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Infection And Immunity > Pathogen-Host Interactions & Normal Flora > Flashcards

Pathogen-Host Interactions & Normal Flora Flashcards

1
Q

What is a pathogen?

A

A biological agent capable of causing disease.

Example: Bacteria, viruses, fungi

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2
Q

Define pathogenicity.

A

The ability of a pathogen to produce an infectious disease in an organism.

Example: Salmonella causing food poisoning

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3
Q

What is pathogenesis?

A

The process by which disease or disorder develops, including factors contributing to onset, progression, and maintenance of disease.

Example: Cancer pathogenesis involves genetic mutations

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4
Q

What is virulence?

A

The degree of damage done by a pathogen or its ability to cause disease.

Example: Highly virulent strains of E. coli

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5
Q

Differentiate between a true pathogen and an opportunistic pathogen.

A

True pathogens cause disease in healthy individuals, while opportunistic pathogens cause disease only in compromised individuals or in the wrong location.

Example: Candida albicans as an opportunistic pathogen

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6
Q

What are virulence factors?

A

Properties that enable a bacterium to establish itself within a host and cause disease.

Example: Toxins, adhesins

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7
Q

Give an example of a virulence factor.

A

Siderophores, which are molecules that bind and transport iron in microbial environments.

Example: Siderophores help bacteria acquire iron for growth

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8
Q

What are exotoxins?

A

Secreted toxins by pathogenic bacteria that damage host cells and tissues.

Example: Botulinum toxin

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9
Q

What are haemolysins?

A

Pore-forming proteins secreted by bacteria that lyse red blood cells.

Example: Streptolysin O

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10
Q

What role do adhesins play in bacterial pathogenicity?

A

Adhesins allow bacteria to adhere to host cells, facilitating infection.

Example: Adhesins help bacteria stick to the gut lining

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11
Q

What is the significance of pili/fimbriae in bacterial adherence?

A

These hair-like structures enable bacteria to attach to host cells, aiding colonization and infection.

Example: Pili in Neisseria gonorrhoeae

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12
Q

What is a biofilm?

A

A community of microbes embedded in an extracellular matrix, providing protection to the bacteria.

Example: Dental plaque biofilm

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13
Q

What are pathogenicity islands?

A

Gene clusters on bacterial chromosomes that encode virulence factors.

Example: E. coli pathogenicity islands

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14
Q

How do flagella contribute to bacterial pathogenicity?

A

They provide motility, allowing bacteria to move towards favorable environments (chemotaxis).

Example: Salmonella flagella for movement

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15
Q

What is the normal microbiota?

A

The collection of bacteria, fungi, and protozoa that live on or in healthy individuals without causing disease.

Example: Lactobacillus in the gut

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16
Q

What is the role of the normal gut microbiota?

A

It helps ferment unused energy substrates, produce vitamins, and prevent colonization by pathogens.

Example: Bacteroides aiding in digestion

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17
Q

How do gut bacteria benefit the host?

A

They produce vitamins like Vitamin K and B vitamins and help train the immune system.

Example: E. coli synthesizing Vitamin K

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18
Q

What is the hygiene hypothesis?

A

It suggests that reduced microbial exposure in early life may lead to increased autoimmune diseases due to altered immune system development.

Example: Asthma prevalence in developed countries

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19
Q

What is the primary cause of pneumonia?

A

Often, Streptococcus pneumoniae, a common upper respiratory tract colonizer, leads to infection.

Example: Pneumococcal pneumonia

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20
Q

What are probiotics?

A

Formulations containing live microbes that help restore a healthy gut microbiota.

Example: Lactobacillus probiotic supplements

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21
Q

What is the purpose of prebiotics?

A

Nutrient formulations designed to support the growth of healthy gut microbiota.

Example: Inulin as a prebiotic

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22
Q

What causes Clostridium difficile infections?

A

Overgrowth of C. difficile after antibiotic use, leading to severe diarrhea and intestinal damage.

Example: C. difficile spore formation

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23
Q

What is a fecal microbiota transplant (FMT)?

A

A procedure that transfers stool from a healthy donor to a patient to restore healthy gut microbiota.

Example: FMT for recurrent C. difficile infection

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24
Q

What is the significance of sterile body sites in diagnostics?

A

The presence of bacteria in sterile sites like the blood or cerebrospinal fluid indicates infection.

Example: Blood culture for sepsis diagnosis

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25
Q

What are the implications of normal flora for respiratory infections?

A

Normal flora from the upper respiratory tract can cause infections if introduced into the lower respiratory tract.

Example: Nasopharyngeal flora causing pneumonia

26
Q

What is bacterial swarming motility?

A

Coordinated movement of bacterial populations across surfaces, often associated with virulence.

Example: Proteus mirabilis swarming on agar plates

27
Q

What is the function of the bacterial flagellar hook?

A

It connects the flagellar filament to the motor and transmits rotational torque, allowing movement.

Example: Hook protein in flagellar structure

28
Q

What is chemotaxis in bacteria?

A

The movement of bacteria in response to chemical stimuli, towards or away from a chemical source.

Example: E. coli moving towards nutrients

29
Q

What are non-fimbrial adhesins?

A

Cell surface proteins that allow bacteria to adhere to host cells without fimbriae.

Example: Fibronectin-binding proteins

30
Q

What role do exopolysaccharides play in biofilms?

A

They form the extracellular matrix that protects the biofilm and allows bacterial adhesion.

Example: Alginate in Pseudomonas aeruginosa biofilms

31
Q

What is commensalism?

A

A type of symbiosis where one organism benefits while the other is neither harmed nor helped.

32
Q

What is mutualism?

A

A symbiotic relationship where both organisms benefit.

33
Q

What is parasitism?

A

A relationship where one organism benefits at the expense of the other, often causing harm.

34
Q

How does bacterial motility contribute to pathogenicity?

A

Motility enables bacteria to move towards favorable environments, avoid immune defenses, and colonize hosts.

35
Q

What are siderophores?

A

Molecules produced by bacteria to scavenge iron from the host, essential for bacterial growth and virulence.

36
Q

What is the significance of pili in bacterial infections?

A

Pili allow bacteria to attach to host cells, preventing clearance by bodily fluids like urine or mucus.

37
Q

How do bacteria use flagella to avoid host defenses?

A

Flagella enable bacteria to swim through viscous environments like mucus, avoiding host immune defenses

38
Q

What is a pathogenicity island (PAI)?

A

A section of the genome containing genes responsible for a pathogen’s ability to cause disease

39
Q

How do toxins contribute to bacterial virulence?

A

Toxins disrupt host cell functions, damage tissues, and evade immune responses, enhancing bacterial survival.

40
Q

What is chemotaxis?

A

The ability of bacteria to move in response to chemical gradients, either towards attractants or away from repellents.

41
Q

What are afimbrial adhesins?

A

Non-fimbrial proteins on the bacterial surface that mediate adherence to host cells

42
Q

Why is adherence important for bacterial pathogens?

A

it is the first step in colonization, helping bacteria attach to host cells and resist mechanical removal, like urination or peristalsis.

43
Q

What are pore-forming toxins (PFTs)?

A

Toxins that create pores in host cell membranes, leading to cell lysis and death.

44
Q

What is swarming motility?

A

The coordinated movement of bacterial populations across surfaces, often associated with virulence in pathogens like Proteus mirabilis.

45
Q

What is biofilm, and why is it important in bacterial infections?

A

A biofilm is a community of microbes embedded in a protective extracellular matrix, providing resistance to immune attacks and antibiotics.

46
Q

How do bacteria invade host cells

A

They either induce host cell endocytosis or survive phagocytosis to gain entry and establish infections.

47
Q

How do normal flora prevent pathogen colonization?

A

by occupying receptor sites on host cells, producing antimicrobial substances, and outcompeting potential pathogens.

48
Q

What is the role of gut microbiota in vitamin production?

A

Gut bacteria like E. coli synthesize vitamins such as Vitamin K and B group vitamins for the host.

49
Q

What are transient flora?

A

microorganisms that are temporarily present in or on the body and may be removed after a short time due to washing, immune defenses, or other factors.

50
Q

What are nosocomial infections?

A

Infections acquired in a hospital setting, often involving antibiotic-resistant bacteria.

51
Q

How does Streptococcus pneumoniae cause pneumonia

A

As a common colonizer of the upper respiratory tract, it can invade the lower respiratory tract, causing inflammation and fluid buildup in the alveoli.

52
Q

How does a fecal microbiota transplant (FMT) help treat Clostridium difficile infections?

A

FMT restores a healthy gut microbiome, which outcompetes C. difficile and helps resolve infection.

53
Q

What is the proton motive force (PMF), and how does it drive flagellar movement?

A

PMF is an electrochemical potential difference across a membrane, used to power flagellar rotation and other cellular processes.

54
Q

What is magnetotaxis in bacteria?

A

The movement of bacteria in response to magnetic fields, often used by aquatic bacteria to orient themselves in relation to the Earth’s magnetic field.

55
Q

How does the microbiota influence the immune system?

A

It helps “train” the immune system by exposing it to microbial antigens, potentially reducing the risk of autoimmune diseases.

56
Q

Why is the distinction between sterile and non-sterile body sites important in diagnostic microbiology?

A

The presence of bacteria in sterile sites like blood or cerebrospinal fluid indicates infection, while bacteria in non-sterile sites may be normal flora.

57
Q

How does antibiotic use disrupt normal flora?

A

Antibiotics can kill beneficial microbes, allowing opportunistic pathogens like Clostridium difficile to overgrow and cause infections.

58
Q

What is the significance of fimbriae in urinary tract infections?

A

Fimbriae on uropathogenic E. coli allow them to attach to urinary tract cells, leading to infection and resistance to being flushed out by urine

59
Q

What is the chaperone-usher pathway?

A

A mechanism used by Gram-negative bacteria to assemble pili on their surface, crucial for attachment to host cells.

60
Q

What are flagellar filaments made of?

A

Flagellar filaments are made of polymerized flagellin protein subunits, forming a spiral structure used for bacterial movement.

Infection And Immunity (2 decks)

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