Can the legacy of industrial pollution influence antimicrobial resistance in estuarine sediments?

Antimicrobial resistance (AMR) represents a major global health threat, as well as a major hazard to sustainable economic development and national security. It remains, therefore, vital that current research aligns to policy development and implementation to alleviate a potential crisis. One must consider, for example, whether drivers of antibiotic resistance can be controlled in the future, or have they already accumulated in the past, whether from antibiotics and/or other pollutants? Unfortunately, industrial heritage and its pollution impact on the prevalence of environmental AMR have largely been ignored. Focussing on industrialised estuaries, we demonstrate that anthropogenic pollution inputs in addition to the natural diurnal environmental conditions can sufficiently create stressful conditions to the microbiome and thus promote selective pressures to shift the resistome (i.e., collection of resistance traits in the microbiological community). Unfortunately, the bacteria’s survival mechanisms, via co-selective pressures, can affect their susceptibility to antibiotics. This review highlights the complexity of estuarine environments, using two key contaminant groups (metals/toxic elements and polyaromatic hydrocarbons), through which a variety of possible chemical and biological pollutant stressors can promote the emergence and dissemination of antimicrobial resistance. We find compelling divers to call on more focused research on historically disrupted ecosystems, in propagating AMR in the real world.

     

Bystander injury evaluation of children from midwestern agricultural operations

Background

With more than a million youth living on agricultural operations, it is important for parents to understand the consequences of bystander injuries that children experience in these environments. We identified the childhood injuries for bystander status and compared the severity of these injuries to the working children in the Regional Rural Injury Study-II (RRIS-II).

Methods

RRIS-II followed 16,546 children (∼ 85% of eligible) from rural communities in the Midwest for two six-month recall periods in 1999 and 2001. Demographic, injury, and exposure data were collected through comprehensive computer-assisted telephone interviews. Child injuries were cataloged using narrative scenarios into four categories: (a) directly work-related; (b) indirectly work-related; (c) non-working accomplice; and (d) non-working attendant; the latter three all being bystander categories. Poisson regression modeling was used to calculate rates of bystander injuries. Frequencies were used for comparison of severity measures.

Results

Among the 463 child injuries (aged < 20 yrs), 102 were bystander injuries. Of the bystander-related injuries, 14 were identified as indirectly work-related (working bystanders), 27 as non-working accomplice (passengers/tag-alongs), and 60 as non-working attendant (playing on the operation). The overall rate of bystander injuries was 6.4 per 1,000 people, 95% CI (5.0, 8.1). Males, compared with females, had more than twice the injury rate (8.7; 95% CI 6.4-11.8, and 3.9; 95% CI 2.7-5.7, per 1,000 people, respectively). Bystanders in this population had more severe injuries with 4% having life-threatening circumstances; of these, 4% of the accomplices and 2% of the attendants subsequently died.

Conclusions

Children who live or work on agricultural operations are vulnerable to many hazards. Therefore, this study examined child injuries and found a clear difference in the consequences of these injuries between working-related and bystanding-related injuries.

Impact on Industry

Unlike occupations such as construction and mining, where laws and organizations have been created for the protection of bystanders, agricultural bystanders have remained unprotected and have had to face the consequent injury and death outcomes. As public health professionals considering these risks, it is necessary that we work to develop more intervention studies and continue to propose suggestive guidelines for child safety in these environments so as to challenge family traditions and possibly spark public policies that will give further protection to this population.     

Graduated Driver Licensing Research, 2007-Present: A Review and Commentary

The evolution of graduated licensing systems in the past 25 years has resulted in dramatic growth in research on this topic. The most recent summary reports have covered the period up to 2007. In the present article more recent and ongoing research is categorized, summarized, and discussed.     

Adaptation to climate change of wheat growing in South Australia: Analysis of management and breeding strategies

Evaluation of adaptive management options is very crucial for successfully dealing with negative climate change impacts. Research objectives of this study were (1) to determine the proper N application rate for current practice, (2) to select a range of synthetic wheat (Triticum aestivum L.) cultivars to expand the existing wheat cultivar pool for adaptation purpose, (3) to quantify the potential impacts of climate change on wheat grain yield and (4) to evaluate the effectiveness of three common management options such as early sowing, changing N application rate and use of different wheat cultivars derived in (2) and given in the APSIM-Wheat model package in dealing with the projected negative impacts for Keith, South Australia. The APSIM-Wheat model was used to achieve these objectives. It was found that 75 kg ha^?1 N application at sowing for current situation is appropriate for the study location. This provided a non-limiting N supply condition for climate change impact and adaptation evaluation. Negative impacts of climate change on wheat grain yield were projected under both high (?15%) and low (?10%) plant available water capacity conditions. Neither changes in N application level nor in wheat cultivar alone nor their synergistic effects could offset the negative climate change impact. It was found that early sowing is an effective adaptation strategy when initial soil water was reset at 25 mm at sowing but this may be hard to realise especially since a drier environment is projected.     

DNA adducts as early bioindicators of chemical exposure

Sensitive analytical methods indicate the presence of hundreds of chemical contaminants in our environment. However, concentration of these pollutants is usually at the low parts per million or parts per billion level. At such low levels, toxicants induce long-term (chronic) rather than short-term (acute) toxicities. Experiments are designed to evaluate chronic toxicity using early bioindicators. Recently, fish have been used as experimental animals because some species show early (weeks as opposed to years in other research animals), sensitive responses. Thus, medaka (Oryzias latipes), following exposure to diethylnitrosamine (DEN), exhibited liver tumors in several weeks; more interestingly its DNA was modified (to a DNA-adduct) after only 24–48 hours exposure. Such adducts show promise as early bioindicators because they are formed within hours of exposure. The formation of DNA-adducts were monitored in medaka and rainbow trout (Salmo gairdneri) exposed to DEN by aqueous or intra-peritoneal routes. Using HPLC-Fluorimetry, O ⁶-ethylguanine (O ⁶-EtGua) was detected and monitored in acid thermal hydrolysates of DNA isolates. (Detection limit for O ⁶-EtGua was as low as 3 ng, 1.7×10^-11 moles). Fourier transform cyclotron resonance mass spectrometry with IR laser desorption/ionization was used advantageously to establish the structure of nucleotides, bases and nucleosides directly, without further cumbersome derivatizations. Other aspects of DNA-adducts are discussed.     

Utilization of partially predated snail shells by the hermit crab Pagurus longicarpus Say, 1817

The hermit crab Pagurus longicarpus was shown to inhabit shells that were partially predated from intertidal areas of Long Island, New York. Among field collections of P. longicarpus, 2.13% of the hermit crabs (46 of 2155) were found with shells with snail tissue present. Over 90% of these partially predated snail shells were occupied by male hermit crabs. Although hermit crabs were in 8 species of snail shells, only Littorina littorea and Nassarius obsoletus were found occupied by hermit crabs and containing snail tissue. In the laboratory, we found that specimens of the spider crab Libinia emarginata were able to pull off the operculum of snails, leaving damage as found in field collections. In contrast, specimens of P. longicarpus were not able to prey on live, healthy snails. When specimens of P. longicarpus were placed in communal tanks, hermit crabs preferred partially predated snail shells to empty and original shells. However, original shells and empty shells were occupied with more frequency than partially predated shells when crabs were isolated. These findings indicate P. longicarpus actively seeks shells soon after attack and abandonment by snail predators, especially in the presence of competitors.     

Predators usurp prey defenses? Toxicokinetics of tetrodotoxin in common garter snakes after consumption of rough-skinned newts

Snakes are common predators of organisms, such as amphibians, with toxic defenses that can be lethal to other predators. Because snakes do not have the option of dissecting prey into edible versus inedible components, they face a full dose of any chemical defenses encountered during attempted predation. This limitation has likely resulted in intense selection favoring the evolution of alternative mechanisms for dealing with prey toxins. These mechanisms can be physiological (e.g., resistance to prey toxins) or behavioral (e.g., toxin sampling and rejection). When physiological resistance arises, the possibility of bioaccumulation of a toxin results. We examined the coevolutionary interaction between the common garter snake (Thamnophis sirtalis) and the rough-skinned newt (Taricha granulosa), which contains a powerful neurotoxin called tetrodotoxin (TTX). In some populations syntopic with newts, individuals of T. sirtalis have evolved resistance to TTX. We examined the persistence of TTX in T. sirtalis after administration of an oral dose of TTX to investigate the possibility that snakes are sequestering TTX. The half-life of TTX in snake liver was estimated at 8.1?days. Accordingly, clearance of 99% of a single dose of TTX averages 61?days. Negative fitness consequences of intoxication during and after newt consumption may be balanced by co-opting the newts?? chemical defense for protection from the snakes?? own predators. Accounting of the coevolutionary dynamic between snakes and newts must incorporate post-consumption affects of lingering TTX.     

Re-creating missing population baselines for Pacific reef sharks

Sharks and other large predators are scarce on most coral reefs, but studies of their historical ecology provide qualitative evidence that predators were once numerous in these ecosystems. Quantifying density of sharks in the absence of humans (baseline) is, however, hindered by a paucity of pertinent time-series data. Recently researchers have used underwater visual surveys, primarily of limited spatial extent or nonstandard design, to infer negative associations between reef shark abundance and human populations. We analyzed data from 1607 towed-diver surveys (>1 ha transects surveyed by observers towed behind a boat) conducted at 46 reefs in the central-western Pacific Ocean, reefs that included some of the world's most pristine coral reefs. Estimates of shark density from towed-diver surveys were substantially lower (<10%) than published estimates from surveys along small transects (<0.02 ha), which is not consistent with inverted biomass pyramids (predator biomass greater than prey biomass) reported by other researchers for pristine reefs. We examined the relation between the density of reef sharks observed in towed-diver surveys and human population in models that accounted for the influence of oceanic primary productivity, sea surface temperature, reef area, and reef physical complexity. We used these models to estimate the density of sharks in the absence of humans. Densities of gray reef sharks (Carcharhinus amblyrhynchos), whitetip reef sharks (Triaenodon obesus), and the group "all reef sharks" increased substantially as human population decreased and as primary productivity and minimum sea surface temperature (or reef area, which was highly correlated with temperature) increased. Simulated baseline densities of reef sharks under the absence of humans were 1.1-2.4/ha for the main Hawaiian Islands, 1.2-2.4/ha for inhabited islands of American Samoa, and 0.9-2.1/ha for inhabited islands in the Mariana Archipelago, which suggests that density of reef sharks has declined to 3-10% of baseline levels in these areas.