Infections Flashcards
What are Koch’s Postulates?
1) Microorganism must be found in abundance in all organisms with the disease and not in healthy organisms
2) Microorganism must be isolated from a diseased organism and grown in pure culture
3) Cultured microorganism should cause disease when introduced to healthy organism
4) Microorganism must be re-isolated from diseased host and be identical to original causative microorganism
How can opportunistic pathogens take hold in a damaged host?
- Immunosupressed
- Tissue damage
- Catheter infections
- Genetic defects
- Change in host bacteria e.g. antibiotics
In a biofilm, what is it called when one bacteria is under stress and sends signals to other bacteria to produce a protein film for protection?
Quorom Sensing
Give examples of toxin production that is a) plasmid encoded and b) phage encoded
a) TSST, tetanus neurotoxin
b) Cholera toxin, diptheria toxin
What 3 proteins are critical for replication of a virus?
Reverse transcriptase, integrase, protease
What virus is more likely to have latency, RNA viruses or DNA viruses? Why?
DNA viruses as this in nucleus of cell whereas RNA in cytoplasm and has to keep replicating
How do yeasts replicate and how do moulds replicate?
Yeast = mitosis, moulds = meiosis
What commensal bacteria has colonised the skin as part of host defence to infections?
Coagulase negative staphylococci
What is hairy oral leukoplakia
a) Caused by?
b) Look like?
c) An indication of?
a) Ebstein Barr Virus (EBV)
b) White striations on lateral surface of tongue
c) HIV
What virus looks like a fried egg under the microscope?
Herpes simplex virus - yolk= spherical capsid, outside= lipid envelope
What is the structure of the measles virus?
Helical RNA coated in capsid. Lipid envelope
What is the structure of influenza virus?
REMEMBER - Spiky!!
Antigens and proetins stick out of cell wall (haemogluttanin and neuroamnidase). Lipid envelope. Capsid coating RNA.
What is the structure of adenovirus?
Capsid is icosahedral. No lipid envelope. Surface proteins
Give 3 examples of double stranded DNA viruses
- Herpes viruses
- Hep B
- Adenovirus
Give 5 examples of single stranded RNA viruses
- Measles
- Mumps
- Influenza
- Rhinovirus
- Hep C
What is different about retrovirus replication e.g. HIV?
Have reverse transcriptase stage: RNA to DNA which is integrated into host DNA to then make mRNA
Give 1 example of a single stranded DNA virus
Parvovirus
Give 1 example of a double stranded RNA virus
Rotovirus
In serology testing what antibodies do they look for?
IgM for acute infection, IgG for past exposure
For Herpes Simplex 1 & 2:
a) Where do they attach and release the capsid?
b) When the new virus is made in the DNA and released, where do they travel?
a) Epithelial cells
b) Sensory neurons to the spinal ganglia - become dormant
What can primary oral herpes present as if not asymptomatic?
Gingivostomatitis
Which type of herpes simplex has oral reactivation presenting as cold sores?
HSV1
Which type of herpes simplex has genital disease reactivation?
HSV2 (primary infection with both HSV1 & 2)
What is Herpetic Whitlow?
Herpes Simplex entering skin around fingernails - children who suck thumbs or healthcare workers with no PPE
How can neonatal herpes simplex infection occur (life-threatening)?
Mother secreting herpes simplex in vaginal secretions, or kissing baby and shedding virus
What complication of herpes simplex can cause lifethreatening brain damage?
Herpes simplex encephalitis (usually HSV1)
What are the treatments (drugs) for Herpes Simplex 1 and 2?
Aciclovir (activated by thymidine kinase from virus), Valaciclovie (better oral bioavailability)
Where does the Varicella Zoster Virus
a) Infect?
b) Replicate to cause primary viraemia?
c) Replicate to cause secondary viraemia?
d) Lie dormant/ latency?
a) Respiratory mucosa and conjunctiva
b) Lymph nodes
c) Spleen and liver
d) Dorsal route ganglion
What does primary and secondary infection of VZV respectively cause?
Primary = chickenpox Secondary = shingles
What nerve does opthalmic zoster affect?
Trigeminal nerve
What family of viruses does Cytomegalovirus (CMV) belong and how is it shed?
Herpes family
Shed via respiratory and genital secretions
What symptoms does EBV cause in young children and adolescents?
Young = sore throat, Adolescents = glandular fever/infectious mononucleosis
What family of viruses does EBV belong? Where is it latent?
Herpes
Latent in B lymphocytes
What is Human Herpes Virus 8 also called? Clinical features?
Karposi’s sarcoma associated virus - HIV or skin malignancies. Clinical feature = dark blotches
For the lab, what colour bottle top should
a) viral swabs
b) clotted blood for serology
have?
a) green top
b) yellow top
What is a normal CD4 count? Where are they most commonly found?
800-1500 and in lymph nodes, GI tract
What oral presentations can be seen in Clinical Stage II HIV?
Angular chelitis
Oral ulcerations
Herpes Zoster
What oral presentations can be see in Clinical Stage III HIV?
Oral candidiasis (thrush) Oral hairy leukoplakia
What oral presentations can be seen in Clinical Stage IV HIV?
Karposi’s sarcoma on hard palate
What is the treatment for HIV?
2 x Nucleotide reverse transcriptase inhibitors (NRTIs)
1 x NNRTI/ protease inhibitor / integrase inhibitor
HAART target = enzyme inhibition and cell entry
What signs of hepatitis can be seen on examination?
- Jaundice
- Spider nevii
- Sialosis (enlargement of salivary glands)
- Scratch marks (deposition of bile salts under skin)
- Bruising (effects clotting factors)
- Dupuytrens contracture
- Liver flap/asterixis (brain irritated by ammonia compounds and hand flaps)
- Gynaecomastia (breast tissue in males, oestrogen not metabolised)
- Palmer erythema
What are the common viral causes and drug causes of hepatitis? What is a very rare cause?
Hep A, B, C and EBV and paracetamol (25g is fatal)
Wilsons Disease
How does acute liver damage occur?
Infection of the hepatocytes with direct killing of hepatocytes by effector lymphocytes.
Self limiting and damage is from the immune response not viral particles
How does chronic liver damage occur?
Long-term infection and long-term low level immune response.
Fibrotic response to repair damaged tissue forms scars, liver tries to regenerate scarred tissue leading to cirrhosis.
6 month +
What is Hepatitis A?
Form of foodpoisoning, never chronic or in carrier state as become unwell then immune system overcomes infection
When can Hepatitis A be fatal?
In pregnancy - severe immune response. In chronic liver disease pts - always vaccinated now.
What is Hepatitis E?
Food poisoning (origin from pork). Acute, chronic only in immunosuppressed or liver disease.
How does a carrier state exist in Hepatitis B and what are the symptoms?
Vertical transmission (mother to baby) - no immune response so no damage to liver but have a high viral load
- High infectivity
- High risk of hepato-cellular carcinoma (cancer) as high viral integration
Why does Hep B cause primary liver cancer?
DNA virus so integrates into genome, especially risky if near oncogene
What is the incubation period for Hep B?
6 weeks acute symptoms start
What test results allow for diagnosis of Hepatitis B?
ALT high - released by damaged liver blood cells
Bilirubin high - liver cant clear it
Alkaline phosphatase high
Albumin low
Prothrombin time low - less clotting factors
What does HepBsAg show?
Surface antigen - marker of viral presence
What does HepBeAg show?
Virus core - marker of degree of viral load and replication, shows severity
What does HepBsAb show?
Surface antibody - Marker of immunity (vaccination or previous infection
What does HepBeAb show?
Marker of low risk in hepatitis pts - +ve = low level of viral infection
What does HepBcAb show?
Core antibody - useful if have mutant virus with no surface antigen
Chronic hepatitis patients with eAg+, eAb-, cAb- are…. risk?
High risk
Chronic hepatitis patients with eAg-, eAb+, cAb+ are… risk?
Low risk - have the infection but also have immunity
What drugs can be given to Hepatitis B patients to help control (but not clear) the virus?
Interferon, Lamivudine, Adefovir
What is Hepatitis C?
An RNA virus that causes chronic disease. Does not integrate into the genome but can still cause cancer from high degree on inflammation
What are the 3 risk groups for Hepatitis C?
- IV drug abusers
- Receivers of blood products (link to haemophilia)
- Factor X - ie the unknown
Remember: Not sexual contact
Why is there no vaccination for Hep C?
Mutates in situ
If a patient has severe jaundice/liver problems and is undergoing GA, what are they at risk of?
Hepato-renal syndrome (renal failure)
If you are giving LA to a patient with liver problems what would you give and why?
Lidocaine limited to 2 cartridges
Articaine and prilocaine may be better as metabolised in lungs
(LA undergoes amide biotransformation in liver)
Why is sedation best avoided in patients with cirrhosis?
Benzodiazepine not metabolised
What are contraindicated in patients with hepatitis/liver problems?
a) Antifungal agents
b) Antibiotics
c) Painkillers
a) Miconazole, fluconazole
b) Erythromycin, Tetracycline, Metronidazole
c) NSAIDs (risk of GI bleed), parecetamol
In the Lancefield grouping of streptococci, what colour are:
a) a-haemolytic
b) b-haemolytic
c) y-haemolytic
a) green
b) clear
c) none (red)
What are the 4 aetiological agents of pharyngitis?
- Viral causes
- Beta-haemolytic streptococci group A,C,G
- Corynebacteria diphtheriae and ulcerans
- Arcanobacterium haemolyticum
What tests can you do to identify Group A streptococcus e.g. S. pyogenes as the cause of pharyngitis?
- Culture on blood agar to see haemolysis
- 16s PCR
- Serology (late stage) i.e. antibodies present
What are the complications of pharyngitis?
- Peritonsillar abscess/quinsy
- Scarlet fever
- Systemic sepsis
- Rheumatic fever
- Acute glomerulonephritis (renal failure)
What does the diphtheria toxin
a) inhibit?
b) symptoms?
a) Protein synthesis
b) Initially pharyngitis, then psuedomembranes form risking airway obstruction, then toxin absorbed and causes myocarditis, paralytic symptoms and nephritis
What is the difference between arcanobacterium haemolyticum and beta-haem strep?
Arcanobacterium is a gram positive bacillus even though it makes blood agar clear
What is gonorrhoea as a bacteria?
Fastidious (hard to culture) gram-negative diplococci
What is syphilis caused by?
Treponema pallidum, a spirochete
What is mycobacterium tuberculosis?
Acid-alcohol fast bacilli
What presents secondary to pulmonary infection with TB?
Oral mucosal lesions - painful ulcerations in posterior part of mouth
Cervical lymphadenopathy - may develop absesses and sinuses
What does primary syphilis present as?
Single, painless, indurated genital ulcer (chancre)
