Microbiology and parasitology

Question 1

what is the definition of microbial resistance?

Answer 1

decreased susceptibility of a fungal strain to an antifungal agent

Question 2

why can microbial resistance occur?

Answer 2

intrinsic resistance or acquired resistance

Question 3

what is the definition of clinical resistance?

Answer 3

therapeutic failure; a patient responds inadequately to an antifungal drug following administration of a standard dose

Question 4

what is the mode of action of polyenes?

Answer 4

bind to ergosterol and form aqueous pores in the plasma membrane

Question 5

name the 3 mechanisms of acquired resistance for polyene

Answer 5

1. reduced amounts of ergosterol in cell membrane
2. alteration of fungal cell membrane
3. alteration of the fungal cell wall

Question 6

what is the mode of action of azoles?

Answer 6

inhibit the biosynthesis of ergosterol

Question 7

name the 5 mechanisms of azole resistance

Answer 7

1. target is changed; reduced drug-target interaction
2. increase in target copy number
3. reduction of intracellular drug concentrations mediated via drug efflux transporters and reduced uptake
4. modification of other ergosterol biosynthesis pathway elements
5. biofilms and persistor cells

Question 8

what is the mode of action of echinocandins?

Answer 8

inhibit the synthesis of B-glucan in fungal cell wall

Question 9

name the 4 fungal drivers of resistance

Answer 9

1. stress pathways
2. generate tolerate cells
3. mutations rise
4. stable resistant isolates

Question 10

name the 3 mechanisms of echinocandin resistance

Answer 10

1. target is changed
2. increase in target copy number
3. biofilms and persistor cells

Question 11

what is the difference between intrinsic and acquired resistance?

Answer 11

intrinsic resistance is natural resistance to anti-fungal drugs without any previous exposure and acquired resistance is resistance acquired through genetic mutation and passage of these resistant genes after exposure to drug

Question 12

name the 3 types of Staphylococcus aureus carriers and describe them

Answer 12

1. non carriers; resistant to colonization of S. aureus
2. intermittent carriers; colonization with unique S. aureus genotype
3. persistent carriers; colonization with one unique strain and resistant to colonization with different strain of S. aureus

Question 13

which type of S. aureus carriers are at high risk for endogenous S. aureus infections?

Answer 13

persistent carriers

Question 14

which microbial factor is involved in the nassal carriage of S. aureus?

Answer 14

staphylococcal protein A (SpA) is positively correlated with carriage duration

Question 15

name the 4 characteristics of a pneumococcal co-infection with influenza virus

Answer 15

1. epithelial damage
2. decreased mucociliary velocity
3. reduced CCL2 expression
4. reduced macrophage functionality

Question 16

how does the pneumococcal capsule contribute to disease?

Answer 16

capsule virulence factor is resistant against phagocytosis

Question 17

what is competence in S. pneumoniae?

Answer 17

• horizontal gene transfer; transformation
• competence is induced by environmental signals (high cell density, stress)
• competence leads to killing neighboring cells
• competence stimulating peptide (CSP) secreted by competent cells

Question 18

which proteins are essential for niche adaptation?

Answer 18

ATP binding cassette (ABC) transporters for nutrient transport

Question 19

what is the function of pneumolysin?

Answer 19

toxin that form pores to induce inflammation for faster clearance and increased transmission

Question 20

name the 3 prominences of S. pneumoniae as a cause of disease

Answer 20

1. high carriage rates
2. genetic adaptibility
3. ability to shift from commensal to a pathogenic interaction with its host

Question 21

name the 2 adaptations that is needed for niche adaptation

Answer 21

1. metabolic adaptation; maintenance of metal levels, different carbon sources
2. immunological adaptation; from non-sterile to sterile site

Question 22

name the 3 limitations of current pneumococcal vaccines

Answer 22

1. protection against a limited number of serotypes
2. pneumococcal vaccines are designed based on prevalence in US and Europe
3. expensive and complex from a development and manufacturing perspective

Question 23

name the 5 requirements for an improved pneumococcal vaccine

Answer 23

1. broadly protective
2. affordable
3. target groups: infants and elderly
4. focus on reduction of carriage
5. potential novel vaccine antigens based on conserved proteins required for colonization

Question 24

name the 3 current pneumococcal vaccines

Answer 24

1. conjugate vaccines (PCV); purified capsular polysaccharides conjugated to carrier proteins
2. PPV23; purified polysaccharides
3. adjuvanted with aluminium phosphate; Th2 adjuvant to increase antibody response

Question 25

what is the mode of action of B-lactam antibiotics?

Answer 25

interrupt cell wall synthesis by binding to penicillin-binding proteins (PBPs) that are essential for peptidoglycan crosslinking

Question 26

name the 3 mechanisms of resistance of B-lactam antibiotics

Answer 26

1. impaired permeability of outer membrane 2. mutated penicillin binding proteins (PBPs) with changed affinity 3. enzymatic hydrolysis of the B-lactam ring

Question 27

what is the mode of action of aminoglycosides antibiotics?

Answer 27

inhibit protein synthesis by binding to the 30S ribosomal subunit

Question 28

name the 3 mechanisms of resistance of aminoglycosides

Answer 28

1. aminoglycoside-modifying enzymes 2. alteration in uptake 3. change in ribosomal binding sites (methyltransferases)

Question 29

name the mode of action of quinolones antibiotics

Answer 29

inhibit DNA synthesis; the activity of DNA gyrase and topoisomerase IV

Question 30

name the 5 mechanisms of resistance of quinolones

Answer 30

1. mutations in DNA gyrase and topoisomerase IV 2. decreased porine-expression 3. activation of efflux pumps 4. inability of the quinolone to bind to the gyrase by hindering of the interfering protein encoded by qnrA 5. degradation by acteyltransferases aac(6')-1b-cr

Question 31

name the 7 risk factors for acquiring ESBL-E amongst travellers

Answer 31

1. traveller's diarrhoea 2. antibiotic use during travel 3. travelled to South Asia 4. behaviour during travel 5. food consumption during travel at street food stalls 6. male gender 7. older age

Question 32

what is the definition of ESBL?

Answer 32

extended-spectrum beta-lactamase; beta-lactamases capable of conferring bacterial resistance to antibiotics by hydrolysis of these antibiotics