Microbiology: Infection and Normal Microbiota

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Questions and Answers

What is the primary function of bacterial pili in the stages of infection?

To produce toxin and cause inflammation

To adhere to mucous membranes (correct)

To colonize and grow at the site of adherence

To evade primary host defenses

Which of the following is NOT a common mode of transmission of infectious diseases?

Fecal contamination of food and water

Skin contact

Airborne respiratory droplets

Through plant consumption (correct)

What is the primary source of Clostridium species that are transmitted to humans?

Animals

Water

Soil (correct)

Fomites

Which stage of infection involves the growth of bacteria at the site of adherence?

Colonization Signup and view all the answers

What is the term for inanimate objects that serve as a source of microorganisms that can cause infectious diseases?

Fomites Signup and view all the answers

Which of the following is an example of a zoonotic disease, where bacteria that commonly cause disease in humans exist primarily in animals?

All of the above Signup and view all the answers

What is the term for the exit of pathogens from the infected patient, which usually occurs via airborne respiratory droplets or fecal contamination of food and water?

Shedding Signup and view all the answers

Which stage of infection involves the production of toxins and inflammation?

Disease symptoms Signup and view all the answers

What is the primary factor that determines the infectious dose of a bacterium?

The number of virulence factors possessed by the bacterium Signup and view all the answers

Which of the following bacteria is an example of a pathogen that requires a higher infectious dose?

Salmonella Signup and view all the answers

What is the term used to describe a disease that is highly communicable?

Contagious Signup and view all the answers

What is the term used to describe a person who is infected with a pathogen but shows no symptoms of disease?

Asymptomatic Signup and view all the answers

Which of the following is an example of a non-communicable infection?

Botulism Signup and view all the answers

What is the term used to describe the stage of an infection where the pathogen has multiplied to sufficient numbers to cause symptoms of disease?

Apparent Signup and view all the answers

Which of the following is an example of a bacterium that can cause an infection through its normal presence in the human body?

E. coli Signup and view all the answers

What is the term used to describe a person who is infected with a pathogen and can transmit it to another susceptible person, even if they show no symptoms of disease?

Carrier Signup and view all the answers

What is the primary mode of transmission of pathogens from mother to offspring?

Across the placenta Signup and view all the answers

Which of the following is NOT a mode of transmission of infection?

Evaporation Signup and view all the answers

What is the primary defense against infection?

Normal skin and mucous membranes Signup and view all the answers

What is an example of indirect contact transmission?

Sharing contaminated drinking cups Signup and view all the answers

What is the term for transmission of pathogens from mother to offspring?

Vertical transmission Signup and view all the answers

What is the most frequent portal of entry of pathogenic bacteria into the body?

Sites where mucous membranes meet with the skin Signup and view all the answers

What is an example of inoculation transmission?

Wounds and burns Signup and view all the answers

Which of the following is an example of horizontal transmission?

Person-to-person transmission Signup and view all the answers

What is the primary function of adherence factors in bacterial virulence?

To allow bacteria to adhere to tissue surfaces Signup and view all the answers

What structure do Neisseria gonorrhoeae and E. coli use to attach to the urinary tract epithelium?

Pili Signup and view all the answers

What is the term for the protective matrix formed by bacteria after attachment?

Biofilm Signup and view all the answers

On which types of surfaces can biofilms form?

On both living and non-living surfaces Signup and view all the answers

What is a consequence of biofilm formation?

Increased antimicrobial resistance Signup and view all the answers

What is the function of glycocalyx in bacteria like Staphylococcus epidermidis?

To allow bacteria to adhere strongly to heart valves Signup and view all the answers

Why are adherence mechanisms essential for certain bacteria?

To attach to mucous membranes Signup and view all the answers

What does biofilm formation help bacteria with?

All of the above Signup and view all the answers

What is the primary function of M protein in Streptococcus pyogenes?

To inhibit phagocytosis Signup and view all the answers

Which of the following mechanisms is used by intracellular bacteria to survive within host cells?

Inhibition of phagosome-lysosome fusion Signup and view all the answers

What is the primary function of protein A in Staphylococcus aureus?

To bind to immunoglobulin G and prevent complement activation Signup and view all the answers

What is the typical duration of the incubation period in acute infectious diseases?

Varies depending on the organism Signup and view all the answers

What is the primary characteristic of the prodrome period in acute infectious diseases?

Nonspecific symptoms such as fever and malaise Signup and view all the answers

What is the primary difference between the diseases caused by different strains of Staphylococcus aureus?

Type of disease caused (inflammatory vs. non-inflammatory) Signup and view all the answers

What is the primary function of the recovery period in acute infectious diseases?

To allow the host to recover from the illness Signup and view all the answers

What is the primary mechanism used by intracellular bacteria to escape degradative enzymes within host cells?

Escape from the phagosome into the cytoplasm Signup and view all the answers

Study Notes

Infection and Disease

Multiplication of normal microbiota bacteria is not considered an infection, but multiplication of pathogenic bacteria (e.g., Salmonella) is considered an infection, even if the person is asymptomatic.
The infectious dose of bacteria varies among pathogens and depends on their virulence factors, such as pili, exotoxins, endotoxins, and capsules.

Stages of Infection

Transmission from an external source into the portal of entry.
Evasion of primary host defenses, such as skin or stomach acid.
Adherence to mucous membranes, usually by bacterial pili.
Colonization by growth of the bacteria at the site of adherence.
Disease symptoms caused by toxin production or invasion, accompanied by inflammation.
Host immune response to each of the mentioned stages.

Transmission of Infection

Modes of transmission include:
- Contact (direct or indirect)
- Inhalation (droplet nuclei)
- Ingestion (food or drink contaminated by pathogens)
- Inoculation (directly into human skin or mucosa)
- Insects (vector-borne transmission)
- Congenital (vertical transmission from mother to offspring)
Portals of entry include:
- Respiratory tract
- Gastrointestinal tract
- Genital tract
- Urinary tract
- Abnormal areas of mucous membranes and skin (e.g., cuts, burns)

Microbial Mechanisms of Pathogenicity

Bacterial virulence factors include:
- Adherence factors (e.g., pili, capsules, glycocalyces)
- Biofilm formation
- Cell wall proteins (e.g., M protein, protein A)
- Intracellular survival mechanisms (e.g., inhibition of phagosome-lysosome fusion, escape from phagosome into cytoplasm)

Typical Stages of Infectious Disease

Incubation period: time between acquisition of organism (or toxin) and beginning of symptoms
Prodrome period: time during which nonspecific symptoms occur (e.g., fever, malaise, loss of appetite)
Specific-illness period: time during which overt characteristic signs and symptoms of the disease occur
Recovery period (convalescence): time during which the illness abates and the patient returns to a healthy state

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Description

Understanding the difference between normal microbiota and pathogenic bacteria, and the infectious dose required to cause disease. Learn about bacteria like Salmonella and Shigella that cause diarrhea.