Microbiology: Antibiotic Resistance Flashcards
How do patients come to acquire a resistant pathogen?
-by transmitting the bacteria that already have the resistance gene in place
-by having their bacteria acquire a gene that codes for resistance
(the first is more common)
Define antimicrobial
A substance that inhibits or kills microbes
What is an antibiotic
a type of antimicrobial synthesized by a living microorganism, usually a fungus
How are most antimicrobials administered>
by intravenous route
all antimicrobials are what? (hint: mechanisms of action)
bacteriostatic or fungostatic
bacteriocidal or fungicidal
differentiate between cidal and static
cidal kills 99%> while static kills 90-99%
static agents ___ growth
arrest
Whether a drug exhibits cidal or static depends on what?
the concentration of drug an organism is exposed to or the mechanism by which a drug inhibits microbial growth
list drugs that act on microorganisms by inhibiting cell wall synthesis
-B lactams
-glycopeptides
-echinocandins
list cell membrane inhibitors
-daptomycin
-colithimethate
-imidazole antifungal agents
list drugs that inhibt protein synthesis in the bacterial ribosome
-aminoglycosides
-macrolides
-tetracyclines
-oxazolidanones
which drugs inhibit nucleic acid synthesis
-fluroquinalones
-the antifungal fluccytosine
-antivirals (acylcovir)
Which drugs inhibit microbial growth by acting on the metabolic pathway?
-ethambutol
-trimethoprime sulfamthoxadole
the effectiveness of antimicrobials is optimized by understanding what?
the minimal inhibitory concentration
define minimal inhibitory concentration
the lowest concentration of a drug that can still inhibit microbial growth
define half-life
quantifies how long the body takes to metabolize half of a drug
What is concentration dependent activity?
achieving a higher concentration in the blood over a short time is most effective
what is one characteristic of concentration dependent drugs?
they usually have a prolonged antibiotic effect (they continue to supress microbial growth long after drug concentration has declined). The goal is to maximize serum or tissue drug concentration
Which drugs are concentration dependent?
aminoclycosides and fluroquinolines
Which drugs depending on maintaining levels above the MIC?
B-lactams
Define time-dependent drugs
lower doses at increased frequency over time
What are the two major side effects of drug use?
allergic and gastrointestinal reactions
True or false. Virtually all antimicrobials inhibit growth in the large intestine
True
How are antimicrobials classified?
based on the broad category of microorganisms against which the drug possesses activity (i.e. antibacterial, antiviral, antifungal, antiparasitic)
What are some antibacterials
-penicillin
-cephlasporins
-monobactams and carbapenems
-fluroquinalones
-macrolides, lincosamides, streptogramins
-aminoglycocides
-vancomycin
The drug of choice for group A streptococcal pharyngitis is
Natural penicillins
Penicillin G lacks activity against what?
gram negative bacteria. Aminopenicillins were developed because of this
What are 3 indications for antimicrobial use?
- Pathogen-directed
- Empirical
- Prophylactic
