Antimicrobial Drug Characterisitcs Flashcards
1
Q
Beta lactams and aminoglycosides are incompatible ______
A
In vitro
- clinicians stagger animnoglycoside and penicillin dosings to avoid high in vivo concentrations
2
Q
How do beta lactams inhibit cell wall synthesis?
A
Bind to penicillin binding proteins to prevent cross-linkage of peptidoglycan cell wall
3
Q
How does the cidal action of beta lactams occur?
A
Osmotic imbalance between hypertonic bacterial cytoplasm and host isotonic environment
- -> protoplasts bulge thru cell wall until cell bursts
- -> if bacteria are in an environment isotonic to their cytoplasm, a static action occurs
4
Q
________ decreases the activity of beta lactams
A
Purulent debris
5
Q
What are the 3 mechanisms of beta lactam resistance?
A
- degradation by bacterial enzymes
- penicillin binding site alteration
- reduced penetration (seen in gram neg structure = impaired crypticity)
6
Q
What allows passage of resistance between species of bacteria and between genera?
A
Plasmids (between species) and transposons (between genera)
7
Q
Crystalline penicillin G
A
IV, IM, SQ
- rapid high concentrations
- short duration of plasma concentrations
8
Q
Procaine penicillin G
A
IM, SQ
- flip flop kinetics
- lower concentrations, but prolonged duration compared to crystalline pen-G
9
Q
Benzathene penicillin G
A
IM
- flip flop kinetics
- extremely low concentrations with prolonged duration
- little benefit in vet med
- increases residue concerns in food animals
10
Q
Penicillin G adverse reactions
A
Primary adverse reactions are allergic
- due to degradation product penicilloic acid
- some toxicity associated with salt (potassium pen G) or ester (procaine)
11
Q
What animals should not be given beta lactams?
A
Guinea pigs, hamsters, rabbits
- due to hind gut floral disruption
12
Q
Penicillinase resistant penicillins
A
Similar to pen G in structure, but not inactivated by penicillinase
- oxacillin or cefoxitin are standard for testing bacteria against drugs of this group due to their better storage stability and reliability
13
Q
Which penicillinase-resistant penicillin is available for intramammary infusion in dairy cows?
A
Cloxacillin
14
Q
Why do broad spec penicillins have better penetration of gram neg bacteria?
A
Increased crypticity
15
Q
Which broad spec penicillin is used as an intramammary infusion?
A
Hetacillin
16
Q
Which broad spec is absorbed twice as well orally in dogs and cats?
A
Amoxicillin over amipicillin
17
Q
Qualitatively compare ampicillin sodium vs ampicillin trihydrate injections
A
Sodium ampicillin (veterinary) is injectable given by all parenteral routes
- rapid absorption and elimination (every 8 hrs)
- repository ampicillin trihydrate formulation may not be able to reach therapeutic concentrations unless organism is very susceptible (low concentration, prolonged duration)
18
Q
Ampi and amoxicillin are not effective against ______, even at higher extra label doses
A
Enteric gram-negative bacteria
- especially true of trihydrate injectable suspensions
19
Q
Adverse reactions of broad spec penicillins
A
- large doses of ampicillin causes diarrhea in horses via entry into the bile (type B)
- disrupts flora if given orally to ruminants (okay by injection)
- trihydrate form too irritating for use in horses –> sterile abscesses
20
Q
Extended spectrum penicillins are also called _________
A
Anti-pseudomonal
- increased crypticity, but able to bind to altered PBP
21
Q
Potentiated penicillins
A
Have a penicillinase inhibitor added to the formulation to release penicillin
- penicillinase inhibitor has no antibacterial properties
- clavulanic acid and sulbactam
- looses stability once hydrated, keep oral tabs in foil
- only works in bacteria resistant via penicillinase
22
Q
______ are susceptible to potentiated penicillin formulations
A
Bacteroides fragilis
23
Q
1st generation cephalosporins
A
Similar to narrow-spec penicillins except:
- not affected by penicillinase = good Staph activity, used in skin and bone infections!!!
- not reliable against obligate anaerobic bacteria
24
Q
How does cefazolin differ from other 1st generation cephalosporins?
A
Is the only injectable 1st gen!!
- better activity against E. coli than other 1st gens
25
Which 1st gen cephalosporins are approved for intramammary infusion for dairy cows?
Cephapirin
26
Which cephalosporins have 4 quadrant coverage?
Cefoxitin and cefotetan
| - have good anaerobic activity, including B. fragilis
27
Which cpehalosporin family has a public health concern?
3rd generation
| - resistance due to extended spectrum beta lactamases is of increasing public health concern
28
Which is the only cephalosporin effective against pseudomonas?
Ceftazidime
29
Which cephalosporin is the drug of choice in treating bacterial meningitis?
3rd generation cephalosporins
| - ceftriaxone (expensive) or ceftazidime (more common)
30
Which cephalosporin family is not effective against carbapenem-resistant enterobacteriaceae?
4th gen, 5th gen, potentiated cephalosporins
31
Naxcel
Ceftiofur sodium
- comes as a powder, requiring reconstitution
- 4 day withdrawal for slaughter, no milk withdrawal!
- cattle: BRDC, foot rot
- swine, sheep: pneumonia
- horses: respiratory infections
- dogs: UTI
32
What is the only systemic antibiotic with no milk withdrawal?
Naxcel
33
Excenel
Ceftiofur HCL
- shelf stable formulation
- swine: respiratory disease, 4 day slaughter withdrawal
- cattle: BRDC, foot rot, acute metritis
- 2 day slaughter withdrawal, no milk withdrawal
- -> exception: spectramast intramammary infusion does have a milk withdrawal of 72 hrs (lactating) or 30 day (dry)
34
Excede
Ceftiofur crystalline free acid (pure ceftiofur)
- approved for cattle for 1 or 2 doses
- approved in swine for respiratory disease (IM injection in the neck)
- approved in horses for lower respiratory infections --> 2 IM injections 4 days apart
35
What is the drug of choice for skin and soft tissue infections due to staph, strep, e. coli, pasterurella, and proteus?
Cefpodoxime proxetil
36
What is the drug of choice for SSTI due to staph, strep, and pasturella and for UTI's due to E. coli?
Cefovecin
- injection once every 7-14 days for 2 injections
- long half life due to protein binding
37
Monobactam spectrum is limited to
Aerobic gram-neg bacilli
| - no activity against gram positives or obligate anaerobes
38
Which beta lactam has the broadest spectrum of activity of any antibiotic?
Carbapenems
| - penetrates BBB and is enhanced in inflammation
39
High doses of imipenem can cause _______
Seizures
| - nephrotoxicity is also seen due to reduction of active drug that reaches the urine, and the metabolite is nephrotoxic
40
Does meropenem cause nephrotoxicity or seizures?
No
41
Carbapenem-resistant enterobacteriaceae
Enterobacteriaceae resistant to all beta lactams including the carbapenems
- reported in all 50 states (hospital and nursing homes)
- resistant to all other antimicrobials used in medicine
42
CRE resistant mechanisms
- carbapenemases
- decreased crypticity
- active efflux pump
43
Resistance to aminoglycosides
Due to plasmid-controlled aminoglycoside degradation enzymes in periplasmic space of gram neg bacteria
- also includes: decreased uptake into cell, modification of ribosome
44
Energy dependent phase 1 of aminoglycoside penetration
Oxygen dependent!
- active uptake occurs at cytoplasmic membrane
- process blocked by hyperosmolarity, low pH, and anaerobic conditions
45
Energy dependent phase 2 of aminoglycoside penetration
Disruption of cytoplasmic membrane, ion leakage is noted before cell death
46
Synergy between beta lactams and aminoglycosides
Beta lactams break bacterial cell wall, allowing greater entry of aminoglycoside
47
Neomycin is too toxic to use _______
Parenterally
- used for enteric and topical infection
- is extremely nephrotoxic!!
48
Gentamicin and amikacin are both veterinary approved for ______
Intra-uterine use in horses
49
Gentamicin
Want the trough to be < 2 mcg/ml
- avoid glass containers
- peak drawn at 1 hr, trough at 2 half lives (3-6 hrs)
50
Amikacin
Toxicity: want the trough to be <8 mcg/ml
| - is less potent than gentimycin (is a more effective drug overall)
51
Nonantimicrobial use of gentamicin
Destroys ciliary body when injected into the eye, use to treat glucoma
52
What are the 3 adverse reactions of all aminoglycosides?
- nephrotoxicity
- ototoxicity
- neuromuscular blockade
53
Toxcitiy of aminoglycosides is due to prolonged ________
High trough concentrations
54
What causes nephrotoxicity with aminoglycosides?
Binds covalently to intracellular organelles of proximal renal tubules
- leads to cell damage/death
- covalent binding is responsible for long residues in the kidney tissue
- slaughter withdrawal for extralabel use in cattle at 18 months (is not illegal, but discouraged)
55
How to avoid aminoglycoside nephrotoxicity
- use 24 hr dosing interval
- keep patient well hydrated
- limit other nephrotoxic drugs
- TDM to optimize efficacy (peak) and minimize toxicity (trough) --> esp. in geriatrics!
- IV calcium gluconate
56
How does amikacin differ from gentamicin relative to suscepibility and risk of nephrotoxicity?
Gentamicin
- gram neg % susceptibility in the low 90s
Amikacin
- gram neg % susceptibility in the high 90s
- less nephrotoxin than gentamicin
57
Ways to monitor aminoglycoside therapy to minimize the risk of nephrotoxicity
Increases in serum BUN or creatinine occur too late to be helpful
- perform serial urinalyses and watch for: increasing tubular casts and protein, decreasing SG and increasing glucose
- perform serial urine GGT: creatinine ratios (an increase in more than 3X baseline may indicate imminent toxicity)
58
Local environments decreasing aminoglycoside activity
- acidic environments
- low oxygen tension (required to have oxygen and active transport to get across cell membrane)
- cellular debris
59
Macrolides have greater activity in an ________ environment
Alkaline
| - also maintain activity in purulent debris!
60
Macrolide resistance
Either chromosomal or plasmid mediated
- inactivates enzymes, changes in drug permeability, active drug efflux mechanisms
* *cross resistance to other macrolides and lincosamides is common**
61
What is the drug of choice to treat chlamydia in cats?
Tetracycline
62
How do the newer macrolides differ in their activity versus older macrolides against gram-neg nonenteric pathogens?
Newer macrolides (ex; tilmicosin) have much greater activity against non-enterics
63
All medicated feeds with ________ are VFD
Macrolides
64
What antimicrobial has shown activity against chlamydia and is sometimes used in human medicine for this purpose?
Azithromycin alternative to doxycycline in human genital chlamydiosis
65
Macolides concentrate ______ due to their weak bases
Intracellularly
- achieve high concentrations in macrophages, prostate, and milk
- do NOT cross BBB
66
Macrolide - adverse reactions
Individual agent specific
- injection site tissue rxn for vet formulations (esp older macrolides) resulting in sterile abscesses
- hyperthermia due to anhydrosis may occur in foals receiving macrolides for R. pneumonia
67
Oral form of erythromycin is used in _______
Medicated feed for chickens (they have low stomach acid)
68
Erythromycin is the drug of choice for ________
Campylobacter enteritis in man (azithromycin is better tolerated)
69
Side effects of erythromycin
GI disturbances
- causes intestinal spasms at antibiotic doses = diarrhea in adult horses and vomiting in dogs
- erythromycin gluceptate and erythromycin lactobionate used at low doses as intestinal motility stimulant
70
Main uses of erythromycin
- feed additive in poultry to control mycoplasma respiratory disease
- rare use of human injectable as prokinetic intestinal stimulant
71
Tylosin is used predominantly in ______
Food animals as a feed additive
- cattle: prevent liver abscesses
- swine: mycoplasma pneumonia
- poultry
72
Non antibiotic use of tylosin
Treat large bowel diarrheas in dogs
- unsure of mechanism
- requires compounding tylosin
73
What animals is tylosin NOT used in?
Horses
| - causes colic and death!
74
Tilmicosin is NOT used in _____
Ducks, goats, horses, pigs (injectable form), and man
| CARDIOTOXIC
75
What was the first repository BRDC treatment?
Tilmicosin
- only used in cattle, rabbits, and sheep
- still see tissue irritation, but not as severe
76
What other medication is used to treat foal R. pneumonia?
Gamithromycin
- not widely used
- similar results to azithromycin+rifampin with 40% incidence of colic and lameness
77
Tildipriosin ______ concentrations exceed _______ concentrations
Tissue; plasma
- lung: 28 days
- bronchial fluid: 21 days
78
What medication is replacing erythromycin in foals and small animals due to fewer side effects and 24 hr dosing?
Azithromycin
| - also used to treat bartonellosis in SA
79
Atovaquone + azithromycin
- used to treat cytauxzoonosis in cats (with early intervention!)
- alternative to imidocarb in canine babesiosis
80
Clarithromycin+rifampin is superior in treating ______
Foals with R. pneumonia
| - protect foals from heat stress during and after treatement
81
Lincosamides resistance
- gram negs are resistant due to impermeable cell membranes and incompatible binding sites
- chomosomal and plasmid-mediated
- complete cross resistance between the lincosamides
- cross resistance with macrolides and virginiamycin
82
Which lincosamide is preferred in small animals?
Clindamycin
- oral: vet med
- injectable: human
83
Which lincosamide is an intramammary product for dairy cattle?
Pirlimycin
84
Clindamycin special spectra
- treats Brachyspira hyodysenteriae in pigs
| - used commonly in dermatology and dentistry for SA
85
Oral clindamycin is not used in ______
Birds
| - would require a 100 mg/kg po q6h dose (not practical)
86
Clindamycin is effective in treating ________
Toxoplasmosis in cats
| - crosses BBB with inflammation only in cats
87
Clindamycin - adverse reactions
- neuromuscular blockade
- mostly GI symptoms with oral use in ruminants and suppresses hind gut flora in horses, rabbits, hamsters, guinea pigs (do NOT use!)
88
Tetracycline - adverse reactions
Injectables are highly acidic! Cause tissue damage (esophageal ulcers in cats given oral doxy, injection site necrosis)
89
Tetracycline - resistance mechanisms
Cross resistance within the group is common
- plasmid mediated
- reduced penetration of drug
- active efflux
- alterations to ribosome
- enzymatic degradation of tetracycline
90
Tetracycline non antibiotic effects
- inhibit collagenase
- may be anti-inflammatory or immunomodulating
- oxytetracycline in single dose helps relax contracted tendons in foals and calves
91
Which family has the broadest spectra, but also has a lot of resistance for common bacterial pathogens?
Tetracyclines
| - applies to wild type bacteria, does not apply to high clinical efficacy
92
What is the drug of choice for all rickettsia and lepto?
Doxycycline!
- clears carrier state and causes remission for lepto
- is also drug of choice for chlamydia in most species
93
______ and ______ are more lipid soluble and cross BBB
Doxycycline and minocycline
94
Chlortetracycline is used to treat _______
Anaplasmosis in cattle
- causes remission, does NOT clear carrier state
- only use as a feed additive
95
What is the primary injectable tetracycline in vet med?
Oxytetracycline
| - sustained release effect due to dose, not the vechicle (if given IV, the sustained effect goes away)
96
Adverse effect of tetracyclines
- potential teratogen in 1st trimester
- staining of teeth from in utero exposure or exposure prior to eruption of adult teeth
- hepatoxocitiy with use during pregnancy in the bitch
- photosensitivity
- GI floral disruption
- nephrotoxic in high doses (especially expired tetras!!)
- sudden collapse with rapid IV administration
- tissue necrosis and pain at injection site
97
What is the most common feed additive antibiotic?
Tetracycline
98
Sulfonamides mechanism of action
Compete with para amino benzoic acid for incorporation into folic acid synthesis = inhibition of protein synthesis
- mammalian cells use preformed folic acid and are not susceptible
- purulent debris decreases activity due to high protein content and PABA content
99
Folic acid pathway
PABA --> folic acid --> folinic acid --> purine and pyrimidines --> DNA
100
Sulfonamide resistance development
Cross resistance between sulfonamides is complete!
- chromosomal and plasmid mediated: altered cell permeability, refractive dihydropeteroate enzymes
- chromosome also causes PABA hyperproduction
101
Which sulfa requires a loading dose to be given?
Sulfadimethoxine (Albon)
| - also give with long acting sulfas
102
Common uses of sulfonamides
- coccidiosis
- nocardia
- bovine foot rot: have an effect on aerobic organisms, so fusobacteria is altered, making them more susceptible
- combos to enhance antibacterial or antiprotozoal activity
103
Which antimicrobial is used orally in ruminants for systemic effects?
Sulfas!!
104
What species is sulfas not used in?
Cats
| - not tolerated well orally
105
Which sulfa crosses the BBB?
Sulfadiazine
106
Sulfa - toxicity
Nephrotoxicity due to crystal urea formation from acetylation (dogs don't have this pathway)
107
Sulfa type A adverse reactions
Crystalluria
- problem with acidic urine and older sulfas (keep animals hydrated! Use triple sulfa to decrease risk while maintaining efficacy)
- prone to drug interactions due to high protein binding
- sulfaquinoxaline: hemorrhagic syndrome in chickens and dogs due to inhibition of intestinal vit K production
108
Sulfa type B adverse reactions
- keratoconjunctivitis sicca
- polyarthropathy
- hepatotoxicity
- cutaneous drug eruptions
- hypothyroidism
* dobermans are most susceptible to type B!*
109
Trimethoprim mechanism of action
Inhibition of DHFR, interfering with pruine and pyrimidine synthesis of the folic acid pathway (inserts between folic acid and folinic acid)
110
Resistance develops quickly to just ______ as a single agent
Trimethoprim
| - often used as a combo with sulfonamide to create a potentiated sulfa
111
Selectivity for DHFR inhibition for trimethoprim and ormethoprim
- bacterial
- protozoal
- mammalian
112
Selectivity for DHFR inhibition fo rpyrimethamine
- protozoal
- mammalian
- bacterial
113
Potentiated sulfas - veterinary form
Trimethoprim + sulfadiazine
| - TMS
114
What renders TMS ineffective in an in vivo situation
Necrotic and tissue exudates for anaerobic infections
115
Sulfadiazine is well absorbed orally in all species except _____
Cattle!
- is destroyed by rumen or undergoes first bypass effect
- may give to neonatal calves extralabelly
116
Adverse reactions to sulfonamide content
```
Type A
- crystalluria due to sulfonamide is not a concern (not enough sulfa in TMS)
Type B
- KCS
- polyarthropathy
- hepatotoxicity
- cutaenous drug eruptions
- hypothyroidism
```
117
Adverse reactions to diaminopyrimide content
Type A
- diaminopyrimidine inhibition on mammalian DHFR = bone marrow suppression and teratogenesis
- -> supplementation of folinic acid serves as an antidote to the above toxicities
118
What antimicrobial family is incrementally modified?
Phenicols
| - chloramphenicol --> thiamphenicol --> florfenicol
119
Phenicols resistance development
Plasmid mediated
120
Chloramphenicol is effective against ______ infections
Enterococcal
- previously drug of choice against Salmonella, resistance now runs at 50%
- is an alternative to treat Rickettsia
121
Chloramphenicol is banned in _____
Cattle
| - destroyed by rumen
122
Florfenicol is used in
Cattle
| - repository (effect is not seen in dogs)
123
Which species is born with near adult hepatic metabolism and how does this relate to chloramphenicol use?
Foals
- glucuronyl transferase activity appears to reach adult levels in 1 week
- would not use in any other neonate!!
124
Which species has the longest chloramphenicol half life?
Cat (6 hours)
| - horse as the shortest (1 hour)
125
Chloramphenicol is not well tolerated in _____
Cats
- leads to anorexia and depression
- prone to drug interactions due to its inhibition of P450 system
- is excreted into milk, so treating dam may affect neonate
126
Florfenicol is contraindicated in ______
Horses
| - causes severe diarrhea and colitis
127
Long term use of ______ can cause bone marrow suppression in all species
Chloramphenicol
| - reversible upon discontinuation of the drug
128
In primates, chloramphenicol can lead to _______
Aplastic anemia
- non dose dependent!
- does not occur with florfenicol
- survives cooking, so it is banned from all food animals!
129
Mammalian cell topoisomerase 2 is not affected by ________ until drug concentrations are at least 100x higher than recommended concentrations
Fluoroquinolones
130
Fluoroquinolones resistance development
Alteration of target, DNA gyrase, or topoisomerase 4
- decreased entry into cell or increased active transport out of cell
- chromosomally mediated!
- cross resistance with other fluoroquinolones can occur
- must have double mutation to be truly resistant
131
What is the drug of choice for human septicemic salmonellosis?
Fluoroquinolones
| - also used commonly in human campylobacter infections
132
Enrofloxacin use in ruminants
Absorbed orally, though this use is banned
133
Fluoroquinolones in horses
Vary in bioavailability
| - ciprofloxacin is not absorbed
134
Which antimicrobial is an enzyme inhibitor?
Fluoroquinolones
| - causes adverse drug rxns, especially in conjuction with theophylline use
135
Which antimicrobial is widely used in exotic animals and wildlife?
Enrofloxacin due to lack of anaerobic spectrum
136
Identify order of susceptibility for each species to fluoroquinolone arthropathy
Horse > dog > cat and cattle
- young animals are more susceptible
- all horse formulations are extra label
- is dose dependent and species dependent
- do not use in large breed dogs up to 1 year and a half
137
Fluoroquinolone adverse reactions
- blindness due to retinal injury in cats
| - pradofloxacin causes bone marrow suppression in dogs
138
Fluoroquinolone public health concern
Monitored by National Antimicrobial Resistance Monitoring System due to resistance to campy and salmonella
- enrofloxacin for poultry was withdrawn in 2005
139
Identify fluoroquinolone that have a higher probability to activity against pseudomonas
Ciprofloxacin and marbofloxacin
140
Ionophore uses
- anti coccidial for ruminants and poultry
- improve feed efficiency, weight gain, or milk production
- prevent fog fever in cattle
- decrease ruminal bload
141
Ionophores are very specific for ______
Gram positive bacteria and coccidia
| - does not affect human health, causes drop in intracellular pH
142
Rank major species regarding susceptibility to ionophore toxicity
- cattle and poultry: relatively resistant
- swine and small animals: intermediate
- horses: most sensitive
143
Ionophore toxicity
Severe muscle damage, myoglobinuria can cause renal damage
144
Spectinomycin is an ________
Aminoicyclitol
| - lacks toxicities seen with aminoglycosides (may cause neuromuscular blockade)
145
_______ is limited to use in pigs only
Avilamycin
- for reduction of incidence/severity of diarrhea with pathogenic e coli in weaned pigs
- alters adhesive villi on gram negs so they cannot attach to enterocyte
146
Bacteria in aerobic conditions are resistant to _______
Nitroimidazoles
- do not possess reduction system
- may function against facultative aerobic bacteria in anaerobic conditions
147
Adverse reactions of metronidazole
- neurologic with high doses in cats, dogs, horses
- anorexia
- bone marrow suppression
- reddish brown urine
- may interfere with olfaction in explosive detecting dogs
148
Nitroimidazole public health concern
Carcinogenic effect in lab animals
| - all nitroimidazoles are banned from use in food animals!
149
What is the human anti-tuberculosis drug?
Rifampin
- resistance develops rapidly during therapy (is never used as a single agent)
- has been used to treat Johne's disease but efficacy is not established
150
Which drugs are used to treat Potomac horse fever?
Rifampin + erythromycin
- as effective as oxytetracycline in resolution of clinical signs, but may not reduce fever as quickly
- are available in oral forms
- oral doxy is also an option
151
Rifampin adverse reactions
- dogs: elevated liver enzymes (rifampin induced hepatitis)
- foals: self limiting diarrhea
- humans: GI, flu like syndrome, blood dyscrasias, interstitial nephritis
- discoloration of urine and tears (pink)
152
Rifampin is an enzyme _______
Inducer!
| - other drug will become subtherapeutic, need to adjust dose up based on TDM
153
Isonizaid toxicity
CNS
| - pyridoxine is antidote
154
Nitrofuran adverse reaction and regulatory issues
Mutagenic and procarcinogenic = ban of extra label use in food animals (even topically)
- furazolidone is MAOI and must be used cautiously with drugs metabolized by this enzyme
155
Novobiocin is approved for _______ with penicillin G for staphylococcal mastitis
Intramammary infusion
156
Which miscellaneous antimicrobial is used to treat swine dysentery?
Tiamulin
| - also associated with swine pneumonia due to Actinobacillus pleuropneumoniae
157
Tiamulin is an enzyme _______
Inhibitor
| - inhibits P450 and decreases metabolism of certain drugs (ionophores) where coadministration may lead to toxicity
158
Which drug is used as a feed additive for the control of swine dysentery associated with S. hyodysenteriae and control of enteric salmonellosis?
Carbadox
159
______, neomycin, and polymxin B make up the triple antibiotic topical ointment
Bacitracin
- too toxic to give parenterally
- orally is used to treat swine dysentery and C. difficile
160
______ is used at extra low doses to bind to endotoxin
Polymyxin B
161
Cats have high allergy to triple antibiotic due to ______
Bacitracin
162
Silver sulfadiazine has antimicrobial activity due to the ______
Silver ion
| - broad spec, including anti-pseudomonal activity
163
Methenamine - effect of urine pH on activity
Requires urinary acidification to be converted into formaldehyde
- urine pH of 5 in humans is preferred, 5.5 in animals
- need to put on acidifying diet and add urinary acidifier (ammonium chloride)
164
Methenamine - efficacy in treating a cystitis versus a pyelonephritis
Will not treat a pyelonephritis!
| - passes thru kidney too rapidly for conversion to occur
165
Which antibiotic is used for multi-drug resistant MRSA and vancomycin resistant E. faecalis and E. faecium?
Linezolid
| - is an MAO inhibitor, use cautiously with other drugs impacting serotonin and catecholamines
