Hospital acquired infections and antibiotic resistance

Question 1

What is an antibiotic?

Answer 1

An antimicrobial agent produced by a microorganism that kills or inhibits other microorganisms

Question 2

What is an antimicrobial?

Answer 2

A chemical that selectively kills or inhibits microbes

Question 3

What are bactericidal and bacteriostatic antibiotics?

Answer 3

Bactericidal - Kills bacteria

Bacteriostatic - Stops bacteria from growing

Question 4

What is an antiseptic?

Answer 4

A chemical that kills or inhibits microbes that is used topically to prevent infection

Question 5

What is a selection pressure?

Answer 5

A condition which favours a subset of a population, making them survive longer and change the population gentically

Question 6

What are the issues associated with antibiotic resistance?

Answer 6

• It causes an increased time to effective therapy
• It causes requirements fro additional therapies (e.g. surgery)
• More toxic drugs are used
• Use of less effective ‘second choice’ antibiotics

Question 7

What are the major antibiotic resistant gram-negative bacteria?

Answer 7

• Pseudomonas aeruginosa
• E. Coli (ESBL)
• E. Coli, Klebsiella spp. (NDM-1)
• Salmonella spp. (MDR)
• Acinetobacter buamannii ( MDRAB)
• Neisseria gonorrhoeae

Question 8

What are the 5 major gram-positive bacteria?

Answer 8

• Staphylococcus aureus (MRSA, VISA)
• Streptococcus pnemoniae
• Clostridium difficile
• Enterococcus spp. (VRE)
• Myobacterium tuberculosis (MDRTB, XDRTB)

Question 9

What are aminoglycosides?

Answer 9

• Bactericidal antibiotics
• Target protein synthesis (30s ribosomal subunit), RNA proofreading and cause damage to cell membrane
• Quite toxic

Question 10

What is rifampicin?

Answer 10

• A bactericidal antibiotic
• Targets RpoB subunit of rRNA polymerase
• Spontaneous resistance is frequent

Question 11

What is the problem with rifampicin?

Answer 11

Causes secretions to go red in colour so patients may not comply with taking the drug

Question 12

What is vancomycin?

Answer 12

• Bacerticidal antibiotic
• Targets Lipid II component of cell wall biosynthesis, as well as crosslinking via D-ala residues
• Toxic

Question 13

What is linezolid?

Answer 13

• Bacteriostatic antibiotic
• Inhibits initiation of protein synthesis by binding to 50s subunit of rRNA
• Gram-positive spectrum of activity

Question 14

What is daptomycin?

Answer 14

• Bactericidal antibiotic
• Targets bacterial cell membrane
• Gram-positive spectrum of activity
• Toxic

Question 15

What is selective toxicity?

Answer 15

As mammals and bacteria are so different there are multiple targets for antibiotic therapy

Question 16

What are the 4 mechanisms of antibiotic resistance?

Answer 16

• Altered target site
• Inactivation of antibiotic
• Altered metabolism
• Decreased drug accumulation

Question 17

How do antibiotic target sites alter in bacteria?

Answer 17

Acquisition of alternative gene or a gene that encodes a target modifying enzyme

Question 18

How do bacteria inactivate antibiotics?

Answer 18

They can degrade them with enzymes or alter/render the antibiotic ineffective

Question 19

How do bacteria alter their metabolisms to become resistant to antiobiotics?

Answer 19

The bacteria can increase the production of enzyme substrates to out-compete the antibiotic inhibitor

Question 20

How do bacteria decrease antibiotic drug accumulation?

Answer 20

They can reduce the penetration of the antibiotic through the bacteria’s membrane or the bacteria can have pumps to efflux the antibiotic out the cell

Question 21

What are macrolides?

Answer 21

• Bacteriostatic antibiotics
• Work against some gram-positive and negative infections
• Target 50s subunit of ribosomes preventing amino-acyl transfer

Question 22

What are quinolones?

Answer 22

• Bactericidal antibiotics?
• Broad spectrum
• Target DNA gyrase in gram-negative bacteria and topoisomerase in gram-positive bacteria

Question 23

What are the sources of antibiotic resistant genes?

Answer 23

Plasmids -Circular strand of DNA, often carry multiple antibiotic resistant genes
Transposons - Integrate into chromosomal DNA and allow transfer of genes from plasmid to chromosome and vice versa
Naked DNA - DNA from dead bacteria released in the environment

Question 24

What are the 3 methods of the spread of antibiotic genes?

Answer 24

1. Transformation (Uptake of extracellular DNA)
2. Transduction (phage-mediated DNA transfer)
3. Conjugation (pilus-mediated DNA transfer

Question 25

How is antibiotic resistance measured?

Answer 25

Streak plating is done on diagnostic agar to identify causative organism
Then the pathogen is streaked over a plate and over laid with strips containing antibiotics

Question 26

Why do hospitals provide strong selection pressures for antibiotic resistance?

Answer 26

Lots of infected people taking high doses of antibiotics

Question 27

What are the risk factors for hospital acquired infections?

Answer 27

• High number of immunosuppressed people
• Presence of pathogens
• Broken skin
• Antibiotic therapy may suppress normal flora
• Transmission by staff - contact with multiple patients

Question 28

What are beta-lactams?

Answer 28

• Bactericidal antibiotic

- Interfere with the synthesis of the peptidoglycan component of bacterial cell walls