Tetracyclines, Macrolides, Clindamycin, Chloramphenicol, Streptogramins and oxazolidinones

Question 1

A 4 year old child is brought to the hospital after ingesting pills that a parent hasd used for bacterial dysentery. The child has been vomiting for more than 24 h and had diarrhea with green stools. She is now lethargic woth ashen color. Other signs and symtpoms include hypothermia and hypotension, and abdominal distention. The drug most likely to caue this problem is

Answer 1

Chloramphenicol

Question 2

Tetracycline are the DOC for RMSF and lyme disease. the mechanism of antibacterial action involves _______

Answer 2

Interference with binding of aminoacyl-tRNA to bacterial ribosomes

Question 3

Peptidyl transferase is inhibited by _________

Answer 3

cholramphenicol

Question 4

Clarithromycin and erythromycin have very similar spectra of antimicrobial activity. The major advantage of clarithromycin is that it

Answer 4

Has greater activity against H. pylori

• M. avium complex
• T. gondii
• Clarithromycin is adminsitered less frequently than erythromycin

Question 5

The primary mechanism of resistance of gram positive organisms to macrolide antibiotics including erythromycin is

Answer 5

Methylation of binding sites on the 50S ribosomal subunit

Question 6

A 26 year oold woman wsa treated for a suspected chlamydial infection at a neighborhood clinic. She was given a prescription for oral doxycline to be taken for 14 days. However patient was non compliant. whats the next step of management?

Answer 6

Treat her in the clinic with a single dose of oral dose of azithromycin

Question 7

A 55 year old patient with a prosthetic heart valve is to undergo periodontal procedure. What is prophylaxis of choice if the aptient is allergic to Penicillin G?

Answer 7

Clindamycin 1 h before the procedure

Question 8

____________ sometimes with gentamicin is recommended for prophylaxis in high risk penicillin-allergic patients undergoinf genitourinary and lower GI surgical procedures?

Answer 8

IV vancomycin

Question 9

Eythromycin can cause cardiac or CNS toxicity with excessive ingestion of _________

Answer 9

caffeine

Question 10

A 5-d course treatment for CAP would be effective using _______________

Answer 10

Azithromycin

Question 11

____________ is an effective drug in treament of MDR streptococcal infections

Answer 11

Quinupristin-dalfopristin

• E. Faecium
• Bactericidal
• Not hepatotoxic

Question 12

Tetracyclines

(Tetracycline, Doxycycline,Minocycline,Tigecycline)

Answer 12

Binds to 30S ribosomal subunit; Bacteriostatic; tigecycline has the broadest specturm adn resitance is less common (too large for efflux pum)

USed in infections due to chlamydiae, mycoplasma, rickerssiae, spirochetes, and H. pylori; treatment of acne (low dose)

Oral, IV. renal and biliary clearance. Doxycycline main GI elimination and long half life

SE: GI upset, deposition in developing bones, and teeth, photosensitivity, superinfection

Question 13

Macrolides

(Erythromycin, Azithromycin, Clarithromycin, telithromycin)

Answer 13

Bind to 50S ribosomal subuniut; bacteriostatic. Least resistance to telithromycin (too large for efflux pump)

Used in CAP, pertussis, corynebacteria, and chlamydial infections

Oral. IV for erythromycin, azithromycin. Hepatic clearance, azithromycin long half life (>40h)

SE: GI upsets, hepatic dysfunction. QT prolongation, CYP450 inhibition (not azithromycin)

Question 14

Lincosamide

(Clindamycin)

Answer 14

Bind to 50s ribosomal subunit. bacteriostatic

Used in skin, soft tissue, and anaerobic infections

Oral. IV. hepatic clearance

SE: GI upsets. C. Difficile colitis

Question 15

Streptogramins

(Quinupristin-dalfopristin)

Answer 15

Binds to 50s ribosomal subunit. bactericidal

Used in staphylococcal infections, vancimycin-resistant E.faecium

IV. renal clearance

SE: infusion related arthralgia and myalgia. CYP450 inhibition

Question 16

Chloramphenicol

Answer 16

Binds to 50s ribosomal subunit. Bacteriostatic

Wide spectrum, but mainly backup

Oral, IV; hepatic clearance, short half-life

SE: dose related anemia. Gray baby syndrome

Question 17

Oxazolidinones

(Linezolid, Tedizolid)

Answer 17

Binds to 23s RNA of 5S subunit; Bacteriostatic

Activitity includes MRSA, PRSP, and VRE strains.

Tedizolid :MRSA(skin and soft tissue infections); once daily dosing (long half life)

SE: Dose related anemia, neuropathy, optic neuritis, serotonin syndrome with SSRIs

Question 18

Resistance to tetracyclines is due to ___________

Answer 18

development of efflux pumps

Question 19

Used in meningococcal carrier state

Answer 19

minocycline

Question 20

Secondary uses of tetracyclines

Answer 20

Alternative drug for syphilis. Prophylaxis against infection inchronic bronchitis

Question 21

Erythomycin is excreted via ____________

Answer 21

biliary system

Question 22

narrow spectrum macrolide that inhibits protein synthesis and is selectively active against gram positive aerobes and anaerobes

Answer 22

Fidaxomicin

Question 23

Mechanism of resitance for clindamycin

Answer 23

Methylation if the binding site on the 50s ribosomal subunit and enzymatic inactivation

Question 24

Used in combination with pyrimethamine for AIDS-related toxoplasmosis

Answer 24

Clindamycin