Pathogenicity and Infection: Microbiology and Disease

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Questions and Answers

What is the primary characteristic of a parasite?

Ability to cause disease

Ability to grow and multiply within a host

Metabolic dependence on a host (correct)

Presence in the environment

Which type of pathogen is part of the normal flora and causes disease when it gains access to other tissue sites?

Virulent pathogen

Primary pathogen

Frank pathogen

Opportunistic pathogen (correct)

What is the term for the chain of events required for a successful infection?

Pathogenicity

Disease cycle

Chain of infection (correct)

Infectious process

What is the natural environmental location where a pathogen normally resides?

Reservoir Signup and view all the answers

What is the term for the ability of a parasite to cause disease?

Pathogenicity Signup and view all the answers

What is the term for an infection passed from an animal to a human?

Zoonosis Signup and view all the answers

What is the minimum requirement for a pathogen to cause a disease?

Contact with a host and survive within it Signup and view all the answers

What is the term for the primary parasitic organism that causes disease by direct interaction with a healthy host?

Frank pathogen Signup and view all the answers

Which of the following is NOT a source of pathogens?

A healthy host's immune system Signup and view all the answers

What is the primary function of virulence factors in pathogens?

To outcompete host cells and resist their defenses Signup and view all the answers

What is the term for the specific substance produced by microbes that damages host cells?

Toxin Signup and view all the answers

What is the period of time during which the pathogen is present in the host, but no signs or symptoms are apparent?

Incubation period Signup and view all the answers

What is the term for the set of characteristic signs and symptoms of a disease?

Disease syndrome Signup and view all the answers

What is the primary goal of microorganisms in order to survive?

To outcompete host cells and resist their defenses Signup and view all the answers

What is the term for the condition caused by the presence of toxins in the blood of the host?

Toxemia Signup and view all the answers

What is the term for the ability of microbes to produce toxins?

Toxigenicity Signup and view all the answers

What is the stage of the infectious disease during which the signs and symptoms are most severe?

Period of illness Signup and view all the answers

What is the term for the diseases that result from the entry of a specific preformed toxin into the host?

Intoxications Signup and view all the answers

What is the primary function of adhesins in the disease process?

To mediate adherence of pathogens to host cells Signup and view all the answers

Which of the following is a characteristic of pathogenicity islands?

They contain several open reading frames Signup and view all the answers

What is the term for the presence of viable bacteria in the blood?

Bacteremia Signup and view all the answers

What is the first step in the disease process?

Adherence and colonization Signup and view all the answers

Which of the following bacteria is non-invasive?

Clostridium tetani Signup and view all the answers

What is the term for the ability of a pathogen to survive outside the host?

Infectivity Signup and view all the answers

Which of the following is an example of passive penetration?

Skin lesions Signup and view all the answers

What is the purpose of virulence factors?

To determine the degree of pathogenicity Signup and view all the answers

What is the term for the degree of pathogenicity?

Virulence Signup and view all the answers

What is the characteristic of exotoxins that makes them highly effective in causing harm?

They are highly immunogenic Signup and view all the answers

What is the primary function of the B subunit in AB exotoxins?

Binding to specific target cells Signup and view all the answers

What is the result of superantigens stimulating T cells?

T cells overexpress and release cytokines Signup and view all the answers

What is the characteristic of endotoxins that makes them different from exotoxins?

They are part of the bacterial cell wall Signup and view all the answers

What is the toxic component of endotoxins?

Lipid A Signup and view all the answers

What is the effect of mycotoxins on food crops?

They contaminate food crops Signup and view all the answers

What is the effect of fibrinolysis on the host?

It leads to decreased blood clotting Signup and view all the answers

What is the result of endotoxins causing general system effects?

All of the above Signup and view all the answers

What is the function of the lipid portion of endotoxins?

It is responsible for the toxic effect of endotoxins Signup and view all the answers

Which type of toxin is produced by Stachybotrys?

Satratoxin Signup and view all the answers

What is the effect of biofilm growth on microbial cells?

Increased resistance to host defense Signup and view all the answers

Which of the following mechanisms is used by pathogens to resist host defenses?

Production of substances that resemble host tissue Signup and view all the answers

What is the characteristic of pathogens that are transmitted through vectors?

Relatively benign in vectors but highly virulent in humans Signup and view all the answers

What is the term for the ability of a pathogen to make contact with appropriate host tissue?

Tropism Signup and view all the answers

What is the characteristic of airborne transmission?

Pathogens are suspended in air and travel ≥1 meter Signup and view all the answers

What is the term for the spread of pathogens through large particles (>5 μm) that travel short distances?

Droplet spread Signup and view all the answers

What is the effect of biofilm growth on the immune system?

Impaired immune response Signup and view all the answers

What is the mechanism used by some pathogens to survive inside host cells?

Ejection from cell to cell using host actin Signup and view all the answers

Study Notes

Pathogenicity and Infectious Disease

Host: A larger organism that supports the survival and growth of a smaller organism, commonly a parasite.
Parasites: Organisms that live on or within a host and are metabolically dependent on it, causing diseases.
Infection occurs when a parasite grows and multiplies within or on a host, not necessarily resulting in disease.

Infection, Pathogen, and Pathogenicity

Pathogen: Any parasitic organism causing infectious disease; can be a primary (frank) pathogen or opportunistic pathogen.
Pathogenicity: The ability of a parasite to cause disease, influenced by various factors.

The Chain of Infection

Successful infections involve multiple factors: agent identity, virulence, dose, means of exposure, and host susceptibility.

Sources of Pathogens

Pathogen sources can be animate (humans, animals) or inanimate (water, soil, food).
Zoonoses: Infections passed from animals to humans.

Infectious Process

Pathogens need to contact a host and survive to establish infection, requiring suitable environments, nutrients, and protection from harmful elements.

Toxigenicity

Toxigenicity refers to a microbe's ability to produce toxins, substances harmful to the host.
Intoxications result from preformed toxins entering the host, whereas toxemia is the presence of toxins in the host's blood.

Course of Infectious Disease

Infectious diseases involve various pathogens and their symptoms and signs.
Incubation period: Time from pathogen entry to symptom onset.
Different stages: prodromal (early symptoms), period of illness (most severe), and convalescence (symptoms decrease).

Virulence

Virulence is the degree of pathogenicity; virulence factors influence damage, invasion, and infectivity.
Pathogenicity Islands: Large DNA segments that enhance bacterial virulence, differing from nonpathogenic bacteria.

Adherence and Colonization

Initial disease occurrence begins with adherence to host cells via specific molecules (adhesins) and colonization does not always cause tissue damage.
Portals of entry include skin, respiratory, gastrointestinal, and urogenital systems.

Invasion

Invasiveness is a pathogen's ability to spread; active and passive penetration methods are employed.
Bacteremia refers to viable bacteria in the blood, while septicemia includes pathogens or toxins present in the blood.

Toxins

Exotoxins are soluble proteins secreted by pathogens and can cause significant host damage.
Types include AB exotoxins, membrane-disrupting toxins, and superantigens, which stimulate immune overreaction.
Endotoxins, found in Gram-negative bacteria, are released during bacterial lysis and can cause systemic effects like fever.

Biofilm Development

Biofilms grow differently from planktonic cells, resulting in chronic infections and increased resistance to antibiotics and host defenses.

Resisting Host Defenses

Successful pathogens have evolved various strategies to evade the immune system, including infection of immune cells, production of decoy proteins, and alterations in antigen expression.

Pathogen Transmission

Transmission methods include airborne, contact, vehicle, vector-borne, and vertical transmission.
Initial pathogen transmission correlates with the degree of virulence; direct contact is usually associated with less virulent pathogens.

Airborne and Contact Transmission

Airborne pathogens can travel long distances and remain suspended in the air.
Contact transmission involves direct (physical interaction) and indirect contact via contaminated intermediates like utensils or bedding.

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Description

Test your knowledge on pathogenicity and infection, including the roles of hosts and parasites, and the differences between infection and infectious disease. Explore the concepts of pathogens, infection, and pathogenicity in this microbiology quiz.