Topic 13 Microbial Resistance

Front 1

What is the number one reason why bacteria become resistant?

Back 1

- acquire genes that encode resistance

Front 2

what are the 4 reasons that were discussed about why bacteria become resistant?

Back 2

1) acquire genes
2) develop resistance by mutation
3) naturally resistant
4) pharmacokinetic Factors

Front 3

What are 2 examples given about bacteria that acquire resistant genes? How are they combated?

Back 3

Beta-lactamase that gives resistance to penicillin
-- Augmentin inhibits beta-lactamase
Chloramphenicol acetyl transferase
--chemical modification of original antibiotic

Front 4

Rifampicin developed resistance by bacterial mutation what is our solution to this?

Back 4

- triple cocktail drug therapy for TB

Front 5

What is one example of a naturally resistant bacteria? what is the solution?

Back 5

aminoglycosides and anaerobic bacteria
--synergism: use penicillin and another antibiotic together

Front 6

What are some pharmacokinetic factors that induce bacterial resistance?

Back 6

- Tissue penetration: antibiotic cant get to right area
- Minimal inhibitory concentration (MIC) cannot get high enough concentration in correct area

Front 7

What are the 4 ways that we discussed about how bacteria become resistant?

Back 7

1) mobile genetic elements that transfer resistance
2) plasmids
3) transposons
4) phages

Front 8

What are plasmids? how are they constructed?

Back 8

- small, circular, episomal, pieces of DNA
- form functional modules, but important part is the replication module

Front 9

What are the importance of imcompatibility groups?

Back 9

- 2 plasmids with same replication module cannot exist in same cell

Front 10

Describe conjugation and plasmids

Back 10

- male reels in female and burrows hole in her
- male makes a copy of his plasmid and gives it to female--female now is male
- how resistance gene is spread, allows exponential amplification of plasmid

Front 11

how does the gene get on the plasmid?

Back 11

- transposons

Front 12

What are transposons?

Back 12

- jumping genes

Front 13

What are 3 important structures of transposons?

Back 13

1) inverted repeats (identifies as jumping gene)
2) transposase (enzyme)
3) direct repeat at site of transposition

Front 14

Why was the fertility "F" plasmid important?

Back 14

- first saw that all isolated R (resistance) plasmids were associated with transposons
- indicated that resistance genes were first part of normal chromosome

Front 15

What is a phage?

Back 15

- bacterial virus

Front 16

Transduction and phages

Back 16

- virus chops up bacterial DNA, some bacterial DNA gets incorporated into viral DNA and passed on to other bacteria
- what does the new DNA contain?

Front 17

What are 4 clinical implications of mobile genetic elements causing antibiotic resistance?

Back 17

1) acquisition is rare: if patient responds to antimicrobial therapy they won't suddenly gain resistance under your watch
2) longer therapy duration wont in itself induce resistance
3) prophylatic administration of antibiotics doesn't promote resistance
4) patients that initially respond to antimicrobials and then get worse most likely have new bug

Front 18

What is the importance of resistance genes?

Back 18

some genes have always been there
--penicillins are natural antimicrobials and evolved with bacteria, normal that bacteria developed resistance against
--some resistance genes recruited for double duty
--evolve by mutating the target from antimicrobial
horizontal gene flow: b/c resistance genes recruited by mobile elements

Front 19

How are resistant bacteria formed?

Back 19

-SELECTION
- kill off bacteria that can be killed my antibiotics, only leaves resistant ones left

Front 20

What is piggyback selection?

Back 20

- may acquire resistance to more than one antibiotic if one resistance gene carries several antibiotic resistance capabilities on one plasmid

Front 21

How can you cope with antibiotic resistance?

Back 21

- new antibiotics
- altruism (reduces selective pressures, and lower use of antibiotics lowers antibiotic resistance frequencies
- limit use of antimicrobials on farm