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Flashcards in miscellaneous abx Deck (42):

Vancomycin (Vancocin) administration/metabolism

IV (poor oral absorption)
-widely distributed and does penetrate the CSF when the meninges are inflamed
-90% of vancomycin is eliminated by renal excretion, adjust dose with renal failure


Vancomycin (Vancocin) MOA

inhibits bacterial cell wall synthesis by binding to the D- alanyl-D-alanine portion of the peptidoglycan pentapeptide, bactericidal


how does resistance to Vancomycin develop?

bacterial enzymes that can induce alterations in the cell wall precursors so that vancomycin can’t bind as well
i.e. Vancomycin resistant enterococci replace D-alanyl-D- alanine with D-alanyl-D lactate or D-alanyl-D-serine


vanco spectrum

MRSA, MSSA, S. epidermidis, Streptococci, Corynebacterium diptheria, Clostridium spp. (the only anaerobe effective against)

NOT against G-s


vanco uses

serious staph infections
G+ infections in pts allergic to PCNs/cephs (tx w. aminoglycoside for synergism)
C. diff colitis (oral vanco)
staph meningitis in a PCN-allergic pt, if caused by S. pneumo include with a 3rd gen ceph


vanco SEs

-Ototoxicity and Nephrotoxicity: (rare)m ore common when given in combo with another ototoxic abx (i.e. amino glycoside)
-“Red man” or “Red Neck” syndrome – If vancomycin is infused too rapidly
is can cause flushing of the face, neck and torso due to histamine release.
minor: Injection site irritation, and chills and fever


Clindamycin (Cleocin)

-oral and parental, distributed widely EXCEPT does not penetrate well into the CNS even with inflammation of the meninges
-does have good abscess penetration


clindamycin MOA: similar to ??

imilar to erythromycin and chloramphenicol – binds to *50 S* ribosomal subunit and inhibits bacterial protein synthesis; bacteriostatic


resistance to clindamycin develops how?

-Mutations in the 50 S bacterial ribosomal subunit which prevents Clindamycin binding
-Modification of the binding site by the enzyme methylase that prevent clindamycin binding
-Enzymatic inactivation of clindamycin
-Bac resistant to clindamycin are usually resistant to
erythromycin. (similar mech)


clindamycin spectrum

most Staph aureus strains (has activity against some community acquired MRSA), Strept. Pneumoniae, but enterococci are resistant.
-NOT useful against G- AEROBES
-is active against G- and G+ anaerobes (B. fragilis and C. perfringens)


clindamycin uses

-anaerobic infections (abscesses)- NOT brain abscesses
-used in combo w. amino glycoside/ceph to tx deep wounds
-*ppx against endocarditis in valvular heart dis. pts who are having dental procedures
-alternative to PCN/ceph in allergic pts
-PCP and toxoplasma gondii (+pyrimethamine) in AIDS pt


clindamycin SEs

*C. diff-induced Pseudomembranous colitis* (tx w. oral Vancomycin, Metronidazole, and Cholestyramine (not orally w. vanco: antagonistic effect)


Nitrofurantoin (Furadantin, Macrobid, Macrodantin)

-Rapidly absorbed after oral admin, metabolized/excreted by glomerular filtration and tubular secretion (40% of free drug is found in the urine), often so quickly drug effects not seen!
-don't use in renal failure
-reduced forms can damage DNA, both bactericidal and static
-admin w. acidifying agent (more active @ pH


nitrofurantoin spectrum?
resistance development??

-G+ and G- bac
-NOT effective against Pseudomonas and many Proteus strains (resistant)
-Bac resistance takes a long time to develop and there is no cross resistance with other abx


nitrofurantoin uses

-tx UTIS and for ppx for recurrent UTIs (used of UTIs caused by E. coli resistant to TMP-SMX and FQs)


nitrofurantoin SEs

*GI: anorexia, N/V
*hemolytic anemia (rare, seen in pts w. G6PD deficiency)
-neurological, pulmonary fibrosis, chronic active hepatitis, allergic reactions
-contraindicated in renal failure, caution w. preggos


Polymyxin B sulfate (generic) MOA

what does resistance involve?

interacts with cell membrane phospholipids, and disrupts cell membrane perm., and causing leakage of intracellular components, bactericidal
-Resistance may involve inability of the polymyxins to pass through the cell wall.


polymyxin B spectrum

only susceptible G- bac (e.g. Enterobacter aerogenes, E. coli, Klebsiella pneumonia, H. influenzae, Acinetobacter baumannii, Pseudomonas aeuriginosa)


polymyxin B uses

topical treatment of Infections of the eye, skin, mucous membranes, ear, wounds, burns (G-s)
-used IV as alternative for drug-resistant resp. tract infections (HAP, HCAP, VAP) caused by DR-G-
-septicemia, UTIs (IV, IM)
-meningitis (typ. in combo)
-irrigate the bladder to prevent bacteriuria/bacteremia assoc. w. indwelling catheters (used w. neomycin)


polymyxin B SEs (both dose-dependent) (why polymyxins are reserved as alternate tx)

*Neurotoxicity*: (facial flushing; dizziness that may progress to ataxia; mental confusion; nystagmus; muscle weakness; drowsiness; giddiness; peripheral paresthesia, visual disturbances, slurred speech, coma and seizures)
*Nephrotoxicity*: (albuminuria, proteinuria, cylindruria, azotemia, inc. in serum creatinine (dec. in creatinine clearance), acute tubular necrosis, oliguria, hematuria, leukocyturia, and excessive excretion of e-lytes)


Metronidazole (Flagyl)

-oral, IV, rectal, topical (vag)
-widely distributed, including the CNS and brain abscesses
-crosses the placenta and appears in breast milk
-metabolized in the liver and exreted by the kidneys


metronidazole MOA

reduction of the drug to compounds that bind to intracellular macromolecules, bactericidal


metronidazole spectrum

-*active against clindamycin-resistant B. fragilis (*drug of choice in adults*)
-bactericidal activity against Anaerobes (including bacteriodes fragilis)
-NOT v. effective against Not very effective against G+ and G- AEROBES


metronidazole uses

-Anaerobic infections (soft tissue infection, intra-abdominal infections, pelvic infections, brain abscesses).
-C. diff Pseudomembranous colitis
-PUD caused by H. pylori (Triple therapy)


metronidazole SEs

-Carcinogenic potential, don’t use in pregnancy or in women during breast
-Disulfiram-like interaction with alcohol.



-opthalmic and dermatologic ointments
-not used much parenterally because of nephrotoxicity


Bacitracin MOA

-inhibits cell wall formation, interferes with the lipid that carries peptidoglycan subunits to the site of cell wall formation.
-No cross resistance with other antimicrobials.


Bacitracin spectrum

-similar spec. to PCN: G+ cocci and bacilli
-G-s such as Neisseria, H. influenzae; and the spirochete Treponema palladium


Bacitracin uses

-topically for open wounds to eradicate mixed microorgs
-eye infections (e.g. conjunctivitis)
(may be used in combo, i.e.: bacitracin + polymyxin + neomycin)


bacitracin SEs

Serious nephrotoxicity from parenteral use; renal failure due to tubular and glomerular necrosis.
-Hypersensitivity reactions from topical use are rare.


Quinupristin/Dalfopristin (Synercid) used for ??

IV tx of bacteremia and other life threatening infections caused by vancomycin-resistant Enterococcus faecium, and complicated skin infections caused by S. aureus and Strep pyogenes (when resistant to other abx, or contraindicated due to allergy)
-Enterococcus faecium, MRSA/MSSA, S. epidermidis, PCN-susc. and resistant S. pneumo


Quinupristin/Dalfopristin (Synercid) MOA

(similar to the macrolide)
-inhibits bac protein synthesis by binding to the *50 S* ribosomal subunit.
-The two drugs bind to different sites on the 50 S ribosome and prevent the extrusion of new proteins which results in bacterial cell death.


Quinupristin/Dalfopristin (Synercid) resistance occurs via ??

Modification of the quinupristin binding site on the 50S ribosomal subunit, enzymatic destruction of dalfopristin or efflux


Quinupristin/Dalfopristin SEs

-Erythema, pain, itching and burning at the site of infusion
-inhibit CYP3A4


Linezolid (Zyvox)

Oral admin, Parenteral

Bacterial protein synthesis inhibitor by binding to the 50S bacterial ribosomal
subunit and prevents formation of the 70S translational initiation complex; Bactericidal for Streptococci with bacteriostatic activity against many other bac


Linezolid Resistance in ?? and ?? is caused by ??

enterococci and staphylococci

point mutations in the 23S rRNA of the 50S subunit.


Linezolid spectrum/uses

-Vanco-resistant Enterococcus facacium
-Nosocomial pneumonia or CAP due to S. aureus
or PCN-susc. Strep pneumo
-Skin/skin structure infections: MRSA and Strep Pyogenes


Linezolid SEs

*reversible inhibitor of monoamine oxidase* (co-
admin with tyramine rich foods can result in HTN)
-oral formulation contains phenylalanine, avoid in PKUs
-C. diff-assoc. colitis


Daptomycin (Cubicin)

-poor oral absorption, admin IV
-avoid IM due to musc. tox
-80% excreted in the urine, adjust dose if creatinine clearance is below 30 mL/min


Daptomycin (Cubicin) MOA

concentration-dependent killing effect by binding to and depolarizing bacterial cell membranes which leads to loss of membrane potential, postassium efflux, and cell death.
-no known resistance mechs


Daptomycin spectrum/uses

-Bactericidal for aerobic, facultative and anaerobic G+ bac
-Complicated skin/skin structure infections caused by MRSA/MSSA, hemolytic streptococci, and vanco-susc. E. faecalis


Daptomycin SEs

Skeletal muscle damage/Myopathy
Peripheral neuoropathy