S1 Intro to Infection and Microbes Flashcards
What is an infection?
Invasion of a host’s tissues by microorganisms that can cause disease
What ways do people get infections?
- Source
- Intermediary (from the source)
- From themselves
- Animals
- Environment (from the source)
How can infections be transmitted?
- Contact (direct, indirect, vectors)
- Inhalation (droplets and aerosols)
- Ingestion
- Vertical transmission (mother to child)
How do microorganisms cause disease? (5 steps)
- Exposure
- Adherence
- Invasion
- Multiplication
- Dissemination
What determines whether an infection causes a disease?
- Pathogen - virulence factors, inoculum size and antimicrobial resistance
- Patient - site of infection and comorbidities
How do you determine if a patient has an infection?
- take a history - symptoms?
- examination - organ dysfunctions?
- investigations - specific and supportive
What are virulence factors?
‘Survival factors’ - improve the chances of reproduction
What are supportive investigations?
- full blood count - raised neutrophils, lymphocytes, etc?
- C-reactive protein
- blood chemistry - liver and protein function tests
- imaging
- histopathology
What are some examples of investigating bacteriology?
- take a specimen - swabs, fluids, tissues
- M, C & S - microscopy, culture, antibiotic susceptibility
- antigen detection
- nucleic acid detection
What are some examples of investigating virology?
- antigen detection
- antibody detection - patients response
- detecting viral nucleic acid
What are the four types of microorganisms causing disease?
- viruses
- bacteria
- fungi
- parasites
What are prions?
Protein particles (no nucleic acid)
Describe the general structure of a virus?
- Nucleic acid inside - either DNA or RNA
- Protein coat
- Envelope
- Spikes (for attaching to specific cell surfaces)
What is the Baltimore classification of viruses?
Viruses are classed dependent on type of genome e.g. DNA or RNA, single-stranded or double-stranded and the method of replication
What are the 3 classes of DNA viruses? Give an example of each
- Single stranded, non-enveloped - Parvovirus 19
- Double-stranded, non-enveloped - Adenovirus
- Double-stranded, enveloped - Hepatitis B
What are bacteriophages?
Viruses that infect bacteria
Could we use them as treatment?
What is the general structure of a bacteria?
- Nucleoid (circular DNA)
- Plasmids
- Ribosomes
- Cytoplasm
- Plasma membrane
- Cell wall
- Capsule
- Bacterial Flagellum
- Pili
What are the bacterial shapes?
- Coccus (Cocci)
- Spirillus
- Bacillus/Rods (Bacilli)
How can cocci be arranged?
Clusters e.g. staphylococci
or
Chains e.g. streptococci
What are the differences in oxygen tolerance in bacteria?
- aerobes
- obligate aerobes
- anaerobes
- obligate anaerobes
What is an obligate aerobe and anaerobe?
Aerobe - require oxygen
Anaerobe - require an oxygen free environment
How do you name bacteria, fungi, parasites? (Taxonomy)
Genus + species
What are the two types of fungi? Give examples
- Yeast (single-celled) - Candida albicans
2. Molds (multicellular) - dermatophytes (ringworm and athletes foot)
What are the two types of parasites? Give examples
- Protozoa (single-celled) - Giardia lamblia and plasmodium falciparum
- Helminths (worms, multicellular) - roundworms and tapeworms
What are the two major categories of bacteria?
- gram negative
* gram positive
What is the gram negative and positive bacteria classification based off of?
Based off the cell wall composition and reaction to the gram stain test
What are the differences between gram negative and positive bacteria?
Positive - cell walls mostly composed of peptidoglycan/murein - stain purple after gram staining
Negative - cell walls have a thin layer of peptidoglycan and an outer membrane with a lipopolysaccharide component - stain red/pink after gram staining
Name one gram positive cocci and one bacilli.
Cocci - staph aureus
Bacilli - bacillus cereus
Name one gram negative cocci and one bacilli.
Cocci - neisseria gonorrhoeae
Bacilli - salmonella typhi
