http://upload.orthobullets.com/topic/9059/images/d zone test 2.jpg
http://upload.orthobullets.com/topic/9059/images/antibiotics_mechanisms_of_action.jpg
Overview of By Mechanism
 
 
 
PENICILLINS
CEPHALOSPORINS
FLUOROQUINOLONES

AMINOGLYCOSIDES

MONOBACTAMS
CARBAPENEMS
MACROLIDES
OTHER
Natrual
First generation
Ciprofloxacin (Cipro)
Levofloxacin (Levaguin) 
Moxifloxacin (Avelox)
Norfloxacin     
 Amikacin
Gentamicin
Kanamycin
Neomycin
Tobramycin
     
 Aztreonam      Ertapenem
Imienem
Meropenem     
Azithromycin
Clarithromycin
Dirithromycin
Erythromycin
Clindamycin
     
Vancomycin
Rifampin
Doxycycline
Linezolid
Tetracycline
Trimethoprim/ sulfamethoxacole

Penicillin G
Penicillin-VK

Cephalothin
Cefazolin (Ancef, Kefzol) 
Cephapririn
Cephalexin (Keflex)
other

Penicillinase Resistant
Second Generation
Methicillin
Nafcillin
Oxacillin
other
Cefacor
Cefotetan (Cefotan) 
other
Aminopenicillins
Third Generation
Ampicillin Ceftriaxone (Rocephin) 
other
 
Fourth Generation
  Cefpirome
Cefepime
 
Antibiotic Grouping By Mechanism
Cell Wall Synthesis Penicillins
Cephalosporins
Vancomycin
Beta-lactamase Inhibitors
Carbapenems
Aztreonam
Polymycin
Bacitracin
Protein Synthesis Inhibitors

Inhibit 30s Subunit
Aminoglycosides (gentamicin)
Tetracyclines
Inhibit 50s Subunit
Macrolides
Chloramphenicol
Clindamycin
Linezolid 
Streptogramins

DNA Synthesis Inhibitors Fluoroquinolones 
Metronidazole
RNA synthesis Inhibitors Rifampin
Mycolic Acid synthesis inhibitors
Isoniazid
Folic Acid synthesis inhibitors Sulfonamides
Trimethoprim
 
Antibiotic Classification & Indications
 
Inhibits Cell Wall Synthesis
Penicillins
(bactericidal: blocks cross linking via competitive inhibition of the transpeptidase enzyme)
Class/Mechanism Drugs Indications (**Drug of Choice) Toxicity
Penicillin Penicillin G
Aqueous penicillin G
Procaine penicillin G
Benzathine penicillin G
Penicillin V

Strep. pyogenes (Grp.A)**
Step. agalactiae (Grp.B)**
C. perfringens(Bacilli)**

Hypersensitivity reaction
Hemolytic anemia
Aminopenicillins Ampicillin
Amoxicillin

Above + 
↑ Gram-negative:
E. faecalis**
E. Coli**

 Above
Penicillinase-resistant-penicillins Methicillin
Nafcillin
Oxacillin
Cloxacillin
Dicloxacillin
Above +
PCNase-producingStaph. aureus
Above + 
Interstitial nephritis
Antipseudomonal penicillins Carbenicillin
Ticarcillin
Piperacillin
Above +
Pseudomonas aeruginosa**

 Above
Cephalosporins
(bactericidal: inhibits bacterial cell wall synthesis via competitive inhibition of the transpeptidase enzyme)
1st generation  Cefazolin
Cephalexin
Staph. aureus**
Staph. epidermidis**
Some Gram-negatives:
E. Coli
Klebsiella
Allergic reaction
Coombs-positive anemia (3%)
2nd generation Cefoxitin
Cefaclor
Cefuroxime
Above +
 Gram-negative
Allergic Reaction
ETOH Disulfiram reaction
3rd generation Ceftriaxone
Cefotaxime
Ceftazidime
Cefepime (4th generation)
Above +
 Gram-negative
Pseudomonas
Allergic Reaction
ETOH Disulfiram reaction
Other Cell Wall Inhibitors
Vancomycin q
(bactericidal: disrupts peptioglycan cross-linkage)
 Vancomycin

MRSA**
PCN/Ceph allegies**
S. aureus
S. epidermidis

Red man syndrome
Nephrotoxicity
Ototoxicity
Beta-lactamase Inhibitors 
(bactericidal: blocking cross linking)
Clavulanic Acid
Sulbactam
Tazobactam

S aureus**
S epidermis**
E.Coli**
Klebsiella**

Hypersensitivity Reaction
Hemolytic anemia
Carbapenems

Imipenem (+ cilastatin)
Meropenem
Doripenem
Ertapenem
Broadest activity of any antibiotic
(except MRSA, Mycoplasma)
 
Aztreonam

Aztreonam Gram-negative rods
Aerobes
Hospital-acquired infections
 
Polymyxins Polymyxin B
Polymyxin E
Topical Gram-negative infections  
Bacitracin Bacitracin Topical Gram-positive infections  
Protein Synthesis Inhibition
Anti-30S ribosomal subunit
Aminoglycosides
(bactericidal: irreversible binding to 30S) q q
Gentamicin
Neomycin
Amikacin
Tobramycin
Streptomycin
Aerobic Gram-negatives
Enterobacteriaceae 
Pseudomonas
Nephrotoxicity
Ototoxicity
Tetracyclines
(bacteriostatic: blocks tRNA)
Tetracycline
Doxycycline
Minocycline
Demeclocycline

Rickettsia
Mycoplasma
Spirochetes (Lyme's disease)

Hepatotoxicity
Tooth discoloration Impaired growth
Avoid in children < 12 years of age
Anti-50S ribosomal subunit
Macrolides
(bacteriostatic: reversibly binds 50S)
Erythromycin
Azithromycin
Clarithromycin
Streptococcus
H. influenzae
Mycoplamsa pneumonia

Coumadin Interaction (cytochrome P450)

Chloramphenicol
(bacteriostatic)
Chloramphenicol H influenzae
Bacterial Meningitis
Brain absces
Aplastic Anemia
Gray Baby Syndrome
Lincosamide
(bacteriostatic: inhibits peptidyl transferase by interfering with amino acyl-tRNA complex)
Clindamycin

Bacteroides fragilis
S aureus
Coagulase-negative Staph & Strep
Excellent Bone Penetration

Pseudomembranous colitis
Hypersensitivity Reaction

Linezolid
(variable)
Linezolid Resistant Gram-positives  
Streptogramins Quinupristin
Dalfopristin
VRE
GAS and S. aureus skin infections
 
DNA Synthesis Inhibitors
Fluoroquinolones
(bactericidal: inhibit DNA gyrase enzyme, inhibiting DNA synthesis)
1st generation   Nalidixic acid Steptococcus
Mycoplasma
Aerobic Gram +

Phototoxicity
Achilles tendon rupture
Impaired fracture healing 
q

2nd generation Ciprofloxacin
Norfloxacin
Enoxacin
Ofloxacin
Levofloxacin
As Above +Pseudomonas as above
3rd generation Gatifloxacin As above + Gram-positives as above
4th generation Moxifloxacin
Gemifloxacin
As above + Gram-positives + anaerobes as above
Other DNA Inhibitors
Metronidazole
(bacteridical: metabolic biproducts disrupt DNA)
Metronidazole (Flagyl) Anaerobics Seizures
Crebelar dysfunction
ETOH disulfram reaction
RNA Synthesis Inhibitors
Rifampin
(bactericidal: inhibits RNA transcription by inhibiting RNA polymerase)
Rifampin Staphylococcus
Mycobacterium 
(TB) q
Body fluid discoloration
Hepatoxicity (with INH)
Mycolic Acids Synthesis Inhibitors
Isoniazid Isoniazidz TB
Latent TB
 
Folic acid Synthesis Inhibitors
Trimethoprim/Sulfonamides
(bacteriostatic: inhibition with PABA)
Trimethoprim/Sulfamethoxazole (SMX)
Sulfisoxazole
Sulfadiazine
UTI organisms
Proteus
Enterobacter

Thrombocytopenia
Avoid in third trimester of pregnancy

Pyrimethamine Pyrimethamine Malaria
T. gondii
 
 
 Bacteria Overview
 
Gram Postive Cocci
Staphylococcus Staph. aureus
MSSA
MRSA
Staph. epidermis
Staph saprophyticus
Streptococcus Strep pneumoniae
Strep pyogenes (Group A) 
Strep agalacticae (Group B) 
Strep viridans
Strep Bovis (Group D)
Enterococci E. faecalis (Group D strep)
Gram Positive Bacilli
Spore Forming

Bacillus anthracis
Bacillus cereus
Clostridium tetani
Clostridium botulinum
Clostridium perfringens
Clostridium difficile

Non-Spore Forming Corynebacterium diphtheriae
Listeria monocytogenes
Gram Negative Cocci
Neisseria Neisseria meningitidis
Neisseria gonorrhoeae
Gram Negative Bacilli
Enterics Escherichia coli
Salmonella typhi
Salmonella enteridis
Shigella dysenteriae
Klebsiella pneumoniae
Serratia
Proteus
Campylobacter jejuni
Vibrio cholerae
Vibrio parahaemolyticus/vulnificus
Helicobacter pylori
Pseudomonas aeruginosa
Bacteroides fragilis
Respiratory bacilli Haemophilus influenzae
Haemophilius ducreyi
Bordatella pertussis
Zoonotic bacilli Yersinia enterocolitica
Yersinia pestis
Brucella 
Francisella tularensis 
Pasteurella multocida 
Bartonella henselae
Other
Gardnerella vaginalis
Other Bacteria
Mycobacteria Mycobacterium tuberculosis
Mycobacterium leprae
MOTTS
Spirochetes Borrelia burgdorferi
Leptospira interrogans
Treponema pallidum
Chlamydiaceae Chlamydia trachomatis
Chlamydophila 
Rickettsia
Ehrlichia
Mycoplasmataceae Mycoplasma pneumoniae
Ureaplasma urealyticum
Fungus-like Bacteria Actinomyces israelii
Nocardia
 
Antibiotic Resistance Mechanisms
  • Bacteria develop ability to hydrolyze these drugs using β lactamase
    • confers resistance to penicillin
    • e.g. E. coli, Staph epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae
    • add β lactamase inhibitor e.g. clavulanic acid in amoxicillin-clavulanate (Augmentin)
  • Genetic mutation of mecA
    • carried by Staphylococcal cassette chromosome (SCCmec) mobile genetic unit
    • a bacterial gene encoding a penicillin-binding protein (PBP2a). 
      • PBP2a has reduced affinity for antibiotics
      • confers resistance to methicillin, oxacillin, nafcillin
      • e.g. MRSA
        • SCCmec type IV has less genetic elements and is specific to CA-MRSA, making CA-MRSA less multi-drug resistant
  • Altered cell wall permeability
    • confers resistance to tetracyclines, quinolones, trimethoprim and β lactam antibiotics
  • Creation of biofilm barrier
    • provides an environment where offending bacteria can multiply safe from the hoste immune system
      • Salmonella
      • Staph epidermidis
  • Active efflux pumps
    • confers resistance to erythromycin and tetracycline
    • e.g. msrA gene in Staph
  • Altered peptidoglycan subunit (altered D-alanyl-D-alanine of NAM/NAG-peptide) 
    • confers resistance to vancomycin
    • e.g. vancomycin resistant enterococcus (VRE) 
  • Ribosome alteration
    • erm gene confer inducible resistance to MLS (macrolide lincosamide streptogranin) agents via methylation of 23s rRNA
    • demonstrate using D zone test   
      • for inducible clindamycin resistance in Staph and beta hemolytic Strep
Penicillins
  • Mechanism
    • interfer with bacterial cell wall synthesis
  • Subclassification and tested examples
    • natural
      • penicillin G
    • penicillinase-resistant
      • methicillin (Staphcillin)
    • aminopenicillins
      • ampicillin (Omnipen, Polycillin)
 
Cephalosporins
  • Overview
    • bactericidal
  • Mechanism
    • disrupts the synthesis of the peptidoglycan layer of bacterial cell walls  
      • does so through competitive inhibition on PCB (penicllin binding proteins)
      • peptidoglycan layer is important for cell wall structural integrity.
    • same mechanicsm of action as beta-lactam antibiotics (such as penicillins)
  • Subclassification and tested examples
    • first generation
      • cefazolin (Ancef, Kefzol)
    • second generation
      • cefaclor (Ceclor)
    • third generation
      • cefriazone (Rocephin)
    • fourth generation
      • cefepime (Maxipime)
Fluoroquinolones
  • Mechanism
    • blocks DNA replication via inhibition of DNA gyrase 
  • Side effects
    • inhibit early fracture healing through toxic effects on chondrocytes 
    • increased rates of tendinitis, with special predilection for the Achilles tendon. 
      • tenocytes in the Achilles tendon have exhibited degenerative changes when viewed microscopically after fluoroquinolone administration.
      • recent clinical studies have shown an increased relative risk of Achilles tendon rupture of 3.7. 
  • Subclassification and tested examples
    • ciprofloxacin (Cipro)
    • levofloxacin (Levaquin)
Aminoglycosides
  • Mechanism
    • bactericidal
    • inhibition of bacterial protein synthesis 
      • work by binding to the 30s ribosome subunit, leading to the misreading of mRNA. This misreading results in the synthesis of abnormal peptides that accumulate intracellularly and eventually lead to cell death. These antibiotics arebactericidal.
  • Subclassification and tested examples
    • gentamicin (Garamycin)
Vancomycin
  • Coverage
    • gram-positive bacteria
  • Mechanism
    • bactericidal
    • an inhibitor of cell wall synthesis 
  • Resistance
    • increasing emergence of vancomycin-resistant enterococci has resulted in the development of guidelines for use by the  (CDC) 
    • indications for vancomycin 
      • serious allergies to penicillins or beta-lactam antimicrobials 
      • serious infections caused by susceptible organisms resistant to penicillins (MRSA, MRSE)
      • surgical prophylaxis for major procedures involving implantation of prostheses in institutions with a high rate of MRSA or MRSE
Rifampin
  • Most effective against intracellular phagocytized Staphylococcus aureus in macrophages 
Linezolid
  • Linezolid binds to the 23S portion of the 50S subunit and acts by preventing the formation of the initiation complex between the the 30S and 50S subunits of the ribosome.
Splenectomy
  • Splenectomy patients or patients with functional hyposplenism require the following vaccines and/or antibiotics 
    • Pneumococcal immunization
    • Haemophilus influenza type B vaccine
    • Meningococcal group C conjugate vaccine
    • Influenza immunization
    • Lifelong prophylactic antibiotics (oral phenoxymethylpenicillin or erythromycin)
 

Please rate topic.

Average 4.1 of 32 Ratings

Questions (10)

(OBQ12.53) What mechanism allows Staphylococcus epidermidis to adhere to surfaces and resist phagocytosis? Review Topic

QID:4413
1

Creation of active efflux pumps

1%

(26/3178)

2

Methylation of 23s rRNA

1%

(20/3178)

3

Biofilm production

93%

(2963/3178)

4

Alteration of cell wall permeability

2%

(71/3178)

5

Beta-lactamase production

3%

(84/3178)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

Staphylococcus epidermidis is a gram-positive bacteria that utilizes a glycocalyx/biofilm to adhere to orthopedic implants and other surfaces and resist phagocytosis.

The biofilm creates a well-protected environment where bacteria can proliferate and thrive essentially undetected by the host immune system. This leads to chronic infections of orthopedic implants that can go undetected for years.

Arciola et al note that S. epidermidis can colonize surfaces in a self-generated viscous biofilm composed of polysaccharides and that the ica genes found in 56% of S. epidermidis isolates were associated with their ability to produce biofilm.

Olson et al discuss the importance of polysaccharide intercellular adhesin (PIA), a substance produced by 50-60% of S. epidermidis strains, in the adherence of S. epidermidis to biomaterials through biofilm creation. PIA plays a critical role in initial adherence of S. epidermidis to biomaterials, biofilm maturation and aggregation.

Illustration A shows microscopy of Staphylococcus epidermidis, which is a gram-positive, coagulase-negative cocci. Illustration B is an overview of the different classes of organisms in microbiology.

Incorrect Answers:
Answer 1,2,4,5: Efflux pump production, hydrolysis of B-lactam drugs with beta-lactamase, alteration in cell wall permeability, and ribosomal alteration are mechanisms that Staphylococcus uses to resists antibiotics.

ILLUSTRATIONS:

Please rate question.

Average 3.0 of 7 Ratings

Question COMMENTS (0)

(OBQ11.70) Which of the following antibiotic families inhibit bacterial DNA gyrase? Review Topic

QID:3493
1

Quinolones

81%

(1194/1482)

2

Penicillins

1%

(11/1482)

3

Aminoglycosides

11%

(169/1482)

4

Macrolides

5%

(71/1482)

5

Sulfonamides

2%

(30/1482)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

Quinolones are a class of antibiotics which act by inhibition of bacterial DNA gyrase. Penicillins interfere with bacterial cell wall synthesis. Aminoglycosides and macrolides interfere with bacterial protein synthesis by acting on the 30S and 50S ribosome subunits respectively. Sulfonamides interfere with bacterial folic acid metabolism.

Levine and DiBona review fluoroquinolones as a class of antibiotics and describe their potential beneficial and adverse effects in the treatment and prevention of musculoskeletal infections. While not frequently used in musculoskeletal infection, fluoroquinolones appear to be very effective in the treatment of osteomyelitis and infections involving prosthetic implants like hip and knee replacements.


Please rate question.

Average 3.0 of 15 Ratings

Question COMMENTS (0)

(OBQ11.138) MecA is the bacterial gene which encodes for a penicillin-binding protein that alters the efficacy of beta-lactam antibiotics. Which of the following species of bacteria are known to produce mecA? Review Topic

QID:3561
1

Clostridium dificile

1%

(8/1265)

2

Clostridium tetani

0%

(2/1265)

3

Vancomycin-resistant enterococcus

3%

(35/1265)

4

Methicillin-resistant staphylococcus aureus

95%

(1199/1265)

5

Streptococcus epidermidis

1%

(16/1265)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

Methicillin-resistant Staphylococcus aureus is the most common carrier of the mecA gene. This gene may also be found in Staphylococcus aureus and Streptococcus pneumoniae species and provide penicillin resistance for these bacteria. None of the other listed bacteria are known to harbor mecA in their bacterial genome.

Marcotte and Trzeciak review community-acquired MRSA with specific focus on diagnosis and treatment. They discuss the differences between community-acquired and hospital-acquired MRSA. Specifically, they emphasize bacterial gene products like mecA which alter the bacterial susceptibility towards common antibiotics, and provide appropriate treatment options for common MRSA infections.


Please rate question.

Average 3.0 of 14 Ratings

Question COMMENTS (0)

(OBQ08.275) What is the mechanism of action of vancomycin? Review Topic

QID:661
1

inhibition of cell wall synthesis

78%

(1268/1617)

2

increase cell wall permeability

10%

(154/1617)

3

ribosomal inhibition

6%

(95/1617)

4

interference with DNA metabolism

5%

(85/1617)

5

antimetabolite action

1%

(9/1617)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

Vancomycin is an inhibitor of cell wall synthesis and is bactericidal for gram positive organisms. Antibiotics exert their effects via five basic mechanisms: (1) Inhibition of cell wall synthesis (cephalosporins, penicillins, vancomycin, imipenem). (2) Increasing cell membrane permeability (Bacitracin). (3) Ribosomal inhibition (gentamycin, erythromycins, linezolid, tetracyclines). (4) interference with DNA metabolism (quinolones), and (5) antimetabolite action (Trimethoprim).


Please rate question.

Average 3.0 of 15 Ratings

Question COMMENTS (5)

(OBQ06.87) Which class of antibiotics inhibit early fracture healing through toxic effects on chondrocytes? Review Topic

QID:198
1

cephalosporins

1%

(6/838)

2

quinolones

86%

(724/838)

3

penicillins

0%

(3/838)

4

macrolides

8%

(71/838)

5

sulfonamides

4%

(34/838)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

Animal models have shown that quinolones inhibit early fracture healing through a toxic effect on chondrocytes. The study by Perry et al demonstrated that fracture calluses in the animals treated with quinolones showed a lower histologic grade as compared with control animals representing a less mature callus with the presence of more cartilage and less woven bone. The study by Huddleston et al demonstrated fracture calluses in the animals treated with ciprofloxacin showed abnormalities in cartilage morphology and endochondral bone formation and a significant decrease in the number of chondrocytes compared with the controls. None of the other antibiotics listed are known to have toxic effects on chondrocytes.


Please rate question.

Average 2.0 of 14 Ratings

Question COMMENTS (0)

(OBQ06.134) Rifampin is highly effective against phagocytized intracellular Staphylococcus aureus especially in combination with other antibiotics because of its: Review Topic

QID:320
1

Hydrophilic activity

7%

(40/555)

2

High cell penetration

81%

(448/555)

3

Structural similarity to penicillin

1%

(7/555)

4

Structural similarity to vancomycin

1%

(7/555)

5

Beta-lactamase activity

10%

(53/555)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

Based on the choices above, rifampin works well synergistically with other antibiotics because of its high cell penetration.

Rifampin is a bactericidal antibiotic that blocks the function of RNA polymerase and subsequent RNA transcription. It is used to treat both staphylococcus and mycobacterium infections. Because of the high rate of cellular penetration, it is effective against intracellular phagocytized staphylococcus.

Darouiche et al. investigated the cellular penetration of seven antibiotics in cultured human umbilical vein endothelial cells. Lipophilic drugs such as minocycline, ciprofloxacin and rifampin had better cell penetration. Although rifampin was found to have limited killing activity, it potentiated the bactericidal activity of other antibiotics when used in combination.

Illustration A shows a schematic detailing the mechanism of rifampin’s bactericidal action.

Incorrect Answers
Answer 1, 3, 4, 5: Rifampin is lipophilic, rendering its ability to cross the cell wall/membrane and exert its actions against RNA polymerase.

ILLUSTRATIONS:

Please rate question.

Average 3.0 of 11 Ratings

Question COMMENTS (1)

(OBQ05.99) A 62-year-old man undergoes an uncomplicated total shoulder replacement 9 months ago. What is an appropriate choice of prophylactic antibiotics to be taken prior to dental work if he has no allergies? Review Topic

QID:985
1

daptomycin 600 milligrams intravenous 2 hours prior to procedure

1%

(3/454)

2

amoxicillin 4 grams oral 1 week prior to procedure

11%

(50/454)

3

levaquin 500 milligrams oral 1 hour prior to procedure

9%

(42/454)

4

trimethoprim-sulfamethoxazole 2 tablets double-strength oral 1 hour prior to procedure

12%

(55/454)

5

cephalexin 2 grams oral 1 hour prior to procedure

67%

(303/454)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

Patients not allergic to penicillin should take 2 grams of Amoxicillin, Cephalexin, or Cephadrine, by mouth one hour prior to the dental procedure. IV antibiotics are very rarely used in dental offices. If allergic to penicillin, clindamycin would be the next best alternative.


Please rate question.

Average 2.0 of 26 Ratings

Question COMMENTS (8)

(OBQ04.42) A splenectomy is performed in a 7-year-old boy following a motor vehicle accident. All of the following are recommended for long-term management EXCEPT: Review Topic

QID:103
1

Pneumococcal vaccination

1%

(11/754)

2

Haemophilus influenza type B vaccination

1%

(6/754)

3

Meningococcal group C vaccination

1%

(11/754)

4

Lifelong prophylactic antibiotics

45%

(338/754)

5

Hepatitis A vaccination

51%

(388/754)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

All of the responses are correct except the need for Hepatitis A vaccine. Hepatitis A is a virus with tropism for hepatocytes which causes infection from fecal-oral contaminated food/water, and shows no increased rate of either infectivity or morbidity in patients with hyposplenism.

Basic recommendations for splenectomized patients include:
1. All splenectomized patients and those with functional hyposplenism should receive pneumococcal immunization.
2. Patients not previously immunized should receive haemophilus influenza type B vaccine.
3. Patients not previously immunized should receive meningococcal group C conjugate vaccine.
4. Influenza immunization should be given.
5. Lifelong prophylactic antibiotics are still recommended (oral phenoxymethylpenicillin or erythromycin). This is seemingly despite lack of good data demonstrating a role for lifelong chemoprophylaxis and the acknowledgement that long-term compliance may be problematic.

Davies et al review the current level of evidence supporting these guidelines for infection prevention in patients with hyposplenism. New to these guidelines are issues regarding occupational exposure and the use of the meningococcal group C and the seven-valent pneumococcal vaccine in non-immunized hyposplenic patients.

Gandhi et al evaluated their nonoperative management of blunt splenic injury in pediatric trauma care. They found compared to historical controls, children with blunt splenic injuries who were hemodynamically stable could be safely monitored with a protocol which required 4 days of inpatient care, 3 weeks of quiet home activities, and 3 months of light activity. This protocol seems to allow for safe return to unrestricted activity.

Incorrect Answer:
Answers 1-4 are incorrect because they are recommended in splenectomy patients.


Please rate question.

Average 1.0 of 58 Ratings

Question COMMENTS (10)

(OBQ04.58) All of the following antibiotics function by interfering with protein synthesis by inhibiting ribosomes EXCEPT Review Topic

QID:1163
1

gentamycin

1%

(4/296)

2

tobramycin

1%

(2/296)

3

vancomycin

72%

(212/296)

4

erythromycin

3%

(10/296)

5

linezolid

23%

(68/296)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

Gentamycin and tobramycin are aminoglycosides that function by inhibition of bacterial protein synthesis via irreversible binding to ribosomal subunits. Erythromycin functions by binding to the 50s subunit of the bacterial 70s rRNA complex and thereby inhibits protein synthesis. Linezolid binds to the 23s portion of the ribosomal subunit and inhibits protein synthesis. In contrast, Vancomycin acts by inhibiting proper cell wall synthesis and does not inhibit the ribosome.


Please rate question.

Average 3.0 of 21 Ratings

Question COMMENTS (3)

(OBQ04.190) All of the following antibiotics function by interfering with cell wall synthesis EXCEPT Review Topic

QID:1295
1

Cefazolin

2%

(8/418)

2

Penicillin G

2%

(7/418)

3

Vancomycin

13%

(54/418)

4

Imipenem

10%

(40/418)

5

Gentamicin

74%

(309/418)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

Cephalosporins (cefazolin), penicillins, vancomycin, and imipenem function by interfering with cell wall synthesis. Gentamicin, an aminoglycoside, functions by inhibiting ribosomes and protein synthesis and does not affect cell wall synthesis.

The reference by Mader et al. is an instructional course lecture that reviews the different mechanisms of antibiotics and their indications in musculoskeletal infections.

Illustration A is a table showing common mechanisms of antibiotics.

ILLUSTRATIONS:

Please rate question.

Average 3.0 of 21 Ratings

Question COMMENTS (7)
Sorry, this question is available to Virtual Curriculum members only.

Click HERE to learn more and purchase the Virtual Curriculum today!


This is a Never-Been-Seen Question that can only be seen in Milestone Exams
for Virtual Curriculum members.

Click HERE to learn more and purchase the Virtual Curriculum today!


EVIDENCE & REFERENCES (16)
Topic COMMENTS (19)