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Questions and Answers
What term describes infections that occur at a persistent, usually low level in a specific geographic area?
What is the first stage of bacterial pathogenesis?
What type of transmission involves the transfer of microbes from mother to offspring?
Which portal of entry is NOT a typical route for bacteria to enter the body?
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What component of exotoxins is responsible for binding to specific receptors on human cells?
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During which stage of infectious disease do characteristic features of the disease occur?
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Which of the following is a possible outcome after the recovery period from an infectious disease?
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What is the prodrome period characterized by?
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What are normal flora organisms primarily composed of?
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Where are normal flora predominantly located in the body?
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What is the term for microbes that can cause disease only in immunocompromised individuals?
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What does virulence measure?
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What is the significance of colonization resistance?
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Which of these describes asymptomatic infections?
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What two mechanisms do bacteria use to cause symptoms of disease?
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What is defined as the presence of microbes in the body?
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Study Notes
Normal Flora
- Normal flora are microorganisms that are permanent residents of the body
- These organisms, also known as commensals, benefit from the host without causing harm
- Most normal flora are bacteria or yeasts but do not include viruses, protozoa, or helminths
- They inhabit body surfaces exposed to the environment like skin, oropharynx, intestinal tract, and vagina
- Normal flora vary in number and type depending on the anatomical site
- These organisms are low-virulence and typically remain nonpathogenic in their usual site
- When normal flora leave their usual site, especially in immunocompromised individuals, they can cause disease
- Colonization occurs when individuals host organisms, either transiently or for long periods, that are not part of their normal flora
- Colonization resistance is a process where normal flora occupy receptor sites on skin and mucosal surfaces, preventing pathogens from binding to those receptors
Bacterial Pathogenesis
- A pathogen is a microbe capable of causing disease in immunocompetent people
- An opportunistic pathogen is a microbe that only causes disease in immunocompromised individuals
- Chronic carriers are individuals who harbor significant numbers of pathogenic organisms and can transmit them to others
- Infection has two meanings: the presence of microbes in the body and symptoms of disease
- The presence of microbes in the body doesn't always lead to symptoms of disease
- Bacteria cause disease symptoms primarily through toxin production (exotoxins and endotoxins) and inflammation
- Virulence is the measure of a microbe's ability to cause disease
- Asymptomatic or inapparent infections occur when host defenses eliminate the microorganism before it can multiply enough to cause symptoms
- Most bacterial infections are communicable, meaning they can spread from person to person
Stages of Bacterial Pathogenesis
- Transmission involves the movement of microbes from an external source to the portal of entry
- Evasion refers to the ability of microbes to bypass primary host defenses like skin or stomach acid
- Adherence is the attachment of bacteria to mucous membranes, typically through pili
- Colonization involves the growth of bacteria at the site of adherence
- Disease symptoms are caused by toxin production or invasion, often accompanied by inflammation
- Host responses include both nonspecific and specific (immunity) reactions
- Progression or resolution of disease depends on the host's response and bacterial factors
Transmission
- Vertical transmission involves the transfer of bacteria, viruses, and other microbes from mother to offspring through the placenta, birth canal, or breast milk
- Horizontal transmission is person-to-person transmission, including from mother to offspring
- Zoonoses are human diseases where animals are the reservoir
Portals of Entry
- The main portals of entry into the body include:
- Respiratory tract
- Gastrointestinal tract
- Skin
- Genital tract
Toxin Production
- Exotoxins are toxins released by bacteria that can cause significant harm to the host
- Many exotoxins have an A-B subunit structure:
- The A (active) subunit possesses toxic activity
- The B (binding) subunit binds the exotoxin to specific receptors on the host cell membrane
Typical Stages of Infectious Disease
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Incubation period is the time between exposure to a microbe or toxin and the onset of symptoms
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Prodrome period is the time when non-specific symptoms occur
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Specific-illness period is the time when characteristic features of the disease occur
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Recovery period is the time when symptoms resolve, and health is restored
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After the recovery period, some individuals may become chronic carriers of the organism, harboring the microbe without signs of disease
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Latent infections can develop, where individuals remain asymptomatic with subclinical infections.
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Description
This quiz explores the concepts of normal flora and their role in human health. It covers their characteristics, locations in the body, and implications when they leave their usual sites. Additionally, it touches on bacterial pathogenesis and the impact of colonization resistance.
