Infectious Diseases Flashcards
What is Reye’s syndrome?
Reye’s syndrome is a post viral reaction to aspirin that manifests as confusion and fatty liver changes in young adolescents.
What serious condition does Shigella-toxin E. coli (STEC) cause? What effect does giving ABx do to the risk of this occurring?
Shigella-toxin E. coli (STEC) may cause HUS, giving Abx may increase the risk to 50%.
What are the ESCAPPM organisms? What is their peculiarity?
ESCAPPM organisms: enterobacter, serratia, citrobacter, aeromonas, proteus, provedincia, morganella
All ESCAPPM organisms have inducible beta-lactamase activity that is chromosomally mediated which increases likelihood of cephalosporin resistance.
What is the MOA of aciclovir?
MOA of acyclovir: analogue of deoxyguanosine that halts DNA production e.g. HSV replication.
Which antibiotic should and should not be used against ESCAPPM organisms?
Regarding the ESCAPPM organisms:
Cephalosporins should NOT be used
Antibiotics that should be used:
1st line: penicillin and aminoglycosides
2nd line: carbapenems or quinolones
Which populations are at risk of varicella-zoster pneumonitis?
Not children.
At-risk (SIP): smokers, immunosuppressed, pregnant.
What 2 conditions can VZV cause and where does it lie dormant in the body?
VZV causes herpes zoster (shingles) and chicken pox.
VZV lies dormant in the DRG.
What is the treatment of VZV?
acyclovir / valaciclovir / famciclovir
What is the likely food-borne pathogen in the following foods:
- Chicken
- Fried rice
- Raw eggs
- Raw oysters
- Soft cheese/Raw milk
- Home packaged food / honey
- Cream-filled pastry / Deserts
- Chicken: campylobacter, salmonella,
- Fried rice: bacillus cereus
- Raw eggs: salmonella
- Raw oysters (VNS): vibrio, norovirus, shigella
- Soft cheese/Raw milk (CLEY): campylobacter, listeria, e. coli (pathogenic), yersinia
- Home packaged food / honey: clostridium botulinum
- Cream-filled pastry / Deserts: staphylococcus aureus
What is Corynebacterium diphtheria?
Corynebacterium diptheria is a gram positive faculative anaerobe with 3 strains:
- Gravis
- Intermedius (most toxic)
- Mitis
Immunocompromised patient is noted to have multiple ring-enhancing lesions on CT/MRI of the brain. What is the pathogen? How is it treated?
Toxoplasma gondii
Empirical Rx:
metronidazole + cephalosporin (ceftriaxone/cefotaxime)
Targeted Rx:
pyrimethamine + sulphonamide
+/- leucovorin to prevent pyrimethamine-induced haematologic toxicity
or Bactrim (trimethoprim-sulfamethoxazole) if patient with sulphur allergy
Which pathogen is suggested by a positive antistreptolysin O antibody?
Group A streptococci (GAS).
ASOT (antistreptolysin O titre) = blood test
What 3 conditions might Group A streptococci (GAS)?
- Post-streptococcal glomerulonephritis - mild AKI to severe nephritic syndrome
- Tonsillar-pharyngitis +/- delayed:
a. scarlet fever (strep. pyogenes) - sandpaper rash
b. acute rheumatic fever (arthritis/carditis/chorea) - Streptococcal toxic shock syndrome
What is significance of the M-protein in virulence of Group A streptococci (GAS)?
M-protein is encoded by the emm gene.
Protects the organism against humoral surveillance and phagocytosis by polymorphonuclear leukocytes.
Which Abx is used for Group A streptococci (GAS)?
Penicillin V (phenoxymethylpenicllin)
What are IV and PO antibiotics that treat MRSA?
IV:
clindamycin OR vancomycin
PO:
clindamycin OR doxycycline OR trimethorpim
If resistant to ALL of these then consider
rifampicin + fusidic acid
How do beta-lactam antibiotics work?
Organism develop resistance with beta-lactamase, how might this resistance be obviated?
Inhibit cell wall biosynthesis
Clavulonic acid is often given intercurrently to inhibit beta-lacatamase activity.
MOA of macrolide antibiotics (Erythromycin, Azithromycin, Clarithromycin, Roxithromycin)?
‘macrolides are from the 1950s’
Block protein synthesis by binding to the 50S ribosomal unit.
MOA of sulphonamide (trimethoprim/bactrim)
sulFOnamides inhibit FOlic acid synthesis
MOA of aminoglycosides (gentamicin, streptomycin)?
‘a young guy in his 30s is now deaf cos he was given gentamicin - tragic!’
Block protein synthesis by binding to the 30S ribsomal subunit.
MOA of Quinolones / Fluoroquinolones (Ciprofloxacin, Norfloxacin, Moxifloxacin)?
‘people who wear FLUOR like to GYRATE TOPless in discos’
Inhibition of DNA gyrase / DNA to topoisomerases
Which pathogen is cutaneous anthrax due to?
Gram positive rod - Bacillus anthracis
Contracted by direct contact with bacteria
What are the clinical features of cutaneous anthrax (3)?
Black eschar
No pus
Painless with widespread oedema
True/False: cutaneous anthrax treated with antibiotics has a lower mortality that pulmonary anthrax.
True.
What type of food is E. Coli 0157:H7 most often found in? How might transmission be reduced?
What condition might it cause?
Which antibiotic should be used?
Meat (beef) - reduce transmission by thoroughly cooking the meat.
May cause HUS: bloody diarrhoea and renal impairment.
Do not treat with antibiotics (increased HUS risk by 50%)
GIven CSF results how do you differentiate:
- Bacterial
- Viral
- TB
- Bacterial:
Glucose: low (less than 1/2 plasma BSL)
Protein: high ( > 1.0g/L)
WCC: up to 5000 PMN - Viral:
Glucose: normal
Protein: high / normal
WCC: up to 1000 Lc - TB (same as bacterial, except with Lc)
Glucose: low
Protein: high ( > 1.0 g/L)
WCC: up to 1000 Lc
What is hypervirulent strain Clostridium Difficile?
What antibiotic is used to treat it?
Clostridium Difficile (aka NAP-1/027 strain) has increased production of toxin A and B (20x) due to mutated TCDC (The C. Diff Crazy) gene.
Due to exposure to fluoroquinolones (15x risk) but may be other too (cephalosporins and macrolides)
Treated with metronidazole / vancomycin (severe cases)
Compare anaerobes E.Coli to C.Diff in terms of bacterial morphology.
E. Coli is a gram NEGATIVE rod
C. Diff is a gram POSITIVE rod (that forms spores)
Patient with hypervirulent C. Difficile suddenly stopd having diarrhoea. Is this a good thing?
No.
Likely ileus with risk of toxic megacolon / perforation.
A patient with hypervirulent C. Difficile is refractory to treatment with metronidazole and vancomycin regimens. What other options are there?
- Rifaximin and PO vancomycin
- Fidaxomicin (non-absorbed ABx) - better than vancomycin (very expensive)
- Faecal transplant
