CH15&16: MICROBIAL MECHANISMS OF PATHOGENICITY DISEASE AND EPIDEMIOLOGY

what is dynamic equilibrium with microorganisms

dynamic equilibrium is the ideal, balanced state where the microorganisms living in and on the body exist without causing disease and contribute to the host's well-being

how does the immune system maintain balance with normal flora

the immune system tolerates beneficial microbes while quickly identifying and neutralizing potential invaders, keeping the microbial communities in check

what characterizes a healthy state in terms of human-microbe interactions

a healthy state is characterized by strong immune defenses and stable, beneficial microbial communities

what is an infection

an infection occurs when a pathogen successfully invades the host's body, and the host is fighting the invader, which may or may not cause symptoms

how is disease different from infection

disease occurs when an infection causes significant damage, resulting in observable signs and symptoms, impairing the body's normal functions

what are normal microbial residents, or microbiota

microbiota are diverse communities of bacteria, fungi, archaea, and viruses that reside in areas like the gut, skin, mouth, and urogenital tract

what is the nature of most microbiota interactions with the host

most microbiota are either commensals, benefiting themselves without affecting the host, or mutualists, benefiting both themselves and the hos

how do microbiota contribute to nutrient production

microbiota, especially gut bacteria, produce essential vitamins such as vitamin K and some B vitamins.

how do microbiota assist in metabolism

microbiota help break down complex carbohydrates that human enzymes cannot digest

how do microbiota help train the immune system

early exposure to microbiota helps the immune system mature and learn which microbes to attack and which to tolerate

what is competitive exclusion in the context of microbiota

competitive exclusion occurs when microbiota occupy space and consume resources, preventing harmful pathogens from colonizing the bod

what happens during the incubation period of an infection

during the incubation period, the pathogen replicates in the host without causing any noticeable symptoms.

what occurs during the prodromal period

the prodromal period is a short stage with mild, general symptoms like fatigue or minor aches

what is the period of illness in an infection

the period of illness, or acute phase, is when the disease is most severe, and specific symptoms are clearly present

what happens during the period of decline or convalescence

during this period, the immune system or medical treatment begins to reduce symptoms, and the body starts returning to health

what is epidemiology

epidemiology is the study of the occurrence, distribution, and determinants of health-related states or events in specified populations

what is incidence in epidemiology

incidence is the number of new cases of a disease in a population over a specific time period

what is prevalence in epidemiology

pevalence is the total number of existing cases, both new and old, in a population at a specific time

what does endemic mean

endemic refers to a disease that is constantly present at a low level in a specific geographic area

what is an epidemic

an epidemic is a sudden increase in the number of disease cases above what is normally expected in a population

what is a pandemic

a pandemic is an epidemic that has spread over multiple countries or continents

what is a biofilm

a biofilm is a complex, slimy community of microbes attached to a surface and encased in a self-produced matrix called extracellular polymeric substance

why are biofilms important for health

biofilms are significant because microbes within them are highly protected from antibiotics and the immune system, making infections difficult to treat

what is colonization of the body by microbesf

colonization is the establishment and multiplication of a microbe on a body surface without causing harm

how is colonization different from infection

colonization does not cause damage or elicit an immune response, whereas infection occurs when the microbe causes harm and triggers the immune system

what is pathology

pathology is the study of disease, focusing on the structural, biochemical, and functional changes in cells, tissues, and organs that underlie disease

what are the key aspects of pathology

the key aspects of pathology include etiology, pathogenesis, morphologic changes, and clinical significance

what are morphologic changes

morphologic changes are visible, structural alterations in tissues and organs that are characteristic of a disease and can be observed either at the gross or microscopic level

what is the clinical significance of morphologic changes

clinical significance refers to the functional consequences of morphologic changes, which manifest as the signs and symptoms observed in the patient

what is etiology

etiology is the study of the cause of a disease, aiming to identify the factors responsible for initiating and developing a specific disease

what are examples of infectious agents as an etiology

infectious agents include pathogens like bacteria, viruses, fungi, or parasites, such as Mycobacterium tuberculosis causing tuberculosis

how do genetic factors contribute to disease etiology

genetic factors include inherited mutations or polymorphisms, such as a mutation in the β-globin gene causing sickle cell anemia

how do chemical factors contribute to disease etiology

chemical factors include exposure to toxins, drugs, or environmental pollutants, such as asbestos exposure causing mesothelioma

how do physical factors contribute to disease etiology

physical factors include trauma, radiation, or extreme temperatures, like ultraviolet radiation exposure leading to skin cancer

how do immunologic factors contribute to disease etiology

immunologic factors involve malfunctions of the immune system, leading to autoimmunity or hypersensitivity reactions

what does it mean when a disease has a multifactorial etiolog

multifactorial etiology means that a disease is caused by a combination of genetic predisposition and environmental triggers

what is a pathogen

a pathogen is a microorganism capable of causing disease, including bacteria, viruses, fungi, protozoa, and helminths

what is virulence

virulence is the measure of a pathogen's ability to cause disease, with highly virulent pathogens being more likely to cause severe illness

what is pathogenicity

pathogenicity is the capacity of a microbe to cause disease, and most microorganisms are harmless or beneficial

how do pathogens cause disease

pathogens cause disease by invading the host, multiplying, spreading, and producing toxins that damage host cells and disrupt normal function

what is pathogenesis

pathogenesis is the study of how disease develops, detailing the sequential process by which a disease agent causes clinical manifestations

what does pathogenesis focus on

pathogenesis focuses on the step-by-step sequence from the initial stimulus to the ultimate expression of disease, including cellular, biochemical, and molecular events

what is an example of pathogenesis in atherosclerosis

in atherosclerosis, pathogenesis involves endothelial injury, lipid deposition, macrophage recruitment, foam cell formation, and plaque developmen

what is infection

infection is the successful colonization of a host by a microorganism

what are the steps a pathogen must take to cause infection

a pathogen must overcome host defenses, enter tissues, multiply within the host, and become firmly established

does infection always lead to disease

no, infection does not always lead to disease; many infections are asymptomatic or are cleared by the immune system without causing functional impairment

what is disease

disease is an abnormal state in which the body is not functioning normally, caused by pathogens or non-infectious factors

how are disease and infection related

a disease that results from an infection is called an infectious disease, and its signs and symptoms are often due to microbial multiplication, toxin production, or the host immune response

what is a sign of disease

a sign is a change in the body that can be measured or observed as a result of disease

what is the key point about sign

signs are objective, meaning they can be detected by a doctor, nurse, or machine and do not depend on the patient's perception

examples of signs of disease

examples of signs include fever, septicemia, leukocytosis, swollen lymph nodes, and tachycardia

what is a symptom of disease

a symptom is a change in body function that is felt by a patient as a result of disease

what is the key point about symptoms

symptoms are subjective, meaning they are experienced by the patient and cannot be directly measured or objectively confirmed by another person

examples of symptoms of disease

examples of symptoms include chills, pain, irritation, nausea, malaise, and fatigue

what is a syndrome

a syndrome is a specific group of signs and symptoms that occur together and characterize a particular disease

what is the key point about a syndrome

a syndrome is a recognizable pattern of manifestations, while a disease is a pathological process with a specific cause

give an example of a syndrome

acquired immunodeficiency syndrome (AIDS) is a syndrome characterized by a collection of specific infections and cancers that result from HIV infection, which is the underlying diseas

what are infectious diseases

infectious diseases are caused by pathogens, such as bacteria, viruses, fungi, protozoa, or parasites, which invade the body, multiply, and interfere with normal body function

are all infectious diseases communicable

no, infectious diseases are often communicable, but the terms are not perfectly synonymous because some infections are acquired from environmental sources rather than from another person

give an example of an infectious disease

malaria is an infectious, zoonotic disease caused by the protozoan Plasmodium falciparum.

what are noninfectious diseases

noninfectious diseases are not caused by pathogens and are also called non-communicable diseases, arising from genetic factors, environmental exposures, lifestyle choices, or physiological malfunctions

give an example of a noninfectious disease

sickle cell disease is a noninfectious disease caused by a genetic mutation in the β-globin gene, resulting in abnormally shaped red blood cells

what are inherited disease

inherited diseases are caused by a genetic defect passed from parent to child, preventing specific proteins or enzymes from functioning properly

can you give an example of an inherited disease

sickle cell anemia is an inherited disease caused by a single gene mutation that produces abnormal hemoglobin

what are congenital diseases

congenital diseases are present at birth or manifest shortly thereafter and can result from genetic factors or environmental influences during fetal development

can you give an example of a congenital disease

down syndrome is a congenital condition caused by an extra copy of chromosome 21 (trisomy 21)

what are degenerative diseases

degenerative diseases involve the progressive and irreversible loss of function of tissues, organs, or body systems over time

give an example of a degenerative disease

parkinson disease is a neurodegenerative disorder where dopamine-producing neurons gradually die, affecting movement and balance

what are nutritional deficiency diseases

nutritional deficiency diseases result from a severe lack of essential nutrients, impairing critical biochemical processes

give an example of a nutritional deficiency disease

scurvy is caused by a severe deficiency of vitamin C, leading to symptoms like bleeding gums, bruising, and poor wound healin

what are endocrine diseases

endocrine diseases involve malfunction of the endocrine glands, causing underproduction or overproduction of hormones

give an example of an endocrine disease

hypothyroidism occurs when the thyroid gland produces insufficient thyroid hormone, slowing metabolism and causing fatigue, weight gain, and cold sensitivity

what are neoplastic diseases

neoplastic diseases, or cancers, are characterized by abnormal, uncontrolled cell growth that can form benign or malignant tumor

give an example of a neoplastic disease

some forms of cancer involve uncontrolled cell proliferation that can invade tissues and metastasize to other parts of the body

what are idiopathic diseases

idiopathic diseases are conditions for which the cause remains unknown after thorough medical investigation

give an example of an idiopathic disease

Idiopathic Juxtafoveal Retinal Telangiectasia (IJRT) is a rare eye disorder with unknown cause involving abnormal, leaky retinal blood vessels

what are communicable diseases

communicable diseases are illnesses that spread from an infected person or animal to another person, caused by pathogens and transmitted directly or indirectl

what is the difference between direct and indirect transmission of communicable diseases

direct transmission occurs through close contact, like touching or coughing, while indirect transmission occurs via intermediates, such as contaminated food, water, or vector

examples of communicable diseases

examples include tuberculosis, herpes, flu, AIDS, chickenpox, mumps, and polio

what are contagious diseases

contagious diseases are highly communicable diseases that spread easily between people, often with a low infectious dose or efficient transmission mode

examples of contagious diseases

examples include measles and sexually transmitted diseases (STDs)

what are noncommunicable diseases (NCDs)

noncommunicable diseases are chronic illnesses that are not spread person-to-person and result from genetic, physiological, environmental, or behavioral factors

examples of noncommunicable diseases

examples include cardiovascular diseases, cancers, chronic respiratory diseases, diabetes, tetanus, and botulism

what is an iatrogenic disease

iatrogenic diseases are health problems caused directly by medical procedures, treatments, drugs, or medical errors

examples of iatrogenic diseases

examples include surgical complications, contracting hepatitis from a blood transfusion, and liver damage from adverse drug reactions

what are zoonotic diseases

zoonotic diseases are naturally transmissible from animals to humans, caused by bacteria, viruses, parasites, or prions

how are zoonotic diseases transmitted

transmission can occur through direct contact with animals, consumption of contaminated food or water, or indirectly via vectors

examples of zoonotic diseases

examples include rabies, COVID-19, Lyme disease, Salmonellosis, and avian flu

what is the incubation period of a disease

the incubation period is the time interval between the initial entry of a pathogen into the host and the first appearance of any signs or symptoms

what is the pathogen activity during the incubation period

during the incubation period, the pathogen is actively replicating, but its numbers are relatively low and beginning to increase exponentially

are symptoms present during the incubation period

no, during the incubation period, there are no signs or symptoms visible or felt by the host, so the host is unaware of the infection

how long can the incubation period last

the incubation period varies depending on the pathogen, the dose of inoculum, and the host's immune defenses, ranging from hours to years

can a person be infectious during the incubation period

yes, a person can be infectious during the incubation period because the pathogen is present and replicating, even if the host is unaware

what is the prodromal period

the prodromal period is a short phase following the incubation period, characterized by the appearance of early, vague, or general symptoms

what is the pathogen activity during the prodromal period

during the prodromal period, the pathogen continues to multiply rapidly, and its numbers increase significantly

what symptoms occur during the prodromal period

symptoms during the prodromal period are general and nonspecific, such as malaise, fatigue, low-grade fever, and body aches

what is the clinical significance of the prodromal period

the prodromal period serves as a warning that an illness is about to reach full intensity

what is the period of illness

the period of illness is the stage during which the disease is most severe and the specific clinical signs and symptoms reach their peak intensity

what happens during the period of decline

during the period of decline, the immune system or medical treatment begins to subdue the pathogen, and signs and symptoms decrease in severity

why is the host vulnerable during the period of decline

the host is still susceptible to secondary infections because the immune system is weakened, and premature cessation of treatment can lead to relapse