Week 1 - Intro to infection and microbes Flashcards
What is an infection?
An invasion of the host’s tissues by microorganisms
What causes disease?
Microbial muliplication
Toxins
Host response
What is microbiota?
The sum total of all the microorganisms carried on the skin and mucosal surfaces
How can microbiota cause disease?
If the microorganisms are transported from one site to another, then they can cause harm as they are not supposed to be at the new site
How can disease spread?
- Physical contact (direct or indirect)
- Airborne (droplets or aerosols)
- Vector
- Ingestion
- Vertically: mother to child, either before or at birth
What do microorganisms need in order to cause disease?
- Exposure
- Adherence
- Invasion
- Multiplication
- Dissemination
What determines disease?
Pathogen: virulence factors, antimicrobial resistance, inoculum size (how much you’re exposed to)
Patient: site of exposure, co-morbidities
How do you identify that a patient has an infection?
History:
- Symptoms: focal or systemic, severity, duration
- Potential exposure
Examination: organ dysfunction
Investigations:
- Supportive: fbcs, U+Es, LFTs, C-reactive protein, imaging, histopathology
- Specific: bacteriology (specimen types [swabs, tissues, fluids], M,C&S [microscopy, culture and antibiotic susceptibility], antigen detection, NA detection, ), virology (antigen detection, viral NA detection, antibody detection)
What disease-causing microorganisms are there?
Bacteria
Viruses
Fungi
Parasites
How can you classify bacteria?
- Gram-positive vs gram-negative
- Shape (cocci, spirillus, bacillus)
- Oxygen tolerance (aerobe vs anaerobe = can survive in presence vs absence of oxygen)
- Eubacteria vs archaebacteria
What is a obligate aerobe?
A bacterium that requires oxygen for survival
How do you classify viruses?
Uses Baltimore classification (7 different classes)
- Type of NA
- Single- vs double-stranded NA
How do you subdivide fungi?
Yeast: single-celled
Mold: multicellular
How do you subdivide parasites?
Protazoa: single-celled
Helminths: worms, multicellular
What are bacteriophages?
A virus that infects and replicates within a bacterium
- The bacteria are producing the viral toxin
- They are able to transfer DNA between each other
