Microbiology Chapter 10: Host-Microbe Interactions

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Questions and Answers

What does ID50 represent in terms of pathogens?

The number of cells needed to establish an infection in 50% of hosts (correct)

The total amount of toxin required to affect 50% of hosts

The rate at which a pathogen spreads within a population

The number of cells needed to cause death in 50% of hosts

Which statement is true regarding a pathogen's ID50 and danger level?

A lower ID50 indicates a pathogen is less infectious.

Highly infectious pathogens may not be especially dangerous. (correct)

More infectious pathogens are always more dangerous.

ID50 is the measure of how quickly a pathogen can spread.

What does LD50 measure in relation to toxins?

The rate of toxin production by pathogens

The total dosage of toxin required for immune response

The amount of toxin needed to infect 50% of hosts

The amount of toxin needed to kill 50% of affected hosts (correct)

Which agent has the ID50 range of 10-50?

Bacillus anthracis Signup and view all the answers

How is LD50 typically expressed?

In micrograms per kilogram of body weight Signup and view all the answers

What role do normal microbiota play in relation to potential pathogens?

They compete with potential pathogens for resources. Signup and view all the answers

What is dysbiosis?

A disruption in normal microbiota balance. Signup and view all the answers

Why might a commensal organism act as a pathogen in different hosts?

Due to the host’s immune response. Signup and view all the answers

What is meant by the term 'tropism' in the context of pathogens?

The preference of pathogens for specific host tissues. Signup and view all the answers

What can result from the use of antibiotics in relation to microbiota?

A rapid proliferation of opportunistic pathogens. Signup and view all the answers

How do normal microbiota contribute to the immune system?

By promoting immune system maturation. Signup and view all the answers

What characterizes a pathogen?

Microbes that cause disease in a host. Signup and view all the answers

What might be a consequence of shifting normal microbiota levels?

Increased risk of opportunistic infections. Signup and view all the answers

What is the primary function of coagulases in pathogens?

To promote blood clotting Signup and view all the answers

What is the role of kinases in relation to pathogens?

To allow pathogens to spread by breaking down clots Signup and view all the answers

Which enzyme is responsible for breaking down lipids?

Lipases Signup and view all the answers

What is the primary purpose of siderophores produced by bacteria?

To snatch iron from transferrin Signup and view all the answers

What kind of effect do cytopathic effects have on host cells?

They can either damage or kill host cells. Signup and view all the answers

Which of the following is not a method by which bacteria induce cytopathic effects?

Transforming host cells into cancer cells Signup and view all the answers

How do extracellular enzymes benefit pathogens?

By breaking down nutrients in the environment Signup and view all the answers

Viral cytopathic effects can include which of the following?

Disrupting normal host cell function Signup and view all the answers

What is the primary definition of pathogenicity?

The ability of a microbe to cause disease. Signup and view all the answers

Which of the following describes the term virulence?

The degree or extent of disease that a pathogen causes. Signup and view all the answers

What is considered a virulence factor?

Mechanisms that help microbes overcome host defenses. Signup and view all the answers

How do many pathogens adapt their virulence factors?

In response to the host and selective pressures. Signup and view all the answers

Virulence factors can damage host cells by which of the following mechanisms?

By directly damaging host cells or provoking harmful immune responses. Signup and view all the answers

Why might a pathogen reduce its investment in certain virulence factors?

If those factors do not offer a clear survival benefit. Signup and view all the answers

What role do fimbriae play in the context of virulence?

They aid in the adhesion of pathogens to host cells. Signup and view all the answers

What is the relationship between host factors and virulence?

Host properties can influence the efficacy of virulence factors. Signup and view all the answers

What is a requirement for personal protective equipment (PPE) in a BSL-3 laboratory?

PPE must be worn at all times Signup and view all the answers

Which facility consideration is specifically required for a BSL-4 laboratory?

Airtight, pressurized full-body suits Signup and view all the answers

What is a common goal of an infection control team in healthcare facilities?

To limit infection risks for workers and patients Signup and view all the answers

Which of the following is NOT a specific requirement for BSL-3 laboratories?

Specialized facility design Signup and view all the answers

Which practice is part of standard precautions in healthcare settings?

Hand hygiene before and after patient contact Signup and view all the answers

What type of access control is mandatory in BSL-4 facilities?

Highly restricted/lockdown access Signup and view all the answers

What is a crucial aspect of waste management in BSL-3 laboratories?

All waste must be decontaminated Signup and view all the answers

What must be done to a worker's clothing before they leave a BSL-4 facility?

Workers must change and shower Signup and view all the answers

What is the primary function of cytolysins in bacterial infections?

To lyse white blood cells and damage host tissues Signup and view all the answers

Which bacterium produces a neurotoxin that causes flaccid paralysis?

Clostridium botulinum Signup and view all the answers

What is a function of cholera toxin made by Vibrio cholerae?

To induce watery diarrhea Signup and view all the answers

Which process follows the entry of a pathogen into a host?

Adhere to host tissues Signup and view all the answers

What is the role of phospholipases in bacterial infections?

To damage host cell membranes Signup and view all the answers

Which task is NOT essential for a pathogen to establish an infection?

Exit the host Signup and view all the answers

Pertussis toxin produced by Bordetella pertussis has what main effect?

Suppresses the host immune response Signup and view all the answers

What characterizes a neurotoxin?

It affects the nervous system, causing paralysis Signup and view all the answers

Study Notes

Microbiology: Basic and Clinical Principles - Chapter 10

Chapter 10 covers Host-Microbe Interactions and Pathogenesis, presented by Janet Dowding, PhD, St. Petersburg College.
The chapter uses a clinical case ("The Case of the Deadly Mistake") to explore host-microbe interactions. Students can visit a dedicated online resource to examine this case.

Host-Microbe Interactions

These interactions are a dynamic exchange, not always harmful.
Normal microbiota (the naturally occurring microorganisms on the body) colonize various body systems (digestive, genital, urinary, and respiratory).
Microbiota help by producing vitamins, competing with harmful pathogens, and promoting immune system maturity.
An imbalance in microbiota (dysbiosis) can lead to diseases. For example, a course of antibiotics can kill off normal gut microbiota, allowing Clostridioides difficile to flourish and cause illness.

Pathogens

Pathogens are disease-causing microbes.
They have adaptations to interact with specific host tissues, making them dangerous.
Pathogenic species can be commensal in one host and pathogenic in another. For instance, Group B streptococci (GBS) are normal vaginal commensals in 30% of women, but associated with newborn sepsis, meningitis, and pneumonia.

Tropism

Tropism is a pathogen's preference for a specific host or tissue within that host.
This preference can, but doesn't always, translate to the development of a disease.
Host factors (age, gender, overall health, etc.) influence the likelihood of disease progression even after successful invasion of the preferred tissue.
Emerging pathogens often broaden their host range over time.

Virulence

Pathogenicity is the ability of a microbe to cause disease.
Virulence describes the degree or extent of disease caused by a pathogen.

Virulence Factors

Mechanisms pathogens use to overcome host defenses include features that adhere to host cells, invade tissues, or induce disease.
Virulence factors often are energy intensive for pathogens to produce, so they are selected for if they cause the pathogen to better survive and spread.

Toxins

Toxins are molecules affecting host responses, including causing tissue damage or suppressing the immune system.
Toxemia refers to toxins in the bloodstream.

Endotoxins

These are lipid-based toxins found in the outer membranes of Gram-negative bacteria (LPS).
They are released upon bacterial cell death or lysis.
These toxins can induce high fever, chills, body aches, hypotension, tachycardia, increased respiratory rate, inflammation, disorientation, nausea, & vomiting.
In large quantities, may cause septic shock and organ failure.
They are not easily neutralized or eliminated.

Exotoxins

These are proteins produced and released by actively growing Gram-positive or Gram-negative bacteria.
These toxins can act on the nervous system (neurotoxins), gastrointestinal tract (enterotoxins), liver (hepatitoxins) or kidneys (nephrotoxins).
Classified into families based on their mode of action:
- Type I: membrane-acting extracellular toxins
- Type II: membrane-damaging toxins
- Type III: intracellular toxins(AB toxins)
Many bacterial exotoxins are potent and cause severe diseases.

Five Steps to Infection

Pathogens complete five steps to successfully infect a host:
1. Enter the host
2. Adhere to host tissues
3. Invade host tissues and obtain nutrients
4. Replicate while warding off immune system
5. Transmit to a new host

Portals of Entry

Mucous membranes are common entry sites.
Other portals of entry include the skin, eyes, ears, and respiratory/urogenital/GI tracts.
Some pathogens have multiple portals of entry.

Portals of Exit

Portals of exit are typically the same as entry. This includes secretions, excretions, wounds, mucus, and bodily fluids (e.g., blood, urine, feces).

Reservoir

Pathogens thrive in reservoirs; these can be environmental (water, soil) or in other organisms.

Safety and Health Care

Healthcare facilities use biosafety levels (BSLs) to classify pathogens based on disease severity, mode of transmission, availability of prevention and/or treatment.
BSL-1: Well-characterized, low disease potential pathogens.
BSL-2: Infectious, not typically airborne.
BSL-3: Serious or lethal pathogens, frequently airborne.
BSL-4: Dangerous, with frequent lethal outcomes in humans; airborne transmission likely.
Proper precautions, including PPE (personal protective equipment), are required. The specific PPE depends on BSL.

Infection Control Practices

Standard precautions treat all patients as potential reservoirs for bloodborne and other infectious agents.
Transmission precautions prevent pathogen transmission by contact, droplet, or airborne routes and often involve specialized isolation rooms.

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Description

Explore the fascinating dynamics of host-microbe interactions in Chapter 10 of Microbiology: Basic and Clinical Principles. This chapter uses a clinical case to delve into the roles of microbiota and pathogens, highlighting their impact on health and disease. Enhance your understanding of how an imbalance in microbiota can lead to serious health issues.