Prior in vitro exposure to voriconazole confers resistance to amphotericin B in aspergillus fumigatus biofilms

Triazoles are the mainstay of treatment for aspergillosis, although resistance to these antifungal agents may be associated with treatment failure. Refractory infections often necessitate a switch to other antifungal agents, including amphotericin B (AmB), although these infections may not resolve. The aim of this study was to investigate the effect of prior azole exposure on AmB sensitivity in Aspergillus fumigatus biofilms. It was hypothesised that sequential antifungal therapy has the potential to impact adaptive resistance mechanisms. Antifungal sensitivity was determined for each isolate against AmB ± voriconazole (VRZ) exposure by a broth microdilution method and an XTT metabolic assay. To analyse the role of extracellular DNA (eDNA) and Hsp90 activation, sensitivity to AmB ± DNA-digesting enzyme (DNase) or Hsp90 inhibitor [geldanamycin (GDA)] was also tested. Finally, scanning electron microscopy was performed to assess phenotypic changes. The in vitro data revealed that A. fumigatus sensitivity to AmB was decreased when it was tested in combination with VRZ. In addition, a two- to four-fold decreased sensitivity to AmB was recorded against VRZ-exposed germlings compared with controls. It was also shown that depletion of eDNA by DNase treatment enhanced AmB activity against VRZ-exposed cells by eight-fold, which visually could be explained by destabilisation of the biofilm when examined microscopically. Pharmacological inhibition of Hsp90 by GDA significantly improved biofilm susceptibility to AmB by four- to eight-fold. In conclusion, A. fumigatus pre-exposure to VRZ concomitantly induces eDNA release and activates the stress response, which collectively confers AmB resistance in vitro

The influence of dietary nitrate and acid suppression on the intragastric environment and the risk of carcinogenesis

In 1975, Correa's original hypothesis for gastric carcinogenesis proposed that atrophic gastritis leads to achlorhydria and secondary colonisation of the stomach with nitrosating bacteria. These organisms reduce dietary nitrate to nitrite, then catalyse the synthesis of potentially carcinogenic N-nitroso compounds (NOC) from nitrite and secondary amines present in gastric juice. Since then, significant advances have been made in our understanding of gastric physiology which are also relevant to our understanding of gastric carcinogenesis. Helicobacter pylori (H. pylori) infection is now a recognised risk factor for gastric carcinogenesis. If it produces a pangastritis, there is an associated degree of gland-loss (atrophy) of the acid-secreting body of the stomach. Atrophic gastritis is a precursor of the development of gastric cancer. H. pylori infection also lowers levels of vitamin C, which is secreted into and concentrated within gastric juice. The synthesis of NOC is inhibited by vitamin C. Advances in the treatment of acid-related disorders have resulted in the prescription of increasingly potent inhibitors of acid secretion. The proton pump inhibitors (PPI's) render H. pylori infected subjects achlorhydric from one dose to the next. They also promote the development of a pangastritis. Whether these effects are harmful in the long term remains hotly debated. Two recent reports suggest that long term PPI therapy does lead to development of moderate-severe atrophy of the gastric body in ~18% of H. pylori infected subjects, compared to 0 - 2% of no-infected subjects, thereby placing these patients at risk of gastric cancer. There are great concerns that the falling incidence of gastric cancer in the developed world may be reversed by widespread prescription of these agents. How PPI's produce gastric atrophy in H. pylori infected patients remains to be elucidated. This thesis postulates that, in the presence of co-existing H. pylori infection, drug-induced achlorhydria alters the intragastric environment in a way that will facilitate bacterial synthesis of carcinogenic NOC which in turn may damage gastric epithelial stem cell DNA. The thesis begins by re-examining the roles of nitrate, nitrite and vitamin C in man. The enterosalivary recirculation of ingested nitrate is described, whereby dietary nitrate is reduced to nitrite in saliva to provide the main source of nitrite to the upper GI tract. The important chemical interactions between nitrite and ascorbic acid in vitro are described with reference to NOC synthesis. NOC synthesis is promoted by a high nitrite : ascorbic acid ratio. The in vivo interactions between saliva nitrite and gastric ascorbic acid are speculated upon and the potential effects of PPI-induced achlorhydria and H. pylori infection on these interactions are considered. To begin, novel studies infused nitrite into the acid stomach to mimic salivary nitrite influx following a nitrate meal. These studies demonstrate for the first time in vivo the interaction between nitrite and vitamin C in the gastric lumen. Gastric juice ascorbic acid is depleted and in the process is converted to dehydroascorbic acid. Nitrite is lost from solution - presumably as nitric oxide. These novel studies were repeated, replacing the nitrite infusion with a solution of nitrate to mimic the effects of ingesting a portion of lettuce. These studies confirm that ingestion of nitrate leads to elevation of saliva nitrite levels via the process of enterosalivary recirculation. (Abstract shortened by ProQuest.)

Soft hybrid intrinsically motile robot for wireless small bowel enteroscopy

BACKGROUND: Difficulties in establishing diagnosis of small bowel (SB) disorders, prevented their effective treatment. This problem was largely resolved by wireless capsule endoscopy (WCE), which has since become the first line investigation for suspected SB disorders. Several types of WCE pills are now used in clinical practice, despite their limitations and complications. WCE pills are large, rigid and immotile capsules. When swallowed, they provide SB enteroscopy downloaded to a data logger carried by the patient. Most of the complications of WCEs result from lack of intrinsic locomotion: incomplete examination, capsule retention and impaction within strictures. In addition, the rigid nature and size of current generation of WCE pills is accompanied by 0.1% inability to swallow the pill by patients with normal esophageal motility. METHODS: The aim of this communication is to describe the initial prototype, P(1), which is thinner and slightly longer than the current generation of WCEs. In addition, it exhibits intrinsic active locomotion, produced by vibrating silicon legs. These generate a controlled-skid locomotion on the small bowel mucosal surface, rendered slippery by surface mucus and intraluminal surfactant bile salts. We demonstrate the mechanism responsible for the active locomotion of P(1), which we consider translatable into a working prototype, suitable for further R&D for eventual clinical translation. RESULTS: The shape and attachment of the rubber vibrating legs to vibrating actuators, have been designed specifically to produce a tight clockwise circular motion. When inserted inside a circular tube in vitro of equivalent diameter to human small intestine, the intrinsic circular clockwise motion of P(1) translates into a linear locomotion by the constraints imposed by the surrounding circular walls of SB and rest of the gastrointestinal tract. This design ensures device stability during transit, essential for imaging and targeting lesions encountered during the enteroscopy. We preformed two experiments: (i) transit of P(1) through a phantom consisting of a segment of PVC tube placed on a horizontal surface and (ii) transit through a transparent slippery nylon sleeve insufflated with air. In the PVC tube, its transit rate averages 15.6 mm/s, which is too fast for endoscopy: whereas inside the very slippery nylon sleeve insufflated with air, the average transit rate of P(1) is reduced to 5.9 mm/s, i.e., ideal for inspection endoscopy. CONCLUSIONS: These in-vitro experiments indicate that the P(1) hybrid soft robot prototype has the potential specifically for clinical translation for SB enteroscopy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00464-021-09007-7

Acoustic emission method to study fracture (Mode-I, II) and residual strength characteristics in composite-to-metal and metal-to-metal adhesively bonded joints.

Failure behaviour of two types of adhesively bonded joints (composite-to-metal, metal-to-metal) has been studied under failure modes (Mode I: double cantilever beam (DCB) and Mode II: three-point end notch flexures (3-ENF)) using acoustic emission (AE) technique. The bonded specimens were prepared using two types of adhesive bond materials with three variations of adhesive bond quality. The effect of the presence of interfacial defects along the interface on the residual strength of the joint has also been studied. It was possible using the maximum AE amplitude method to select the AE events of mechanical significance. However, it proved difficult to propose a definitive AE trait for the mechanical phenomena occurring within specific AE event signals, for all adhesive types, bond qualities, and substrate configurations; therefore, all specimen combinations. There was a notable shift in spectral energy proportion as the AE source of mechanical significance varied along the specimen length for specimen combinations. However, it was difficult to confirm this distinctive trait for all specimen combinations due to difficulty in confirming the location and exact mechanical source. The proposed measurement technique can be useful to assess the overall structural health of a bonded system and may allow identification of defects