antimicrobials Flashcards
which antibiotics’s mechanism of action is inhibiting cell wall synthesis or function?
beta lactams
common antibiotics prescribed in dentistry
beta lactams group
- penicillin v
- amoxicillin
macrolide group
- clarithromycin
- metronidazole
is beta lactams penicillin related
yes
members of the beta lactam housing tree
- penicillins
- penicillinases resistant
- cephalosporins
- carbapenems
how do beta lactams work?
they work against the peptidoglycan layer in gram positive bacteria
they interfere with penicillin binding proteins which are needed for making the peptidoglycan layer
PBP
penicillin binding proteins
what is the name of the enzyme that breaks down beta lactams?
beta lactamases (antibiotic resistance)
what micrograms produces beta lactamases
prevotella
fusobacteria
mostly gram negative
what is the function of clavulanic acid?
beta lactamase inhibitor,
thus protecting the beta lactams from getting broken down before it gets the chance to work
augmentin contains what
amoxicillin and clavulanic acid
the clavulanic acid protects amxocillin
little use in dentistry tho
what is ABR?
when microorganisms change in ways that render medications used to cure the infections they cause ineffective
basically
antibiotic => penicillin, beta lactams
ABR from bacteria => penicillinases and beta lactamases
relevance of klebsiella pneumoniae in dentistry
this bacteria is present in ESBL infections
this bacteria is resistant to MANY antibiotics, hard to treat
ESBL full name
Extended-spectrum beta-lactamases
how to treat ESBL infections?
carbapenems
carbapenems function
ultimate beta lactam
they are able to fight against extended spectrum beta lactamases
Enterobacteriaceae structure
intestinal bacteria of the small rod family
plasmid encoded
thick capsule
other names of Enterobacteriaceae
coliforms
enteric rods
why is it so hard to get rid of Enterobacteriaceae with antibiotics?
surrounded by thick capsule that antibiotics have trouble penetrating
they are resistant to very many antibiotics
what enzyme does Enterobacteriaceae produce
carbapenemase
CPE
carbapenemase producing enterobactericeae
why do we need to worry about CPE?
- carbapenem antibiotics are seen as the last therapeutic option to treat complex infections, and yet CPE can fight these antibiotics, no “higher” antibiotic available
- transmitted easily in healthcare facilities
- plasmids can transfer resistance to other strains and species
can we find Enterobacteriaceae in the oral cavity? where else
yes, can be carried in the oral cavity
dental relevance also in maxillofacial surgery
how to screen for CPE?
rectal swab
what are the CPE protocols for a positive patient in dental hospital?
SIPCEPs
mode of transmission of CPE
pets
travels
household members
food
what is the mechanism of action of macrolides and clindamycin?
inhibits protein synthesis and inhibits 50S subunit
what family does erythromycin and clarithromycin come under
macrolide
what is the mechanism of action of tetracyclines?
inhibit 30S subunit
inhibit protein synthesis
what is the mechanism of action of metronidazole?
inhibits nucleic acid synthesis or function
creates free radicals which interfere with the structure and function of bacteria dna
PFOR enzyme in anaerobes adds an electron, making metronidazole a reactive anion species that can destroy dna
drugs that interferes with 30s subunit on bacteria ribosome?
tetracyclines
drugs that interferes with 50s subunit on bacteria ribosome?
macrolides and clindamycin
what is metronidazole effective against?
strictly anaerobes
which pathogens are strict anaerobes?
anerobic streptococci
prevotella species
(can be found in acute dental abscess and perio disease)
key system in anaerobes that metronidazole acts on?
PFOR system = pyruvate ferredoxin oxido reductase
NIM genes
nitro imidazole reductases
what happens when bacteria gets the NIM genes
they add two electrons and hydrogen to metronidazole
so it bypass the PFOR system to render metronidazole inactive
why has there been a 17% increase in dental amoxicillin since 2019?
penicillin v is now recommended as a first line antibiotics for acute dentoalveolar infections
how is resistance defined from a biological perspective?
minimum inhibitory concentration MIC
disc diffusion testing
automated susceptibility testing system - vitek
disc diffusion testing measures?
measures zone of inhibition
breakpoint
chosen conc of an antibiotic which defines whether a species of bacteria is susceptible or resistant to the antibiotic
clinical resistance (EUCAST def)
when infection is highly unlikely to respond even to maximum doses of antibiotics
MIC
minimum inhibitory concentration
what are some confounding variables, ie variables that affect how an antibiotics performs?
- co morbidities (can affect metabolism of antibiotics)
- pus collection (antibiotic cannot penetrate to the center of a pus)
- foreign bodies
- site of infection (some AB has poor penetration of bone)`
- biofilms
susceptible vs resistant
susceptible = high likelihood of therapeutic success using a standard dosing regimen
resistant = high likelihood of therapeutic failure even when there is increased exposure
what does it mean to increase exposure to antibiotics
increase dosage
dosing intervals shorter
mode of administration
distribution of antibiotic
interactions with bacteria at site of infection
why is pen v recommended over amoxicillin
because amxoxicillin is a broader spectrum antibiotics than can disrupt the commensal flora and cause more harm, example c.diff infection or candidasis
does pen v or amxoxicillin have better oral absorption
amox has a higher peak, better oral absorption
why do you need to dose more frequently for pen v?
lower peak conc
less time above MIC
how to determine the killing effect of beta lactams?
killing effect dependent on time ABOVE MIC
is beta lactam activity concentration dependent?
no
is anginosus streptococci sensitive to pen v and amoxicillin?
yes!
is the choice of antibiotics important in treating dental abscess?
all equally as effective once drained,
local surgical interventions more important
colonization resistance def
Protection against growth of opportunistic microorganism like c diff and candida
antimicrobial stewardship
limiting unintended consequences of antimicrobial use
does antibiotics cure toothache
no
first line therapy in treating dental abscess
pen v
recommended dosage for pen v
500mg
6h
5 days
does giving a larger dose improve success
larger doses less frequently improves success
effect of antibiotic is dependent on what for success
concentration and time
**but rmb that pen v and amoxicillin is not dependent on concentration, only time above the MIC
does increasing dose increase efficacy ?
increasing dose to achieve higher concentration does NOT increase efficacy once above MIC
peak conc of amox and pen v
peak conc amox is 7.5ug/ml
peak conc pen v is 4ug/ml
