Clinical Uses of Antibiotics & Resistance Flashcards Preview

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Flashcards in Clinical Uses of Antibiotics & Resistance Deck (100)
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1

Ceftriaxone...

Pseudomonas?

No.

other 3rd gen cephs do, but ceftriaxone does not.

2

Why are we reluctant to use Aminoglycosides?

Nephrotoxicity
Ototoxicity

3

Do aminoglycosides work on pseudomonas?

yes.

4

What are the 4 big considerations for empirical therapy?

1. Infectious syndrome (site)
2. Pathogens that cause this syndrome?
3. Antibiotic resistance of the possible bugs?
4. Most appropriate AntiB to use...?

5

Why are E. Coli more likely to undergo R-factor plasmid transfer via conjugation than Pseudomonas?

Both are Gram ? C or R?

E. Coli are enteric so they hang out and conjugate with one another. Pseudomonas are non-enteric, less likely to conjugate.

Both are GNR

6

What are the Bactericidal Drugs (by class) drugs and the exceptions.

1. Cell Wall Synth. Inhibitors
PCN, Ceph, Vanc.
2. Aminoglycoside (protein synth. inhib, exception)
3. DNA gyrase fn. inhibitors

7

What are the Bacteriostatic (by class) durgs and what are the exceptions?

Protein Synthesis Inhibitors are bacteriostatic

...with the exception of aminoglycosides which are bacteriocidal.

8

Aminoglycosides don't work well at _______ pH.

low

9

Breakpoints for whether an antimicrobial will be effective against a given bug...

1. Susceptible - likely to get a response
2. Intermediate - intermediate or uncertain response. Higher dose may work.
3. Resistant - probably no response.

10

The labratory-defined in vitro susceptibility testing breakpoints do not take into account ...

1. infection site (penetrate?)
2. # of bugs (abscess needs to be drained first)
3. host conditions (pH at infection site)
4. patients host defenses (immuno-compromised?)

11

The minimum requirement for considering a bug to be resistant to an anti-bug...

Cp > MIC

maximal serum concentration should be greater than the minimum inhibitory concentration

12

Why is E. Coli resistant to penicillin?

What sort of resistance is this?

What drug (in the same class) is effective on E. coli and why?

PCN can't get thru the PORINS in the outer membrane of E. coli (gram neg).

Intrinsic Resistance

Ampicillin is able (more hydrophobic side chain) to enter thru the porin to reach the PBP and inhibit c.w. synth.

13

Why is Mycoplasma resistant to beta lactams?

No cell wall --> no effect from the c.w. synth inhibitors.

Intrinsic Resistance.

14

Why is pseudomonas resistant to multiple agents?

...

15

3 types of resistance

Intrinsic
Tolerance
Acquired

16

Give 4 _tolerance_ resistance mechanisms

Biofilms
Metabolic bypass (sulfonamides example)
Anaerobic growth
Stationary phase

17

3 acquired resistance mechanisms

1. Inactivate or modify the drug
2. Alter the antibacterial target
3. Prevent the drug & target from meeting (efflux)

18

Pseudomonas resistance mechanism(s) to Fluoroquinolones

1. Efflux
2. Altered bacterial target site

19

Pseudomonas resistance mechanism(s) to beta lactams?

Decreased entry

20

MRSA resistance mechanism(s) to beta lactams?

1. Altered bacterial site (alter PBP)
2. Enzymatic degradation (beta lactamase)

21

Streptococci resistance mechanism to sulfonamides?

Bypass pathway (metabolic)

22

Porin channels exist on which bugs?

gram negative only

23

Role of porin channels in gram negative bacteria?

Selective uptake of nutrients etc.
Conduit for hydrophillic antiB's to get inside cells

24

How can porins contribute to antiB resistance

Can be intrinsic: prevent antiB entry
Can be acquired...alter structure or # or porins

25

Efflux pumps exist on which bugs?

Gram (+) and Gram (-)


26

What is the normal function of efflux pumps?

get rid of substrates from bacterial cytoplasm

27

efflux pumps are plasmid or chromosomally encoded?

both

28

how do efflux pumps contribute to antiB resistance?

can pump antiB out of cell preventing drug from reaching target

29

are efflux pumps drug specific or multi-drug?

can be both.
pseudomonas - multi drug resistance via efflux pumps

30

How do bacteria become resistant to beta lactams?

1. MODIFY THE DRUG: BETA LACTAMASES
2. MODIFY THE TARGET: CHANGE PBP

(also porin channels and efflux pumps)