5.7). CONCLUSIONS: TB transmission dynamics can vary significantly as a function of a population's historical experience with TB. Populations at different stages along the epidemic trajectory may be amenable to different types of interventions.

Low-virulence Citrobacter species encode resistance to multiple antimicrobials.

Citrobacter spp. are gram-negative commensal bacteria that infrequently cause serious nosocomial infections in compromised hosts. They are often resistant to cephalosporins due to overexpression of their chromosomal beta-lactamase. During a recent study of multidrug-resistant Enterobacteriaceae (MDRE) in solid-organ transplant patients, we found that almost half of patients colonized with MDRE carried one or more cefpodoxime-resistant Citrobacter freundii, Citrobacter braakii, or Citrobacter amalonaticus strains. Pulsed-field gel electrophoresis showed that 36 unique strains of Citrobacter were present among 32 patients. Genetic and phenotypic analysis of the resistance mechanisms of these bacteria showed that the extended-spectrum beta-lactamase (ESBL) SHV-5 or SHV-12 was encoded by 8 strains (26%) and expressed by 7 strains (19%). A number of strains were resistant to other drug classes, including aminoglycosides (28%), trimethoprim-sulfamethoxazole (31%), and fluoroquinolones (8%). PCR and DNA analysis of these multiresistant strains revealed the presence of class I integrons, including the first integrons reported for C. braakii and C. amalonaticus. The integrons encoded aminoglycoside resistance, trimethoprim resistance, or both. Despite the prevalence of MDR Citrobacter spp. in our solid-organ transplant patients, only a single infection with a colonizing strain was recorded over 18 months. Low-virulence Citrobacter spp., which can persist in the host for long periods, could influence pathogen evolution by accumulation of genes encoding resistance to multiple antimicrobial classes.

Nonspecific esterase activity in astrocytes of the goldfish brain.

We examined the distribution of nonspecific esterase (NSE) activity in the brain of the goldfish, Carassius auritus, and found that the enzyme is expressed at high levels in cells that appeared to be radial astrocytes. Several instances in which neurons expressed NSE activity were also seen. To confirm the identity of the radial profiles as astrocytes, similar sections were labeled with antiserum against goldfish glial fibrillary acidic protein (GFAP). The concordance between the NSE and the anti-GFAP data in both the visual system and the telencephalon was essentially complete, confirming that the NSE reaction was labeling astrocytes in these structures. The two methods also gave similar results in both the cerebellum and the vagal lobes, although the concordance between them in these instances was somewhat less complete. Both the NSE reaction and immunohistochemistry with anti-GFAP serum revealed labeled nonradial cells lying free in the cerebellar molecular layer. We suggest that these cells may represent free astrocytes, a cell type that has not previously been reported in morphological studies of the teleostean brain. On the basis of our observations, we suggest that the NSE reaction may be a useful adjunct in morphological studies of teleost astroglia. Finally, we propose that the expression of NSE activity in goldfish astrocytes may he related to their ability to internalize neural debris during Wallerian degeneration.