Hospital acquired infections and antibiotic resistance Flashcards
(28 cards)
What is an antibiotic?
An antimicrobial agent produced by a microorganism that kills or inhibits other microorganisms
What is an antimicrobial?
A chemical that selectively kills or inhibits microbes
What are bactericidal and bacteriostatic antibiotics?
Bactericidal - Kills bacteria
Bacteriostatic - Stops bacteria from growing
What is an antiseptic?
A chemical that kills or inhibits microbes that is used topically to prevent infection
What is a selection pressure?
A condition which favours a subset of a population, making them survive longer and change the population gentically
What are the issues associated with antibiotic resistance?
- 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
What are the major antibiotic resistant gram-negative bacteria?
- Pseudomonas aeruginosa
- E. Coli (ESBL)
- E. Coli, Klebsiella spp. (NDM-1)
- Salmonella spp. (MDR)
- Acinetobacter buamannii ( MDRAB)
- Neisseria gonorrhoeae
What are the 5 major gram-positive bacteria?
- Staphylococcus aureus (MRSA, VISA)
- Streptococcus pnemoniae
- Clostridium difficile
- Enterococcus spp. (VRE)
- Myobacterium tuberculosis (MDRTB, XDRTB)
What are aminoglycosides?
- Bactericidal antibiotics
- Target protein synthesis (30s ribosomal subunit), RNA proofreading and cause damage to cell membrane
- Quite toxic
What is rifampicin?
- A bactericidal antibiotic
- Targets RpoB subunit of rRNA polymerase
- Spontaneous resistance is frequent
What is the problem with rifampicin?
Causes secretions to go red in colour so patients may not comply with taking the drug
What is vancomycin?
- Bacerticidal antibiotic
- Targets Lipid II component of cell wall biosynthesis, as well as crosslinking via D-ala residues
- Toxic
What is linezolid?
- Bacteriostatic antibiotic
- Inhibits initiation of protein synthesis by binding to 50s subunit of rRNA
- Gram-positive spectrum of activity
What is daptomycin?
- Bactericidal antibiotic
- Targets bacterial cell membrane
- Gram-positive spectrum of activity
- Toxic
What is selective toxicity?
As mammals and bacteria are so different there are multiple targets for antibiotic therapy
What are the 4 mechanisms of antibiotic resistance?
- Altered target site
- Inactivation of antibiotic
- Altered metabolism
- Decreased drug accumulation
How do antibiotic target sites alter in bacteria?
Acquisition of alternative gene or a gene that encodes a target modifying enzyme
How do bacteria inactivate antibiotics?
They can degrade them with enzymes or alter/render the antibiotic ineffective
How do bacteria alter their metabolisms to become resistant to antiobiotics?
The bacteria can increase the production of enzyme substrates to out-compete the antibiotic inhibitor
How do bacteria decrease antibiotic drug accumulation?
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
What are macrolides?
- Bacteriostatic antibiotics
- Work against some gram-positive and negative infections
- Target 50s subunit of ribosomes preventing amino-acyl transfer
What are quinolones?
- Bactericidal antibiotics?
- Broad spectrum
- Target DNA gyrase in gram-negative bacteria and topoisomerase in gram-positive bacteria
What are the sources of antibiotic resistant genes?
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
What are the 3 methods of the spread of antibiotic genes?
- Transformation (Uptake of extracellular DNA)
- Transduction (phage-mediated DNA transfer)
- Conjugation (pilus-mediated DNA transfer
