Micro W8 Part 5: Microorganisms MOA, Epidemiology, Vaccination, Control & Prevention

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Questions and Answers

What defines resident flora in the human body?

Microbes that are only temporarily present and can be harmful.

Microbes that always lead to noticeable symptoms of infection.

Microbes that establish for life and have beneficial functions. (correct)

Microbes that cause diseases by disrupting normal functions.

Which type of infection is characterized by the pathogen remaining confined to a specific tissue or area?

Local Infection (correct)

Secondary Infection

Focal Infection

Systemic Infection

What is a primary infection?

An infection caused by multiple infectious agents at the same site.

An infection that appears suddenly but resolves quickly.

The initial infection that occurs in a person. (correct)

An infection that leads to noticeable symptoms.

Which infection pattern involves multiple infectious agents concurrently at the same site?

Mixed Infection Signup and view all the answers

How does transient flora differ from resident flora?

Transient flora come and go depending on contact with others. Signup and view all the answers

What characterizes a subclinical infection?

Persists for a long time without noticeable symptoms. Signup and view all the answers

What is the initial step in the stages of infection?

Contamination Signup and view all the answers

What type of infection typically follows a primary infection and is usually caused by a different microbe?

Secondary Infection Signup and view all the answers

What percentage of bacteria responsible for hospital infections are resistant to at least one common antibiotic?

70% Signup and view all the answers

Which agency is primarily responsible for public health information and initiatives in Canada?

Public Health Agency of Canada Signup and view all the answers

What term describes diseases that occur constantly in a specific population or area?

Endemic Signup and view all the answers

Which of the following best describes incidence in terms of disease monitoring?

Number of new cases over a specific time period Signup and view all the answers

What is the primary source of epidemiological data in the United States?

Centers for Disease Control and Prevention (CDC) Signup and view all the answers

What is the most effective way to prevent infectious diseases?

Vaccinations Signup and view all the answers

What is the primary focus of the CDC’s Global Immunization Division?

Worldwide vaccination efforts Signup and view all the answers

Which of the following describes a pandemic?

A global epidemic affecting multiple countries Signup and view all the answers

What primarily causes opportunistic pathogens to become harmful?

Disruption of the balance between the body and normal flora Signup and view all the answers

Which of the following best describes 'virulence'?

The degree to which a microbe can cause disease Signup and view all the answers

What is the significance of adhesion in microbial infection?

It is essential for bacteria to bind to host cells Signup and view all the answers

What type of infections are known as exogenous infections?

Infections originating from the hospital environment Signup and view all the answers

Which factor does NOT influence pathogenicity?

Host's psychological state Signup and view all the answers

Which type of toxin is released from a bacterium only when it dies?

Endotoxin Signup and view all the answers

What mechanism do capsules serve for certain pathogens?

Protecting against host immune systems Signup and view all the answers

Which statement about endotoxins is true?

They can cause an inflammatory response upon bacterial lysis. Signup and view all the answers

How can opportunistic pathogens enter the bloodstream?

When normal flora migrate to inappropriate sites in the body Signup and view all the answers

What role do invasins play in the pathogen's lifecycle?

They assist in invading host tissues. Signup and view all the answers

Which of the following is a common cause of nosocomial infections?

Pre-existing health conditions Signup and view all the answers

What is the primary characteristic of endogenous infections?

They are the result of normal flora becoming harmful. Signup and view all the answers

Which of the following best describes antimicrobial resistance?

Pathogens become harder to treat due to resistance to drugs Signup and view all the answers

Study Notes

Normal Flora

Microbes establish themselves on the body from birth, forming normal flora which helps protect against harmful organisms
Resident flora stay in the body for life and are beneficial
Transient flora come and go, attaching to the skin when there is direct contact with another person or object
Transient flora can spread disease
Example: Bacillus laterosporus helps control fungi like Candida

Etiology of Infectious Disease

This is the study of the causes of disease, focusing on how infectious agents lead to pathological changes and disrupt normal body functions

Patterns of Infection

Local Infections: Pathogen remains confined to a specific tissue
Focal Infections: Pathogen starts in one area and spreads to others
Systemic Infections: Infection spreads throughout the body via the circulatory system, affecting multiple sites and fluids
Mixed Infections: Multiple infectious agents establish themselves concurrently at the same site
Acute Infection: Appear rapidly with severe symptoms that vanish quickly
Chronic Infection: Less severe symptoms that persist for long periods
Primary Infection: Initial infection
Secondary Infection: Follows primary infection and is caused by a different microbe, often leading to more severe health issues
Subclinical Infection: Infection without noticeable symptoms

Stages of Infection

Contamination: Microbes are present on or in the body
Infection: Microorganism enters and grows in the body (except normal flora), entry into host tissues is required, infection does not always result in disease

Opportunistic Pathogens

A pathogen is a germ that can cause disease.
Opportunistic pathogens are harmless microbes that can turn into pathogens when the balance between the body and normal flora is disrupted
Opportunistic pathogens don't usually cause problems in a healthy person
Causes of opportunistic pathogens:
- Compromised immune system (e.g. AIDS, malnutrition, stress, age, chemo/radiation)
- Changes in normal flora (loss of protective competition between microbes)
- Flora in the wrong place (when normal microbes enter areas where they don't usually exist (e.g., bloodstream or organs))

Virulence & Pathogenicity

Virulence: The degree to which a microbe can cause disease, determined by its virulence factors
Pathogenicity: Influenced by factors such as:
- Number of microorganisms
- Portal of entry
- Host defenses
- Intrinsic characteristics of the organism
- Virulence factors

Adhesion

Importance: The first and most crucial step of infection, without it organisms can be expelled through natural body processes by ciliary motion (e.g., coughing, sneezing, swallowing, urine flow, tears, peristalsis)
Mechanism: Bacteria must bind to host cells using structures such as pili, fimbriae, or specific membrane receptor sites
Types of Adhesion:
- Specific: Targeted binding to particular receptors (“lock & key”)
- Nonspecific: Involves electrostatic attraction and molecular vibrations

Colonization & Invasion

Colonization: Pathogens typically settle in tissues that are exposed to the external environment, such as the urogenital, digestive, respiratory tracts, and conjunctiva, process by which species spread to new areas
Invasion: Pathogens can invade host tissues by producing extracellular substances that damage host cell membranes
Invasins: Substances that help break down both primary and secondary barriers of the host, allowing the pathogens to grow and spread easily.

Evasion of Host Defense

Capsules: Many pathogens have capsules that protect them from the host's immune system
Protein Production: Some microbes produce proteins that bind to host antibodies, preventing their action
Mutation: Pathogens can mutate to change their surface antigens, making it harder for the immune system to recognize them
Strategies Against Phagocytes:
- Avoiding contact with phagocytes
- Inhibiting the engulfment process by phagocytes
- Surviving within phagocytes after being ingested
- Producing substances that kill or damage phagocytes before or after they ingest the pathogens

Toxins

Toxigenic Organisms: Microbes that produce toxins
Role: Are primary ways microorganisms cause disease
Types of Toxins:
- Endotoxins: Found within the bacterial cell wall and released when the bacteria die, less potent and specific.
- Exotoxins: Secreted by bacteria into their environment, more potent and specific

Nosocomial Infections

Infections patients get while receiving treatment in a hospital or similar setting, unrelated to their original illness
In Canadian hospitals (2016-2020):
- MRSA bloodstream infections increased by 33%
- VRE bloodstream infections increased by 72%
In the U.S., healthcare-associated infections (HAIs) are one of the top 10 causes of death

Types & Transmission of HAIs

Exogenous Infections: Caused by pathogens from the hospital environment
Endogenous Infections: Caused by microbes already living in the patient’s body
Transmission of HAIs:
- Direct Contact: from staff, visitors, or other patients through physical contact
- Indirect Contact: through fomites in contaminated objects
- Airborne Transmission: germs spread through the air or ventilation systems

Antimicrobial Resistance in Healthcare Settings

Drug-resistant pathogens are becoming harder to treat
Over 70% of bacteria causing hospital infections are resistant to at least one common antibiotic
- This makes infections more dangerous and limits treatment options, highlighting the need for careful antibiotic use and infection control

Control and Prevention

Safety Programs and Training: Each facility follows policies to prevent the spread of germs
Hygiene: Emphasis on proper handwashing and cleanliness
Infection Control Committee: All accredited hospitals have a team dedicated to managing infection control

Epidemiology and Public Health

Epidemiology: The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems
Importance: Epidemiology is crucial for public health departments to monitor and control diseases
Key Agencies:
- Public Health Agency of Canada: Responsible for public health information and initiatives in Canada
- Centers for Disease Control and Prevention (CDC): The primary source of epidemiological data in the U.S.
- Morbidity and Mortality Weekly Report (MMWR): Provides data on disease incidence, morbidity, and mortality rates for various notifiable diseases

Diseases in the Population

Prevalence: Total number of existing cases in the entire population
Incidence: Number of new cases over a specific time period, compared to the healthy population
Monitoring: Changes in prevalence and incidence are tracked both seasonally and over longer periods

Disease Categories

Endemic: Constantly present in a specific population or area
Sporadic: Occurs occasionally and irregularly
Epidemic: Surges beyond usual levels in a specific area or population
Pandemic: A global epidemic affecting multiple countries

Vaccinations

Most Effective Prevention: Vaccines are the best way to stop infectious diseases
Available Vaccines: Health Canada lists 26 vaccine-preventable diseases
Global Efforts: The CDC's Global Immunization Division focuses on worldwide vaccination efforts
Impact: Vaccinations prevent epidemics, pandemics, and have eradicated diseases like smallpox and polio

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