Infectious Disease Flashcards
1
Q
A child returns from travelling with suspected cerebral malaria, which organism are you likely to find?
A
All species of Plasmodium can cause Malaria but only P. Falciparum causes cerebral malaria.
2
Q
Causes of cervical lymphadenopathy?
A
Abscess/lymphadenitis Atypical TB Cat scratch Mumps Malignancy e.g. lymphoma EBV Toxopasmosis Brucellosis Salivary stones
3
Q
Causes of atypical lymphocytosis?
A
EBV CMV Toxoplasmosis Mumps TB Malaria
4
Q
Causes of eosinophilia?
A
Atopy (asthma, eczema, EO)
Parasitic disease (hookworm, amoebiasis, schistosomiasis)
Psoriasis
Hodgkin’s lymphoma + eosinophilic leukaemia
Drug sensitivity
5
Q
Causes of hydrops fetalis?
A
- 10-15% “immune” - fetal anaemia due to anti-D/anti-Kell
- 85-90% “non-immune” - parvovirus, toxo, syphilis, aneuploidy, SVT, congenital heart block, TTT syndrome, muscular dystrophy, alpha thalassaemia major
6
Q
Prognostic markers in HIV?
A
- HIV viral load is most important predictor of progressive disease in early stages of HIV infection
- CD4 count is important prognosticator in late stage disease
7
Q
India ink stain with halo indicates which organism?
A
- Cryptococcus neoformans - commonest cause of fungal meningitis in immunocompromised patients.
- Onset may be insidious.
- India ink stain is the classic stain for this organism and the halo is due to the stain being unable to penetrate the capsule of the organism.
8
Q
What type of organism is gonorrhea?
A
Gram negative diplococcus
9
Q
What are the contraindications for BCG vaccination?
A
- Immunocompromised
- HIV or suspected HIV
- Generalised infected skin condition
- Positive IGRA or mantoux and <8m age
10
Q
When are patients with chickenpox contageous?
A
From 24-48 hours before the rash appears and until all the vesicles have crusted over
11
Q
Describe the antigen/antibodies in these situations: A: Acute hepatitis B infection B: Chronic hepatitis B infection C: Hepatitis D superinfection D: Past hepatitis B vaccination E: Previous hepatitis B infection
A
A: Acute hepatitis B infection - HBsAg positive, anti-HBc positive, IgM anti-HBc positive
B: Chronic hepatitis B infection - HBsAg positive, anti-HBc positive, IgM anti-HBc negative
C: Hepatitis D superinfection - this should be suspected in a patient with chronic hepatitis B whose condition suddenly worsens
D: Past hepatitis B vaccination - HBsAg negative, anti-HBc negative, anti-HBs positive
E: Previous hepatitis B infection - HBsAg negative, anti-HBc positive, anti-HBS positive
12
Q
Which antibiotic is most likely to cause oesophageal ulceration if not taken with fluids or food and at least 1 hour prior to going to sleep?
A
Doxycycline
13
Q
What are the blood film freatures in HUS?
A
- Schistocytes/helmet cells = fragmented cells
- Microangiopathic anaemia
- Thrombocytopenia
14
Q
What is the mechanism of weakness in infantile botulism?
A
- Inhibition of neurotransmitter release by neurotoxins produced by the Clostridium botulinum bacterium
- Symmetric descending paralysis beginning with cranial nerves/bulbar palsy
- It presents with: constipation, poor feeding, drooling, choking, weak cry, increasing weakness and floppiness and breathing difficulties
- Medical emergency. Needs ventilation, IVF, antitoxin early
15
Q
Cut off values for mantoux test?
A
> 5mm or more is considered positive in:
A recent contact with TB, HIV +ve, fibrotic x-ray changes, immunosuppressed
>10mm or more is considered positive in: Recent immigrants (<5 years) from high prevalence countries, <4y/o, high risk exposure
> 15mm or more is considered positive in:
Any person
16
Q
Describe the mechanism behind tick paralysis
A
- Holocyclus = tick causing paralysis in Australia
- Toxin released by the tick blocks acetylcholine at the neuromuscular junction
- Results in dilated pupils, lethargy, weakness, ataxia, slurred speech, ascending paralysis, depressed deep tendon and gag reflexes
- Sensory symptoms absent (differentiates from Guillain Barre which has frequent prodromal sensory symptoms).
- Can resemble botulism.
- Treatment: remove tick, although this may create short term worsening in symptoms. Toxin antidote can cause serum sickness in humans
17
Q
Discuss Lyme disease
A
- Caused by borrelia burgdorferi, transmitted by ticks
- Erythema migrans (red, circular rash with central bullseye) at site of bite
- Malaise, lymphadenopathy, paresthesia, headaches, myalgia, difficulties with memory and concentration
- 21 day course of doxycycline, majority of patients recover
18
Q
What are the risk factors for cerebral abscess?
A
- Congenital heart disease
- Trauma
- Surrounding infection (e.g. ocular, ear)
- Surgery
- Immunocompromised patients
19
Q
What is the steeple sign?
A
- Narrowing of the trachea on x-ray (looks like a church steeple)
- Seen in croup
20
Q
What are the risks of neisseria gonorrhoeae conjunctivitis?
A
- Severe keratitis
- Endophthalmitis (purulent inflammation of intraocular fluid)
- Disseminated infection (ophthalmia neonatorum)
- Gram -ve diplococci
- Treat with IM ceftriaxone, saline irrigation. Need CSF and blood cultures
21
Q
Conjunctivitis with intracytoplasmic inclusion bodies?
A
Chlamydial conjunctivitis
22
Q
What is a common gram negative coccobacillus?
A
Haemophilus influenzae
23
Q
What is the attack rate, spread, and incubation period of measles?
A
90%
Airborne or person-to-person
Incubation 6-21 days
Infective -5 to +4 from rash
24
Q
Describe the presentation of parechovirus in young infants
A
- Severe sepsis-like presentation
- Diffuse erythematous maculopapular rash
- May have diarrhoea
- Shocked, extreme tachycardia and tachypnoea
- Can develop encephalitis with long term white matter injury
25
Describe HSV infection in a neonate
- Rash, lethargy, fever
- Neonatal encephalitis with prolonged focal seizures
- Characteristic T2 hyperintensity in temporal and basal frontal lobes
- Surviving infants have lifelong epilepsy and intellectual disability, especially if treatment is delayed
26
Describe subacute sclerosing panencephalitis (SSPE)
- Late onset after measles infection
- Progressive neurological disorder with memory loss, dementia, behavioural change, myoclonus, pyramidal and extrapyramidal signs
- Leads to vegetative state and death in 1-3 years
- MRI: signal change in PV white matter
- EEG: Radermecker complex
- CSF: high titre measles IgM and IgG antibodies
27
What is the mechanism of resistance in the SPACE group organisms?
- Serratia, pseudomonas, acinetobacter, citrobacter, enterobacter
- May produced AmpC beta-lactamase, which rapidly hydrolyses penicillins and cephalosporins
- If low levels of AmpC, can become resistant with prolonged treatment courses (inducible resistance)
- Therefore, even if reported as susceptible, cephalosporins not recommended as 1st line therapy for serious infections caused by SPACE organisms
28
What type of vaccine is the HPV-9 vaccine?
- Recombinant subunit vaccine containing virus-like particles
- Covers 6, 11, 16, 18, 31, 33, 45, 52, 58
29
What are examples of an inactivated vaccine?
Influenza, cholera, plague, polio
30
What are examples of an attenuated vaccine?
Yellow fever, MMR, TB
31
What are examples of a toxoid vaccine?
Tetanus, diphtheria, snake bites
32
What are examples of a subunit vaccine?
Hepatitis B, HPV
33
What are examples of a conjugate vaccine?
Haemophilus influenza
34
What organisms can be present after animal bites?
- Cat - pasteurella multocida, staph aureus
- Dog - pasteurella canis, staph aureus, bacteroides, fusobacterium
- Monkey - herpes B virus (monkeypox, herpes simia)
- Rabies
35
A child who has a known diagnosis of HIV develops massive splenomegaly. Splenic aspirate reveals multiple amastigotes.
- Leishmani donoavani
- Visceral Leishmaniasis can present with massive splenomegaly, hepatomegaly, lymphadenopathy
- Can test on urine antigen, gold standard is identifying amastigote
- Small spherical or oval bodies which are transmitted by sandflies. Splenic aspirate is >95% sensitive.
36
A child from East Africa has been diagnosed with scabies which has been resistant to treatment. A skin snip reveals multiple microfilariae.
- Onchocerca volvulus
- Filarial worm responsible for river blindness, transmitted by simulium flies who breed in rapidly flowing water
- Intensely itchy rash which can be misdiagnosed as scabies
- Presence of microfilariae on skin snip
37
What are the alternative names for human herpes virus 1-8?
- HSV1 and HSV2
- HSV 3 = VZV/varicella
- HSV 4 = EBV
- HSV 5 = CMV
- HSV 6 and 7 = roseola
- HSV 8 = kaposi-associated herpes virus
38
What antibiotics are protein-synthesis inhibitors?
Aminoglycosides, tetracyclines, chloramphenicol and macrolides.
- Tetracyclines and aminoglycsides inhibit binding of tRNA at the ribosome
- Aminoglycosides also stuff up the reading of mRNA
- Chloramphenicol inhibits peptidyltransferase activity at the ribosome
- Erythromycin inhibits translocation
39
Side effect of ribavirin (for Hep C)
Haemolytic anaemia
40
Conjugate vs polysaccharide vaccines
- Conjugate (polysaccharide + protein = more potent) more effective in infancy, don't develop response to polysaccharide vaccines
- Conjugate gives higher antibody response and more effective protection
- Polysaccharide (e.g. pneumovax) doesn't provide herd immunity, no booster response, T-cell independent
41
Discuss meningicoccal disease
- Men B most common cause in industrialised countries
- Poorly immunogenic therefore vaccine development difficult (as polysaccharide capsule similar to fetal nerve cells)
- Very reactogenic vaccine - give paracetamol pre dose as high risk fever
- Men W increasing - covered by quadrivalent vaccine (A, C, W, Y)
- New 4cMenBV vaccine - also covers MenB
- Men A - bad in Sub-Saharan Africa
42
Rotavirus vaccine and intussusception
- Aim to start and complete course early (6w + 3m) as risk of intussusception increases from 6-12m age
- Elevated risk day 1-7, decreased after 2nd dose
43
Main cause of genital warts?
HPV 6 and 11
44
Main cause of cervical cancers?
HPV 16 and 18
45
Time-dependent killing
- Beta lactams, macrolides, vancomycin
- Most important factor is the time above MIC i.e. dosing interval
- Reach maximum kill rate at 2-4x MIC
- No post antibiotics effect
46
Concentration-dependent killing
- Aminoglycosides, fluoroquinolones (ciprofloxacin)
- Most important factor is peak concentration
- Max bactericidal activity achieved when levels much higher (10x) than MIC
- Significant post-antibiotic effect also concentration dependent, so better with a larger peak
- Once daily dosing means large doses given less frequently
- CMax/MIC = aminoglyc, fluoro
- AUC/MIC = vancomycin, aminogly, azithro
47
Which antibiotics act on cell wall synthesis?
- Beta lactams: penicillin, cephalosporin, carbapenems, monobactams
- Vancomycin
48
Which antibiotics act on folate synthesis?
- Sulfonamides
| - Trimethoprim
49
Which antibiotics act on protein synthesis: 50S subunits?
- Macrolides
- Clindamycin
- Chloramphenicol
50
Which antibiotics act on protein synthesis: 3OS subunits?
- Tetracyclines
| - Aminoglycosides
51
Which antibiotics act on DNA gyrase?
- Quinolones (ciprofloxacin)
52
Enterococci are intrinsically resistant to?
- Cephalosporins
- Low affinity for enterococcal penicillin binding proteins
- Need penicillin, amox, or vancomycin
53
Pseudomonas is intrinsically resistant to?
- Cefotaxime
| - Low affinity for pseudomonal penicillin binding proteins
54
Penicillin is good for treating?
- Streptococci
- Enterococci
- Neisseria
- Listeria
- Syphilis
- > has poor penetration into CSF, so lower threshold for defining penicillin resistance in meningitis than at other sites
55
Flucloxacillin is good for treating?
- Staph
- Strep
- Not enterococcus
56
Augmentin is good for?
- Beta lactamase inhibitor
- Restores activity against staph aureus
- Improved activity against gram -ve bacteria
57
Discuss cephalosporins
- Same mechanism as penicillins but with differing affinity for penicillin binding proteins
- No activity against enterococci
- Resistant to beta lactamase
- As you go to newer generations, have better gram negative cover, poorer gram positive cover (until get to 4-5th generation)
58
Discuss carbapenems
- Very broad spectrum - gram positive, gram negative, ESBL, pseudomonas
- ADRs: neurotoxicity, lowers seizure threshold esp imipenem
59
Are beta lactams bactericidal or bacteriostatic?
Bactericidal
60
Mechanisms of beta lactam resistance
- Beta-lactamase production - E.Coli, staph aureus
- Altered penicillin binding proteins i.e. altered binding site e.g. MRSA
- Reduced drug entry - reduces susceptibility but not usually resistant
- Removal of drug (efflux pumps) - pseudomonas
61
Extended spectrum beta lactamases (ESBLs)
- Confer resistance to penicillins, cephalosporins, monobactam
- Retain susceptibility to carbapenems (eg meropenem)
- Hydrolyse beta lactam rings, some only do this to penicillin so may still be able to use augmentin/cephalosporin
- e.g. Klebsiella, E.Coli
- Important amongst travellers esp SE Asia
- Can still use nitrofurantoin for lower UTI
62
What is the mechanism of MRSA resistance?
- Altered receptor binding
| - Resistant to all penicillins and cephalosporins
63
MRSA treatment options?
- Cotrimoxazole
- Clindamycin
- Vancomycin
- Linezolid
- Daptomycin
64
Discuss clindamycin
- Protein synthesis inhibitor
- Limits exotoxin production and improves outcome in toxic shock syndrome with strep, ? same effect in staph toxin
- If erythromycin resistance than risk of inducible clindamycin resistance, therefore don't use
- Good in MRSA, increasing literature for use in pneumonia, empyema, bone/joint (not for infective endocarditis alone)
65
Ecthyma gangrenosum is associated with?
- Pseudomonas
| - Bacterial invasion of walls or blood vessels in skin and subcut tissue
66
Early transplant infection (first 30 days) likely to be caused by?
Gram -ve bacteraemia, especially hospital acquired - E.Coli, pseudomonas, Klebsiella
(after day 30 get aspergillosis, invasive fungal infections)
67
Stenotrophomonas maltophilia is resistant to?
Universal resistance to beta-lactam antibiotics
68
What drugs can you use to treat pseudomonas?
Gentamicin, ceftazidime, tazocin, meropenem
69
Treatment of invasive aspergillus?
Voriconazole
70
Discuss aspergillus
- Pathogen after first 30 days post HSCT
- Usually causes pulmonary disease (80%)
- CT - halo sign, air crescent (once develop neutrophils cavitation will occur). Infarcted lung tissue full of hyphae
- Diagnosed on BAL
- Treated with voriconazole, 2nd line caspofungin
- Is resistant to fluconazole
71
Which antifungal would you use:
1) prolonged fever and neutropenia
2) candidemia or invasive candidiasis
3) invasive aspergillosis
1) amphotericin B
2) fluconazole (if sense) or amphotericin B
3) voriconazole
72
Side effects of antifungals
- Amphotericin B - nephrotoxicity, hypokalaemia
- Azoles - interact with vincristine
- Caspofungin - does not penetrate CSF
73
Discuss invasive candida infection
- immunocompromised
- Can involve any site, multiple focal liver or spleen lesions
- Can be in eyes and skin
- Unexplained fever or signs of severe sepsis while on antibiotics - suspect candida
- Can be rapidly fatal
- Treat with amphotericin B
74
Treatment of CMV?
- Ganciclovir (IV) - 1st line
- Foscarnet (2nd line) - nephrotoxic
- Valganciclovir (oral agent, causes neutropenia)
75
Post-transplant lymphoproliferative disorder
- EBV, B lymphocyte proliferation
- Spectrum of disease from fever/LAN to high grade lymphoma
- High risk: child, first 2 yrs post transplant, EBV+ve transplant in EBV-ve patient, heavy immune suppression, amount of lymphoid tissue transplanted (lung/liver/heart > renal)
- Worse if associated CMV
- Tx: reduce immunosuppression, rituximab (anti CD20), low dose chemotherapy
76
Discuss antiretrovirals for HIV treatment
- Need combination of 3 drugs: 2 x NRTI + 1 x NNRTI or 1 x protease inhibitors
- Multiple drug interactions
- ADRs: N+V, diarrhoea, pancreatitis, hepatitis, osteopenia, hyperlipidaemia , SJS
77
Side effects of TB treatment?
- Rifampicin - red/orange tears/secretions, P450 induction
- Isoniazid - sideroblastic anaemia, peripheral neuritis, hepatitis
- Pyrazinamide - inc uric acid
- Ethambutol - eyes, optic neuritis, decr visual acuity
78
Discuss cat scratch disease
- Bartonella henselae
- Regional lymphadenopathy, commonly axillary, 25% suppurate
- Can have: PUO, encephalitis, pneumonitis, hepatitis, loss of vision, skin rashes
- Tx: self-limiting unless immunosuppressed - then use azithromycin, ciprofloxacin, cotrimoxazole
79
Neonate with blueberry muffin rash
- CMV
- Will also have jaundice and hepatosplenomegaly
- Chorioretinitis, IUGR, anaemia
80
Most common cause of non hereditary congenital deafness?
CMV
81
Encapsulated bacteria
```
S - strep pneumoniae
K - klebsiella
H - haemophilus influenzae
P - pseudomonas aeruginosa
N - neisseria meningitidis
C - cryptococcus neoformans
```
82
Discuss congenital CMV
- Primary maternal CMV infection - 30-50% transmission
- Only 10% symptomatic at birth: jaundice, blueberry muffin, HSM, microcephaly, retinitis, 50% deaf
- Another 10% develop SNHL within 5-7yrs
- Ix: urine CMV culture/PCR, paired maternal and infant serology - if IgM+ve baby then confirmed CMV
- MRI, opthal
- Tx: if <28d old, mod symptomatic disease: PO valganciclovir (improves ID and SNHL) for 6/12 total (can cause neutropenia)
- Universal antenatal screening not currently recommended. No evidence that treating maternal primary infection will decrease risk congenital CMV
83
Discuss toxoplasmosis infection
- Self limiting non specific illness
- Cats, kitty litter, gardening, raw veges
- Highest risk transmission in 3rd trimester, but risk of congenital abnormalities highest in 1st trimester
- Ix: maternal + fetal IgG and IgM, amniotic fluid PCR, neonate PCR CSF
- Tx: maternal spiramycin 3g/day to reduce fetal transmission (doesn't treat fetus as doesn't cross placenta)
If confirmed fetal infection then pyrimethamine + sulfadiazine + folinic acid AN and PN until 12m old
- 85% babies normal at birth. Most develop chorioretinitis, hearing loss 30%, GDD 20-75%
84
Tx neonatal HSV
- IV acyclovir 14 days (mild) or 21 days (CNS/disseminated)
- Then 6m PO aciclovir post above to improve neurodevelopmental follow up
- 30% mortality with disseminated disease, 6% with CNS infection
- Oral aciclovir poor bioavailability and poor CNS penetration
85
Treatment neonatal GBS infection
- Amoxycillin and gentamicin (provides synergy) until blood/CSF sterile
- Or 10 days bacteraemia, 14-21 days meningitis
- 30% have residual neurodisability
- Can get recurrent infection ~40 days later
86
Signs of neonatal syphillis infection
- Snuffles, hemorrhagic rhinitis
- Skin: bullous lesions, mucous patches, desquamating skin
- Unexplained large placenta
- Hepatomegaly +/- spleen, jaundice
- Non immune hydrops
87
Mangement of neonatal syphillis
- Ix: TPPA (trep), RPR (non-trep) tests, paired with maternal serology
- Long bone x-rays - periosteal reactions
- LP - CSF VDRL, protein, WCC
- Spirochetes on placenta
- Tx: 10days IV benpen, follow up serology 3,6,12m
88
Outcome of neonatal Hep B infection
- 90% become chronically infected
- 25% develop cirrhosis or HCC in adult life
- Higher risk transmission if maternal HBeAg positive, and if untreated (up to 90% risk, decr. to 30% treated)
- Neonate Hep B vaccine and HBIG within 12hrs birth, then 2 x vaccine as per imms schedule. Check serology 9m age
89
Risk of parvovirus in pregnancy?
- 1st trimester - 10% risk fetal loss
- 9-20 weeks, high risk of fetal hydrops - can give IU transfusion
- No medication to prevent fetal infection
90
Discuss congenital rubella
- Highest risk preconception or 1st trimester (50%)
- SNHL (60%), cataracts/retinopathy/microphthalmia, cardiac (PA stenosis and PDA), ND disability
- High infectious
91
VZIg guidelines for neonates?
- Maternal VZV 7d before to 7d after delivery - VZIg or IVIG
| - Any baby <28 weeks gestation if exposure
92
Multiple ringforms in blood cells
Falciparum plasmodium
