Characterization of Shewanella oneidensis MtrC: a cell-surface decaheme cytochrome involved in respiratory electron transport to extracellular electron acceptors

MtrC is a decaheme c-type cytochrome associated with the outer cell membrane of Fe(III)-respiring species of the Shewanella genus. It is proposed to play a role in anaerobic respiration by mediating electron transfer to extracellular mineral oxides that can serve as terminal electron acceptors. The present work presents the first spectropotentiometric and voltammetric characterization of MtrC, using protein purified from Shewanella oneidensis MR-1. Potentiometric titrations, monitored by UV–vis absorption and electron paramagnetic resonance (EPR) spectroscopy, reveal that the hemes within MtrC titrate over a broad potential range spanning between approximately +100 and approximately -500 mV (vs. the standard hydrogen electrode). Across this potential window the UV–vis absorption spectra are characteristic of low-spin c-type hemes and the EPR spectra reveal broad, complex features that suggest the presence of magnetically spin-coupled low-spin c-hemes. Non-catalytic protein film voltammetry of MtrC demonstrates reversible electrochemistry over a potential window similar to that disclosed spectroscopically. The voltammetry also allows definition of kinetic properties of MtrC in direct electron exchange with a solid electrode surface and during reduction of a model Fe(III) substrate. Taken together, the data provide quantitative information on the potential domain in which MtrC can operate

Development, confirmation, and application of a seeded Escherichia coli process control organism to validate Salmonella enterica serovar Typhi environmental surveillance methods

Salmonella enterica serovar Typhi (S. Typhi) is the causative agent of Typhoid fever. Blood culture is the gold standard for clinical diagnosis, but this is often difficult to employ in resource limited settings. Environmental surveillance of waste-impacted waters is a promising supplement to clinical surveillance, however validating methods is challenging in regions where S. Typhi concentrations are low. To evaluate existing S. Typhi environmental surveillance methods, a novel process control organism (PCO) was created as a biosafe surrogate. Using a previous described qPCR assay, a modified PCR amplicon for the staG gene was cloned into E. coli. We developed a target region that was recognized by the Typhoid primers in addition to a non-coding internal probe sequence. A multiplex qPCR reaction was developed that differentiates between the typhoid and control targets, with no cross-reactivity or inhibition of the two probes. The PCO was shown to mimic S. Typhi in lab-based experiments with concentration methods using primary wastewater: filter cartridge, recirculating Moore swabs, membrane filtration, and differential centrifugation. Across all methods, the PCO seeded at 10 CFU/mL and 100 CFU/mL was detected in 100% of replicates. The PCO is detected at similar quantification cycle (Cq) values across all methods at 10 CFU/mL (Average = 32.4, STDEV = 1.62). The PCO was also seeded into wastewater at collection sites in Vellore (India) and Blantyre (Malawi) where S. Typhi is endemic. All methods tested in both countries were positive for the seeded PCO. The PCO is an effective way to validate performance of environmental surveillance methods targeting S. Typhi in surface water

Wastewater surveillance for bacterial targets: current challenges and future goals

Wastewater-based epidemiology (WBE) expanded rapidly in response to the COVID-19 pandemic. As the public health emergency has ended, researchers and practitioners are looking to shift the focus of existing wastewater surveillance programs to other targets, including bacteria. Bacterial targets may pose some unique challenges for WBE applications. To explore the current state of the field, the National Science Foundation-funded Research Coordination Network (RCN) on Wastewater Based Epidemiology for SARS-CoV-2 and Emerging Public Health Threats held a workshop in April 2023 to discuss the challenges and needs for wastewater bacterial surveillance. The targets and methods used in existing programs were diverse, with twelve differentdifferentdifferenttargets and nine different methods listed. Discussions during the workshop highlighted the challenges in adapting existing programs and identified research gaps in four key areas: choosing new targets, relating bacterial wastewater data to human disease incidence and prevalence, developing methods, and normalizing results. To help with these challenges and research gaps, the authors identified steps the larger community can take to improve bacteria wastewater surveillance. This includes developing data reporting standards and method optimization and validation for bacterial programs. Additionally, more work is needed to understand shedding patterns for potential bacterial targets to better relate wastewater data to human infections. Wastewater surveillance for bacteria can help provide insight into the underlying prevalence in communities, but much work is needed to establish these methods

Aerosol Sampling in a Hospital Emergency Room Setting: A Complementary Surveillance Method for the Detection of Respiratory Viruses

This study aimed to evaluate environmental air sampling as an alternative form of active surveillance for respiratory pathogens in clinical settings. Samples were collected from three locations in the Emergency Department at Duke University Hospital Systems from October 2017 to March 2018. Of the 44 samples collected, 12 were positive for known respiratory pathogens including influenza A, influenza D, and adenovirus. Results suggest bioaerosol sampling may serve as a complement to active surveillance in clinical settings. Additionally, since respiratory viruses were detected in aerosol samples, our results suggest that hospital infection control measures, including the use of N95 respirators, could be used to limit the spread of infectious viruses in the air

Molecular positivity for PCV2 detected via rPCR in samples collected from 11 farms, 2 abattoirs, and 3 live animal markets in Sarawak, Malaysia in June and July of 2017.

<p>Sites beginning with ‘F’ denotes farm, ‘A’ denotes abattoir, and ‘M’ denotes market; porcine circovirus 2 (PCV2).</p

Molecular positivity for respiratory viruses detected via rPCR or rRT-PCR in samples collected from animal environments in Sarawak, Malaysia in June and July of 2017.

<p>Molecular positivity for respiratory viruses detected via rPCR or rRT-PCR in samples collected from animal environments in Sarawak, Malaysia in June and July of 2017.</p

The transnational mobilization of ‘irregular migrants’

This chapter explores the transnational movements of so called ‘irregular migrants’. We investigate why and how transnational collective action is taken by people in situations of vulnerability and ask how those with limited resources manage to mobilize at the transnational level. In order to frame that core arguments, we analyse one particular event which occurred in 2012, namely the European March of sans-papiers and migrants. We explore how the movement was triggered, how it was organized, what claims were made, and what impact it had. We argue that the movement was subversive in three different ways: irregular migrants sought to act like any other citizen; they questioned the boundaries of the nation state; and they refused to be defined and limited by the global social order. We show that the transnational character of the mobilization is closely related to the root of the problems it sought to address such as European migration policies. Finally, we illustrate how mobilization at a transnational level reinforces the social movements of ‘irregular migrants’

Unadjusted odds ratios for risk factors associated with PCV2 molecular positivity of 55 pig fecal samples and 49 pig oral secretions or water samples collected from 11 pig farms in Sibu, Sarawak, Malaysia in July 2017.

<p>Unadjusted odds ratios for risk factors associated with PCV2 molecular positivity of 55 pig fecal samples and 49 pig oral secretions or water samples collected from 11 pig farms in Sibu, Sarawak, Malaysia in July 2017.</p

Perceptions of efficacy of personal protective equipment (PPE) at preventing cross-species infection, reported use, and viral positivity among PPE users in 77 worker nasal wash samples collected from farms, abattoirs, and live animal markets in Sarawak, Malaysia in June and July of 2017.

<p>Viral positivity is defined as a positive rPCR or rRT-PCR result for at least one of the following viruses: adenovirus, coronavirus, enterovirus, encephalomyocarditis virus, influenza A-D, porcine circovirus 2, or porcine rotavirus C.</p