Biological Sciences
Susceptible Host
A susceptible host is an individual who is at risk of contracting a disease or infection due to their lack of immunity or resistance to the pathogen. This can be due to various factors such as age, genetics, underlying health conditions, or lifestyle choices. Identifying susceptible hosts is important in preventing the spread of infectious diseases.
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3 Key excerpts on "Susceptible Host"
eBook - PDF- Rodney P. Anderson, Linda Young, Kim R. Finer(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
Think Critically Which host factor(s) can you most control to help reduce your risk of acquiring an infectious disease? 428 CHAPTER 16 Microbial Pathogenesis Host Factors Not all hosts are susceptible to every specific pathogen because they may have prior immunity to the infectious agent. Therefore, the major factor in determining suscepti- bility to infectious disease is immune status (Figure 16.11). Healthy individuals who are not immune to a pathogen are only susceptible to a group of microbes known as primary pathogens. A healthy immune system protects a person from opportunistic infections, infections caused by pathogens that require a host’s defenses to be compromised to cause disease. Immune defenses may be compromised by diseases associated with stress, diabetes, heart disease, cancer, obesity, injury, and aging (see What a Microbiologist Sees). Having an existing infection makes you more suscep- tible to infection by a new infectious agent because your immune system is already compromised. This is known as a secondary infection. Genetic makeup of the host also affects susceptibility and resistance to microbial disease. For example, infection by Mycobacterium tuberculosis causes active tuberculosis in only approximately 10% of the population. The other approxi- mately 90% of infected people carry the pathogen in its latent state—in which a person is infected but doesn’t develop active disease. Although the development of active tuberculosis is the result of many different factors, human genetic factors play a role. Behavioral and environmental conditions can also significantly increase the risk for acquiring an infectious dis- ease. For example, type I diabetics are more susceptible to foot infections, alcoholics are at a higher risk for pneumonia by Klebsiella pneumoniae, and the elderly are more susceptible to S. pneumoniae. a. A marathon training schedule indicates how many miles to run each day.
eBook - ePub- Marinus te Pas, Henri Woelders, André Bannink, Marinus te Pas, Henri Woelders, André Bannink(Authors)
- 2011(Publication Date)
- Wiley-Blackwell(Publisher)
In a general sense, the research field of host–pathogen interactions is well developed due to its impact and importance of infectious diseases that threaten human and animal health. The field is closely linked to our growing fundamental understanding of the host's innate and adaptive immune system and to our current understanding of the wide variety of mechanisms that pathogenic microorganisms use to invade, reside, and replicate within hosts. Quantitative and qualitative aspects of host–pathogen interactions determine whether pathogens are able to invade hosts, survive and replicate, spread throughout the body, and transmitted to other hosts. These aspects also determine the pathology and severity of the disease resulting from the interplay between host and pathogen: either elimination or colonization of the microbe without causing clinical signs of disease, or colonization of the microbe causing diseas, ranging from mild to deadly. Both microbial virulence as well as host disease susceptibilities are frequently seen as traits of pathogens and hosts, respectively. However, this is not correct since both depend on dynamic interactions between the two (Casadevall and Pirofski, 2000).Recent studies focusing on host–pathogen interactions increasingly use high-throughput -omics technologies that generate ten to several hundred of thousands of data points. They provide genome-wide global views of the molecular structures and molecular compositions of biological samples. Such studies have shed light on several virulence strategies used by microbes, on a number of defense strategies used by hosts, and on several mechanisms by which the interactions between hosts and pathogens are influenced by external factors, such as nutrition and stress. However, biological functions do not simply manifest themselves from the addition of the properties of system components, but rather arise from the dynamic interactions of these components. In addition, individual studies usually focus on one specific biological level, i.e., genes, cytokines, or macrophage activity, on particular cells or tissues, i.e., dendritic cells (DCs) or spleen, a particular time frame, and either host-response or pathogen inference. However, to understand the genetics and physiology of host–pathogen interactions, it is required to get data information from different time frames and different scales, i.e., genes, molecules, networks, pathways, cells (host as well as pathogens), tissues, organs, organisms.
eBook - PDF- Anthony A. Nash, Cedric A. Mims, Nigel J. Dimmock, John Stephen(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
11 Host and Microbial Factors Influencing Susceptibility Genetic factors in the microorganism 329 Genetic factors in the host 333 Hormonal factors and stress 345 Other factors 350 References 354 A host may be susceptible to infection by a given microorganism but rarely suffer harmful effects. In the old days everyone was susceptible to infection with polioviruses or tubercle bacilli, but relatively few became paralysed or developed pulmonary tuberculosis. Not only this, but host susceptibility to infection often varies independently of suscep-tibility to disease. From the microorganism's point of view, infectious-ness or transmissibility is not the same as pathogenicity. Transmissibility in fact depends on the extent of shedding of micro-organisms from the infected individual, on the stability of micro-organisms outside the host, and on the ease with which infection is established in new hosts. Each of these factors shows great variation. Variations in the ease with which infection is established are illustrated in Table 11.1. It can be seen that the dose required to pro-duce infection, disease or death, depends on the microorganism, the route of infection, the host, and on other factors. The word virulence is sometimes used to refer to the infectiousness or transmissibility of a microorganism, but the word as used here will refer instead to its pathogenicity, or ability to cause damage and disease in the host. An infection can be totally harmless and asymptomatic or lead to a lethal disease, depending on the results of the encounter between microorganism and host. The characteristics of both the microbe ('seed') and the host ('soil') contribute to the outcome of an infection, and either can exercise a determining influence. To put it as a platitude, it takes two (microbe and host) to make an infection or a disease. Some of the host and microbial factors influencing susceptibility to disease are discussed in this chapter. 328
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