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Bowel disorders
Published in Henry J. Woodford, Essential Geriatrics, 2022
Noroviruses are RNA viruses that commonly cause acute gastroenteritis, especially in hospital and care home settings. Following a 12-to-24-hour incubation period, infections present with abdominal cramping, watery diarrhoea, nausea and vomiting.49 However, up to 30% of infected people are asymptomatic.50 Norovirus infection produces a brief and self-limiting illness in most people (within three days) but frail older people are at increased risk of morbidity (e.g. dehydration or aspiration pneumonia) and mortality.49 In people aged over 85, symptoms commonly last four to nine days.50 Transmission is by person to person, contact with contaminated surfaces or consuming contaminated food (i.e. infected food handlers). Person to person spread is by far the commonest factor in health and care settings.49 Norovirus is highly infectious due to the combination of high viral shedding in vomit and stools, low infectious dose required and environmental stability of the organism.
Remote Sensing and Computational Epidemiology
Published in Abbas Rajabifard, Greg Foliente, Daniel Paez, COVID-19 Pandemic, Geospatial Information, and Community Resilience, 2021
Viruses spread in many ways. One transmission pathway is through disease-bearing organisms known as vectors: for example, viruses are often transmitted from plant to plant by insects that feed on plant sap, such as aphids; and viruses in animals can be carried by blood-sucking insects and vampire bats. The infectious dose required to produce infection in humans is less than 100 particles in Influenza viruses [11, 12] and to some extent in COVID-19. The variety of host cells that a virus can infect is called its “host range”. This can be narrow or broad, meaning a virus is capable of infecting only few species, or infecting many.
Brucella: A Foodborne Pathogen
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
One of the important characteristics of Brucella is the number of species in the genus that are capable of causing zoonotic infections in humans. Most virulent strains of Brucella express the O polysaccharide (homopolymer of 4,6-dideoxy-4-formamido-α-D-mannopyranosyl units) on their lipopolysaccharide (LPS) and are known as “smooth” strains. With the exception of B. canis, which does not express the O side chain (a “rough” strain), most zoonotic strains of Brucella are smooth strains. Cumulative data suggest dosages of virulent Brucella species required for 50% infection rates across mucosal surfaces of hosts other than guinea pigs or mice are most likely in the 103–104 CFU range.20,21 Some studies have reported that infectious dose is only 10–100 bacteria, but that was based on a calculated dose using respiratory parameters in a closed system. The original paper on this low infectious dose for Brucella required a bacterial suspension of 2.74 × 106 CFU/mL to achieve an estimated inhaled dose of 60 bacteria. In addition, the calculations ignore potential deposition of bacteria on the conjunctiva, oral mucosa, nasal mucosa, or tonsil.22 Although virulent strains of Brucella have a predilection for lymphoreticular tissues and the reproductive tract, most also frequently localize in mammary tissues and are shed in milk.
Diagnostic performance of an in-house multiplex PCR assay and the retrospective surveillance of bacterial respiratory pathogens at a teaching hospital, Kelantan, Malaysia
Published in Pathogens and Global Health, 2023
Nik Mohd Noor Nik Zuraina, Suharni Mohamad, Habsah Hasan, Mohammed Dauda Goni, Siti Suraiya
Another drawback of this assay is its inability to identify drug-resistant bacteria. Although the development of a molecular-based detection method for screening antimicrobial resistance can be very challenging, such test can guide to rapid and effective treatment strategies. Apart from that, further evaluation study on the analytical sensitivity is required to determine the limit of detection of this assay. As a qualitative-based PCR, it is another limitation of this assay to distinguish between the true pathogens and the colonizing bacteria. The cutoff detection limit that is equal to or more than bacterial infectious dose (105 CFU/ml) [44] might be helpful to increase certainty of bacterial respiratory infections in symptomatic patients. In addition to microbiological testing, the clinical presentations and radiographic findings from patients are used to facilitate the diagnosis and therapeutic decision by the clinicians.
Statistical optimization of bile salt deployed nanovesicles as a potential platform for oral delivery of piperine: accentuated antiviral and anti-inflammatory activity in MERS-CoV challenged mice
Published in Drug Delivery, 2021
Mohamed Y. Zakaria, Eman Fayad, Fayez Althobaiti, Islam Zaki, Ali H. Abu Almaaty
Forty female 10 weeks old female C57BL/6 mice (150 ± 10 g) were obtained from Biological Production Unit (BPU) of Theodore Bilharz Research Institute (Giza, Egypt) were accommodated for 7 days in standard polypropylene cages under standard laboratory conditions of temperature, humidity, and light 12 h of dark/light cycles with a free access to standard laboratory diet and water ad libitum as to reduce variation (Mohammed et al., 2020). The experimental protocol was approved by Research Ethics Committee, Portsaid University. The animals were inoculated intranasally with 50 µl of viral solution containing 105 p.f.u. resembling 50% tissue culture infectious dose (TCID50) of MERS-CoV (Iwata-Yoshikawa et al., 2019), then they were subdivided into four groups (10 mice in each group), and allocated randomly receiving different dosage regimen according to Table 2 their body weight and survival were monitored.
Mechanisms of bacillary dysentery: lessons learnt from infant rabbits
Published in Gut Microbes, 2020
Shigella flexneri is the causative agent of bacillary dysentery (blood in stool) in humans.1 There are more than 270 million cases of shigellosis annually, resulting in more than 200,000 deaths.2 This inflammatory disease is characterized by a dramatic ulceration of the colonic mucosa,3,4 herein referred to as epithelial fenestration. S. flexneri is transmitted via the fecal-oral route and is extremely contagious. Studies in human volunteers showed that the attack rate is above 90% with an infectious dose as low as 100–1000 bacteria per individual.5 Infected patients are usually treated with fluid replacement and antibiotics. The lack of an effective vaccine and the emergence of multiple antimicrobial-resistant (AMR) strains are a major health concern worldwide.6