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MRCP Revision > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

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1
Q

Abx inhibiting cell wall formation

A

penicillins, cephalosporins, carbopenems
glycopeptides

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2
Q

Cephalosporins MOA

A

beta lactam, bactericidal, disrupt synthesis of bacterial cell walls by inhibiting peptidoglycan cross-linking

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3
Q

Cephalosporin resistance

A

changes to penicillin-binding-proteins, which are types of transpeptidases (cross-link peptidoglycan chains to form rigid cell walls)

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4
Q

Vancomycin MOA

A

Binding to D-Ala-D-Ala moieties, preventing polymerisation of peptidoglycans

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5
Q

Vancomycin resistance

A

alteration to terminal amino acid residues of NAM/NAG-peptide subunits

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6
Q

Vancomycin SE

A

nephrotpxic, ototoxic, thrombophlebitis, red man syndrome (with rapid infusion. Flushing, erythema, pruritis affecting face, neck, upper torso, due to mast cell and basophil histamine release. Resolves within 20 mins of stopping/slowing infusion)

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7
Q

50S protein synthesis inhibitors

A

Macrolides, chloramphenicol, clindamycin, linezolid, streptogrammins

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8
Q

Chloramphenicol

A

Inhibits peptidyl transferase
SE: aplastic anaemia

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9
Q

Clindamycin

A

Inhibits translocation
SE: C Diff

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10
Q

Macrolides

A

Inhibits translocation
SE: nausea (esp erythromycin), P450 inhibitor, prolonged QTc

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11
Q

Linezolid

A

Oxazolidinone, bacteriostatic + bacteriocidal
Highly active vs: MRSA, VRE, GISA
SE: thrombocytopenia (reversible), avoid tyramine (like MAOi)

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12
Q

30S protein synthesis inhibitors

A

aminoglycosides
tetracyclines

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13
Q

aminoglycosides

A

Gentamicin
Causes misreading of mRNA
SE: ototoxicity, nephrotoxicity (ATN). Contraindication: Myasthenia. Monitoring: peak + trough levels

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14
Q

Tetracyclines

A

Blocks binding of aminoacyl-tRNA
Resistance: increased efflux by plasmid-encoded transport pumps, ribosomal protection
SE: teeth discolouration, photosensitivity, angioedema, black hairy tongue
Contraix: pregnant, breastfeeding women, children <12yrs

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15
Q

DNA synthesis inhibitors

A

quinolones

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16
Q

Quinolones

A

cipro/levofloxacin.
Inhibits topoisomerase II (DNA gyrase) and IV.

Resistance with mutations to DNA gyrase, efflux pumps as well.

SE: lowers seizure threshold, tendon damage (increased with steroids), cartilage damage, long QTc.

Contraindicated in pregnancy/breastfeeding and G6PD

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17
Q

Metronidazole

A

damages DNA

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18
Q

Folic acid formation inhibitors

A

trimethoprim, sulphonamides

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19
Q

Trimethoprim

A

MOA: inhibits dihydrofolate reductase (may interact with methotrexate) → inhibits DNA synthesis

SE: myelosuppression, transient creatinine rise (due to competitive inhibition of tubular creatinine secretion, with creatinine rise by 40, reversible), Type 4 RTA (blocks ENaC channel in distal nephron), teratogenic

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20
Q

Rifampicin MOA

A

inhibits RNA synthesis

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21
Q

Bacteriocidal vs bacteriostatic abx

A

Bacteriocidal Abx: penicillins, cephalosporins, aminoglycosides, nitrofurantoin, metronidazole, quinolones, rifampicin, isoniazid

Bacteriostatic abx: chloramphenicol, macrolides, tetracyclines, sulphonamides, trimethoprim

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22
Q

Azoles

A

MOA: inhibits 14alpha-demethylase → reduces ergosterol production from lanosterol → reduces plasma membrane structural integrity/stability
SE: P450 inhibition, hepatotoxic

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23
Q

Terbinafine

A

MOA: inhibits squalene epoxidase → ultimately, reduced ergosterol production → reduces plasma membrane structural integrity/stability
SE: pancytopenia, agranulocytosis, hepatotoxic
Used orally to treat fungal nail infections

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24
Q

Echinocandins

A

(Gaspofungin/any -fungins)

MOA: beta-glucan synthase inhibition → prevents transport of beta glucans to cell wall to be used for its formation
SE: flushing

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25
Amphotericin B
MOA: binds to ergosterol forming transmembrane channel makining little tears (AmphoTEARicin)→ leads to monovalent ion (K, Na, H, Cl) leakage + cell death SE: nephrotoxicity, flu-like sx, hypoK, hypoMg, hepatotoxic, phlebitis Used for systemic fungal infections
26
Nystatin
MOA: binds to ergosterol forming transmembrane channel makining little holes → leads to monovalent ion (K, Na, H, Cl) leakage + cell death Very toxic, can only be used topically (e.g. for oral thrush)
27
Griseofulvin
MOA: interacts with microtubules, disrupts mitotic spindle SE: CYP450 inducer, teratogenic
28
Flucytosine
MOA: converted by cytosine deaminase to 5-fluorouracil, inhibits thymidylate synthase → attacks DNA → disrupts fungal protein synthesis SE: vomiting
29
DNA polymerase inhibitor antivirals
aciclovir, ganciclovir, foscarnet
30
Aciclovir
MOA: guanosine analogue, phosphorylated by thymidine kinase, inhibits viral DNA polymerase For HSV, VZV SE: crystalline nephropathy
31
Ganciclovir
MOA: guanosine analogue, phosphorylated by thymidine kinase, inhibits DNA polymerase For CMV SE: myelosuppression/agranulocytosis
32
Foscarnet
MOA: pyrophosphate analogue, inhibits DNA polymerase For CMV, HSV (2nd line) SE: nephrotoxicity, hypoCa, hypoMg, seizures
33
antiviral mRNA group
IFN alpha, ribavirin
34
IFN alpha
MOA: inhibits mRNA synthesis For HBV, HV, hairy cell leukaemia SE: flu like sx, myelosuppression
35
Ribavirin
MOA: guanosine analogue, inhibits IMP dehydrogenase, interferes with mRAN capping For chronic HCV, RSV SE: haemolytic anaemia
36
M-group antivirals
amantadine, oseltamivir
37
Amantadine
MOA: inhibits M2 protein and uncoating of virus, releases dopamine from nerve endings For influenza, PD SE: confusion, ataxia, slurred speech
38
Oseltamivir
MOA: neuraminidase inhibitor For influenza
39
Cidofovir
MOA: acyclic nucleoside phosphonate, independent of phosphorylation by viral enzymes For CMV retinitis in HIV SE: nephrotoxicity
40
E coli gastroenteritis
Cause: E Coli (facultative, anaerobic, lactose-fermenting, G-ve rod). ETEC produces toxins stimulating intestinal lining → excessive fluid. EHEC can cause bloody diarrhoea Incubation period 12-48hrs Sx: onset within 1st wk of travel. Commonest cause of traveller’s diarrhoea (at least 3 episodes within 24hrs). Watery diarrhoea, abdo cramps, nausea
41
Giardiasis
Transmission: Giardia lamblia, faeco-oral. RF: travel, swimming/drinking from river/lake, male-male sexual contact Incubation period >7 days Sx: prolonged non-bloody diarrhoea, steatorrhoea, bloating, abdo pain, lethargy, flatulence, weight loss, malabsorption, lactose intolerance Ix: stool MCS for trophozoites, cysts (sensitivity 65%), stool antigen detection assay (greater sensitivity, faster), PCR assays. Rx: metronidazole
42
Cholera
Cause: vibrio cholerae (G -ve) Sx: profuse, watery diarrhoea with severe dehydration, weight loss, hypoglycaemia Rx: oral rehydration therapy. Abx: doxy, ciprofloxacin
43
Shigella
Cause: S sonnei (mild), S flexneri, dysenteriae (severe) Incubation period: 48-72hrs Sx: bloody diarrhoea, vomiting, abdo pain Rx: self limiting, but ciprofloxacin if severe, bloody or immunocompromised
44
Salmonella
Cause: aerobic, G-ve rods of Salmonella group, are not gut commenals. Salmonella typhi and paratyphi (types A, B, C) cause enteric fevers. Faeco-oral transmission Incubation period 12-48hrs Sx: Enteric fever (headache, fever, arthralgia), relative bradycardia (Faget sign), abdo pain, distension, constipation (more common than diarrhoea), rose spots on trunk 40% (more common in paratyphoid) Compl: osteomyelitis (esp in Sickle cell disease), GI bleed/perforation, meningitis, cholecystitis, chronic carriage (1%, more likely with adult F) Ix: Large volume blood culture Rx: Typhoid - ceftriaxone. Non-typhoid - ciprofloxacin
45
S aureus gastroenteritis
Incubation period: 1-6hrs Sx: severe vomiting
46
Campylobacter
Cause: Campylobacter jejuni (G-ve bacillus), faeco-oral, undercooked poultry, unpasteurised milk incubation period 1-6 days Sx: prodrome (headache, malaise), bloody diarrhoea, abdo pain, mimics appendicitis Rx: self-limiting. Clarithromycin if severe (high fever, bloody diarrhoea, >8 stools/day, >1wk) or immunocompromised. Alt: ciprofloxacin Compl: GBS, reactive arthritis, septicaemia, endocarditis, arthritis
47
Bacillus cereus
Cause: undercooked rice Incubation period 1-6hrs Sx: Vomiting within 6hrs or diarrhoeal after 6hrs
48
Amoebiasis
Cause: entamoeba histolytica, faeco-oral. 10% chronically infected Incubation period >7 days Sx: can be asymptomatic, mild diarrhoea or gradual onset bloody diarrhoea, abdo pain, lasting several wks, can form liver/colonic abscesses Amoebic dysentery: Sx: profuse, bloody diarrhoea, long incubation period Ix: Stool microscopy - trophozoites (examine within 15 mins or keep warm - ‘hot stool’) Amoebic liver abscess: Sx: fever, RUQ pain, systemic, hepatomegaly, ‘anchovy sauce’ contents of liver Ix: ultrasound, serology >95% Rx: oral metronidazole + luminal agent (e.g. diloxanide furoate
49
S aureus pneumonia
post-influenza, cavitation lung lesions (esp with strains producing Panton-Valentine Leukocidin cytotoxin → necrotic, haemorrhagic pneumonia)
50
S pneumoniae assx
herpes labialis
51
Mycoplasma pneumoniae
Sx: younger pts, epidemic every 4 yrs, prolonged, gradual onset, flu-like sx then dry cough Compl: cold agglutinins (IgM), haemolytic anaemia, thrombocytopenia, erythema multiforme, erythema nodosum, meningoencephalitis, GBS, bullous myringitis (painful vesicles on tympanic membrane), pericarditis/myocarditis, hepatitis, pancreatitis, acute glomerulonephritis Ix: CXR b/l consolidation, dx by serology. +ve cold agglutination test, blood smear shows RBC agglutination Rx: doxycycline/macrolide (lacks peptidoglycan cell wall)
52
Legionella CAP
Cause: Legionella pneumophilia, intracellular bacterium, water tanks (dodgy air-conditioning, foreign travel) Sx: flu-like 95%, dry cough, relative bradycardia, confusion Ix: dx by urinary antigens, hypoNa, deranged LFTs, lymphopenia, CXR (mid-lower zone consolidation, pleural effusions 30%) Rx: macrolide
53
Pstitacosis
Cause: Chlamydia psittaci. An obligate intracellular bacterium. Via birds/bird secretions Sx: flu-like + resp (dry cough). Sometimes hepatosplenomegaly Ix: CXR consolidation, serology Rx: 1. Doxy. 2. macrolides
54
Klebsiella pneumonia
Cause: G -ve rod, part of normal gut flora. Common in alcoholics (due to ETOH-induced dysbiosis → intestinal immune response alterations). May occur following aspiration Sx: ‘red-currant jelly’ sputum, often affects upper lobes. Cavitation lesions Prognosis: commonly causes lung abscess formation + empyema, mortality 30-50%
55
HAP Rx
<5 days of admission: co-amox/cefuroxime >5 days post-admission: tazocin/broad-spectrum ceph/quinolone
56
CURB65
confusion (AMTS<8), Urea >7, RR>30, BP <90/60, Age>65. Admit if 2 or more.
57
LUTI causes
E Coli commonest (G -ve) Staphylococcus saprophyticus 2nd most common in sexually active young women (G +ve, clusters, coagulase -ve)
58
Rx for LUTI
Non-pregnant: if symptomatic, trimethoprim/nitrofurantoin 3 days Pregnant: 1. Nitrofurantoin 2. amoxicillin/cefalexin. Avoid trimethoprim in 1st trimester. Treat for both asymptomatic + symptomatic Men: 7 days trimethoprim/nitrofurantoin Catheterised: treat only if symptomatic
59
Pyelonephritis Rx
ceph/quinolones 10-14 days
60
Meningitis causes
0-3months: Group B strep (esp neonates), E Coli, Listeria monocytogenes 3months - 6yrs: (NHS) N meningitidis, H Influenzae, S pneumoniae 6-60yrs: (-H to NHS) N meningitidis, S pneumoniae >60yrs: (replace H with L in NHS) N meningitidis, S pneumoniae, Listeria monocytogenes Immunosuppressed: Listeria monocytogenes Viral: non-polio enteroviruses (Coxsackie, echovirus), mumps, HSV, CMV, HZV, HIV, measles
61
CSF in meningitis types
Bacterial: cloudy appearance, low glucose (<50% of plasma), high protein, WBC polymorphs Viral: clear/cloudy, glucose 60-80% of plasma (low glucose in mumps, Herpes encephalitis), WBC lymphocytes TB: slightly cloudy, fibrin web, low glucose (<50% of plasma), high protein, WBC lymphocytes. Zielh-Neelson stain only 20% sensitive, PCR more sensitive (75%) Fungal: cloudy, low glucose, high protein, WBC lymphocytes
62
Abx in meningitis
<3 months: cefotaxime + amoxicillin 3 months - 50 yrs: cefotaxime/ceftriaxone >50 yrs: cefotaxime/ceftriaxone + amoxicillin Meningococcal: benzylpenicillin or cefotaxime/ceftriaxone Pneumococcal: cefotaxime/ceftriaxone Haemophilus influenzae: cefotaxime/ceftriaxone Listeria: amoxicillin + gentamicin Pen/ceph allergic: chloramphenicol
63
When to avoid dex in meningitis
Avoid in septic shock, meningococcal septicaemia, immunocompromise, post-surgical meningitis
64
Contacts Rx in meningitis
for those exposed to meningococcus (risk highest 1st 7 days, persists for 4 wks) oral ciprofloxacin/rifampicin (cipro just needs one dose), meningococcal vaccination when serotypes available, including boosters, no prophylaxis for pneumococcal
65
Meningitis compl
sensorineural hearing loss (most common), seizures, focal neuro def, infective (sepsis, abscess), pressure (herniation, hydrocephalus), Waterhouse-Friderichsen syndrome (from meningococcal meningitis → adrenal haemorrhage → adrenal insufficiency
66
Cellulitis causes
S pyogenes, S aureus (less common)
67
Eron classification
I: no signs of systemic toxicity, no uncontrolled comorbidities II: systemically unwell/ well + comorbidity (e.g. PAD, venous insufficiency, obese) that may complicate/delay resolution III: significant systemic upset (confusion, tachycardia, tachypnoea, hypotension) or unstable comorbiditie IV: sepsis with life-threatening infection such as nec fasc
68
cellulitis rx
Oral fluclox if Eron I. Alt: clarithromycin, erythromycin, doxycycline. 2nd line: clindamycin IV Abx if Eron II admit if Eron III/IV, severe/rapidly deteriorating cellulitis, very young/frail, immunocompromised, significant lymphoedema, facial/periorbital cellulitis. Choice of abx: co-amox, clindamycin, cefuroxime, ceftriaxone
69
Necrotising fasciitis causes
Type 1: mixed anaerobes, aerobes, often post-surgical, diabetics (most common) Type 2: S pyogenes
70
Nec fasc RF
skin factors (trauma, burns, soft tissue inf), DM, SGLT-2 inh use, IVDU, immunosuppression
71

MRCP Revision (10 decks)

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