Infection S1 (Done) Flashcards
This flashcard series incorporates info from lectures, workbook, group work and self study.
For my first ever flashcard of ESA 3
What is an infection and how is it caused?
Invasion of a host’s tissues by micro-organisms
AND
Subsequent disease caused by:
- Microbial multiplication
- Toxins
- Host response
What is meant by ‘commensal’
How are they relevant to humans and infection?
Commensalism is a relation between two organism where one derives benifit and the other is unharmed
Microbiota living on the skin and mucosal surfaces engage in a commensal relationship with humans
Normally harmless or even beneficial however transfer to other sites can be harmful (cause infection)
List the ways in which we might get an infection from our environment.
For each give an example of an infection we might acquire via this route.
Food
- Gastroenteritis
Air
- Influenza
Water
- Cholera
Animals
- Malaria
Surfaces
- Tetanus
Human Contact
- Syphilis
What is meant by the terms ‘vertical transmission’ and ‘horizontal transmission’?
Give an example of infection that could be transmitted vertically
Horizontal Transmission
- Transmission between organisms
Vertical Transmission
- Transmission of infection from mother to child at or before birth
- E.g. HIV
What is an ‘vector’ in regards to infection?
Give an example
An organism that can transfer pathogens and parasites from one organism to another, usually remaining uninfected itself
E.g. Mosquitoes are a vector for malaria
What are the modes of horizontal infection?
Hint: 3 basic categories
Contact:
- Direct
- Indirect
- Vectors
Inhalation
- Droplets (small clusters of liquid particles in air)
- Aerosols (colloid of fine solid/liquid particles in gas/air)
Ingestion
- E.g. Faecal-oral transmission
What are the 5 stages of an infection?
Exposure
Adherence
Invasion
Multiplication
Dissemination
What factors determine the course/severity of an infection?
Pathogen
- Virulence factors
- Inoculum size
- Antimicrobial resistance
Patient
- Site of infection
- Co-morbidities
- Immune response
Give some examples of virulence factors
How do they cause disease?
Virulence factors
- Exotoxins (Enzymes, AB toxins, Superantigens, Cytolytic)
- Endotoxins
These can cause damage either directly, or damage can be consequent to host immune response
What are the 3 basic steps to determining if a patient has an infection?
History
Examination
Investigations
You are taking a patient history and suspect infection, what things are particularly important to ask about?
Symptoms
- Focal/systemic
- Severity
- Duration
Potential exposures
- What have you been doing?
- Who with?
- Where?
- Were there animals?
Give some examples of supportive investigations you might carry out with a patient with suspected infection
Full blood count
- Neutrophils + Lymphocytes
C reactive protein
- Inflammation
Liver and kidney function tests
Imaging
- Xray
- Ultrasound
- MRI
Histopathology
How might you test a patient for bacterial infection and determine the specific species responsible?
Take a specimen
- E.g. Swab, fluid, tissue
M, C&S
- Microscopy (Bacterial and host cells)
- Culture bacteria
- Test antibiotic Susceptibility
**Antigen detection **
- ELISA
Nucleic acid detection
- PCR
- Sequencing/Hybridisation
What methods are available to test specifically for viral infection?
Antigen/antibody Detection
- ELISA
Viral nucleic acid detection
- PCR
- Sequencing/Hybridisation
Who might be involves in treatment of patients with infections?
All Clinicians
Specialties with specific interest
- Infectious disease
- Medical microbiology and virology
- Genitourinary
- Health protection
What is pictured here?
Label the lines
A Virus
Top Left Clockwise
- Envelope
- Spikes (for attaching to specific cell surfaces)
- Nucleic acid (DNA or RNA)
- Protein Coat
What are some common symptoms of infection?
What micro-organisms are typically associated with the two major categories of symptom?
Systemic (generally viral):
Fever
Fatigue
Weight loss/loss of appetite
Aches, pains, burning, itching (Can be localised)
Localised (generally bacterial):
Redness
Heat
Swelling
Pain
How are viruses classified by nucleic acid?
Baltimore classification (I to VII)
Classifies virus by nucleic acid type:
I - dsDNA
II - ssDNA
III - dsRNA
IV - (+)ssRNA
V - (-)ssRNA
VI - ssRNA-RT
VII - dsDNA-RT
How are class VI and VII of viruses different to classes the other classes of viruses?
VI:
Retroviruses (ssRNA-RT) that replicate with reverse transcriptase (creating a DNA intermediate) as opposed to host machinery
VII:
Similar to retroviruses, dsDNA-RT viruses replicate through the use of reverse transcriptase (creating an RNA intermediate) as opposed to host machinery
Give examples of Non-enveloped DNA viruses
Single stranded:
Parovirus 19
Double stranded:
Adenovirus
BK virus
HPV
JC virus
Give examples of Enveloped DNA viruses
Double stranded:
Herpes
Hep B
Molluscum
Contagiosum
How might we classify viruses by capsid shape?
Icosahedral or helical
Apart from nucleic acid type and capsid shape, how else might we classify viruses?
Enveloped or Non-enveloped
Give examples of ss(+), icosahedral, non-enveloped viruses
Coxsachievirus
Echovirus
Enterovirus
Hep A, E
Norovirus
Give examples of ss(+), Enveloped viruses
HIV
Hep C
Rubella
Encephalitis viruses
Yellow fever virus
West nile virus
Give examples of ss(-), Helical, Enveloped viruses
Ebola, Lassa, Marburg
Measles, Mumps
Influenza, parainfluenza viruses
Respiratory syncytial virus (RSV)
Give an example of a ds, Icosahedral, Non-enveloped virus
Rotavirus
What are bacteriophages?
Viruses that infect bacteria and replicate within the bacteria
May be DNA or RNA based
What is shown in this diagram?
Label the black boxes
Bacteriophage
From top anticlockwise:
Head
Collar
Tail
Long tail fibres
Base plate
What are the 3 bacterial shapes?
Coccus
Spirillus
Bacillus (plural bacilli)
What are the common arrangements of bacterial cocci?
Clusters
Chains
(honorable mention to diplococci, which could be both, depending on how you look at things)
What is the structural difference between gram negative and gram positive bacteria?
Why do they stain differently and what colours are they?
Gram positive:
Plasma membrane is surrounded by thick peptidoglycan cell wall
Stains purple
Thick peptidoglycan cell wall retains crystal violet
Gram negative:
Plasma membrane is surrounded by thin peptidoglycan cell wall and then a lipopolysaccharide outer membrane
Stains red
Thin peptidoglycan cell wall doesn’t retain crystal violet and instad retains red counter stain
How does oxygen tolerance of bacteria differ?
Aerobes:
Can survive in the presence of oxygen
Obligate anaerobes require oxygen
Anaerobes:
Can survive in absence of oxygen
Obligate anaerobes require an oxygen free environment to survive (unless able to form spores)
What are bacterial spores?
What is their relevance to disease?
Resistant form of bacteria that can survive extreme conditions (high temperature, dessication, lack of nutrients)
Generally, spores cannot cause disease directly, must first germinate in favourable conditions (however some can secrete toxins)
Give examples of gram positive bacteria classified by bacterial shape
Cocci:
Staph aureus
Coagulase neg staph
Alpha and beta haemolytic streptococci (strep pyogenes = beta)
Streptococcus pneumoniae
Enterococcus faecalis
Bacilli:
Listeria monocytogenes
Bacillus anthracis
Bacillus cereus
Give examples of gram negative bacteria classified by shape
Cocci:
Nesseria meningitidis/gonorrhoeae
Moraxella catarrhalis
Acinetobacter baumannii
Bacillus:
E. coli
Klebsiella pneumoniae
Proteus spp
Salmonella typhi
Pseudomonas aeruginosa
Haemophilis influenzae
What are the mechanisms of bacterial pathogenesis?
Give an example of a cell feature involved in each mechanism
Virulence factors:
Host entry (Polysaccharide capsule)
Adherence (Pili)
Invasiveness (Enzymes such as collagenases)
Iron sequestration (siderophores)
Toxins:
Endotoxins (lipopolysaccharide toxins)
Exotoxins (E.g. Diptheria toxin)
What are the broad categories of fungus?
Give examples of each category
Yeasts (Single-celled):
Candida albicans
Cryptococcus neoformans
Pneumoystis jiroveci
Molds (multicellular):
Aspergillus spp
Dermatophytes (ringworm, athlete’s foot)
What are the broad categories of parasites?
Give examples for each category
Protozoa (single celled):
Giaria lamblia
Cryptosporidium parvum
Plasmodium falciparum
Trypsnodoma cruzi
Heminths (Worms, Multicellular)
Roundworms
Tapeworms
Flukes
