A series of heterostructured BiVO4/WO3 photoanodes were successfully prepared via a two-step method of hydrothermal deposition and impregnation. The optimized BiVO4/WO3 sample showed the highest photocurrent density of ∼880 μA/cm2 at 0.8 V (vs Ag/AgCl) in 0.1 M KH2PO4 aqueous solution (pH 7) under simulated AM1.5 illumination. The optimized BiVO4/WO3 photoanode was coupled with a Pt/C air-breathing cathode to build up a visible-light responsive PFC system. The as-prepared PFC system showed outstanding photoelectrocatalytic performances in converting organics into electricity, and when glucose was used as the 'fuel', the maximum power density (Pmax) and the short-circuit current density (Isc) were 8.58 μW/cm2 and 91.8 μA/cm2, respectively. Degradation experiments showed that the removal rate of tetracycline hydrochloride in PFC with BiVO4/WO3 photoanode and Pt/C air-breathing cathode was ∼87.2% in 8 h, which was much higher than photolysis and photocatalysis process. The mechanism responsible for the enhanced photoelectrocatalytic performance of the as-prepared PFC system was also discussed.

Abiotic mechanisms of oxytetracycline degradation by redox-active minerals, Fe(III)-saturated montmorillonite (Fe-SWy) and birnessite (δ-MnO2), were studied to better understand the environmental behavior of tetracycline antibiotics in aqueous systems. Kinetics of dissipation (adsorption, oxidation and formation of transformation products (TPs)), was investigated up to 7 days, and reaction mechanisms were elucidated based on identification of TPs by liquid chromatography mass spectrometry. Oxytetracycline was completely removed from solution by both minerals, however kinetics, TPs and mechanisms were distinct for each mineral. Oxytetracycline oxidation by δ-MnO2 occurred within minutes; 54 identified TPs were detected only in solution, most of them exhibited decreasing levels with time. In contrast, oxytetracycline was completely adsorbed by Fe-SWy, its degradation was slower, only 29 TPs were identified, among them 13 were surface-bound, and most of the TPs accumulated in the system with time. Oxytetracycline transformation by δ-MnO2 involved radicals, as was proven by electrochemical degradation. Reductive dissolution was observed for both minerals. X-ray photoelectron spectroscopy demonstrated accumulation of Fe(II) on Fe-SWy surface, whereas Mn(II) was primarily released from δ-MnO2 surface. Highly oxidized carbon species (i.e., newly formed TPs) were observed on the surface of both minerals interacting with oxytetracycline. This study demonstrates the impact of structure and reactivity of redox-active minerals on removal and decomposition of tetracycline antibiotics in aqueous systems.

Tetracycline (TC) as a typical antibiotic has been used extensively and detected in soil, surface water, ground water and drinking water, which results in toxic effect and bacterial resistance. In this study, aluminum-based metal organic framework/graphite oxide (MIL-68(Al)/GO) pellets were prepared through the addition of sodium alginate (SA), a natural crosslinking agent, and applied as a novel adsorbent for aqueous TC removal. The adsorption materials were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption-desorption analysis and X-ray photoelectron spectroscopy (XPS). Results demonstrated that the pellets maintained similar chemical structure with parent MIL-68(Al)/GO powder. It is noted that the surface area and total volume of the pellets decreased obviously due to the disappearance of micropores. Besides, the efficiency of MIL-68(Al)/GO pellets for TC removal was evaluated by adsorption properties compared with parent powder, including key influential parameters, and adsorption isotherms, kinetics and mechanisms. It is found that the adsorption process was conformed to pseudo-first-order kinetics model and more suitably described through Langmuir isotherm model, with 228 mg g-1 of the maximum adsorption capacity. Moreover, these pellets which were separated easily and quickly presented high adsorption capacity and good stability in a wide pH range. The adsorption mechanism of the pellets may be ascribed to the complex interactions of hydrogen bonding, π-π stacking as well as Al-N covalent bonding. Overall, the MIL-68(Al)/GO pellets might be a promising adsorbent and show great potential for the removal of aqueous TC.

Clostridioides (formerly Clostridium) difficile produces two major toxins, TcdA and TcdB, upon entry into stationary phase. Transcription of tcdA and tcdB requires the specialized sigma factor, σTcdR , which also directs RNA Polymerase to transcribe tcdR itself. We fused a gene for a red fluorescent protein to the tcdA promoter to study toxin gene expression at the level of individual C. difficile cells. Surprisingly, only a subset of cells became red fluorescent upon entry into stationary phase. Breaking the positive feedback loop that controls σTcdR production by engineering cells to express tcdR from a tetracycline-inducible promoter resulted in uniform fluorescence across the population. Experiments with two regulators of tcdR expression, σD and CodY, revealed neither is required for bimodal toxin gene expression. However, σD biased cells towards the Toxin-ON state, while CodY biased cells towards the Toxin-OFF state. Finally, toxin gene expression was observed in sporulating cells. We conclude that (i) toxin production is regulated by a bistable switch governed by σTcdR , which only accumulates to high enough levels to trigger toxin gene expression in a subset of cells, and (ii) toxin production and sporulation are not mutually exclusive developmental programs. This article is protected by copyright. All rights reserved.

Husbandry practices for laying hens in commercial egg production is a topic of interest from a social, economic, and regulatory standpoint. Animal welfare concerns regarding the use of conventional cages have arisen and consumer perceptions of hen welfare have led to a higher demand for cage-free eggs. The aim of this study was to assess the impact of housing systems on prevalence, persistence, and antimicrobial resistance (AMR) of Campylobacter from laying hens and shell eggs. A total of 425 samples were collected over a 10-month period from the North Carolina Layer Performance and Management Test and Campylobacter isolates were identified by serological, biochemical, and molecular tests. Genetic variability was evaluated using pulsed-field gel electrophoresis (PFGE) and AMR testing was performed. Prevalence of Campylobacter spp. ranged from 11.1% in the enrichable cages to 19.7% in the conventional systems. A greater prevalence of Campylobacter was found in the fecal swab samples from free-range birds compared with those of birds housed in the more intensive housing systems (p > 0.05). Overall, 72 isolates were confirmed as Campylobacter spp. by PCR. More than 90% of the isolates (n = 66) were identified as Campylobacter jejuni, followed by Campylobacter coli (n = 6). C. jejuni isolates displayed high levels of resistance to tetracycline (67%). Genetic variability of Campylobacter was high, with more than 20 PFGE patterns identified. Pattern "a" comprised 42% of isolates from all housing systems and was also the most persistent. This study suggests that housing systems of laying hens used for commercial shell egg production may impact the rate of Campylobacter shedding by layers. Isolation rates and tetracycline resistance levels of this pathogen are still of concern, emphasizing the need for well-implemented biosecurity measures on the farm.

Enterococcus faecalis and Enterococcus faecium are ubiquitous opportunistic pathogens found in the guts of humans and farmed animals. This study aimed to determine the occurrence, antimicrobial resistance, virulence, biofilm-forming ability and genotypes of E. faecalis and E. faecium from swine farms. Correlations between the genotypes, virulotypes, antibiotic resistance, and the environmental factors such as locality of farms and farm hygiene practice were explored.

Increased resistance to antimicrobials in clinically important bacteria has been widely reported. The major mechanism causing multidrug resistance (MDR) is mediated by efflux pumps, proteins located in the cytoplasmic membrane to exclude antimicrobial drug. Some efflux pumps recognize and expel a variety of unrelated antimicrobial agents, while other efflux pumps can expel only one specific class of antibiotics. Previously, we have reported that xylose decreases the efflux-mediated antimicrobial resistance in Salmonella typhimurium, Pseudomonas aeruginosa, and Acinetobacter baumannii in vitro. In this work, we assessed the effectiveness of combining xylose with antibiotics to kill resistant Acinetobacter baumannii and Klebsiella pneumoniae in a murine model of skin infection. Skin infections were established by seeding 109 bacteria onto eroded skin of mice. Mice treated with the antibiotic alone or with a mixture of glucose and antibiotics or xylose and antibiotics were compared to a control group that was infected but received no further treatment. We observed that the mixtures xylose-tetracycline and xylose-chloramphenicol produced a decrease of at least 10 times viable Acinetobacter baumannii and Klebsiella pneumoniae recovered from infected skin, compared with mice treated with the antibiotic alone. Our results show that xylose improves the antibiotic activity of tetracycline and chloramphenicol against efflux-mediated resistance Acinetobacter baumannii and Klebsiella pneumoniae, in a murine model of skin infection. We envision these combined formulations as an efficient treatment of skin infections with bacteria presenting efflux-mediated resistance, in both humans and animals.

Empirical selections of antimicrobial therapy based on clinical observations are common clinical practices in Ethiopia. This study identified common external ocular infections and determined antibiotic susceptibility testing in northwest Ethiopia.