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Epidemiology, Disease Transmission, Prevention, and Control
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
The environment influences human health favorably or unfavorably in many direct and indirect ways. We interact with all living things with which we have contact, i.e., plants, animals, and microorganisms, as well as with inanimate objects. Of particular importance to health are the organisms producing disease, the so-called pathogenic organisms. Pathogenicity refers to the organisms′ virulence and invasiveness, factors which determine their capability to produce disease. The higher the virulence, the higher will be the morbidity, mortality, and communicability of the infection and thus the epidemiological importance of the disease caused by the organism.
Pathobiology of Amebiasis
Published in Roberto R. Kretschmer, Amebiasis: Infection and Disease by Entamoeba histolytica, 2020
Ruy Pérez-Tamayo, Ingeborg Becker, Irmgard Montfort, Ruy Pérez-Montfort
Both for working on the pathogenesis of amebiasis, as well as for writing this chapter, our group has found it convenient to distinguish between the concepts of pathogenicity and virulence, which in the literature are often used interconvertibly. By pathogenicity we understand the capacity to cause disease of a given strain of amebas, so on the basis of this property we consider only two types of amebas: pathogenic and nonpathogenic. On the other hand, by virulence we refer to the degree to which pathogenicity is expressed, usually graded as low, intermediate and high, on the basis of arbitrary and subjective criteria. It follows that there can be no pathogenic amebas without virulence, or nonpathogenic amebas with some degree of virulence. We believe that this separation of the concepts of pathogenicity and virulence should be preserved as long as the mechanisms of both features are not completely and clearly delineated. Of course, we are fully aware that pathogenicity and virulence are not absolute properties of the parasite, but rather expressions of the specific host-parasite model under consideration, which also includes many important environmental conditions. Nevertheless, there are some indications that in human and in some experimental forms of amebiasis, pathogenicity, and virulence may depend more on the parasite than on the host.
Bacterial Infections of the Oral Cavity
Published in K. Balamurugan, U. Prithika, Pocket Guide to Bacterial Infections, 2019
P. S. Manoharan, Praveen Rajesh
Bacterial infections contribute to a major deal in the dental, oral, and general health of the individual. Dental caries and periodontal disease are the most common diseases of the oral cavity. The disease-causing microorganisms seem to exhibit a definite site specific pathogenicity. Streptococcus mutans—a caries-producing microorganism causes lesion only when on the tooth structure. Lactobacillus acidophilus is commonly seen in deep carious lesions. Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis, which are associated with periodontal infections when present on enamel structure, was not found to be cariogenic. But species particular to caries or periodontal disease are not isolated, although associations were present (Aas et al., 2005). The complexity of the oral environment demands the study of pathogens to be carried out as a consortium of microorganisms. Culture-independent molecular techniques, site, and subject specificity of the microorganisms seem to play a major role in isolating the etiology and understanding the behavior of the bacterial infections (Loesche et al., 1992). Periodontal disease is not a universal phenomenon. It is surprising that severe forms of this disease affect a group of population who are abnormally susceptible (Genco and Borgnakke, 2013).
Post COVID-19 Myelin Oligodendrocyte Glycoprotein Antibody-Associated Optic Neuritis
Published in Neuro-Ophthalmology, 2022
Daniela Ximena Rojas-Correa, José Alberto Reche-Sainz, Alfredo Insausti-García, Cristina Calleja-García, Manuel Ferro-Osuna
Additional disorders with neuro-ophthalmological implications have been related to typical COVID-19 infection including Fisher syndrome; Guillain-Barré syndrome, Kawasaki disease, anti-phospholipid antibody syndrome; and neuromyelitis optica spectrum disorder (NMOSD).1,5,9 They represent para-infectious or post-infectious autoimmune disorders, which could be triggered by virus infection, since SARS-CoV-2 can induce dysregulation of the immune system. The exact aetiology of autoimmune diseases remains unclear, but it is assumed that there is a genetic predisposition and environmental triggers, such as infections. There are viruses with known immuno-pathogenicity, such as parvovirus B19, Epstein-Barr virus, herpes virus 6, human T-lymphotrophic virus, hepatitis A and C virus and rubella virus.8 These viruses have the ability to trigger an autoimmune response through molecular mimicry and bystander mechanism activation (autoreactive immune T cells).2,10 Structurally similar viral antigens from SARS-CoV-2 may have incited a host immune response against endogenous MOG in our patient.9 When circulating MOG antibodies enter the central nervous system (CNS) through disruption of the blood-brain barrier, pathology is mediated by T cells and activated complement, producing various clinical disorders, such as optic neuritis, transverse myelitis and acute disseminated encephalomyelitis (ADEM).2
Oral prosthetic microbiology: aspects related to the oral microbiome, surface properties, and strategies for controlling biofilms
Published in Biofouling, 2021
Douglas Roberto Monteiro, Victor Eduardo de Souza Batista, Anne Caroline Morais Caldeirão, Rogério de Castilho Jacinto, Juliano Pelim Pessan
Regarding the prevalence of Candida species in CD wearers, cultures from palatal mucosa and internal denture surface have identified several species, which are listed in descending order of prevalence: Candida albicans, Candida glabrata, Candida tropicalis, Candida dubliniensis, Candida parapsilosis, Candida krusei, Candida guilliermondii, and Candida lipolytica (Zomorodian et al.2011). Isolates of Saccharomyces cerevisiae, Trichosporon capitatum, and Trichosporon beigelii have also been found, but at lower prevalence (Zomorodian et al.2011). Denture biofilm exhibits higher Candida colonization compared with dental biofilm, probably due to the greater adhesion capacity of this species to acrylic surfaces (Kang et al.2013). Other factors associated with Candida colonization include low salivary pH and sugar intake (Martori et al.2017). However, it should be noted that the adhesion of Candida species depends on the coaggregation to the pre-formed biofilm via interactions with different microorganisms. These interactions may be synergistic, potentiating the growth of some species and invasion of the mucosa by Candida spp. (Diaz et al.2012), with significant impacts on the pathogenicity of the microorganisms involved.
Environmental pH modulates biofilm formation and matrix composition in Candida albicans and Candida glabrata
Published in Biofouling, 2020
Bruna Gonçalves, Liliana Fernandes, Mariana Henriques, Sónia Silva
The pathogenicity of Candida species is mediated by several virulence factors, including the ability to form biofilms on mucosal surfaces and indwelling medical devices (Harriott et al. 2010; Bouza et al. 2014). C. albicans forms thick, spatially organised complex biofilms comprised of a multilayered and intertwined network of blastospores, pseudohyphae and hyphae, partially embedded in an extracellular matrix (Seneviratne et al. 2009). Importantly, although readily formed in planktonic cultures, in the presence of specific nutritional cues, hyphae are a characteristic feature of C. albicans biofilms and required for their proper formation (Nobile et al. 2012; Gulati and Nobile 2016). The hyphae contribute to the architectural stability of biofilms by forming a scaffold that provides a robust support for the extracellular matrix as well as the blastopores, pseudohyphae and other hyphae (Seneviratne et al. 2009; Gulati and Nobile 2016). Nevertheless, studies on C. glabrata, which does not naturally form true hyphae, suggest that hyphal morphology is not a prerequisite for biofilm formation. Indeed, C. glabrata develops thin and patchy, rather compact biofilms, exclusively of blastospores embedded within an extracellular matrix (Seneviratne et al. 2009). The association of microorganisms into biofilms contributes to their survival under hostile environmental conditions (Donlan and Costerton 2002).