Antimicrobials Flashcards
What is the structure of beta lactam?
beta-lactam ring
looks like a house with a garage
What is a common antibiotic used that has the beta-lactam structure?
phenoxymethyl penicillin (pen v)
What are families of antimicrobials that have a beta-lactam ring?
penicilins
cephaloporins
carbapenems
monobactams
What are types of penicillins and what are examples of each?
natural - pen V
aminopenicilin - amoxicilin
penicilinase resistant - flucloxacilin (meticilin)
extended spectrum - piperacilin
How do the beta-lactams work?
by interfering with penicilin binding proteins (PBP) on bacteria which are responsible for cross-linked structure of peptidoglycan cell wall
What did bacteria evolve to develop against beta-lactams?
enzymes called beta-lactamases
very common in gram negative bacteria (provotella and fusobacterium)
What is a example of beta-lactamase inhibitor and how does is work?
block active site of bacteria beta-lactmase
clavulanic acid
How do bacteria overcome beta-lactmase inhibitors?
produce lots and lots of beta-lactmase to overwhelm the inhibiors
What is an esbl infection and how did it arise?
extended spectrum beta lactamase infection
from extended spectrum antibiotics that created a resistant extended spectrum beta lactamase
How is a ESBL infection treated?
carbapenems
What is the new class of beta-lactam antibiotics?
carbapenems
What bacteria developed after carbapenems?
carbapenmase producing bacteria
What is an example of a bacteria that produces carbapenemase?
carbapenemase producing enterobactericeae ( CPE)
rectal swab for screening
What types of infection do CPE/CRE cause?
Pneumonia
UTI
Wound infections
Bacteraemia
Why are CPE’s important to control?
- They can be efficiently transmitted in healthcare facilities
- Plasmids can transfer Resistance to other strains and species
- Often the last resort for treating multidrug-resistant (MDR) infections.
What do macrolides (erythromycin, clarithromycin) and lincosamides (clindmycin) inhibit?
inhibit 50S subunit of protein synthesis
What do tetracyclines inhibit?
inhibit 30S sub unit of protein sythesis
Wha does metronidazole inhibit and create?
inhibit nucleic acid synthesis or function
creates free radicals
What kind of bacteria does metronidazole kill?
what are examples?
strict anaerobes
(anerobic streptococci, prevotella)
What enzyme does metronidazole use?
pyruvate ferredoxin oxido reductase (PFOR)
What type of ring is the chemical structure of metronidazole?
imidazole with nitro group
What gene helps bateria bypass metronidazole and how does it work?
nim gene
adds two electrons and hydrogen metronidazole making it inactive
What antibiotic is used most in dentistry?
metronidazole
What did the governement change as first line antibiotic for dentoalveolar infections?
from amoxicillin to pen V
What is the minimum inhibitory concentration?
minimum concentration of antibiotic required to inhibit the bacteria
What is an example of an automated susceptibility testing system?
VITEK
What is a breakpoint?
chosen concentration (mg/L) of an antibiotic which defines whether a species of bacteria is susceptible or resistant to the antibiotic
What is clinical resistance?
when infection is highly unlikely to respond even to max does of antibiotic
What are the areas of confounding variables found in clinical that affect resistance?
co-morbidities
pus collections
foreign bodies
biofilm
site of infection
What is S in EUCAST defined as?
susceptible standard dosing regime
when there is a high likelihood of therapeutic success using a standard dosing regimen of the agent
What is I in EUCAST defined as?
susceptible increased exposure
when there is a high likelihood of therapeutic success because exposure to the agent is increased by adjusting the dosing regimen or by it’s concentration at the site of infection
What is R in EUCAST defined as?
high likelihood of therapeutic failure even when there is increased exposure (not just numbers, pus mode of administration etc)
What are pharmacokinetics?
the absorption, distribution and elimination of drug
affected by physiological factors (site of injection)
drug factors (protein binding)
What are pharmacodynamics?
relationship between concentration of drug and the antimicrobial efffect
What is the killing effect of beta lactams dependent on?
time above the minimum inhibitory concentration (MIC)
Which is better, Pen V or amoxicillin and why?
amoxicillin possesses the same spectrum as Pen V (against oral strep, anaerobes, and selected gram negative cocci)
plus
more active against gram negative cocci and members of the family enterobacteriaceae
What is angiosus streptococci sensitive to?
both pen v and amoxicillin
What do antimicrobial agents do to the ecological balance?
disturb the balance between the host and normal microflora
Why is amoxicillin not used anymore?
amoxicillin has a broader spectrum of activity than peniciliin V, it has a greater impaact on selection of resistance in the host microflora
not needed
