Antimicrobial chemotherapy: mechanisms of bacteria and resistance to bacteria Flashcards
Name two healthcare acquired infections
Clostridium difficle
MRSA
What are antibiotics active against
bacteria
Bactericidal
Bacteriostatic
An antimicrobial that kills bacteria
An antimicrobial that inhibits growth of bacteria
When is an organism considered sensitive
it is inhibited or killed by levels of the antimicrobial that are available at the site of an infection
When is an organism considered resistant
it is not killed or inhibited by levels of the antimicrobial that are available at the site of an infection
What are the three routes of administration for antibiotics
Topical - skin surface
Systemic - Orally/Internally
Parenteral - IV or intramuscularly
What are the three metabolic areas that antibiotics inhibit to kill bacteria
Cell wall
Nucleic acid synthesis
Protein synthesis
Why are human cells not affected by antibiotics
as human cells do not have a cell wall
What antibiotics inhibit cell wall synthesis
Penicillins
Cephalosporins
Glycopeptides
What are Penicillins and Cephalosporins classed as and who do they inhibit call wall growth
Beta- Lactams
Disrupt peptidoglycan synthesis by inhibiting enzymes responsible for cross linking the carbohydrate chains
what happens to a bacteria when the cell wall has been disrupted
Organism finally killed by autolytic enzymes
What is the structural component of the bacterial cell wall and the enzymes known as
Penicillin binding proteins
What was the original B- Lactam discovered and why are gram negative organisms resistant
Benzyl Penicillin
Impermeability of gram negative cell wall
Whats a MIC (minimal inhibitory concentration)
Min conc of antimicrobial needed to inhibit visible growth of a given organism
What is a MBC (minimal bactericidal concentration)
Min conc of the antimicrobial needed to kill a given organism
What are two glycopeptide antibodies
Vancomycin and Teicoplanin
How do glycopeptides work
Inhibit peptidoglycan precursor acting prior to B-Lactam
What Bacteria can glycopetides not penetrate
Gram negative, therefore only act on Gram positive
Where are glycopeptides not absorbed and how are they administrated
GI tract
Usually Parentally
What is a common problem with vancomycin
toxicity
What antimicrobials inhibit protein synthesis
Aminoglycosides
Macrolides and Tetracyclines
Oxazoldinones
Cyclic Lipopeptide
What is a common aminoglycoside and and what infections do they provide a useful treatment
Gentamicin
Gram negative coliform infections including pseudomonas
Why does Gentamicin dosage have to be monitored
Because of it toxicity
What are Macrolides and Tetracyclines are used as alternatives to penicillin to treat
Gram positive infections
What are examples of Macrolides
erthromysin
clarithromysin
What is an example of a Oxazolidinones, and what is it active against
Linezolid
Good activity against MRSA and held in reserve for serious infections
What is an example of a cyclic lipopeptide and what is it active against
Daptomycin
Active against Gram positives and MRSA
Used in serious infections
How do antibiotics inhibit nucleic acid synthesis
By interrupting the supply of precursors for DNA synthesis
What antimicrobials inhibit nucleic acid synthesis
Trimethoprim and Sulphamethoxazole
Fluoroquinolones
What is Co- Trimoxazole
the combined drug of Trimethoprim and Sulphamethoxazole
What does Co- Trimoxazole commonly used to treat
Urine infections
What is an example of a Fluoroquinolones antibiotic and why is it good and more active against
ciproflaxin
Inhibits DNA synthesis more directly
Effective against gram negative organisms including pseudomonas
Who can ciproflaxin not be used on and why
On children can interfere with cartilage growth
In some cases all strains of a given species are resistant to antibiotic because
Inability of drug to penetrate the bacterial cell wall
What is acquired resistance
resistance may be present in some strains of species but not in others
What are the two ways resistance can be acquired
A spontaneous mutation (target has changed)
Genes that code fro resistance transferred via plasmid or transposons
How does the widespread of antibiotics cause selective pressure
encourages new resistant organisms to outgrow sensitive strains
what are b-lactamases
Bacterial enzymes that cleave the b-lactam ring of antibiotics = inactive
Example of a strain producing b-lactamase and what its resistant to
staphylococcus - staph aureas MRSA
resistant to - benzyslpenacillin
What is the two ways is B- lactase combats b-lactamase and examples
By adding a second component B-lactamase inhibitor
eg co-amoxiclav
Modify antibiotic side chain, (make antibiotic resistant)
eg Flucloxacillin
What is a modified from of penicillin
Flucloxacillin
What is the name of gram negative organisms resistant to carbapems
Carbapenemas producing enterobacteriaceae (CPE)
CPE organims is worrying because
Carbapems is a wide range of antibiotics
and this type of resistance is the same for a multiple form antibiotics
What is the two ways micro-organisms develop resistance to B-lactams
B-lactamase production to inactivate antibiotic
Alteration of penicillin biding proteins
When does the addition of B- lactamase inhibitor make no difference to antibiotic
when bacterias penicilian binding sites are altered
What is an example of bacteria with altered penicillin binding protein
MRSA methicin resistant staph aureas
What is MRSA resistant to
all penicillins and cephalosporins
What are extended spectrum B-lactamases resistant produced by and what are they resistant to
produced by some gram negative organisms
resistant to all B-lactam agents
What effect do Vancomycin resistant enterococci gram positive bacteria have on the antibiotic
peptidoglycan precursor to which the antibiotic vancomysin normally binds on a gram positive bacteria have altered = resistant
What antibiotic inhibits purine synthesis
trimethoprim
