Pharmacology Exam 2 Questions

A. 5-flucytosine and C. Fluconazole

"Bert" is a four year old, MC 18 lb American cocker spaniel that presents to you with a history of lethargy and inappetance. On physical examination, you note that the dog is somewhat thin, has a head tilt, and is circling to the left. It also appears to you that the dog has altered mentation, beyond the behavioral changes expected from lethargy. CBC shows a nonregenerative anemia and lymphopenia. When a urine sample obtained by cystocentesis is spun down, yeast-like organisms are identified in the sediment, but no bacteria are isolated. Based on the appearance of the organisms in the urine, a cryptococcal antigen latex agglutination serology sample is submitted from serum and urine; both are positive for Cryptococcus. You diagnose Bert with cryptococcal cystitis and meningitis. What would be the antifungal treatment of choice for this dog? A. 5-flucytosine B. Terbinafine C. Fluconazole D. Amphotericin B deoxycholate E. Itraconazole

e) Chloramphenicol Rationale: Staphylococcus spp. are gram positive aerobes/facultative anaerobes. Enrofloxacin is indicated for prostatitis but this infection is resistant to it. Chloramphenicol is likely to accumulate in acidic tissues, so it is good for prostatitis and mammary tissues.

"Butch" is an eight year old intact male Rottweiler that is straining to urinate and defecate. The initial physical examination is normal and the history indicates that the dog is eating, drinking, and otherwise behaving normally. A CBC shows a mild neutrophilia but serum biochemistry is within normal limits. An enlarged and painful prostate can be palpated by digital examination. A fine needle aspirate is obtained under anesthesia and submitted for cytology, culture, and sensitivity testing. Degenerate neutrophils containing intracellular bacteria are seen on cytology. Staphylococcus spp. is cultured from the prostate fluid and from urine obtained by cystocentesis. The isolate is sensitive to all antibiotics tested, except for resistance to enrofloxacin and tetracycline. Which of the following would be the best choice of long-term antibiotic therapy for Butch's prostatitis? a) Cephalexin b) Amoxicillin c) Enrofloxacin d) Metronidazole e) Chloramphenicol

d) Retinal degeneration

"Cleo" is a twelve-year-old, FS calico, domestic short hair cat brought to you for examination after a cat fight. You find several bite wounds, which you clean. You elect to send Cleo home with a course of orbifloxacin to prevent infection of her wounds. Although unlikely at therapeutic dosages, which of the following is the orbafloxacin side effect of greatest concern in this patient? a) Ototoxicity b) Arthropathies c) Red-stained tears d) Retinal degeneration e) Discoloration of teeth

e. Gram positive and Gram-negative anaerobes

"Kitkat" is a 9 year old DSH MC cat that is presented to you for foul breath. An inspection of his oral cavity reveals multiple areas of gingivitis, periodontitis, and osteomyelitis. You schedule a future procedure for anesthesia, radiographs, and dental extractions and cleaning as needed. You know that anaerobic bacteria such as Bacteroides and Peptosptreptococcus are commonly associated with periodontal disease in dogs and cats. Consult the article on Moodle "Antibiotics in cats" and the Antibacterial Study Guide to answer the following. Where do the target organisms fall in the bacterial species quadrant system? a. Gram positive aerobes b. Gram negative anaerobes c. Gram negative aerobes d. Gram positive anaerobes e. Gram positive and Gram-negative anaerobes f. Gram positive and gram-negative aerobes

A.Idoxuridine

"Mittens" is a two year old, male neutered cat that was recently adopted from a shelter. Mittens presents to you with sneezing, bilateral nasal discharge, bilateral conjunctivitis, and blepharospasm. Body temperature is 104 F. You make a presumptive diagnosis of herpetic rhinitis and conjunctivitis. Which of the following is an ophthalmic preparation that is commonly applied to the eyes in cats with herpetic conjunctivitis? A.Idoxuridine B.Famciclovir C.Oseltamivir D.Valacyclovir E.Zidovudine (AZT)

a. Whether there is a bacterial infection present

"Moxie" is a 4 year old, FS DSH cat. She is presented for urinary signs: straining to urinate, a lot of time spent digging in the litter box, inappropriate elimination (peed on the sofa). Physical exam and history: uninteresting. Before administering antimicrobial drugs for inappropriate elimination, what must you first determine? a. Whether there is a bacterial infection present b. Whether the animal is allergic to antimicrobials by using a skin allergen test c. What exact antimicrobial to use by performing bacterial sensitivity test d. Whether bactericidal drugs are indicated due to immunosuppression

e) Ceftazidine Rationale: Ceftazidine is indicated for pseudomonas and exotics.

"Romeo" is a seven-year-old male green iguana with a swollen jaw. Appetite is normal and history indicates appropriate food and housing. You anesthetize Romeo and incise the area over the swelling, due to a high index of suspicion of a bacterial abscess. You find a yellow tinged, cheesy-textured mass that appears to be inspissated pus. You submit the mass and a swab of the capsule of the abscess for aerobic culture and sensitivity, flush the abscess site with dilute chlorhexidine, and recover the iguana from anesthesia. Empirically, you suspect Pseudomonas spp. as the causative agent. Injectable formulations of which of the following would likely be the most effective therapeutic to send Romeo home with while awaiting C&S results? a) Ceftiofur b) Penicillin c) Cefazolin d) Ampicillin e) Ceftazidine

b. Macrolides

1Injection site reactions, GI upset and cardiotoxicity are adverse events common to what class of drug? a. Lincosamides b. Macrolides c. Tetracyclines d. Aminoglycosides e. Fluoroquinolones

a. Bacterial change of the 50s ribosomal subunit and expression of efflux pumps

1Tilmicosin is a macrolide that is effective against our organism above (gram negative aerobe/facultative anaerobe). However, there have been recent reports of acquired resistance of the organism to this and other macrolides. Which answer below lists two common mechanisms that lead to resistance to macrolides: a. Bacterial change of the 50s ribosomal subunit and expression of efflux pumps b. Bacterial change of the 30s ribosomal subunit and enzymatic inactivation c. Efflux pump expression and change in 30s ribosomal target d. Multi drug resistance and adaptive resistance

E.inhibiting DNA synthesis.

5-flucytosine suppresses fungal growth by: A.inhibiting the formation of ergosterol. B.directly binding to ergosterol. C.inhibiting the mitotic spindle. D.boosting the immune system. E.inhibiting DNA synthesis.

d) Cephalexin Rationale: A, B, and C are injection only. E is used primarily for Pseudomonas spp. Cephalexin is indicated for pyoderma.

A dog presents to you with what you determine to be pyoderma (infection of the skin), secondary to atopy (seasonal allergies). Your Gram stain shows numerous Gram-positive cocci that you presume to be staphylococcal organisms. Otherwise, your physical exam is within normal limits. Which of the following antibiotics would be the best first choice option to treat the pyoderma in this dog? (Hint: Don't forget to consider spectrum of activity, site of infection, patient factors like species-specific use, drug formulation, and route of administration) a) Cefoxitin b) Cefazolin c) Cefepime d) Cephalexin e) Ceftazidime

D. Oxytetracyline- IV

A horse presents to your clinic with severe watery diarrhea. He is dehydrated and in shock and is immediately admitted to your ICU. You suspect Neorickettsia risticii. You best first choice of antibacterial therapy for this horse is: (Hint: in a very sick animal like this, we prefer to administer an injectable antimicrobial drug!) A. Oxytetracycline-PO B. Doxycycline-IV C. Doxycline- PO D. Oxytetracyline- IV E. Tetracycline- PO

e. Imidazoles, tetracyclines or penicillin

Adjunct antibacterial treatment may be co-administered with first line treatments in the therapy of lumpy jaw. Given that Actinomyces bovis is actually an anaerobic, Gram-positive bacteria, and reading the "Dosage" section of "Iodide" which of the following antibacterial drugs that are approved for use in food animals and effective against bacteria in this quadrant. a. Sulfas, aminoglycosides or tetracyclines b. Azoles, aminoglycosides and Iodides c. Cephalosporins, aminoglycosides or quinolones d. Furacin, sulfas and terbinafine e. Imidazoles, tetracyclines or penicillin

f. Iodides

After determining that the cattle are suffering from lumpy jaw, what is the first-line therapeutic agent recommended for the treatment of this condition? a. Macrolides b. Azoles c. 5-Flucytosine d. Griseofulvin e. Terbinafine f. Iodides

b) Amoxicillin is not degraded Rationale: Clavulanate is not an effective antimicrobial alone, but they inactivate b-lactamase activity making co-administered beta lactam more active.

Amoxicillin is often combined with clavulanate, so that: a) Clavulanate is not degraded b) Amoxicillin is not degraded c) Clavulanate is not metabolized in the kidney d) Amoxicillin is not metabolized in the kidney e) Spectrum of activity is extended to Pseudomonas

C.inhibiting the fungal P450 enzymes

Azoles (ketoconazole, itraconazole, and fluconazaole) suppresses fungal growth by: A.inhibiting the formation of ergosterol. B.directly binding to ergosterol. C.inhibiting the fungal P450 enzymes D.boosting the immune system. E.inhibiting DNA synthesis.

a) Ampicillin/sulbactam Rationale: Enterobacteriaceae are gram negative anaerobes. Ampicillin/subactam is broad and includes gram negative. It is often used IV for ICU in small animals. Cefazolin/clindamycin are used for gram positive anaerobes. Azithormycin/rifampin are used for anaerobes and gram positives. Clindamycin/cephalexin are gram positive anaerobes. Enrofloxacin cannot be used in growing animals and metronidazole is used for anaerobes.

Benji is a seven-week-old puppy that is presented for severe diarrhea, vomiting, lethargy, and dehydration. A snap test is positive for parvovirus. Benji is anemic, leukopenic, and neutropenic with hypoalbuminemia and hypoproteinemia. Benji is hospitalized and placed on fluid therapy. Which of the following combinations would be the best (safe and efficacious) initial antibiotic to prevent translocation of Enterobacteriaceae bacteria and resulting sepsis? a) Ampicillin/sulbactam b) Cefazolin/clindamycin c) Azithromycin/rifampin d) Clindamycin/cephalexin e) Enrofloxacin/metronidaole

a. True

Clindamycin is a capsule or bitter tasting liquid. Which formulation the cat will accept depends on the cat and owner. Mixing the cold drug with cold baby food could allow the mix to be palatable. Owners able to pop capsules in the throat can do so but follow with water or baby food or other to make sure that the pill doesn't dissolve in the esophagus and cause strictures! Is this statement True or False when considering treatment in Kitkat? a. True b. false

b) This bacteria is resistant, pick another antimicrobial drug. Rationale: MIC are specific to the organism cultured, while serum breakpoints are specific to the host and the drug. Bacteria are susceptible to a drug if they have an MIC below the breakpoint. Breakpoint should be > MIC for a susceptible isolate.

Culture and sensitivity reveal a bacterial infection with an MIC significantly higher than the breakpoint of an antimicrobial with flexible labeling. Which one of the following assessments and therapeutic plans is most appropriate? a) This bacteria is resistant, double the dose. b) This bacteria is resistant, pick another antimicrobial drug. c) This bacteria is sensitive, use the antibiotic at the lowest labeled dose. d) This bacteria is intermediately sensitive, use the antibiotic at a lowest labeled dose. e) This bacteria is intermediately sensitive, use the antibiotic at the highest labeled dose.

B. This bacteria is resistant, pick another antimicrobial drug.

Culture and sensitivity reveal a bacterial infection with an MIC significantly higher than the breakpoint of an antimicrobial with flexible labeling. Which one of the following assessments and therapeutic plans is most appropriate? Note: flexible labeling allows us to use a dose range with the lower dose applying to most bacteria that are expected to be highly sensitive to the drug, while the higher dose may be used if an isolate is intermediately sensitive to the antimicrobial. A. This bacteria is resistant, double the dose B. This bacteria is resistant, pick another antimicrobial drug. C. This bacteria is sensitive, use the antibiotic at the lowest labeled dose. D. This bacteria is intermediately sensitive, use the antibiotic at a lowest labeled dose. E. This bacteria is intermediately sensitive, use the antibiotic at the highest labeled dose.

b. Chlorhexadine (nolvasan)

Giving that Furacin solution, is no longer approved for use in veterinary medicine. Dilution in water of which of the following would be the most appropriate replacement solution for flushing an abscess of a pregnant cow? a. Nitrofurantion b. Chlorhexadine (nolvasan) c. Itraconazole d. Griseofulvin e. Amphotericin B

b. Valacyclovir, good oral absorption

EHV-1 as the causative agent of equine herpesvirus myeloencephalopathy (EHM) has become an important disease of the equine industry. Give the antiherpetic drug that is most commonly used to treat this condition and why is this drug preferred to its most closely related antiherpetic drug. a. Acyclovir, is the most selective of antivirals b. Valacyclovir, good oral absorption c. Oseltamivir, evidence of efficacy in horses d. Famciclovir, enhanced absorption

a. True

Enrofloxacin has the abbreviation "HP-CIA" next to it. What does this abbreviation stand for, how is this term defined, and do you agree with this explanation below? HP-CIA= highest priority critically important antimicrobial. This abbreviation is used to help veterinarians identify which antimicrobials should be used as a last resort in order to help manage antibacterial resistance. We agree with this designation because it is one of the few drugs primarily excreted in active form in the urine. If bacteria become resistant, we do not have many other potent drugs primarily excreted in the urine. It also causes a dose dependent retinopathy in cats. If bacteria become resistant, we cannot increase the dose in cats without causing toxicity. a. True b. False

d. Famciclovir and Idoxuridine

FHV-1 is an important disease in cats. Give the preferred systemically (PO) administered and the topically (ophthalmic) administered antiherpetic drugs that are most commonly used to treat this condition in cats. a. Idoxuridine and Zidovudine b. Zidovudine and Idoxuridine c. Valacyclovir and Idoxuridine d. Famciclovir and Idoxuridine e. Interferon and Zidovudine

E. the peak serum concentration

For agents that exhibit concentration-dependent killing, the best efficacy is associated with maximizing: A. the elimination rate B. the mutant population C. the trough concentration D. the volume of distribution E. the peak serum concentration

C. the trough concentration

For agents that exhibit time-dependent killing, the dosing regimen with the best efficacy is associated with maximizing: A. the elimination rate B. the mutant population C. the trough concentration D. the volume of distribution E. the peak serum concentration

b. NSAIDS may decrease clinical signs.

For the therapy of sporadic cystitis in dogs and cats, the guidelines suggest NSAIDs as possible first-line therapy. What is the rationale for NSAID administration? a. NSAIDS have potent anti-microbial effects b. NSAIDS may decrease clinical signs. c. NSAIDS are administered primarly to increase the glomerular filtration rate d. NSAIDS would only be effective in recurrent UTI cases

c. Influenza virus

For which veterinary viral pathogens are oseltamivir most rationally used (that is, what viral disease best matches the MOA of oseltamivir?) a. Herpesvirus b. Feline retroviruses c. Influenza virus d. Parvovirus e. Coronavirus

C.inhibiting the mitotic spindle.

Griseofulvin suppresses fungal growth by: A.inhibiting the formation of ergosterol. B.directly binding to ergosterol. C.inhibiting the mitotic spindle. D.boosting the immune system. E.inhibiting DNA synthesis.

a. To cure the bacterial cystitis (clinical cure) with minimal risk of side effects with only the possibility of totally or partially eliminating the causative pathogen (microbiological cure).

How do we define successful therapy? Examine the section Treatment under Recurrent bacterial cystitis. What is stated as the most appropriate goal of therapy? a. To cure the bacterial cystitis (clinical cure) with minimal risk of side effects with only the possibility of totally or partially eliminating the causative pathogen (microbiological cure). b. To treat the recurrent cystitis (clinical cure) without any antimicrobial resistance and with total eradication of the offending organism (microbiological cure) c. To achieve first a partial or total eradication of the causative agent (microbiological cure) and then proceed to possibly achieve a clinical cure (cure the cystitis with few side effects) d. To eliminate the causative organism (microbiological cure) and the possibility of curing the bacterial cystitis (clinical cure).

a. Latent viruses are unaffected by antivirals

How does the timing of therapy generally affect the success of antiherpetic therapy? a. Latent viruses are unaffected by antivirals b. IC50 is a strong determinant factor c. Timing of therapy does not affect success d. Plasma drug concentration and IC50 correlates well with efficacy

a. True

If pyelonephritis is suspected, serum breakpoints should be used instead of urine breakpoints in Culture and Sensitivity testing. a. True b. False

a. Organism, target organ, patient and drug factors, administration and cost factors

In devising an antimicrobial plan to treat these cattle (that are at a high risk for BRD), the following should be considered: a. Organism, target organ, patient and drug factors, administration and cost factors b. Organism, susceptibility, target organ, PK properties, mechanism of action c. Organism, susceptibility, therapeutic drug monitoring, PD/PK properties, cost d. Problem, differential diagnosis, therapy, culture and sensitivity, diagnostics

True

In terms of PK/PD efficacy metrics, Florfenicol is best characterized as a time-dependent antibacterial agent. True False

D. Ducks

In which of the following species is the extralabel use of oseltamivir prohibited? A. Dogs B. Sheep C. Cattle D. Ducks E. All food animals

b. Bacteroides spp. Rationale: enrofloxacin should not be used for anaerobes. It has a broad spectrum of activity and works well against pseudomonas and intracellular pathogens. Bacteroides in a gram negative anaerobe. All others are aerobes.

Of the following bacteria, enrofloxacin is expected to be least active against: a. Manheimia spp. b. Bacteroides spp. c. Escherichia coli d. Pseudomonas spp. e. Staphylococcus spp.

C. Pseudomonas spp. Rationale: There are a relatively small list of drugs that are particularly effective against Pseudomonas. From our study guide, we've listed: Ticarcillin, 3rd gen cephalosporins (ceftazidine but not ceftiofur), 4th gen cephalosporin (cefepime), imipenem, aztreonam, aminoglycosides, fluoroquinolones (esp marbofloxacin), silver sulfadiazine, polymyxin B

Of the following bacteria, erythromycin is expected to be least active against: A. Chlamydia spp. B. Rhodococcus spp. C. Pseudomonas spp. D. Staphylococcus spp. E. Peptostreptococcus spp.

c) Pseudomonas spp. Rationale: Metronidazole is effective for anaerobes and protozoans. Pseudomonas is the only aerobe. All others are anaerobes.

Of the following bacteria, metronidazole is expected to be least active against: a) Clostridium spp. b) Bacteroides spp. c) Pseudomonas spp. d) Fusobacterium spp. e) Peptostreptococcus spp.

C. Because chloramphenicol is not eliminated by the kidneys Rationale: Chloramphenicol is not excreted intact in the urine, so urine concentrations will be low.

Lady is a 10 year old spayed collie that has been presented to you with multiple episodes of lower urinary tract infections. The latest culture and sensitivity shows E. coli that are resistant to all of the drugs in your panel except for chloramphenicol. Irregardless, why would chloramphenicol be a poor choice to treat this cystitis? A.Because chloramphenicol is illegal to use in dogs B.Because chloramphenicol can only be given parenterally C.Because chloramphenicol is not eliminated by the kidneys D.Because chloramphenicol is not active against gram-negative bacteria E.Because chloramphenicol must be used with a macrolide to prevent resistance

a) to provide metaphylaxis.

Mr. Jones, a local farmer, has just received a small herd of healthy stocker calves that were shipped interstate. You believe that the calves are at particular risk for developing shipping fever from a stressful time at transit. Therefore, you elect to give all of the calves a dose of an anti-bacterial agent, ceftiofur crystalline free acid, immediately upon arrival. The goal of therapy as defined in class, assignments, and assigned readings would be: a) to provide metaphylaxis. b) to cure the shipping fever. c) to provide palliative therapy. d) to avoid side effects of therapy. e) to provide a short duration of therapy.

a. Oral-fluoroquinolones, cefpodoxime; IV- Cefotaxime, ceftazidime.

Name two orally administered and two intravenously administered initial first-choice agents for the therapy of pyelonephritis. a. Oral-fluoroquinolones, cefpodoxime; IV- Cefotaxime, ceftazidime. b. Oral-aminoglycosides, ceftiofur; IV-cefpodoxime, cephalexin c. Oral-amoxicillin, penicillin; IV-oxytetracyclines, ampicillin d. Oral-doxycycline, ampicillin; IV-amikacin, amoxicillin/clavulanic

c) Doxycycline

Pele is a five-year-old beagle that is presented for lethargy and inappetance. Physical examination reveals a fever of 104º, petechiae, and ecchymotic lesions. Thrombocytopenia is noted on a CBC. Which of the following would be the best choice of therapy if the presumptive diagnosis is infection with Ehrlichia ewingii? a) Imipenem b) Cefovecin c) Doxycycline d) Metronidazole e) Amoxicillin/clavulanate

b) Arthropathies Rationale: Arthropathies seen in growing animals. Retinal degeneration seen in cats.

Petey is a 10-week-old Great Pyrenees puppy that was attacked during the night by an unknown animal. You examine Petey and find several bite wounds, which you flush and clean. You elect to send Petey home with a course of antibiotics to prevent infection of his wounds. Although enrofloxacin can be excellent for some skin infections, the likelihood of which potential adverse effect would make enrofloxacin a poor choice for this patient? a) Ototoxicity b) Arthropathies c) Red-stained tears d) Retinal degeneration e) Discoloration of teeth

B.directly binding to ergosterol.

Polyene macrolides (amphotericin B and Natamycin) suppresses fungal growth by: A.inhibiting the formation of ergosterol. B.directly binding to ergosterol. C.inhibiting the mitotic spindle. D.boosting the immune system. E.inhibiting DNA synthesis.

a. Remdesivir is the prodrug for GS-441524, which has been tested in cats with FIP

Recent events have put the antiviral therapy of coronaviruses very much on the map. What is the relationship between the drugs remdesivir and GS-441524? a. Remdesivir is the prodrug for GS-441524, which has been tested in cats with FIP b. Clinical trials have shown that remdesivir is effective against FIP, so GS-441524 may also be effective. c. There is no current available therapy for FIP, therefore both remdesivir and GS-441524 are routinely used for this disease. d. Only GS-441524 is approved for FIP, not remdesivir. e. Since a successful clinical trial has been performed, both remdesivir and GS-441524 are recommended by veterinarians for cats with FIP.

a. No, the primary treatment of dental disease is cleaning and surgery. Routine use of antibiotics will increase the chance of developing resistance.

Should antibiotics be routinely administered to all cats with dental disease? Kitkat had rather severe dental disease, with osteomyelitis noted. Other cats may present for a dental cleaning with milder gingival and periodontal disease. Should systemic antibiotics be routinely administered to all cats with dental disease? Consider where such use falls within the concept of the judicious use of antimicrobial agents. Unsure? a. No, the primary treatment of dental disease is cleaning and surgery. Routine use of antibiotics will increase the chance of developing resistance. b. No, Dental infections can be exacerbated by antibacterial drugs c. Yes, because the benefit outweighs the risk d. Yes, to prevent spreading of infections to the systemic circulation Yes, to prevent permanent loss of teeth

A.inhibiting the formation of ergosterol.

Terbinafine suppresses fungal growth by: A.inhibiting the formation of ergosterol. B.directly binding to ergosterol. C.inhibiting the mitotic spindle. D.boosting the immune system. E.inhibiting DNA synthesis.

C.30S ribosomal subunit

Tetracyclines work by inhibiting A.DNA gyrase B.Folic acid synthesis C.30S ribosomal subunit D.Bacterial cell wall synthesis E.DNA-dependent RNA polymerase

C.breakpoint

The C&S MIC that is associated with an achievable plasma concentration of an antibiotic in a particular host and some evidence of clinical efficacy for that bacterial species in that patient species is known as A.minimal bactericidal concentration B.antibiotic effect C.breakpoint D.minimal inhibitory concentration

d. They are not used as first choice agents because they are rarely needed for efficacy and due to concerns about selecting for antimicrobial resistance.

The guidelines discuss the use of nitrofurantoin, fluoroquinolones and 3rd generation cephalosporins as first-line therapy for sporadic bacterial LUTI. What role should these specific agents play as first-line therapeutics for sporadic bacterial LUTI? a. They are expensive for owners to buy and not readily available. b. These medications have severe side effects so are only used when the need for efficacy outweighs their high toxicity. c. They are not able to reach high urine concentrations in comparison to amoxicillin and other first-choice agents. d. They are not used as first choice agents because they are rarely needed for efficacy and due to concerns about selecting for antimicrobial resistance. e. They are first-choice agents in this setting because so many pathogenic urinary bacterial isolates are resistant to all other antimicrobial agents.

B.have a peak concentration that is 10X the MIC.

The most best dosing regimen for an aminoglycoside, like amikacin, will produce plasma concentrations that: A.have a trough concentration of 8X the MIC. B.have a peak concentration that is 10X the MIC. C.exceed the bacterial MIC for the entire dosing interval. D.have either a peak of 10X the MIC or AUIC of at least 125. E.have an area under the inhibitory curve (AUIC) of at least 125.

B. enzymatic degradation of the drug by acetyltransferase enzyme

The most common mechanism of resistance to chloramphenicol is A. reduced accumulation due to change in porins B. enzymatic degradation of the drug by acetyltransferase enzyme C. Ribosomal protection proteins D. alteration in DNA gyrase binding site

A.Diarrhea

The most commonly observed adverse effect of therapeutic doses of erythromycin is A.Diarrhea B.Neurotoxicity C.Nephrotoxicity D.Allergic dermatitis E.Orange colored secretions (tears and urine)

a) have a peak concentration that is 8-10X the MIC

The most effective dosing regimen for an aminoglycoside, like amikacin, will produce plasma concentrations that: a) have a peak concentration that is 8-10X the MIC b) have a trough concentration below the bacterial MIC c) have an area under the inhibitory curve (AUIC) of at least 125 d) exceed the bacterial MIC for the majority of the dosing interval e) are low enough not to cause anaphylaxis in hypersensitive patients.

A. have a peak concentration that is 8-10X the MIC

The most effective dosing regimen for gentamicin will produce plasma concentrations that: A. have a peak concentration that is 8-10X the MIC B. have a trough concentration below the bacterial MIC C. have an area under the inhibitory curve (AUIC) of at least 125 D. exceed the bacterial MIC for the majority of the dosing interval E. are low enough not to cause anaphylaxis in hypersensitive patients.

a) True

Transfer of resistance genes can occur by conjugation between a non-pathogenic bacterium and another pathogenic bacterium in the gastrointestinal tract. a) True b) False

e. Enrofloxacin + Ampicillin

Unfortunately, Freckles does have systemic signs of disease. While awaiting the C&S results, empirical antibacterial therapy was initiated for Freckles. Which of the following would be a recommended empirical therapy for this patient? a. Trimethoprim + Sulfadmethoxazole b. Clindamycin + Ampicillin c. Cefazolin + Gentamicin d. Tylosin + Amoxicillin e. Enrofloxacin + Ampicillin

D. Broad spectrum, Gram-positive + Gram-negative + anaerobes

Which of the following best describes the spectrum of activity of florfenicol? A. Gram-positive + intracellular bacteria B. Most effective against protozoans + anaerobes C. Narrow spectrum, primarily Gram-negative bacteria D. Broad spectrum, Gram-positive + Gram-negative + anaerobes E. Narrow spectrum, primarily Gram-positive bacteria + anaerobes

a. The low end of the dose range may be used since the result indicates the isolate is quite sensitive to the antimicrobial

Using the principles of judicious antimicrobial drug use, what dosing recommendation should you make if culture and sensitivity reveals a bacterial infection with an MIC (<0.25 mcg/mL), which is substantially lower than the breakpoint (5 mcg/mL) of an antimicrobial with flexible labeling? (Note: flexible labeling indicates that the label lists a range of possible dose rates, such as 2.5-7.5 mg/kg, rather than just a single dose rate.) a. The low end of the dose range may be used since the result indicates the isolate is quite sensitive to the antimicrobial b. The higher end of the dose range should be used since the result indicates the isolate is intermediately sensitive to the antimicrobial c. The isolate is not sensitive to the microbial drug therefore a drug with "S" on the culture test should be used Since this antibacterial has flexible labelling, randomly select any dose from the 2.5-7.5mg/kg range

a. Less than or equal to, sensitive, no interpretation

What do "<=", "S" and "NI" indicate? a. Less than or equal to, sensitive, no interpretation b. Loss of, single and no inhibition c. Less of, Sanction and no increase d. Limit, sensitization and nil interpretation

a. Clindamycin

What drug is particularly effective against anaerobes in the tooth roots, tooth abscesses and surrounding bone? a. Clindamycin b. Amikacin c. Macrolides d. Tetracyclines e. Fluoroquinolones

d. Doxycycline

What drug is recommended for the empirical first-choice treatment of mild pneumonia IF the patient does not have systemic clinical signs (no fever, dehydration, respiratory distress, lethargy, etc.)? a. Clindamycin b. Enrofloxacin c. Trimethoprim-sulfa d. Doxycycline e. Ampicillin

d) The penicillin binding protein of the staph isolate has altered due to acquired resistance, so no penicillin is likely to be effective.

What is the clinical significance of isolating methicillin resistant Staphylococcus aureus (MRSA) in a septic patient? a) Methicillin resistant isolates will also be resistant to aminoglycosides. b) Only fourth generation cephalosporins will be effective against this isolate. c) Only those penicillins that are administered with beta-lactamase inhibitors will be effective. d) The penicillin binding protein of the staph isolate has altered due to acquired resistance, so no penicillin is likely to be effective. e) Methicillin resistant isolates have overexpressed efflux pumps, so will be resistant to all antibiotics.

E. Inhibition of reverse transcriptase

What is the pharmacological mechanism of action by which zidovudine (AZT) exerts its intended pharmacological effect? A. Inhibition of DNA polymerase B. Inhibition of phosphodiesterase C. Inhibition of squalene epoxidase D. Inhibition of the actions of cAMP E. Inhibition of reverse transcriptase

d) Cilastatin decreases renal metabolism of imipenem Rationale: Cilastatin prevents imipenem degradation in the kidney and prolongs imipenem elimination and therefore increases duration of action.

What is the primary rationale for adding cilastatin to imipenem? a) Cilastatin inhibits beta-lactamase enzyme b) Cilastatin enhances absorption of imipenum c) Cilastatin facilitates penetration into the eye d) Cilastatin decreases renal metabolism of imipenem e) Cilastatin increases the spectrum of activity to intracellular Ehrlichia

a. Good tissue penetration and high activity against Enterobacteriaceae

What properties make the above agents good first-choice drugs for pyelonephritis? a. Good tissue penetration and high activity against Enterobacteriaceae b. Good tissue penetration and high activity against Staphylococcus c. High urine concentrations and high activity against Pseudomonas d. High urine concentrations and high activity against Bacteroides

b) Bacteriostatic Rationale: - MBC/MIC is small = cidal - MBC/MIC is large = static

When the minimum bactericidal concentration (MBC) and the minimum inhibitory concentration (MIC) are very different from one another, it is likely that the antibacterial drug is best classified as: a) Bactericidal b) Bacteriostatic c) Likely to produce mutants d) A broad spectrum antibiotic e) Having a wide therapeutic index

E. Sodium iodide

Which of the following agents would be most appropriate to treat Actinomyces (lumpy jaw) in a steer? A. Lime sulfur B. Terbinafine C. Griseofulvin D. 5-flucytosine E. Sodium iodide

a. Amoxicillin OR Trimethoprim-sulfamethoxazole

Which of the following antibacterial agents are listed as two first-choice therapeutics for sporadic LUTI? a. Amoxicillin OR Trimethoprim-sulfamethoxazole b. Ampicillin OR Enrofloxacin c. Chloramphenicol OR Doxycycline d. Azithromycin OR Erythromycin e. Marbofloxacin OR Meropenem

B. Tetracycline

Which of the following antibiotics should be used only as a last resort (relatively contraindicated) in a young puppy due to concern about discoloring and damaging the teeth? A. Amikacin B. Tetracycline C. Clindamycin D. Azithromycin E. Chloramphenicol

b. Primary gram negative bacteria

Which of the following best describes the spectrum of activity of amikacin at typical therapeutic doses? a. Protozoans + anaerobes b. Primary gram negative bacteria c. Gram positive + intracellular bacteria d. gram positive + gram negative + anaerobes e. primary gram positive bacteria + anaerobes

e) Broad spectrum, Gram-positive + Gram-negative + anaerobes

Which of the following best describes the spectrum of activity of pradofloxacin? a) Gram-positive + intracellular bacteria b) Most effective against protozoans + anaerobes c) Narrow spectrum, primarily Gram-positive bacteria d) Narrow spectrum, primarily Gram-negative bacteria e) Broad spectrum, Gram-positive + Gram-negative + anaerobes

D. Broad spectrum, Gram-positive + Gram-negative + anaerobes

Which of the following best describes the spectrum of activity of tetracycline? A. Gram-positive + intracellular bacteria B. Most effective against protozoans + anaerobes C. Narrow spectrum, primarily Gram-negative bacteria D. Broad spectrum, Gram-positive + Gram-negative + anaerobes E. Narrow spectrum, primarily Gram-positive bacteria + anaerobes

d) Enrofloxacin Rationale: There is no extralabel use in food animals.

Which of the following cannot legally be administered to a dairy cow for any indication that is not on the label? a) Ceftiofur b) Penicillin c) Tilmicosin d) Enrofloxacin e) Oxytetracycline

d) Chloramphenicol Rationale: Chloramphicol is prohibited in food animals.

Which of the following cannot legally be administered to a dairy cow for any indication? a) Ceftiofur b) tilmicosin c) enrofloxacin d) Chloramphenicol e) Sulfadimethoxine

e) Ceftiofur crystalline free acid

Which of the following is a depot formulation with a prolonged duration of action due to slow absorption from the injection site? a) Amoxicillin b) Ceftazidime c) Cefpodoxime d) Potassium penicillin e) Ceftiofur crystalline free acid

D. Zidovudine (AZT)

Which of the following is the antiviral agent with the best activity against RNA viruses? A. Acyclovir B. Guanosine C. 5-flucytosine D. Zidovudine (AZT) E. Idoxuridine

e) Inhibits cross-linkage of peptidoglycan in cell wall Rationale: PBP to inhibit cross linking of cell wall

Which of the following is the primary antibacterial mechanism of action of cefovecin? a) Inhibits ergosterol b) Inhibition of DNA gyrase c) Inhibits the 30s ribosomal subunit d) Inhibits the 50s ribosomal subunit e) Inhibits cross-linkage of peptidoglycan in cell wall

c) Inhibits folic acid metabolism

Which of the following is the primary antibacterial mechanism of action of sulfadiazine? a) Inhibits cyclooxygenase b) Inhibition of DNA gyrase c) Inhibits folic acid metabolism d) Inhibits the 30s ribosomal subunit e) Inhibits cross-linkage of peptidoglycan in cell wall

D. Inhibits the 30s ribosomal subunit

Which of the following is the primary antibacterial mechanism of action of tetracycline? A. Inhibits cyclooxygenase B. Inhibition of DNA gyrase C. Inhibits folic acid metabolism D. Inhibits the 30s ribosomal subunit E. Inhibits cross-linkage of peptidoglycan in cell wall

E. Valacyclovir

Which of the following is the prodrug for acyclovir? A. Zidovudine B. Ganciclovir C. Oseltamivir D. Famciclovir E. Valacyclovir

a) Modification of the antimicrobial target site.

Which one of the following is the most common mechanism of bacterial resistance to fluoroquinolones? a) Modification of the antimicrobial target site. b) Increased intracellular accumulation of the antibiotic. c) Activation of the antimicrobial drug by bacterial enzymes. d) Production of excess bacterial albumin to bind the antibiotic. e) Induction of hepatic enzymes to increase metabolism of the antibiotic.

e. Interferon

While great strides have been made in the last 25 years in the development of safe and effective antiviral therapies in people, antiviral therapeutics in veterinary species have lagged behind. Nonetheless, several nonspecific immunostimulants and human-approved antiviral drugs have been used in veterinary species. A nonspecific immunostimulant that has been used in veterinary species for viral infections is: a. Acyclovir b. Idoxuridine c. Zidovudine d. Oseltamivir e. Interferon

D. The Clinical Laboratory Standards Institute.

Who sets breakpoints for the sensitivity of veterinary isolates to specific antibacterial drugs? A. Breakpoints are usually set at Veterinary Teaching Hospitals for the surrounding region. B. Each practitioner sets his or her individual breakpoints for each patient. C. The State Diagnostic Laboratory sets breakpoints for the state. D. The Clinical Laboratory Standards Institute.

D. Several macrolides partition into lung and pulmonary white blood cells

Why are macrolides particularly useful for the therapy of respiratory infections, like BRD? A. Macrolides are more effective against BRD pathogens, like Staphylococcus, than any other drugs B. Macrolides decrease the immune response and so decrease the "cytokine storms" damaging lung parenchyma C. Resistance to macrolides is rare, so respiratory isolates will be sensitive D. Several macrolides partition into lung and pulmonary white blood cells

d) Penicillin doesn't penetrate LPS outer membrane/capsule well of Gm- bacteria

Why are most Gm- bacteria constitutively resistant to penicillin? a) Gm- bacteria generally develop adaptive resistance to penicillin. b) The P-glycoprotein pumps of Gm- bacteria pump penicillin out of the cell. c) Plasmids encode for beta-lactamase enzymes that transfer to Gm- bacteria. d) Penicillin doesn't penetrate LPS outer membrane/capsule well of Gm- bacteria e) Oxygen is required for enzymatic activation of penicillin, allowing passage through the inner membrane

d. Empirical antimicrobial therapy (no C&S) for sporadic cystitis is easier to defend in dogs than it is in cats

Why do the recommendations for diagnosis of sporadic bacterial lower urinary tract infection differ in cats versus dogs? a. There is no difference in recommendation between these species b. Potential comorbidities should be assessed in dogs but are unlikely in cats c. Since a contradiction for cystocentesis is common in animals with sporadic cystitis, cystocentesis is not recommended d. Empirical antimicrobial therapy (no C&S) for sporadic cystitis is easier to defend in dogs than it is in cats

e) surgically open the abscess, and treat with ceftiofur at twice the labeled dose

You are asked to exam a Holstein dairy cow for a large swelling on her shoulder. Ultrasound reveals a thick capsule and fluid center. You suspect a well-developed abscess. Of the following options, your best primary therapy is: a) surgically open the abscess b) treat with enrofloxacin at the labeled dose c) treat with cephalexin at twice the labeled dose d) administer a long-acting, injectable product, like cefovecin e) surgically open the abscess, and treat with ceftiofur at twice the labeled dose

A.Lime-sulfur

You are presented with "Tiger", a newly adopted, 3 mo old MC cat with mutifocal areas of alopecia and skin crusting. A CBC and plasma biochemistry panel are WNL. No mites are seen on skin scrapings, so you submit a hair sample for culture on dermatophyte testing media. Tiger lives with several young children, so you wish to begin empirical therapy while awaiting culture results. Which of the following would be expected to most rapidly kill the dermatophytes that are currently present in Tiger's fur? A.Lime-sulfur B.Itraconazole C.Terbinafine D.Griseofulvin E.Terbinafine

E. Antibiotics are not presently indicated. Rationale: Our first factor to consider is Organism. If we don't think that a bacterial organism is responsible for a patient's clinical signs, then antibiotics are not indicated.

You are presented with Bailey, a five year old male domestic longhaired cat. Bailey has been spending more time than normal in the litterbox, has been yowling during urination, and has urinated in the owner's bed. The patient is overweight, but otherwise the physical exam is within normal limits. You obtain urine by cystocentesis and submit it for a urinalysis, culture, and sensitivity. The urinalysis reveals protein and red blood cells. There is no bacterial growth on the culture. Which of the following is the most appropriate therapy for Bailey: Hint! Consider the Factors for Appropriate Antibiotic Use! A. Oral imipenem. B. Intravenous vancomycin. C. Oral amoxicillin + clauvulanic acid. D. Intravenous ampicillin + sulbactam. E. Antibiotics are not presently indicated.

c) Enrofloxacin Rationale: For UTI's you want a drug that is excreted intact in the urine. This would include beta-lactams, aminoglycosides, tetracyclines, nitrofurantoin, polymyxin B, and fluoroquinolones. Enrofloxacin is indicated for UTI's in small animals. Doxycycline is not excreted in urine at high levels but can achieve levels that are effective against some pathogens.

You are presented with Sonja, a five year old female spayed German shepherd dog. The owner reports that Sonja is urinating indoors, although she was previously well housetrained. The physical exam, CBC, and chemistry panel are within normal limits. You obtain urine by cystocentesis and submit it for a urinalysis, culture, and sensitivity. The urinalysis reveals protein, red blood cells, white blood cells, and numerous rod shaped bacteria. While the culture and sensitivity is pending, which of the following is the most appropriate therapy for Sonja: a) Imipenem b) Doxycycline c) Enrofloxacin d) Chloramphenicol e) Penicillin/amikacin

c) Tilmicosin Rationale: Tilmicosin has a high concentration in the lungs and WBC.

You are presented with a 10-month-old calf that is inappetant and dull. Physical examination reveals fever, tachypnea and consolidation of the ventral lung fields. You make a presumptive diagnosis of bovine respiratory disease. Which of the following would be most likely to accumulate at much higher concentrations in the lung of this calf as compared to plasma? a) Ceftiofur b) Penicillin c) Tilmicosin d) Florfenicol e) Enrofloxacin

d) Clindamycin

You are presented with a 12 year old Chihuahua, Pancho, with foul breath. An oral examination reveals gingivitis and several necrotic teeth. You anesthetize Pancho, take dental radiographs, and extract the damaged teeth. The foul smell and your clinical experience suggest that anaerobic bacteria are associated with the infected tooth roots. Which of the following would be the best choice to send home with Pancho for the dental infection? a) Cefoxitin b) Neomycin c) Vancomycin d) Clindamycin e) Enrofloxacin

a. No, antibiotics are not indicated for the therapy of viral infections except in special circumstances

You are presented with a 2 year old Paint colt that was recently transported to his first halter show. Four days after the show, the colt presents with cough, fever (105ºF), lethargy, inappetance, and a serous (clear) bilateral discharge from the nares. Auscultation of lower airways and a CBC are within normal limits, leading you to strongly suspect a viral infection. Considering the principles of judicious antimicrobial drug use, should antibacterial drugs be administered? a. No, antibiotics are not indicated for the therapy of viral infections except in special circumstances b. Yes, in this instance, the benefit outweighs the risk and antibiotics should be administered c. Yes, an antiviral drug should be administered as first-line therapy and antibiotics as an adjunct therapy d. No, antibiotics are not indicated because bacterial sensitivity testing is always performed first

d) No antibiotics

You are presented with a 3 year old male castrated cat, Luke, that is straining to urinate. CBC/chemistry panel/urinalysis are within normal limits. The bladder feels normal on palpation and can be easily expressed. You submit urine for culture and sensitivity testing, but there is no bacterial growth. Which of the following would be the most appropriate therapy? a) Cefovecin b) Amoxicillin c) Enrofloxacin d) No antibiotics e) Trimethoprim sulfadiazine

c) Amoxicillin

You are presented with a 3-year-old male castrated cat, Luke, that is straining to urinate. CBC/chemistry panel are within normal limits, but pyuria and cocci are noted on the urinalysis. You submit urine for culture, and a heavy growth of Staphyloccus spp is reported. Sensitivity testing reports "S" for amoxicillin, ampicillin, ceftiofur, enrofloxacin, and trimethoprim/sulphamethoxazole, imipenem, but "R" for tetracycline. Considering all aspects of therapeutic decision-making, which of the following would be the most appropriate therapy? a) ceftiofur b) imipenem c) Amoxicillin d) doxycycline e) no antibiotics

b) Doxycycline and tilmicosin Rationale: - Rifampin and florfenicol = narrow gram positives; broad anaerobes - Doxycycline and tilmicosin = broad anaerobes; broad anaerobes - Enrofloxacin and gentamicin = broad no anaerobes; gram neg no anaerobes - Penicillin, gentamicin, metronidazole = narrow gram positive, gram neg no anaerobes; anaerobes - Clindamycin, enrofloxacin, penicillin = gram positive, anaerobes; broad, no anaerobes; narrow gram positive)

You are presented with a 4-year-old Standardbred gelding with tachypnea and inappetance. The horse is febrile and you ascult a lack of breath sounds in the ventral lung fields, and crackles in dorsal lung fields. Ultrasound and radiographs support a diagnosis of pleuropneumonia. Pleurocentecis reveals foul smelling fluid, which is submitted for culture and sensitivity testing. Which of the following is most likely to be safe and effective against the likely pathogens (Gram-negative, Gram-positive, and anaerobes) in this horse? a) Rifampin and florfenicol b) Doxycycline and tilmicosin c) Enrofloxacin and gentamicin d) Penicillin, gentamicin, metronidazole e) Clindamycin, enrofloxacin, penicillin

C.A diagnosis of bacterial cystitis should be established.

You are presented with a five year old female spayed DSH cat that is straining to urinate. Before beginning rational antimicrobial therapy, which is the most important, initial consideration? A.The patient must have normal hepatic and renal function before beginning therapy. B.Hypersensitivity to penicillin needs to be ruled out before beginning therapy. C.A diagnosis of bacterial cystitis should be established. D.Sensitivity patterns must first be assessed in the urine.

a) florfenicol Rationale: Fusobacterium necrophorum is a gram negative anaerobe. Florfenicol is broad and works against anaerobes and intracellular pathogens.

You are presented with a four-year-old beef cow that is lame on the right hind limb. Physical examination reveals interdigital dermatitis, with foul-smelling, necrotic material present. Knowing that Fusobacterium necrophorum is the most common causative agent associated with this condition, which of the following would be the best therapy for this cow? a) florfenicol b) azteonam c) gentamicin d) Enrofloxacin e) metronidazole

D.Itraconazole

You are treating an 8 year old, intact male, mixed breed dog with blastomycosis affecting the lungs and skin. Which of the following agents has good efficacy against blastomycosis as monotherapy, and also has a wide therapeutic index? A.Amphotericin B B.5-flucytosine C.Griseofulvin D.Itraconazole E.Terbinafine