Bacterial disease is caused by the multiplication of bacteria in a patient. How do pathogenic bacteria harm a patient?

Host Susceptibility

Resistance to bacterial infections is enhanced by phagocytic cells and an intact immune system. Initial resistance is due to nonspecific mechanisms. Specific immunity develops over time. Susceptibility to some infections is higher in the very young and the very old and in immunosuppressed patients.

Bacterial Infectivity

Bacterial infectivity results from a disturbance in the balance between bacterial virulence and host resistance. The “objective” of bacteria is to multiply rather than to cause disease; it is in the best interest of the bacteria not to kill the host.

Host Resistance

Numerous physical and chemical attributes of the host protect against bacterial infection. These defenses include the antibacterial factors in secretions covering mucosal surfaces and rapid rate of replacement of skin and mucosal epithelial cells. Once the surface of the body is penetrated, bacteria encounter an environment virtually devoid of free iron needed for growth, which requires many of them to scavenge for this essential element. Bacteria invading tissues encounter phagocytic cells that recognize them as foreign, and through a complex signaling mechanism involving interleukins, eicosanoids, and complement, mediate an inflammatory response in which many lymphoid cells participate.

Genetic and Molecular Basis for Virulence

Bacterial virulence factors may be encoded on chromosomal, plasmid, transposon, or temperate bacteriophage DNA; virulence factor genes on transposons or temperate bacteriophage DNA may integrate into the bacterial chromosome.

Host-mediated Pathogenesis

In certain infections (e.g., tuberculosis), tissue damage results from the toxic mediators released by lymphoid cells rather than from bacterial toxins.

Intracellular Growth

Some bacteria (e.g., Rickettsia species) can grow only within eukaryotic cells, whereas others (e.g., Salmonella species) invade cells but do not require them for growth. Most pathogenic bacteria multiply in tissue fluids and not in host cells.

Virulence Factors

Virulence factors help bacteria to (1) invade the host, (2) cause disease, and (3) evade host defenses. The following are types of virulence factors:

Adherence Factors: Many pathogenic bacteria colonize mucosal sites by using pili (fimbriae) to adhere to cells.

Invasion Factors: Surface components that allow the bacterium to invade host cells can be encoded on plasmids, but more often are on the chromosome.

Capsules: Many bacteria are surrounded by capsules that protect them from opsonization and phagocytosis.

Endotoxins: The lipopolysaccharide endotoxins on Gram-negative bacteria cause fever, changes in blood pressure, inflammation, lethal shock, and many other toxic events.

Exotoxins: Exotoxins include several types of protein toxins and enzymes produced and/or secreted from pathogenic bacteria. Major categories include cytotoxins, neurotoxins, and enterotoxins.

Siderophores: Siderophores are iron-binding factors that allow some bacteria to compete with the host for iron, which is bound to hemoglobin, transferrin, and lactoferrin.

Explanation:

why many students visually perceive stem as a vapid class?

for many students, however, stem subjects are optically discerned as vapid, tedious, and destitute of authentic-world applications. science and math have always been a major part of the high school curriculum, but many students have disengaged from these subjects because they don’t optically discern that they have any pertinence to the authentic world or students’ daily lives. for them, math and science have become a set of rules, procedures, laws, theorems, and formulas to memorize. some students even develop math apprehensiveness and cerebrate they are incapable of learning higher-level mathematics.

why is stem paramount?

as the u.s. economy changes, the ordinant dictation for stem-capable workers is growing. in may of 2014, the u.s. bureau of labor statistics counted more than 8.3 million stem jobs, which accounted for 6.2 percent of total employment in the cumulated states. that number is expected to perpetuate to increment as u.s. companies grow and innovate to compete in the ecumenical economy. according to the u.s. department of labor, the average salary for all stem jobs is $85,570, which is virtually double the average salary for all jobs.

many people still envision stem professionals as wearing a white lab coat and conducting research in a laboratory. in authenticity, some of the most in-demand stem fields are petroleum engineering, process engineering, and computer engineering. these fields that are experiencing shortages of qualified candidates are additionally among the highest paying, with the average petroleum engineer earning an annual salary of $147,520 in may 2014 according to the u.s. bureau of labor statistics.

in additament, stem subjects edify students valuable skills that are vital for prosperity in all vocations, even those that do not directly require stem erudition. engagement in stem subjects avails students develop quandary-solving, critical mentally conceiving, and leadership skills. these skills are so ecumenical, in fact, that statistics relinquished in the summer of 2013 by the u.s. census bureau designated that about three-quarters of the people with a bachelor’s degree in stem fields are not working in those vocations. many non-stem employers are poaching stem-qualified job candidates because they are more ingenious and collaborative than their non-stem counterparts.

as the ecumenical economy perpetuates to evolve, the desideratum for stem-capable workers will perpetuate to grow. by getting edifiers and students involved in the stem kineticism, an incipient generation of adroit workers will be poised to energize and expand this exhilarating field.

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