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Questions and Answers
Opportunistic pathogens frequently cause disease in immunocompetent individuals.
Opportunistic pathogens frequently cause disease in immunocompetent individuals.
False (B)
What does the term LD50 refer to?
What does the term LD50 refer to?
- The number of organisms required to kill half the hosts. (correct)
- The number of organisms required to cause infection in half the hosts.
- The number of organisms required to cure half the hosts.
- The number of organisms required to cause disease in all hosts.
Which of the following is not a stage of bacterial pathogenesis?
Which of the following is not a stage of bacterial pathogenesis?
- Transmission
- Adherence to mucous membranes
- Production of antibodies (correct)
- Evasion of host defenses
What are the two main types of inflammation caused by bacterial infection?
What are the two main types of inflammation caused by bacterial infection?
What is the term for human diseases where animals are the reservoir?
What is the term for human diseases where animals are the reservoir?
What is the primary mechanism by which bacteria adhere to human cells?
What is the primary mechanism by which bacteria adhere to human cells?
Coagulase is an enzyme that degrades hyaluronic acid in the subcutaneous tissue.
Coagulase is an enzyme that degrades hyaluronic acid in the subcutaneous tissue.
What is the process by which bacteria can evade host defenses by living within cells?
What is the process by which bacteria can evade host defenses by living within cells?
Which of the following is not a mechanism used by bacteria to survive and grow intracellularly?
Which of the following is not a mechanism used by bacteria to survive and grow intracellularly?
Which of the following is not a feature of exotoxins?
Which of the following is not a feature of exotoxins?
What is the main mechanism by which bacteria cause disease, besides the production of toxins?
What is the main mechanism by which bacteria cause disease, besides the production of toxins?
Immunopathogenesis refers to the direct damaging effects of bacteria on host tissues.
Immunopathogenesis refers to the direct damaging effects of bacteria on host tissues.
What is the term for the time period between exposure to a pathogen and the appearance of symptoms?
What is the term for the time period between exposure to a pathogen and the appearance of symptoms?
What is the term for the period during which nonspecific symptoms occur, before the characteristic features of the disease appear?
What is the term for the period during which nonspecific symptoms occur, before the characteristic features of the disease appear?
What is the term for the period during which an individual remains asymptomatic despite being infected with a pathogen?
What is the term for the period during which an individual remains asymptomatic despite being infected with a pathogen?
What is the term for individuals who continue to harbor a pathogen after recovering from an infection, potentially shedding the pathogen without exhibiting symptoms?
What is the term for individuals who continue to harbor a pathogen after recovering from an infection, potentially shedding the pathogen without exhibiting symptoms?
Latent infections are characterized by persistent symptoms that can recur after periods of remission.
Latent infections are characterized by persistent symptoms that can recur after periods of remission.
Flashcards
Pathogen
Pathogen
A microbe capable of causing disease.
Opportunistic Pathogen
Opportunistic Pathogen
Organisms that rarely cause disease in healthy individuals but can cause serious infections in immunocompromised patients.
Virulence
Virulence
A quantitative measure of pathogenicity, indicating the number of organisms needed to cause disease.
LD50 (Lethal Dose 50)
LD50 (Lethal Dose 50)
The number of organisms required to kill 50% of the hosts.
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ID50 (Infectious Dose 50)
ID50 (Infectious Dose 50)
The number of organisms needed to cause infection in 50% of the hosts.
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Portal of Entry
Portal of Entry
The initial point where a pathogen enters the body.
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Adherence
Adherence
The ability of bacteria to stick to surfaces, usually mucous membranes.
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Pili
Pili
Fibrous structures extending from bacteria that mediate attachment to host cells.
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Glycocalyx
Glycocalyx
A polysaccharide slime layer secreted by some bacteria, enhancing adherence.
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Bacterial Enzymes
Bacterial Enzymes
Enzymes secreted by bacteria that aid in tissue invasion.
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Hyaluronidase
Hyaluronidase
An enzyme that degrades hyaluronic acid in subcutaneous tissue, facilitating bacterial spread.
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Coagulase
Coagulase
An enzyme that accelerates fibrin clot formation, shielding bacteria from phagocytosis.
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IgA Protease
IgA Protease
An enzyme that degrades secretory IgA, allowing bacteria to attach to mucous membranes.
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Leukocidins
Leukocidins
Substances that can destroy neutrophils and macrophages.
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Capsule
Capsule
A protective capsule surrounding bacteria that hinders phagocytosis.
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Pyogenic Inflammation
Pyogenic Inflammation
A defensive response to the presence of bacteria, involving neutrophils, antibodies, and complement.
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Granulomatous Inflammation
Granulomatous Inflammation
A defensive response to intracellular bacteria, involving macrophages and CD4-positive T cells.
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Intracellular Survival
Intracellular Survival
The ability of bacteria to survive and multiply within host cells.
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Exotoxin Production
Exotoxin Production
The process of releasing toxins by bacteria into the surrounding environment.
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Endotoxin Production
Endotoxin Production
Toxic components of the bacterial cell wall that are released upon bacterial death.
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Immunopathogenesis
Immunopathogenesis
The immune response to a pathogen that causes disease symptoms, not the pathogen itself.
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Incubation Period
Incubation Period
The time period between exposure to a pathogen and the appearance of symptoms.
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Prodrome Period
Prodrome Period
The period with nonspecific symptoms preceding the characteristic features of the disease.
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Specific Illness Period
Specific Illness Period
The period when the characteristic features of a specific disease occur.
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Recovery Period (Convalescence Period)
Recovery Period (Convalescence Period)
The period of recovery and restoration of health after illness.
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Chronic Carrier
Chronic Carrier
A persistent carrier state where an organism continues to grow in the host, with or without symptoms.
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Latent Infection
Latent Infection
An infection where the pathogen remains dormant but can reactivate and cause symptoms.
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Subclinical Infection
Subclinical Infection
An infection where the individual is infected but does not show any symptoms.
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Zoonoses
Zoonoses
Diseases for which animals are the natural reservoirs of the pathogen.
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Human-to-Human Transmission
Human-to-Human Transmission
The transmission of a pathogen from one infected person to another.
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Vector-Borne Transmission
Vector-Borne Transmission
The transmission of a pathogen indirectly through a vector such as an insect.
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Animal-to-Human Transmission
Animal-to-Human Transmission
The transmission of a pathogen from an animal to a human.
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Microbial Virulence Factors and Pathogenesis
- A microorganism is a pathogen if it can cause disease. Some are highly pathogenic, causing disease often, while others cause it rarely.
- Opportunistic pathogens rarely cause disease in healthy individuals but can cause serious infection in immunocompromised people.
- Virulence is a measure of pathogenicity, quantified by the number of organisms needed to cause disease (LD50 – 50% lethal dose) or infection (ID50 – 50% infectious dose). A lower LD50/ID50 indicates higher virulence.
Stages of Bacterial Pathogenesis
- Most bacterial infections originate from external sources, but some are caused by normal flora.
- Transmission occurs by several routes (e.g. human to human, animal to human).
- Infection involves several stages
- Entry into the body
- Evading the host's primary defenses (skin, stomach acid)
- Adherence to mucous membranes (usually by pili)
- Colonization by growth at the site of adherence
- Disease symptoms caused by toxin production or invasion.
- Host response with inflammation.
- Progression or resolution of the disease.
Determinants of Bacterial Pathogenesis
- Transmission: Microbes can spread through direct contact, vectors (e.g., insects), or indirect contact (e.g., contaminated food, water, or soil).
- Adherence to Cell Surfaces: Pili or glycocalyx facilitate attachment to host cells or surfaces.
- Invasion, Inflammation, and Intracellular Survival: Bacteria may invade tissue, trigger inflammation (pyogenic or granulomatous), or survive within host cells to evade immune responses. This survival can be aided by a variety of factors such as inhibiting lysosome-phagosome fusion or inhibiting acidification.
Toxin Production
- Toxins are another key virulence factor that causes disease.
- Exotoxins and endotoxins are different in their source, chemical composition, and toxicity. Exotoxins are protein-based molecules produced and secreted by bacteria. Endotoxins are part of the cell wall of certain gram-negative bacteria.
Immunopathogenesis
- In some diseases, the immune response to the organism, not the organism itself, causes the symptoms.
- (e.g, antibodies against the M protein of Streptococcus pyogenes cross-react with tissues, causing arthritis, carditis and chorea in rheumatic fever)
Typical Stages of an Infectious Disease
- Incubation period: Time between exposure and symptom onset
- Prodrome period: Time of nonspecific symptoms
- Specific-illness period: Characteristic symptoms appear
- Recovery period (convalescence): Symptoms resolve and health returns
- Subclinical infections: individual infected but asymptomatic. Antibody presence indicates a prior infection.
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