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Infectious Diseases Flashcards

1
Q

What infections are commonly associated with IRIS?

A

CMV, HSV, Mycobacterium avium complex (MAC), Pneumocystis pneumonia, and Mycobacterium tuberculosis (TB)

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2
Q

What is ivermectin used for?

A

Strongyloides

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3
Q

What is the mechanism of action of Toculizumab?
When is Toculizumab best used in COVID-19 infections?

A

IL-6 inhibitor
Used in severe COVID infection BEFORE patients are placed on ventilator

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4
Q

Which type of antibiotics do not cross the blood brain barrier in high concentrations?

A

Aminoglycosides (Gentamicin), erythromycin, tetracyclines (doxycycline), clindamycin, and first generation cephalosporins

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5
Q

What is the mechanism of action of Gentamicin, an aminoglycoside?

A

works by inhibiting bacterial protein synthesis, leading to the death of bacteria.

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6
Q

What is a key difference in Gram-positive activity between first and second-generation cephalosporins?
Examples of each

A

First-generation cephalosporins have better activity against Gram-positive bacteria, while second-generation cephalosporins have a broader Gram-negative spectrum.
First gen = Cefalexin
Second gen = Cefuroximine

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7
Q

What is the spectrum of activity for second-generation cephalosporins?

A

Improved activity against Gram-negative bacteria (e.g., Haemophilus influenzae, Enterobacter species) while maintaining good activity against many Gram-positive bacteria.

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8
Q

examples of second-generation cephalosporins.

A

Cefuroxime, Cefaclor, Cefoxitin

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9
Q

What are the 3 carbapenams?
Which one does NOT have activity against pseudomonas?

A

Meropenem, Imipenem and Ertapenem.
Ertapenem has NO activity against pseudomonas aeruginosa.

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10
Q

what is the best screening test for syphilis?

A

T. pallidum Enzyme Immunoassay (EIA)

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11
Q

Which anti-TB drug should be used in HIV infected patients receiving ART for treatment of latent or active TB?
Why?

A

Rifabutin NOT Rifapentin is recommended
Due to greater drug interactions

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12
Q

Does a negative IGRA test exclude active TB?

A

No, a negative IGRA does not exclude active TB as IGRA cannot differentiate between active and latent TB.

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13
Q

What should be done for patients with a positive IGRA but without findings suggestive of active TB disease?

A

Patients with a positive IGRA should be considered for treatment of LTBI, based on the likelihood of developing active TB and the risk of adverse events from treatment.

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14
Q

Name 3 drugs used to treat multi-drug resistant TB?
Which two first line anti-TB drugs are often not effective against MDR-TB?

A

Used: Amikacin, Linozolid, Moxifloxacin
Resistant: Rifampicin +
Isoniazid

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15
Q

What is the mechanism of action of azole anti-fungals?
What is the mechanism of action of echinocandins anti-fungals? What is an example?

A

Azoles = inhibitr ergosterol synthesis
Echinocandins = inhibit glycan synthesis
example = Caspofungin

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16
Q

Why is Daptomycin not used to treat pneumonia?

A

Inactivated by pulmonary surfactant

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17
Q

What are beta-lactamases?

A

A group of enzymes capable of hydrolysing the 4-membered betalactam ring of betalactam antibiotics, thus inactivating the antibiotic.

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18
Q

What is the defining lesion features of small pox compared to chicken pox?

A

smallpox = lesions in same body part are at same stage of development. all lesions in one area progress synchronously through their stages (macules, papules, vesicles, pustules, and scabs).
chickenpox = lesions at different stages of development (crops) on the same body part at the same time.

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19
Q

What bacteria causes Pertussis/ whooping cough?
What type of bacteria is this?

A

caused by Bordetella pertussis
Type = Gram-negative coccobacillus

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20
Q

What is the rationale for using dexamethasone as an adjunct in the treatment of bacterial meningitis, even before Gram stain results are available?

A

Is primarily to diminish the rate of hearing loss and other neurologic complications.

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21
Q

What is the most consistently observed risk factor for hospital acquisition of VRE (vancomycin-resistance enterococci)?
Why?

A

Previous treatment with antimicrobials, particularly vancomycin and cephalosporins.
The use of multiple agents with broad spectrum activity may predispose patients to colonization with resistant enterococci, probably by altering the guts normal flora.

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22
Q

What are the two ntibiotics of choice for listeria meningitis?
What other antibiotic is used for synergistic effects?
Which patient group needs this additional antibiotic?

A

ABx = Ampicillin or penicillin G
Synergistic = gentamicin
Patients = severe cases, neonates or in immunocompromised.

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23
Q

What is progressive multifocal leukoencephalopathy?
What virus causes this?
What patient group does this occur?

A

A demyelinating disease of the central nervous system. Caused by reactivation of the JC virus, a polyomavirus
Patient group = Immunosuppression, most commonly seen in patients with HIV/AIDS.

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24
Q

What is the radiological difference between PML and Toxoplasmosis encephalitis?

A

PML = Lack of mass effect and absence of contrast enhancement
Toxo = ring-enhancing lesions with mass effect.

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25
Q

What antibiotics are used for strep. pneumonia encephalitis based on penicillin MIC?

A

<0.4mg/L = Benzylpenicillin <1mg/L = ceftriaxone or cefotaxime
Ceftriaxone or cefotaxime MIC 1.0 to 2.0 mg/L = either ceftriaxone or cefotaxime PLUS vancomycin.

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26
Q

What antibiotic is first choice for Neisseria meningitidis encephalitis?
What if they have an allergy to this?
Whats third line if allergy to both?

A

Benzylpenicillin.
hypersensitive = IV ceftriaxone or IV cefotaxime. For patients with immediate penicillin or cephalosporin hypersensitivity, use IV ciprofloxacin OR IV chloramphenicol.

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27
Q

What antibiotic is first choice for Listeria encephalitis?
What if they have an allergy to this?

A

benzylpenicillin.
hypersensitive = trimethoprim + sulfamethoxazole.

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28
Q

What antibiotic is first choice for Haemophilus influenzae type b encephalitis?
What is second line?
What if they have an allergy to this?

A

First line = ceftriaxone or cefotaxime
Second line = benzylpenicillin. hypersensitive to penicillin or cephalosporin, use IV ciprofloxacin or IV chloramphenicol.

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29
Q

What is Aseptic meningitis?
What is the most common cause of aseptic meningitis?
What are the two most common examples?
What season is high risk?

A

Aseptic meningitis, characterized by meningeal inflammation without the presence of bacterial pathogens in the cerebrospinal fluid (CSF), is most frequently caused by viral infections.
Cause = Enterovirus.
Examples = coxsackieviruses and echoviruses
Season = summer and early fall in temperate climates.

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30
Q

Why is Gentamicin not used in CNS infections?

A

Poor Penetration into the Central Nervous System

31
Q

Why is Gentamicin not used in brain abscesses from a microbiological point of view?

A

Brain abscesses are often caused by a mixture of aerobic and anaerobic bacteria, including streptococci, staphylococci, and various anaerobes. Gentamicin’s spectrum of activity does not adequately cover many of these organisms, especially anaerobes and many Gram-positive bacteria.

32
Q

Why is Clindamycin use in necrotising fascitis particularly in group A strep infections??

A

Clindamycin is a protein synthesis inhibitor, which helps to reduce the production of streptococcal toxins and enzymes that contribute to tissue destruction and systemic toxicity.

33
Q

What are the following common infective endocarditis bacterial linked to;
Streptococcus bovis/gallolyticus?
Streptococcus mutans and Streptococcus viridans group streptococci?
Enterococcus faecalis?

A

Strep Bovis/gallolyticus = colorectal neoplasms
Strep mutans/viridans = oral flora, endocarditis following dental procedures or in the presence of poor dental hygiene.
Enterococcus = healthcare settings or gastrointestinal/genitourinary tract procedures.

34
Q

What does Coxiella burnetii cause?
how is it treated?

A

Q fever
doxycycline for 2 weeks

35
Q

Why is continuous exposure to procaine penicillin (i.e. IM injection) important when treating syphilis?

A

This continuous exposure is important for effectively eliminating the slow-growing treponemes, which can have varying replication cycles. The prolonged presence of penicillin disrupts the bacterial cell wall synthesis, leading to the eradication of the pathogen.

36
Q

Which tests are best used to monitor disease activity in syphilis?
What about diagnosis?

A

Activity = VLRL + RPR
Diagnosis = T. pallidum EIA

37
Q

What does the acronym ACE-R stand for in regards to MAC treatment?

A

Azithromycin
Clarithromycin
Ethambutol
Rifabutin

38
Q

What is the major determinant of the risk of perinatal transmission of hepatitis B virus?
What are the preventive measures for the newborn?

A

Maternal viral load.
Prevention = administration of HBV vaccine and HBV Ig to the newborn.

39
Q

The annual influenza epidemics are best explained by antigenic drift or shift?
What does this mean?
What is it in regards to the viral proteins?

A

Antigenic drift
gradual accumulation of mutations in the viral genome, leading to changes in the antigenic properties of the hemagglutinin and neuraminidase proteins on the surface of the influenza virus.
Drift is the change in the H (hemagglutinin) and N (neuraminidase) proteins of influenza A.

40
Q

What type of viral change causes influenza pandemics?
What is this?
Why does it cause of pandemic?

A

Antigenic shift
Sudden, major change in the influenza A virus, resulting in new hemagglutinin and/or neuraminidase proteins. This can lead to the emergence of a novel influenza A virus subtype against which the general population has little to no immunity, potentially causing a pandemic.

41
Q

What is the mechanism of action of Neuraminidase inhibitors?

A

Neuraminidase inhibitors work by blocking the function of the viral neuraminidase enzyme, which is essential for the release of newly formed influenza viruses from infected cells, thereby limiting the spread of infection within the respiratory tract.

42
Q

Why do reverse transcriptase inhibitors such as those used in HIV treatment not effective for influenza?

A

Influenza viruses do not contain reverse transcriptase as they are RNA viruses that do not undergo reverse transcription.

43
Q

What is the most sensitive and specific test for the diagnosis of pertussis (whooping cough) caused by Bordetella pertussis?

A

PCR

44
Q

List of vaccines NOT allowed in immunocompromised patients: My Very Happy Japanese BOY

A

MMR
Varicella
HSV
Japanese encephalitis
BCG
Oral typhoid/rotavirus
Yellow fever

45
Q

What type of gram stain is Listeria?
What about strep pneumonia?

A

Gram-positive rod (bacillus)
Gram positive coccus

46
Q

What are 8 different gram negative baccili?

A

E.coli
Haemophilus influenzae
Klebsiella
Shigella
Salmonella
Legionella
Pseudomonas
Campylobacter/Helicobacter

47
Q

How does vancomycin resistance occur in Enterococci infections?

A

Primarily due to the acquisition of genes that alter the terminal D-alanyl-D-alanine proteins in the bacterial cell wall to D-alanyl-D-lactate or D-alanyl-D-serine.

48
Q

What is the mechanism of resistance of Haemophilus influenzae to ampicillin?

A

most commonly due to the production of beta-lactamase.

49
Q

What is the primarily function of Aminoglycoside antibiotics?
How do they do this?

A

Inhibition of protein synthesis.
They achieve this by binding to the bacterial 30S ribosomal subunit, which leads to misreading of mRNA and disruption of the initiation complex of protein synthesis.

50
Q

Inhibition of cell wall synthesis describes the action of what type of antibiotics? example

Interference with bacterial folic acid metabolism is the mechanism of action of which type of antibiotics? example

A

Cell wall = beta-lactam antibiotics (such as penicillins and cephalosporins) and glycopeptides (such as vancomycin)
Folic acid = antimetabolite antibiotics like sulfonamides and trimethoprim

51
Q

In people over the age of 65, which vaccine is more likely to improve survival, pneumococcal or influenza?
Why is this?

A

Pneumococcal
The pneumococcal vaccine directly targets the bacteria that can cause severe and invasive diseases, thereby potentially having a more direct impact on survival.

52
Q

Which invasive fungal infection carries the highest mortality rate in immunocompromised patients?
What is the mortality for invasive aspergillosis?

A

Aspergillosis
94%

53
Q

What disease is carried on the Aedes mosquitoes?
How does it typically present?

A

Dengue fever
Acute onset of fevers, rigors, headache “behind eyes”, malaise, nausea, and vomiting
Rash over the trunk and face (characteristic) - often appears a few days after the onset of fever
No respiratory symptoms

54
Q

How does Typhoid present?
What is the typical description of the rash?

A

Sustained high fever, abdominal pain, and constipation or diarrhea
Rash = Rose spots

55
Q

What type of mosquito transmits malaria?
What is the parasite called?

A

Anopheles mosquitoes.
Plasmodium parasite

56
Q

What type of mengitis has the highest evidence for corticosteroids?
Why?

A

Tuberculous meningitis
Why = often causes increased intracranial pressure, steroids reduce swelling which reduces pressure

57
Q

P. falciparum malaria is the most virulent malaria species; why is this?

A

its ability to infect a higher proportion of red blood cells compared to other Plasmodium species, leading to higher parasitemia levels and more severe clinical manifestations.

58
Q

primaquine therapy for malaria places some patients at risk of haemolysis; what needs to be ruled out to reduce this risk?

A

G6PD deficiency

59
Q

What specific type of parasite infection are Artesunate, doxycycline and quinine used for?

A

Malaria falciparum

60
Q

What two travel related infectious diseases can Tinidazole treat?

A

Amoebic liver abscess
Giardia

61
Q

What are the main differences between HIV-2 compared to HIV-1?
Where in the world is HIV-2 mainly seen?

A

less virulent
lower viral load
lower rates of vertical transmission
slower progression
Seen mainly in western central Africa and southern and western India.

62
Q

What infection is Fidaxomicin used for?

A

C diff

63
Q

How many days after exposure does the HIV RNA viral load test become useful?
What is this timeframe called?

A

Can identify HIV infection within 9 to 11 days after exposure “window period’

64
Q

What becomes positive first for HIV testing; p24 or antibody tests?

A

p24

65
Q

Why is Candida auris infection bad?

A

Antifungal resistance
Mortality rate 30-60%.
Persists on surfaces for weeks
Difficult to diagnose (skin rather than rectal swab)

66
Q

What is the effect of being Heterozygous for CCR5 Delta 32 allele in the development of HIV and AIDS?

A

Slower disease progression to AIDS

67
Q

Which drug has less renal side effects: Tenofovir alafenamide (TAF) VS Tenofovir disoproxil fumarate (TDF)?
What type of drugs are they?

A

TAF = decreased renal side effects
Drug = NRTI’s

68
Q

What overseas infection does Praziquantel treat?
What organs does this infection involve?

A

Praziquantel = schistosomiasis, also known as snail fever or bilharzia,
Organs = Urinary tract or bowels

69
Q

Which of the following is least likely to be associated with a rash?
Malaria
Dengue
Typhoid
Rickettsial infection
Brucellosis

A

Malaria

70
Q

Hep B: Treatment with WHAT should be commenced when the hepatitis B viral load is above WHAT in the third trimester?
What will the baby receive?
Can the mother still breast feed?

A

Tenofovir
200,000 IU/mL
Baby = IVIg Hep B + Hep B vaccine
Breast feed = yes

71
Q

A 37-year-old man presents to the emergency department with symptoms of meningitis. Gram stain of the cerebrospinal fluid reveals the presence of gram-negative diplococci.
What is the most likely pathogen?
Which of the following antibiotic should his 12-week pregnant partner receive as prophylaxis?

Ciprofloxacin.
Erythromycin
Ceftriaxone
Rifampicin.

A

Meningococcal infection
Ceftriaxone

Chemoprophylaxis is indicated in close contacts of patients with meningococcal infection and should be given as early as possible following the exposure.
Options: rifampin, ciprofloxacin, and ceftriaxone.

Rifampin is not recommended for pregnant women because the drug is teratogenic in laboratory animals.
Ciprofloxacin is not generally recommended for persons aged <18 years or for pregnant and lactating women because the drug causes cartilage damage for immature laboratory animals.

72
Q

Whats thew difference between homozygous vs heterozygous CCR5 mutation in HIV disease?

A

Heterozygous = slowed progression of disease
homozygous = high level of protection against HIV infection.

73
Q
A

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