Ch. 10 Mechanisms of Infectious Disease

Colonization

the presence of an infectious agent

virulence

disease-producing potential

pathogen

microorganisms capable of causing disease

What is an infection? How can it be prevented?

an infection is a harmful process caused by microorganisms like bacteria, viruses, fungi, or parasites entering and multiplying in the body. This invasion triggers an immune response, which can lead to symptoms like fever, fatigue, and pain, but can also result in symptoms like redness, swelling, or pus at a wound site. Infections spread through various modes, including direct contact, airborne particles, contaminated surfaces, contaminated food or water, or vectors like mosquitoes, and can be prevented by practices such as handwashing and proper hygiene.

What are the common pathogens?

Viruses, bacteria, fungi, protozoa, worms

What are some risk factors for infection?

When an imbalance develops, the potential for infection increases. Risk factors not only include an imbalance in the body's defense mechanisms but also include environmental and developmental factors (age), along with characteristics of the invading pathogen.

A healthy person can usually fight off infection with the body's defense mechanisms. What are the body's defense mechanisms?

intact skin, normal flora, lysozymes, cilia, and immune response

Prions

protein particles that lack any kind of demonstrable genome (RNA or DNA), that are able to transmit infection. They lack reproductive and metabolic functions

What are transmissible neurodegenerative diseases?

PRIONS:

-Creutzfeldt-Jakob

-BSE - Mad Cow

BSE- Mad Cow

Progressive, non-inflammatory neurodegeneration (loss of coordination - ataxia; dementia; death in months to years - no cure as prions are stable and therefore resistant to most antibiotics).

Viruses

smallest known organisms. Made of a RNA (retroviruses) or DNA nucleus surrounded by protein (need a host to replicate). The majority cannot live for long amounts of times (like viruses on a desk).

What are common viral infections?

-Chickenpox (varicella), mumps, rubella, smallpox

-Cytomegalovirus (CMV)

-Flu

-Herpes (simplex and zoster)

-HIV

-Common cold

-Ebola

Oncogenic Viruses

certain viruses have the ability to transform normal host cells into malignant cells during the replication cycle.

-Retroviruses (HIV)

-DNA viruses (herpesviruses; adenoviruses (more so in animals than humans); papoviruses)

Bacteria

Simple one celled organisms. There are lots of different ways to classify them.

How are bacteria classified?

They are classified by shape (bacilli, cocci, spirilla), oxygen requirements (aerobic - requires oxygen, anaerobic - no oxygen required (causes people to be more sick because there is not good blood supply)), and stain uptake (positive or negative). Knowing the classification of the bacteria is good because it can tell you how sick the patient is or is about to get. It also tells you how easy, or not, the bacteria is to treat.

What are common bacterial infections?

Strep throat, Conjunctivitis, Meningitis, Otitis media, Some Pneumonias, TSS, Some UTIs, Whooping Cough.

Where are bacteria commonly found?

on keyboards, water fountains, toilets...

Spirochetes

Gram negative, anaerobic rods

-in humans - spread by direct contact, bites, contact with infected animals' excretions (syphilis, leptospirosis, Lyme disease)

Mycoplasmas

Bacteria-like organisms that have no cell-wall and can be many shapes, also called the "soft cell". They independently replicate. "walking" pneumonia. Transmission is airborne. Makes you feel bad, but you won't be very sick. (ex: like transformers or shape-shifters).

How do people spread M. pneumoniae?

People spread M. pneumoniae by coughing and sneezing, which creates small respiratory droplets that contain the bacteria. Other people can get infected if they breathe in those droplets.

Rickettsia

Gram-negative organisms that can cause life-threatening illness. They are irregularly shaped and need a host to survive. They have no cell wall and are "leaky". They are transmitted by the bite of arthropod and through exposure to their waste. (Rocky Mountain Spotted Fever).

Chlamydia

Transmitted by direct contact. Commonly infect the urethra, bladder, fallopian tubes and prostate. Chlamydia is the most frequently reported bacterial sexually transmitted infection in the US (middle school students are rapidly increasing in this). Can cause sterility.

How does Chlamydia affect the body?

What are common fungal infections?

Fungal infections usually infect body surfaces and openings. They can cause life-threatening opportunistic diseases. Generally, fungal infections are topical. Can have a yeast-caused urinary infection. Large weather events that disrupts the environment (large-scale disruption - like a tornado) can cause fungal infections to become airborne.

-Candida UTI

-Ringworm

-Athletes foot

-Yeast infections

-Sinusitis

-Pneumonia

Protozoa

can cause a variety of diseases in humans. They are transmitted by: Fecal-oral route (toxoplasmosis, giardia - drinking unfiltered water), insect vectors (mosquitoes, sand flies; ex: Malaria), Sexual transmission (trichomoniasis).

Helminths/worms

Helminthic infections are caused by parasitic worms that enter the body through ingesting contaminated food or water, skin contact with infected soil, or by eating raw or undercooked infected meats.

Source of infection

community acquired or nosocomial/Hospital acquired

What is community acquired infection?

development of an infection less than or equal to 48 hours after admission to a hospital/undergoing dialysis/wound care/outpatient surgery (Mycoplasma pneuomonia)

What is Nosocomial/Hospital acquired?

development of an infection greater than 48 hours after admission to a hospital (Pseudomonas)

What are the stages of infection?

-Incubation: Ranges from instantaneous to years (days to years)

-Prodromal stage: the contagious host has vague complaints (start feeling first symptoms)

-Acute Illness: sudden onset and a short duration, typically lasting from days to weeks, and often requiring prompt medical attention. Common examples include the flu. (when you feel most sick and usually when diagnosed with disease).

-Convalescence: Body's defense mechanisms have invading pathogen under control, healing of damaged tissue begins.

What are the sites of infection?

itis, emia, confined pathogen, systemic pathogen, abscess

itis

indicates inflammation can be associated with infection

emia

the presence of an infection in the blood

confined pathogen

not a systemic infection - appendicitis

systemic pathogen

cause infection throughout the body - sepsis (fever, anorexia, malaise).

abscess

localized pocket of infection

What is the diagnosis of infection?

History and physical, WBC count with differential, erythrocyte sedimentation rate (ESR), culture, additional tests (x-rays, CT scans, etc.).

standard precautions

Standard Precautions are the minimum infection prevention practices that apply to all patient care, regardless of suspected or confirmed infection status of the patient, in any setting where healthcare is delivered. These practices are designed to both protect HCP and prevent HCP from spreading infections among patients.

Standard Precautions include: 1) hand hygiene, 2) use of personal protective equipment (e.g., gloves, gowns, masks), 3) safe injection practices, 4) safe handling of potentially contaminated equipment or surfaces in the patient environment, and 5) respiratory hygiene/cough etiquette.

bioterorism

Category A agents, Category B Agents, Category C Agents

Bioterorism - Category A Agents

transmitted through direct or indirect contact, including airborne (aerosol) and droplet transmission from an infected person, fecal-oral transmission from contaminated food or water, and direct contact with infectious materials, bodily fluids, or contaminated surfaces

-Anthrax (inhaled if it is white powder or spore entering through cut in skin), Yersinia Pestis/bubonic plague, Tularemia, Smallpox, Ebola, Botulinum

Bioterorism - Category B Agents

Water and foorborne transmission

-Salmonella (uncooked food), Shigella (uncooked food), Cholera (unclean water), E-coli (spoiled, uncooked, unclean food/water).

Bioterorism - Category C Agents

transmission can be airborne, direct contact with infected animals, bites, fecal-oral

-Tuberculosis, hantavirus, Yellow fever, Cryptosporidium