Antibiotics Flashcards
what happens to clostridium difficile during the use of some antibiotics?
they are the normal flora of the bowels, can start to produce toxins and form spores and can become harmful when changed by antibiotics
what happens when there is an increase in the prescribing of antibiotics?
increase in rate of antibiotic resistance
what is antibiotic stewardship?
aim to reduce antibiotic consumption, it restricts worst offender agents and promotes logical antibiotic choices. also limits co-lateral damage
what is guided therapy?
the antibiotics are prescribed depending on the identifying cause of infection and selecting agent based on sensitivity testing. antibiotics are picked depending on which ones are going to be most effective for the specific bacteria
what is empirical therapy?
the best educated guess is used based on clinical/epidemiological acumen. used when therapy cannot wait for the culture.
what is prophylactic therapy?
prevents the infection before it begins,
when is guided therapy used?
-when condition is not critical
-for mild infections eg cystitis and mild wound infections
-rationalising therapy patients who’s cultures come back
what is empirical therapy used for?
-patients with more severe infection eg sepsis and meningitis
-when a delay in therapy would result in worsening of the condition
what is prophylactic therapy used for?
-healthy people exposed to infection eg surgery, injury, infected material
-immunocompromised individuals HIV, transplantation and splenectomy
what are the ideal target effects of antibiotics?
-highly toxic to bacteria causing infection
-can penetrate the body area affected by the infection eg brain barrier
-limits the release of toxins from bacteria as some bacteria can release harmful toxins when they die
-convenient administration eg drip
what is the ideal co-lateral damage of antibiotics?
-non toxic to patient
-limited effect on colonising bacteria
-low potential for bacteria to escape treatment through developing resistance
what are characteristics of narrow spectrum antibiotics?
-limited penetration to the site of infection
-limited action to the bacteria causing infection
-achieve clinical cure with as little impact on colonising bacteria as possible
what are the characteristics of broad spectrum antibiotics?
-extensive action against my bacteria which might be causing infection
-need to penetrate broadly throughout the body
-may impact colonising bacteria and resistance
how do bactericidal antibiotics work?
-achieve sterilisation of the infected site by directly killing the bacteria
-lysis of bacteria can lead to release of toxins and inflammatory material
how do bacteriostatic antibiotics work?
-suppress growth but do not directly sterilise the infected site
-requires additional factors to clear bacteria- immune mediated killing
why do gram negative bacteria stain purple?
thick peptidoglycan wall absorbs the stain and it isn’t washed away with the acetone
why do gram negative bacteria stain pink?
their peptidoglycan cell wall is to thin to absorb the stain and it is washed out and restrained pink.
what do antibiotics target?
-they with off DNA production in bacteria
-target the cell wall as human cells don’t have one
-they block functions and switch off protein production
how is penicillin classified?
-they are classified by their beta lactic ring
-rapid bacterial killing and low toxicity
-chemically produced derivatives have altered pharmacology and antibiotic action
-they vary widely in the antibiotic spectrum
-they get into the active sites and prevent metabolism
how does vancomycin work?
large molecule - cannot penetrate gram negative cell wall
useful against penicillin resistant bacteria such as MRSA
what classifies doxycycline and clarithromycin?
highly concentrated within cells and is useful against intra cellular pathogens. it is also useful in infections caused by both gram + and gram - organisms
what classifies ciprofloxacin?
good broad spectrum of action. damage to DNA leads to rapid bacterial cell death. resistance has now become widespread
what classifies trimethoprim?
one of the earliest antibiotics. the resistance has become extremely common, mostly now used for non severe UTI
what are the mechanisms of antibiotic resistance?
-mutation/ modification of target site
-inactivating enzymes
-limited access eg reduced permeability or increased efflux
genes mediating resistance can often be easily transferred
