intro to antibiotic Flashcards
—- substance that, in small amounts, kills or inhibits the growth of bacteria
—- substance that, in small amounts, kills or inhibits
the growth of micro-organisms (includes antibiotics, antivirals, antifungals)
antibiotic
anti microbial
why do we prescribe antimicrobials:
1- to — infection ( prophlyxis) as:
a) — prophylaxis – clean-implant, contaminated surgical procedures
b) — prophylaxis – chemotherapy, transplant immunosuppression, post splenectomy
2- to — suspected infection
a) Start smart by – therapy: antibiotic treatment before specific culture results reported or confirmed
b) Then focus by — therapy: Treatment focused to known pathogen & its susceptibility
3- — reasons which is less common as anti-inflammatory properties (azithromycin), prokinetic properties(erythromycin)
prevent
surgical
medical
treat
empiric
targeted
non infection
the ideal antimicrobial drug ( there’s no perfect drug ) :
1. selective — : against pathogen but not host
2. — rather than –
3. Favorable — : reach target site in body with effective concentration (good — )
4. Spectrum: – if required, or — as required
5. Lack of —
– High Therapeutic Index: difference between effective & toxic dose is –
6. Little — developing – can withstand bacterial resistance mechanisms
toxicity
bactericidal
bacterstatic
pharmokinetics
bioavailability
broad
narrow
side effects
high
little resistance
antibacterials can be classified by:
- Anti-bacterial family
- Mechanism of action (See relevant
lecture) - Spectrum: broad or narrow-
spectrum - Activity: bactericidal or
bacteriostatic
1- antibiotic families as
: * b-lactams
* Glycopeptides
* Aminoglycosides
* Quinolones
* Macrolides
* Tetracyclines
2- antimicrobial spectrum can be:
— anti-bacterials active against a limited range of bacteria e.g. —
—- anti-bacterials active against a wide range of different bacteria e.g.
3- —- antibiotics prevents bacteria from multiplying while — antibiotics kill the bacteria
narrow
benzylpencilin
broad
co-amoxiclav
bacteriostatic
bacterocicidal
1- bactericidal activity:
* The level of antimicrobial activity that – the organism.
* Determined in –
* Minimum bactericidal
concentration (MBC) refers to the – concentration of antibiotic that kills — of the population
2- bacteriostatic :
* The level of antimicrobial
activity that inhibits the — of an organism.
* Determined in – .
* Minimum inhibitory
concentration (MIC) refers to the – concentration that inhibits the growth of the organisms
kills
vitro
lowest
99.9%
growth
vitro
lowest
How do we know which antimicrobial will work against which organism?
1- in — testing:
* Individual bacterium incubated with antimicrobial in lab to determine inhibition of growth
* The bacterium is “susceptible” or “sensitive” if its growth is inhibited by an antibiotic & “resistant” if it
is not
* There are several methods of susceptibility testing
in vitro suspectibility
2- disk diffusion testing ( multiple antibiotics) which is a — test :
- bacteria in broth spread over —
- — disks impregnated with standard amount of antimicrobial
applied to agar (each disk with different antimicrobial)
- — diffuses into the agar & inhibits growth of organism (if — )
- The — the zone of inhibition, the more susceptible the organism
- There are internationally-agreed ‘ —- ’, relating to the diameter of these zones of inhibition classifying ‘resistance’ or ‘susceptibility’ to each agent
qualitative
agar surface
cellulose disks
antimicrobial
susceptible
larger
breakpoints
minimum inhibtory contectration MIC is a — testing:
* The MIC doesn’t always — with how well the antimicrobial works in real life (in vivo)
* Variable concentrations of antibiotic
– in broth or in agar (next slide)
* Concentrations chosen for testing reflect — concentration
* Detects changes in — ; a — test
* Useful for predicting —
– e.g. —- , —
* Determination important in the — of certain
infections e.g. —
quantitive
correlate
tissue
susceptibility
quantitive test
clinical response
s penumomiea n pencilin
management
endocarditis
true or false
broth micodiluation is a gold standard
true
ETEST an agar based quantitive suspectibiltiy test can be used by –
* Utilizes a — strip
–> impregnated with an – concentration of antibiotic
–> a numerical scale corresponds to — concentration
* MIC = where the elliptical zone of clearing intersects with the strip
* A separate strip is needed for each antibiotic
MIC
plastic test
increasing
anitibitoc
MIC by ETEST :
1- solutions of bacteria in – both spread over agar surface
2- Strip with – antimicrobial at – concentrations
applied to agar
3- .Antimicrobial diffuses into
agar & inhibits bacterial
growth
( check slide 21 sooo important for pic )
broth
single
reducing
in automated MIC systems:
* Several commercial systems available
* Conveniently prepared & formatted
microdilution panels, inoculated with
the test bacteria, with instrumentation
& automated reading
* These methods are intended to
reduce — & lengthy preparation –
reduce technical errors
times
molecular testing for antimicrobial resistance:
* Increasing use in recent years
* – results
* Doesn’t tell you if the antimicrobial will inhibit growth of the bacterium
or not…..allows you to —
resistance by detecting a certain –
* e.g. – tests available for genes for multi-drug-resistant tuberculosis (MDR-TB),(MRSA)
rapid
allows u to predict
gene
pcr
mechanism of action of anti bacterials :
1- —- Beta lactams (e.g. penicillins, cephalosporins, carbapenems)
Glycopeptides (e.g. vancomycin)
Polymixin (e.g. colistin)
2- — daptomycin
3- —- quinlones , metrandazole
4- —- trimethoprim , sulphonamide
5- —- Aminoglycosides (e.g.
gentamicin) , Tetracyclin
6- — rifampicin
7- —-
—- (e.g. clarithromycin )
— (e.g. clindamycin)
— (e.g. linezolid)
cell wall inhibitors
calcium channels
dna sythesis
antimetabolites
protein sythesis (30s)
protein sythesis ( 50s)
macrolide
lincosamides
oxazolidioones
b lactams antitonic defined by the presence of b lacram ring and the four types are: — , — , — , —
* Standard penicillin
e.g. benzylpenicillin/Penicillin G- (intravenous only) or acid-
stable Penicillin V (used orally)
Use examples: —-
* Anti-staphylococcal
e.g.— not inhibited by —
* Aminopenicillins
Contain an amino group. Not effective against —
but enhanced activity against – infections
e.g. ampicillin, amoxicillin
Use examples: H. influenza, E. coli, Salmonella & Shigella
* Anti-pseudomonal penicillins
Similar to aminopenicillins (no Staphylococci activity) with enhanced activity against Pseudomonas aeruginosa e.g.
piperacillin, a — ; and ticarcillin, a —
Penicillins( first used in treatment of human infection ) , Cephalosporins, Carbapenems, Monobactams
streptococci , meiignicocci , syphlilitis
flucloxicillin
beta lactamase ( resistant to degradation )
staphylococci
gram -ve
ureidopencilin
carboxypenciliin
examples of pencilin antibiotics:
1- benzylpeniclin which is — penicillin
- — spectrum used for :
- limited for — as :
- used for treatment of :
2- ampicillin , amoxilin are–
- — sprecum including —- but resistance increasing in – , —
- not effective against —
- good oral absorption
- used treatment of:
standard
narrow
Gram positive cocci e.g.
Streptococci & Staphylococci.
Gram negative cover e.g. Neisseria spp. (Gram negative cocci)
meningitis, endocarditis, cellulitis
broad
Gram negative bacilli
e coli h influenza
staphylococci
respiratory tract infection, urinary tract infection (only as targeted therapy for UTI because of resistance)
examples of cephalosporins
1st generation cephalosporins
* Good anti-Gram – activity
* Orally active e.g. cephalexin
* — & — infections (e.g. Streptococci, Staphylococci, E. coli)
2nd generation cephalosporins
* Retain anti-Gram positive activity with anti-Gram negative activity
* Oral & IV, e.g. cefuroxime for — prophylaxis
* Activity against H. influenzae and B. fragilis
3rd generation cephalosporins
* Good anti-Gram— activity, less anti-Gram – activity
* Most IV, e.g. cefotaxime, to treat —
positive
respiratory n urinary infections
surgical
-ve
+ve
meningitis
- Not inactivated by staphylococcal b- lactamase
- Narrow spectrum
- Used for susceptible S. aureus infections – not
MRSA
known as
fluloxacillin ( PENICILLINASE-STABLE PENICILLINS)
carbpanes are example of b lactams :
* Very – spectrum – active against Gram-negative & Gram- positive organisms
* Stable to — (active against ESBL producers)
* Meropenem, ertapenem
* Some cross reactivity in
penicillin allergy but less than —
* Critically important antimicrobial
broad
beta lactamase
cephalosporins
- Active against Gram-negative
organisms only – no activity
against Gram-positive organisms
or anaerobes - Suitable for patients with
penicillin allergy
azteronam ( exmaple of monobactam which is a b lactam )
glycopeptides are used for gram – only and used to treat — by — and treats — by —
main examples of glycopeptide are:
postive
mrsa iv NOT oral
C. difficile oral NOT iv
vancomycin , teicoplannin
— as gentamicin
* IV only - not absorbed orally
* Active against Gram-negative bacilli, S. aureus,
mycobacteria, brucella – inactive against
anaerobes
* In combination to treat — infection (mixed flora) / infective — (synergy)
* Must monitor blood levels to minimise —
ahminoglycosides
intra abdominal
endocarditis
toxicity ( nerphtoxic , ototoxic for hearing n balance )
clarithromycin, erythromycin &
azithromycin are examples of:
they are — but – in some species
used for — “atypical” pathogens (e.g. Mycoplasma spp., Coxiella spp., Chlamydia spp.);
b-lactams ineffective
– Mycoplasma spp. have no cell wall
– Coxiella/ Chlamydia spp. replicate intracellularly
* Associated with prolonged QTc– avoid if history of —
macrolide
bacteriostatic
bactericidal
respiratory infection
arthrymia
quinlones inhibit —
* Ciprofloxacin, levofloxacin, moxifloxacin, etc.
* Good oral bioavailability
* Mainly against Gram – bacilli
* Urinary & intra-abdominal infections, but not – choice agents
* Newer quinolones e.g. levofloxacin also have anti-Gram positive activity & used to treat respiratory infections
* Significant side-effect profile, e.g. —
dna gyrase
-ve
first
bone/joints
tetracycline inhibits — subunit as doxyclincs
- used to treat infections caused by Chlamydia, Rickettsia, Coxiella,
Mycoplasma
- caused growing teeth to become —
- Contraindicated in children & pregnant women
30s ribosomal
yellow brown
— is an Anti-anaerobic & anti-protozoal
* For known or suspected anaerobic
infections, e.g. intra-abdominal infections
* Bacteroides spp., Fusobacterium spp. &
Clostridium spp.
* In combination for prophylaxis in bowel
surgery & to treat abdominal infection
* Inactive against staphylococci & aerobic
GNBs such as E. coli
metronidazole
summary :
- b lactams n glycopeptides inhibits — synthesis and have — activity
- FQ as ciprofloxacin is inhibitor of — with — activity
- amino glycoside inhibits — with — and macrolide inhibits — without —
- tetracycline inhibit —- without —
cell wall
bactericidal
dna replciation
bactericidal
protein sytheis
bactericidal
protein sytheuss
noooo bactericidal
protein sythesis
not bactericidal
reasons to use more than 1 antimicrobial :
1. To broaden the antimicrobial spectrum for– therapy, e.g. anti-bacterial & anti-fungal for abdominal infection
2. To prevent the emergence of —
organisms during therapy, e.g. four drugs initially for TB
3. To achieve a – killing effect, e.g. bacterial endocarditis.
empiric
resistant
synergic
1- If two antimicrobials given together achieve a better effect than the sum of their individual effects, they are –
2- If two antimicrobials are
given together & one
interferes with the action of
the other, they are —
synergic
antagonistic
when should we NOT use anti bacterials :
1. Infections not caused by
bacteria e.g. —
2. To “treat” – i.e. if
bacteria grow from specimens, e.g. surgical site (wound) but no clinical
evidence of infection
3. “Prophylaxis” when not – e.g. after a surgical procedure (too late)
viral infection
colonisation
indicated
principles when choosing anti microbial :
1- — assessment : what’s likely site of infection
2- — where do we think the patient got the infection is it by community/hopsitals or by local factors as antibiotic resistance rates
3- previous including from gp n other hospitals
4- previous — result
5- history of –
clinical
acquisition
antibiotic
microbiology
allergy
factors to consider after starting anti microbial :
1.Revision of — when culture results available – empiric to targeted
2. — of therapy, e.g. six weeks for acuteosteomyelitis, 3-5 days for cystitis
antimicrobial therapy
duration
5 prescribing options at 24-48 hours:
1. — antimicrobial(s)
– no evidence of bacterial infection, or infection resolved
2. – from intravenous to oral antimicrobial(s)
– if patient meets criteria for oral switch
3. — antimicrobial(s)
– narrower spectrum, if possible
– broader spectrum, if indicated
4. – current antimicrobial(s)
– review again after further 24 hours
5. Outpatient parenteral antimicrobial therapy
(OPAT)
– consult with local OPAT team
stop
switch
change
continue
start – :
1. Start antibiotics only if there is clinical evidence of bacterial infection
– Check local antibiotic guidelines
2. Obtain appropriate cultures beforehand
3. When writing up the prescription,
specify the Route, Indication & Duration
4. Give antibiotics within 4h of prescription
– within 1 hour for sepsis
focus :
At 24-48 hours after
starting antibiotics,
make an Antimicrobial
Prescribing Decision:
– Review the clinical
diagnosis
– Review laboratory/
radiology results
– Choose one of the
five prescribing
decision options
( aka the stop switch etc)
smart
