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BPT > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

1
Q

Most common cause of Otitis Externa

A

Pseudomonas aeruginosa

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2
Q

What is Antigenic Shift (and which virus does it occur in?)

A

Reassortment of viral genome from two different strains of Influenza B, leading to an abrupt change in structure/familiarity to immune system

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3
Q

What is antigenic drift?

A

Continuous mutations of haemagglutinin proteins, prevents formation of long lasting immune response to Influenza as specific IgA antibodies formed won’t continue to work

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4
Q

When is Oseltamivir most useful?

A

Only works in first 12 hours post infection, as well as in prophylactic role.

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5
Q

What organism is associated with UTI following bladder instrumentation?

A

Staphylococcus aureus

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6
Q

What’s the most sensitive test of osteomyelitis in diabetic foot infections?

A

Positive probe-to-bone test

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7
Q

Which antibiotics are best at penetrating biofilms?

A

Quinolones (Ciprofloxacin, norfloxacin, moxifloxacin)
Rifampicin
Linezolid

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8
Q

What beta lactams have high oral bioavailability?

A

Amoxicillin and Cephalexin

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9
Q

What organisms become more likely in an early acute PJI?

A

More likely to include gram negatives such as E coli and enterococci

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10
Q

Which Malaria species can develop dormant liver stage?

A

Vivax (2 years) and Ovale (4 years)

Asymptomatic interval in brackets

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11
Q

Gold standard investigation for Malaria

A

Thick and thin films
Thick film: high sensitivity
Thin film: higher specificity, can determine species and density
Schuffner granules, crescent shaped granules
If negative, repeat 12-24hrly for 3 tests

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12
Q

Malaria antigen testing

A

Faster
Less sensitive
Doesn’t determine density
Can stay positive post treatment
Can have false negatives due to gene mutations

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13
Q

Most virulent Malaria species

A

Plasmodium falciparum

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14
Q

Dominant malaria species outside sub Saharan Africa

A

Plasmodium vivax

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15
Q

Markers of severe Malaria

A

High parasitaemia- >2%
Anaemia: Hb <50, Hct <0.20 with parasite count >10,000
Jaundice
Seizures
Kidney Injury
Shock
Impaired consciousness
Prostration
Hypoglycaemia <2.2mmol/L

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16
Q

Antifungal for Moulds

A

Voriconazole

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17
Q

Septate dichotomous hyphae

A

Aspergillus
Treat with Voriconazole

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18
Q

What are the two key yeast infections, and what antimicrobial is indicated?

A

Cryptococcus and Candida
Fluconazole

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19
Q

Treatment for severe Malaria

A

Artesunate

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20
Q

Dengue Fever

A

Fevers, myalgia, retro-orbital pain, malaise, thrombocytopaenia, macular rash

Mosquito transmitted flavivirus: aedes aegypti, A. albopictus, A polynesiensis

Most common arbovirus infection in humans, transmitted in urban environments during the day (unlike Malaria)

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21
Q

What impact does serotype have on recurrent Dengue Fever infection?

A

Same serotype = protective
Different serotype = increased risk of severe disease

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22
Q

Abrupt onset illness with non productive cough, coryza, conjunctival suffusion, fevers, delayed development of rash starting on face and spreading to body

A

Measles

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23
Q

Dengue Fever Incubation

A

7 days, rarely >14

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24
Q

Measles incubation period

A

10-14 days

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25
Q

Yellow Fever Vaccination

A

Single dose required for lifelong protection
90% of individuals protected within 10 days, nearly 100% within 3-4 weeks

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26
Q

Febrile illness with black eschar after return from rural SE Asia/Northern Australia

A

Scrub typhus

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27
Q

Scrub typhus

A

Mite borne disease from rural areas of southeast or east Asia and northern Australia

Gram -ve coccobacillus

Symptoms within 10 days: fever, headaches, myalgia, mental status change, lymphadenopathy, pneumonia

Non pruritic macular or maculopapular rash with characteristic eschar

Treat with Doxycycline, often fever will resolve dramatically after a single dose

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28
Q

Lyme Disease

A

Tick borne illness caused by Borreliella species in America, Europe and Asia

Erythema migrans is classic rash and occurs within 1-2 weeks at site of bite

Neuroborreliosis: Lymphocytic meningitis, cranial nerve palsies, encephalomyelitis

Carditis: AV block +/- myopericarditis

Ceftriaxone, Cefotaxime, penicillins for CNS disease

Doxy for isolated facial nerve palsy

29
Q

A returning traveller from a safari trip to Zambia. Fever, HA, photophobia, altered mental status. Blood smear

A

African trypanosomiasis

30
Q

Indian gnetleman from India with thickening of skin on face

A

Leprosy

31
Q

Meningoencephalitis after swimming in a fresh and warm water source

A

Primary amoebic meningoencephalitis (Naegleria fowleri)

32
Q

Vomiting, diarrhoea, peri-oral paresthesias, metallic taste, blurred vision, temperature-related dysesthesias (cold stimuli perceived as hot) after eating coral fish in Fiji

A

Ciguatera fish poisoning

33
Q

MSM (men having sex with men) presents with liver abscess following trip to Southeast Asia

A

Amoebic Liver abscess (entamoeba hystolytica)

34
Q

Fever, headache, agitation, confusion, following a dog bite in Indonesia

A

Rabies

35
Q

Immigrant from Caribbean, wheezing and cough, deteriorates after treated with prednisone

A

Strongyloidiasis (Strongyloides hyperinfection)

36
Q

White water rafting in Hawaii, fever, headaches, conjunctival suffusion, thrombocytopaenia, raised LFTs

A

Leptospirosis

37
Q

Mechanism of MRSA

A

Altered penicillin binding protein 2a (PBP2a), often due to genetic change of mecA gene

38
Q

Clavulanic Acid and MRSA

A

Beta lactamase inhibitors such as clavulanic acid do not overcome MRSA’s mechanism of resistance as it is not enzymatic

39
Q

Mechanism of penicillin resistance

A

Beta lactamase enzyme hydrolyses penicillin

40
Q

Linezolid

A

Bacteriostatic antibiotic
Inhibits bacterial protein synthesis by binding to both 30S and 50S ribosomal subunits
Can suppess toxin production
Broad spectrum against gram positives
Reversible bone marrow suppression, irreversible neuropathy
Serotonin syndrome
100% bioavailability, good bone, lung, CNS penetration

41
Q

Daptomycin

A

Cyclic lipopeptide
Bactericidal
Depolarises bacterial cell membranes
Inactivated by surfactant -> doesn’t work for respiratory tract infection
SEs: Myopathy, eosinophilic pneumonia, peripheral neuropathy
CK monitoring required
Loading and renal dose adjustment necessary

42
Q

Tigecycline

A

Bacteriostatic
Eliminated via biliary tract -> not effective for UTI
Covers gram positives and negatives, including MRSA, VRE, ESML, AmpC, anaerobes, atypicals
Doesn’t work against Pseudomonas
Not good for bacteraemia due to high volume of distribution
Doesn’t get into CNS well

43
Q

Mechanism of Vancomycin Resistance

A

Change in protein structure in bacterial cell walls from
D-Ala D-Ala to D-Ala D-Lac
Vancomycin then can’t bind and inhibit bacterial wall synthesis

44
Q

Teicoplanin versus Vancomycin

A

Both glycopeptides
Similar efficacy
Teicoplanin can be given IM and has long half life so daily dosing
Teicoplainin fewer side effects
But expensive

45
Q

Mechanism of Pneumococcal Penicillin resistance

A

Similar to MRSA - due to changes in penicillin binding proteins
Thus beta lactamase inhibitors such as Clavulanic acid don’t work

However can be overcome if penicillin concentration at site of infection is higher than MIC of organism for 40-50% of dose interval

Respiratory infections can often still be treated with penicillins, but harder to treat CNS infections as resistance occurs at a lower MIC

46
Q

Macrolide and Penicillin use in resistant Pneumococcal Infection

A

Higher doses of penicillin can overcome resistance
Higher dose of Macrolides don’t overcome resistance

47
Q

Most common mechanism of beta lactam resistance in Gram Negative bacteria

A

Beta lactamases are the most common mechanism of resistance.

ESBL, AmpC, KPC, etc. all beta lactamase driven

48
Q

ESCHAPPM Organisms

A

Enterobacter
Serratia marcescens
Citrobacter freundii
Hafnia alvei
Acinetobacter and Aeromonas
Proteus vulgaris
Providencia
Morganella morganii

First three most important. For Proteus and Citrobacter it is species specific, so other Citrobacters and Proteus organisms don’t have same resistance

49
Q

What antibiotic resistance do ESCHAPPM Organisms have?

A

AmpC Beta-Lactamase

50
Q

Which key Cephalosporin is active against AmpC?

A

Cefepime

51
Q

What antibiotics should be used for ESCHAPPM Organisms?

A

Carbapenems are empiric antibiotic of choice
Cefepime suitable

Quinolones, Bactrim and aminoglycosides can be appropriate once sensitivities done

52
Q

What mechanisms of antibiotic resistance develop during treatment?

A

Inducible cephalosporinase
Selection of derepressed mutant via the antibiotic therapy

53
Q

Which HIV patients should receive ART?

A

All patients

54
Q

Normal CD4 count

A

> 500

55
Q

How does HIV infect humans?

A

HIV glycoprotein120 binds to CD4 receptors on immune cells as well as to co receptor CCR5 or CXCR4. Then Glycoprotein 41 attaches to cell membrane and fuses to enter cells. HIV then has a reverse transcriptase enzyme which turns HIV RNA into DNA to be integrated in host cell chromosome

56
Q

Testing for HIV

A

Antigen and antibodies should both be tested - 4th generation testing.

Then confirmatory testing if possible.

If combination Ag/Ab testing is negative two weeks post exposure, HIV is essentially excluded

57
Q

What specific presentations of HIV indicate a need to delay ART?

A

Cryptococcal meningitis - survival improved if ART commencement delayed 6 weeks, likely due to immune reconstitution syndrome

CNS TB

58
Q

Tenofovir Disoproxil Fumarate
- drug type/mechanism/indication
- Key side effect

A

NRTI
Causes Fanconi Syndrome

59
Q

In addition to HIV, what else does Tenofovir treat?

A

HBV

60
Q

Naming conventions of HIV drugs

A

NRTIs: variable
NNRTIs: -virine or -verine
Proteinase Inhibitors: - navir
Integrase Inhibitors: -gravir

61
Q

Starting Regimens for HIV treatment

A

Integrase Inhibitor + 2x NRTI
Or can go single NRTI if no resistance and no HBV

62
Q

Ritonavir

A

Protease Inhibitor for HIV
Part of Paxlovid for COVID
Inhibits CYP3A4 → many interactions
Very poorly tolerated
Prolongs half life of the other Protease Inhibitors

63
Q

Why doses PJP cause Tension Pneumothorax?

A

Cyst formation → pneumothorax

64
Q

Steroids and PJP infection

A

While prolonged steroid use is a risk factor for PJP, also important role in patients with infection. Reduce mortality in hypoxic patients

65
Q

When should PJP prophylaxis be given?

A

HIV patients with CD4 <200
Prolonged steroid use - ≥20mg for more than a few weeks
HIV patients who’ve had PJP and now recovered

66
Q

Treatment of Cryptococcus Meningitis

A

Amphotericin plus Flucytosine initially then followed by high dose Fluconazole. Total therapy 1 year.
Superior to fluconazole or amphotericin monotherapy

67
Q

Most common CNS infection in HIV patients not on treatment or prophylaxis

A

Toxoplasmosis

Causes enhancing lesions in brain, can treat without biopsy with bactrim

Intracellular protozoan parasite

68
Q

What form of disease does MAC cause in HIV?

A

Disseminated disease and focal lymphadenitis

BPT (20 decks)

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