Antimicrobials Flashcards
overall, what are the 3 main types of antibacterial antibiotics?
- bacterial cell wall synthesis inhibitors
- bacterial protein synthesis inhibitors
- nucleic acid synthesis inhibitor
what are bacterial cell wall synthesis inhibitors usually used for?
those bacteria that are gram-stainable; cocci and rods
what are the 2 classes of bacterial cell wall inhibitors?
- beta lactams (penicillin, special penicillin, cephalosporins, carbapenem and monobactams)
- glycopeptide (vancomycin)
what is the general MOA of bacterial cell wall inhibitors?
binds to enzyme transpeptidase and prevents cross linking = weakened cell wall = lyse
*only works in actively dividing bacteria
what is the general side effect of bacterial cell wall inhibitors?
TOXICITY TO ALL:
- hepatotoxicity and neurotoxicity
- some extent of renal toxicity too
OTHERS:
- c-diff associated colitis
- SJS, Toxic epidermal necrosis
how is strep pneumo resistance conferred?
mutations to penicillin-binding receptors = not susceptible to beta lactams anymore
how is staph resistance conferred?
activation of mecA gene = production of beta lactamases = not susceptible to beta lactams anymore
what are examples of penicillin?
- benzylpenicillin
- cloxacillin
- amoxicillin
- piperacillin
what does benzylpenicillin target?
- gram pos and neg cocci
- some gram pos rods
- spiral bacteria: treponema pallidum
NOTE: usually for streps
what does cloxacillin target?
for MRSA
what does amoxicillin target?
same as benzylpenicillin (gram pos and neg cocci + gram pos rods)
additional: gram neg rod (listeria)
what does piperacillin target?
pseudomonas aeruginosa (who usually can also be targeted by the same tx for E. coli)
what are the examples of special penicillins?
co-amoxiclav (amoxicillin + clavulanate)
what does coamoxiclav target?
generally: gram neg and pos bacteria
but more so for bacteria causing LRTI and UTI
e.g. burkholderia pseudomallei, E. coli
what are the examples of cephalosporins?
1st/2nd gen
3rd gen: ceftriaxone, ceftazidime, cefixime
4th gen: cefepime
5th gen: ceftaroline
what does ceftriaxone target?
generally:
- gram pos and neg cocci
- gram pos and neg rods
what does cefapime target?
same as 3rd gen but extra coverage of pseudomonas
what does ceftaroline target?
widest coverage, including MRSA
what are the examples of carbapenems?
imipenem
what does imipenem target?
essentially same as the above but is only used in really really serious infections
what are the examples of monobactams?
aztreonam
what does aztreonam target?
alternative for penicillin allergic patients
but only targets gram neg cocci and rods
what are the examples of glycopeptides?
vancomycin
what does vancomycin target?
mostly gram positive cocci and rods
especially for MRSA and CDAC
note about vancomycin upon first administration
may cause red man syndrome
moving on from bacterial cell wall synthesis inhibitors, let’s talk about bacterial protein synthesis inhibitors - what are the diff classes of them?
30S inhibitors:
Tetracyclines
Aminoglycosides
Glycylcycline
50S inhibitors:
Macrolides
Clindamycin
Linezolid
what is the general MOA of protein synthesis inhibitors?
inhibits 30S/50S units of ribosomes and prevent binding of tRNA
what are the general side effects of protein synthesis inhibitors?
TOXICITY:
- hepatotoxicity
- phytotoxicity for TA
- ototoxicity for G + MCL
OTHERS:
- rare to have SJS or other hypersensitivity reactions
- macrolides have many DDI’s
- tetracyclines not used in young and pregnant
what are the examples of tetracyclines?
tetracycline and doxycycline
what does tetracycline and doxycycline target?
broad spectrum gram neg and pos bacterial (e.g. burkholderia pseudomallei - DCCC)
but more for intracellular obligate parasites (rickettsia)
what are the examples of aminoglycosides?
gentamicin
streptomycin
tobramycin
what do aminoglycosides target?
gram neg aerobic rods (e.g. listeria, corynebacterium, bacillus)
but honestly is not very commonly used
important! what are the 6 NO’s of aminoglycosides?
- NO protein synthesis
- only for gram Negative Organisms
- administered Not Orally (by IV instead)
- NO pregnancy
- NO csf penetration
- Nephrotoxicity and Ototoxicity
what are the examples of gylcylcyclines?
tigecycline
what does tigecycline target?
MRSA (but we usually use vancomycin for this)
what are the examples of macrolides?
erythromycin
clarithromycin
azithromycin
what does erythromycin target?
alternative to penicillin for patients allergic to penicillin (similar to aztreonam)
used specifically for campylobacter jejuni
what does clarithromycin target?
same as erythromycin but has additional bacterial targets
used specifically for h. pylori
what does azithromycin target?
same as erythromycin but more specific to gram neg bacterial related to respiratory infections
what does clindamycin target?
anaerobic bacteria + gram pos cocci
not very commonly used
what does linezolid target?
all the resistant gram positive bacteria e.g. MRSA, penicillin-resistant strep, cephalosporin-resistant enterococcus
moving on from cell wall synthesis and protein synthesis inhibitors, let’s talk about nucleic acid inhibitors - what are the different classes?
- fluoroquinolones
- folic acid inhibitor
- urinary antiseptic
what is an example of fluoroquinolone and its MOA?
ciprofloxacin/levofloxacin/moxifloxacin
inhibits dna gyrase in gram negs and topoisomerase 4 in gram pos = no making of supercoils
what is the side effects of fluoroquinolones?
TOXICITY:
1. phytotoxicity
OTHERS:
- GI and CNS disturbance
- cannot be used in pregnant and young
- peripheral neuropathy
what does ciprofloxacin target?
mostly enterobacteriaceae and pseudomonads
what does levofloxacin and moxifloxacin target?
known as respiratory quinolones
used as second line therapy for TB
what are examples of folic acid synthesis inhibitors?
cotrimox, sulfonamides, trimethoprim
what is the MOA of folic acid synthesis inhibitors?
binds to enzyme that synthesises folate acid = no purine or pyramiding synthesis
what are the general side effects of folic acid synthesis inhibitors?
TOXICITY:
1. nephrotoxicity
OTHERS:
- cannot give to G6PD deficiency people as it would include hemotopoietic disturbances
what does sulfonamide target?
enterobacteriaceae
what does trimethoprim target?
same as sulphonamide but stronger
what is cotrimox? (aka bactrim)
combination of trimethoprim and sulfamethoxazole
what does cotrimox target?
UTI-causing bacteria, respiratory tract bacteria and pneumocystis jiroveci
what are examples of urinary antiseptics?
nitrofurantoin
what is the MOA of urinary antiseptics?
blocks enzymes involved in protein synthesis and DNA
what are the general side effects of urinary antiseptics?
TOXICITY:
1. pulmonary toxicity in elderly and babies < 1 month
OTHERS:
- CNS and GI disturbances
- haemolytic anemia in G6PD deficient patients (like folic acid synthesis inhibitor)
what does nitrofurantoin target?
only E. coli
moving on from anti-bacterials, let’s talk about anti-fungals - what are the 3 most important anti-fungals?
- amphotericin B
- 5-flucytosine
- azoles
- nystatin
what is the general MOA of anti-fungals?
similar to cell wall synthesis inhibitors; in which it binds to ergosterol in plasma membrane of fungal cells to form pores = lysis
what are the general side effects of anti-fungals?
TOXICITY:
1. nephrotoxicity
OTHERS:
- hematopoeitic dysfunctions (like folic acid inhibitors and urinary antiseptics)
out of the 4 important anti-fungals, which target systemic infections?
the first 3 - amphotericin b, 5-flucytosine and azoles
what is amphotericin b used for?
used to treat candida, histoplasma, aspergillus and cryptococcus
what is 5-flucytosine used for?
used in combination with amphotericin b
why? because it has high risk of resistance if used as monotherapy
what are azoles used for?
same as amphotericin b
can azoles be used easily with other drugs?
no as it has many DDI’s (like macrolides)
lastly, let’s talk about anti-protozoal drugs - what is the most important type?
metronidazole
what are the general side effects of anti-protozoal?
TOXICITY:
1. neurotoxicity
OTHERS:
- bitter metallic taste
- GI discomfort
what is metronidazole used for?
- giardia/entamoeba
- and also c. diff
what anti-bacterials are safe to use in pregnancy?
- beta lactams (cell wall synthesis)
- macrolides (50S protein synthesis)
- clindamycin (50S protein synthesis)
