2 Bacterial Diseases Flashcards
*Q: What are the sources of bacterial infection? (3)
A: Extrinsic - from outside you
Intrinsic - from inside you
Mythical - mythical explanations e.g. catching a cold from being outside in the cold
*Q: Name intrinsic sources. (6) What are they all?
A: non sterile sites
- nasal cavity and sinuses / upper respiratory tract
- mouth
- stomach
- small intestine / biliary tract / large intestine
- skin
- lower genital tract (vagina)
Q: What are ‘normal microbiota’?
A: those found normally in the body
*Q: What are the 2 types of infection routes/portals of entry?
A: expected (normal/harmless microbiota entering via an expected route eg newborn is exposed to maternal microbiota)
un-expected (normal microbiota entering unsual site OR pathogenic microbiota entering any site)
Q: How are pathogens that target the upper respiratory tract usually acquired? how?
A: extrinsically from other people as respiratory tract droplets or airborne (hand can act as intermediate)
Q: What is the HSV and what does it cause?
A: herpses simplex virus- causes cold sores (stays in nerve endins)
Q: What is the EBV and what does it cause?
A: Epstein–Barr virus- glandular fever
Q: What does Neisseria meningitidis cause? Vaccine?
A: miningococcal meningitis- but can be part of normal microbiota : can stay in pharynx
(we’ve all been vaccinated against it)
Q: What are the consequences of bacterial infection acquired via the upper respiratory tract? (4 subheadings- 3,3,3,1)
A: Upper Respiratory Tract Infection
- Pharyngitis (back of nose and mouth)
- Tonsilitis
- Sinusitis
Lower Respiratory Tract Infection
- Bronchitis
- Pneumonia
- Empyema (plural space)
Spread to Adjacent Tissues
- Brain abscess (those with untreated sinusitis)
- Meningitis
- middle ear infection (spread from sinuses)
Spread to Blood Stream
-pneumococcal, meningococcal bacteraemia
Q: What are upper respiratory tract infections usually?
A: self limiting- eventually immune response copes with it- either innate or adapted
Q: What are sinuses?
A: air spaces in skull
Q: How are pathogens that target the urogenital tract acquired? What’s the most common source? Gender difference?
A: -extrinsic or intrinsic
- lower bowel
- females are more prone to getting these infections as smaller distance to reach uro. tract (particularly urethra, then bladder)
Q: What are the consequences of bacterial infection acquired via the urogenital tract? (4 subheadings- 2,2,1,1)
A: urinary tract infection
- cystitis (bladder)
- pyelonephritis (kidney-travelled from bladder)
genital tract infection
- Gonococcal urethritis
- pelvic inflammatory disease
pregnancy related infection (bad for baby)
-neonatal group B strep infection
spread to blood stream
-E coli bacteraemia
Q: How do pathogens enter via ‘broken skin’? (6)
A: -Surgery/any wound
- skin diseases including: Varicella - chicken pox, eczema, pressure sores, burns, athletes foot
- IVDA: Intravenous Drug Abuse
- insect bites
- Human bites (unexpected)
- cannulae (hospital)
Q: What are the consequences of infection via broken skin? (7) Main cause?
A: 1. superficial infection (eg spot)
- If the infection spreads across the skin layer it’s called CELLULITIS - you get red inflammation of the skin
- Abscess - pus filled pocket
- Myositis - infection spread deeper into the muscle and causes inflammation
- Gangrene/Necrotic Infection - any layer of skin or soft tissue can be subject to necrosis (=cell death underneath the superficial layer)
- Bacteraemia
- fasciitis- layer below skin (connective tissue between skin and muscle)
STAPH AUREUS
Q: What are the disease consequences of bacterial infection acquired via the GI tract? (6)
A: Diarrhoeal illnesses
- vomiting
- diarrhoea
- dysentry (blood diarrheoa- suggests invasive infection that caused gut wall to bleed)
Bacteremia/Systemic Infections
- Listeriosis (Lysteria monocytogenes)
- Salmonellosis and septic arthritis, aortitis
toxin mediated disease
-D and V (eg aureus enterotoxin)
Q: Why is Listeria problem?
A: Listeria isn’t a major cause of diarrhoea and vomiting but if it gets into the blood stream it can cause serious disease in neonates, the elderly and people who are immunocompromised
Q: What do toxins tend to cause in the GI tract?
A: vomiting type illnesses
Q: What is pathogenicity of bacteria? 3 groups? 3 examples?
A: ability of a bacterium to cause disease
- Commensals - don’t cause disease eg lactobacillus in vagina and GI tract
- True Pathogen - can cause disease in normal, healthy people eg staphylococcus aureus from skin causing large abscess and bacteraemia
- Opportunistic Pathogen - can only cause disease when they are given the chance (if it’s given a leg up) eg staphylococcus epidermidis from skin causing prosthetic hip joint infection
*Q: What affects pathogenicity? (5)
A: Infectivity - the ability to get into the host system and establish themselves
-> Complete immune evasion
Virulence - features that enhance disease causation - enhance the bugs ability to make you unwell
Toxins
Enzymes
*Q: What are the factors involved in infectivity? (4)
A: -Transmission to host
- Ability to colonise host
- Ability to find unique niche (place in body)
- Ability to replicate
*Q: What are the factors involved in virulence? (4)
A: -Toxin production
- Enzymes that degrade host molecules
- Complete immune evasion
- interruption of normal host processes
*Q: What is the infective dose? What affects it? (4)
A: number of bacteria/pathogen required to initiate an infection
- Route of Transmission - e.g. stomach acid means that higher infectious dose is usually required
- Tropism and Motility
- Replication Speed
- Immune Evasion
Q: Mycobacterium tuberculosis. Infective dose? Replication rate? What increases pathogenicity? (2)
A: low infective dose, low replication rate, can survive inside macrophages and resist killing
*Q: Describe features that enhance disease causation (virulence) in Streptococcus pneumoniae. (2)
A: Toxin Production - e.g. pneumolysin: cholesterol dependent pore forming toxin affecting lung architecture
Degradation of Host Molecules e.g. hyaluronan lyase-degrades host hyaluronic acid matrix for nutrition and spreads
*Q: Describe features that enhance disease causation (virulence) in S aureus. (2)
A: Interference with Host Cell Function - e.g. superantigens interfere with normal T cell function (cause immune system to make too many cytokines -> sends body into toxic shock)
Immune Evasion - e.g. S. aureus makes leukocydins which causes neutrophil death and abscess formation
*Q: What causes tonsilitis? Transmission?
A: Strep. pyogenes -mouth: droplet transmission
*Q: What causes Meningococcal sepcticaemia? Transmission?
A: Neisseria meningitidis colonises the nasopharynx asymptomatically before invading epithelial, then endothelial cells
-mouth: droplet transmission
Q: What causes pneumonia? Where?
A: Strep pneumoniae- respiratory tract
Q: What causes nasal sinuses and into brain? (2)
A: S. pneumoniae, Haemophilus influenzae
*Q: What’s the transmission of cholera? Vibrio cholerae. Infective dose? Movement? Produces? (2) role? result? symptom?
A: Faeco-oral
- HUGE INFECTIVE DOSE
- Use flagella to penetrate mucus
- Makes 2 component toxins A + B -> bind to GM gangliosides on gut -> triggers production of cAMP -> CHLORIDE EFFLUX (ion exchange between gut epithelial cells and gut luminal)-> Sodium ions and water flood out leading to rice water stools
*Q: Describe genital tract colonisation with group B strep (from GI tract). 3 results?
A: leads to invasive group B strep infection in neonates:
meningitis, septicaemia, death
Q: How does Staphylococcus aureus enter? What does it cause?
A: - through the skin
-Produces a family of leukocydins - toxins which destroy neutrophils producing characteristic pus
Q: Name 7 Gram negative pathogens.
A: -neiseria (miningitidis and gonorrhoeae)
- haemophilus influenzae
- escherichia coli (EPEC, EHEC, ETEC, UPEC)
- salmonella spp.
- vibrio cholerae
- shigella
Q: Name 10 Gram positive pathogens.
A: -staphylococcus aureus
- streptococcus
- > Group A= S. pypgenes
- > Group B= S. agalactiae
- > Viridans strep= dental bacteria
- > Pneumococcus = S. pneumoniae
- clostridium (difficile, tetani, botulinum, pergringens)
- listeria spp.
Q: Name 2 opportunistic gram negative bacterial pathogens.
A: pseudomonas aeruginosa
-eg. indwelling long term urinary catheters and multiple UTIs previously treated with antibiotic
acinetobacter baumanii
-eg. open battlefield trauma heavy prophylaxis with broad sprectrum antibiotics followed by ICU stay and nosocomial transmission
Q: Name 2 opportunistic gram positive bacterial pathogens.
A: staphylococcus epidermidis
-eg. prosthetic joint and valve infections, metal work, central line infections
enterococcus
-eg. abnormal heart valves
Q: List 7 sources of bacteria.
A: 1. Upper respiratory tract (intrinsic + extrinsic)
- Lower GI tract (intrinsic + extrinsic)
- Sexual/Urogenital tract (intrinsic + extrinsic)
- Skin (intrinsic + extrinsic)
- Nosocomial/Hospital Acquired (all of the above)
- Food and Water
- Animals
