Guided Reading 5

When does infection occur

When a pathogen or micro-organism causes disease

4 steps or processes that must occur for infection to occur

1. Portal of Entry

2. Attachment to Host Cells

3. Colonization & Evasion of Host Defenses

4. Damage to Host

What is a microbe or microorganism?

It is a Bacteria, Viruses, Fungi, and Protozoa

What are pathogens?

A disease that is produced by a microbe

- Once the pathogen binds to a specific receptor in the human host it causes disease

What are the three elements of the mechanism of disease, once the pathogen attaches to the host cell?

1. Direct destruction of the host cell by the pathogen

2. Interference with the host cell's metabolic function

3. Exposing the host cell to toxins produced by the pathogen

Pathogenicity

Qualities that promote the production of disease

- Potency, Invasiveness, Speed of replication, production of toxins, adherence to host cells, and degree of tissue damage

Virulence

Potency of a disease in a population

- Indicated by a ratio of the number of cases to the number of people exposed to the microorganism in a population

Infectivity

Based on the exposure of the infection in an individual and how a pathogen has the ability to enter, survive, and multiply in hosts

Toxigenicity

Ability of a pathogen to produce harmful toxins that increase host cell and tissue damage

Antigenicity

When a pathogen is viewed as foreign by the host immune system

Antigenic Variability

When an antigen alters its surface so the human host cell defenses cannot recognize it and attack it effectively

What are pathogenic defense mechanisms?

Ways a pathogen can avoid being destructed by the host cell

Coinfections

Hosting two or more pathogens at the same time

Superinfections

An infection that occurs when one is already present

Bacteria

Stimulates the inflammatory response

- Cocci, Bacilli, Vibrio, and Spirochetes

- Most common are when it gets into the bloodstream, Urinary Tract infections, pneumonia, surgical wounds, central line infections, and osteomyelitis

- Manifestations: Fever, tachycardia, Tachypnea, Hypotension, decreased strength, and cool extremities

- Tests: Blood Cultures, Wound Cultures, Sputum Cultures, and Urine Cultures

Viruses

Binds to specific receptors on the host cell and then moves into the host cell

- Can only replicate inside of the host cell

- Converts host cellular metabolism to nucleic acids and proteins that are encoded and controlled by the virus

- Paramyxovirus, Coronovirus, Rhinovirus, and RSV

Fungi

They have a nuclear membrane, cytoplasm, and organelles

- Larger than bacteria

- Yeast or Mold and viruses

Protozoa

Irregular of fluctuating shape with a cell wall that are motile and unicellular complex microorganism

- Malaria, Giardiasis, Amebiasis, or Trichomoniasis

- Transmission: Sexual Contact, Contaminated Food or Water, and an insect or other arthropod

- Some are parasites and are capable of living independent of the host

- The parasites deprive host cells of nutrition, causing tissue destruction

Aerobic Bacteria

Require oxygen for growth

Anerobic Bacteria

Don't require oxygen for growth

- Survive best in deep tissues of the body where oxygen supply is limited

Endotoxins

Complex of phospholipid-polysaccharide molecules that form the structural component of the Gram-negative cell wall

- Presence of it in the Gram-negative bacterial cell wall activates the plasma protein systems

What type of bacteria release the most damaging endotoxins?

Gram-Negative Bacteria

What type of bacterial is most likely to cause sepsis and septic shock?

Pyogenic Bacteria

- Massive inflammatory response that can result in a state of septic shock accompanied by severe diarrhea, fever, and leukocytosis

pyogenic

Pathogens that induce fever

Exotoxins

Bacteria capable of producing toxin

- Bacterial-derived proteins, released into the surrounding tissues that cause local or systemic injury to the host

Manifestations of septic shock?

Process of systemic vasodilation due to severe infection, often with Gram-negative bacteria

What does 'pan' culture mean?

Taking samples from everywhere that could show where an infection is coming from

- Blood, Urine, Mucus, or Wound Drainage

Why is it so very important to 'pan' culture?

Helps identify where exactly the infection is coming from and what's causing it

What is the normal range of white blood cell count?

4,000 to 10,000 cells per microliter

- Assess for leukocytosis and leukopenia

Why is important to obtain blood cultures?

Helps find if there are any bacteria or fungi in the bloodstream

- Helps detect sepsis and what kind of infection

What are manifestations of inflammation?

- Redness (Rubor)

- Heat (Calor)

- Swelling (Tumor)

- Pain (Dolor)

- Loss of function (Disability)

what is the 'distinct difference between' the manifestations of inflammation and infection?

- Inflammation is the body's response to injury or irritation

- Infection is when microorganisms (like bacteria, viruses, or fungi) actually invade and multiply in the body

How do viruses 'enter' into cells?

Viruses can't reproduce on their own, so they have to get inside a living cell to survive and make more copies

- Attaching to cells, penetrating them, and then uncoating to release genetic information

Identify the viral receptors for Influenza, HIV, and Covid 19

- Influenza: Hemagglutinin and Sialic acid receptors

- HIV: gp120 and CD4 receptor (co-receptors CCR5 or CXCR4)

- Covid 19: Spike (S) protein and ACE2 receptor

Which viruses are transmitted via respiratory droplet

- Adenovirus

- Coronavirus (SARS)

- Coronavirus — novel coronavirus (COVID-19, SARS-CoV-2)

- Human parvovirus B19

- Paramyxovirus (measles)

- Respiratory syncytial virus (RSV)

- Rhinovirus

Which viruses are transmitted via rectal-oral route

- Adenovirus

- Coxsackievirus (from stool or secretions)

- Rotavirus

Adenovirus Manifestations

Respiratory form: runny nose, sore throat, fever, feeling tired

Intestinal form: diarrhea and vomiting

Coronavirus (SARS) Manifestations

High fever, headache, body aches

Cough, pneumonia, and sometimes diarrhea

Novel Coronavirus (COVID-19) Manifestations

- Fever, chills, headache, cough, sore throat, congestion

- Fatigue, muscle aches, shortness of breath

- Loss of taste or smell

- Nausea, vomiting, or diarrhea

Coxsackievirus Manifestations

- Fever

- Sores in the mouth

- Rash or blisters on the hands and feet

Human Parvovirus B19 Manifestations

- Mild rash with bright red cheeks ("slapped-cheek" look)

- Fever, general tiredness or malaise

Paramyxovirus Manifestations

- Fever, runny nose, cough

- Rash that spreads over the body

Respiratory Syncytial Virus (RSV) Manifestations

- Fever, runny nose, cough, wheezing

- Trouble breathing (in infants)

Rhinovirus Manifestations

- Fever, runny or stuffy nose, sore throat

- Body aches, feeling tired or unwell

Rotavirus Manifestations

- Severe, watery diarrhea

- Vomiting

- Can lead to dehydration (especially in children)

Acute localized presences of infection during initial exposure: incubation phase, prodromal phase, clinical illness phase and convalescence phase

- Incubation Phase: Time between exposure to the infectious agent and the first signs of symptoms

- Prodromal phase: Early, mild symptoms start to appear as the infection begins to take hold

- Clinical illness phase: The infection becomes localized and intense (When acute is present and actively fighting)

- Convalescence phase: Recovery period after the infection is under control

Acute systemic presences of infection during initial exposure: incubation phase, prodromal phase, clinical illness phase and convalescence phase

- Incubation phase: The pathogen has entered the body and is multiplying quietly

- Prodromal phase: The infection begins to trigger the immune system

- Clinical illness phase: The infection has spread widely, and the immune response is in full force (Acute systemic is present)

- Convalescence phase: The immune system starts to clear the pathogen and repair damage

Common laboratory

Place where medical tests are done on blood, urine, stool, or other body fluids to help diagnose, monitor, or prevent diseases

Diagnostic tests

- Performed based on cellular screening tests

- Evaluation of tissue is completed to obtain an accurate diagnosis and to form the basis of treatment

- Ex: Colposcopy

CBC

Complete Blood cell count

- Hemoglobin, Reticulocytes, White Blood Cells, Granulocytes, and Bands

Serum

Clear, yellowish fluid part of blood that's left after it clots and the blood cells are removed

Antibodies

Immunoglobulins that react with an antigen in a specific way

Culture

Test used to find and identify microorganisms (like bacteria, fungi, or viruses) that cause an infection

Sensitivities

Lab test done after a culture to find out which antibiotics can kill or stop the growth of the bacteria causing the infection

Influenza

- Etiology: Influenza viruses — types A, B, and C

- Pathophysiology: Virus invades airway epithelial cells → destroys cilia and mucus defense → inflammation and necrosis → possible pneumonia

- Manifestations: Sudden fever, chills, sore throat, cough, congestion, body aches, weakness, malaise

- Diagnostic tests: History, physical exam, rapid influenza test (A/B), PCR testing if needed

Viral Hepatitis

Etiology: Caused by hepatitis viruses A, B, C, D, E

Pathophysiology: Virus infects hepatocytes → cell necrosis + inflammation; Kupffer cells remove necrotic cells; hepatocytes regenerate

Manifestations: fatigue, anorexia, malaise, headache, jaundice, dark urine, clay-colored stools, or low-grade fever

Diagnostic Tests: Serology, Liver function tests, Kidney Function tests, and HBsAg

Tuberculosis

etiology

pathophysiology

manifestations

diagnostic tests

urinary tract infections

etiology

pathophysiology

manifestations

diagnostic tests

meningitis

etiology

pathophysiology

manifestations

diagnostic tests

malaria

etiology

pathophysiology

manifestations

diagnostic tests