Osteomyelitis Study Questions

How are CRP and ESR different?

CRP -> produced by the liver -> in response to inflammatory process

ESR -> RBCs settling at the bottom of a test tube -> gravitational forces; response to fibrinogen levels in the blood

What can limit the accuracy of CRP?

Liver dysfunction

What can limit the accuracy of ESR?

Dehydration

Anemia (# of RBCs)

What antibiotic therapy should be initiated for the Gram-positive and Gram-negative organisms commonly isolated in osteomyelitis?

Broken into treatment choices for each individual organisms following this card

First Choice treatments for Staphylococci, oxacillin SUSCEPTIBLE

Nafcillin IV or Oxacillin IV

Cefazolin IV (1st gen)

Ceftriaxone (3rd gen)

Alternative treatment for Staphylococci, oxacillin SUSCEPTIBLE

Vancomycin IV

Daptomycin IV

Linezolid PO/IV

Levofloxacin IV + Rifampin PO

Clindamycin IV

First choice treatment for staphylococci, oxacillin RESISTANT

Vancomycin IV

Alternative treatment for staphylococci, oxacillin RESISTANT

Daptomycin IV

Linezolid PO/IV

Levofloxacin IV + Rifampin PO

First choice treatment for Enterococcus species, penicillin SUSCEPTIBLE

Penicillin G IV

Alternative treatment for Enterococcus species, penicillin SUSCEPTIBLE

Vancomycin IV

Daptomycin IV

Linezolid PO/IV

First choice treatment for Enterococcus species, penicillin RESISTANT

Vancomycin IV

Alternative treatment for Enterococcus species, penicillin RESISTANT

Daptomycin IV

Linezolid PO/IV

First choice treatment for B-hemolytic streptococci

Penicillin G IV

Ceftriaxone IV (3rd gen)

Alternative treatment for B-hemolytic streptocococci

Vancomycin IV

First choice treatment for pseudomonas aeruginosa

Cefepime IV (4th gen)

Meropenem IV (Q8H)

Doripenem IV (Q8H)

Alternative treatment for pseudomonas aeruginosa

Ciprofloxacin PO/IV

Aztreonam IV

(severe penicillin allergy)

(Quinolone resistance)

Ceftazidime / avibactam IV (3rd gen)

First choice treatment for Enterobacteriaceae (Non-Salmonella species) [gram (-)]

Cefepime IV (4th gen)

Ertapenem IV (No PA coverage, Q24H)

Alternative treatment for Enterobacteriaceae (Non-Salmonella species) [gram (-)]

Ciprofloxacin PO/IV

First choice treatment for Salmonella species

Ciprofloxacin PO/IV

Alternative treatment for Salmonella species

Ceftriaxone IV (3rd gen., No PA coverage)

What are the responses generated in class to questions in slides 23-25?

Broken into individual cards following this one

OM, a 70 year old male, presents to the diabetes clinic with an ulcer on his left big toe. The lesion began as a red spot about 5 months ago, but was ignored due to it not causing him pain. The ulcer is NOT foul smelling. OM has had T2DM for 30 years and is currently being treated with glimepiride and metformin.

What risk factor does this patient have for osteomyelitis?

How is the ulcer not causing him pain clinically important?

Is the ulcer not being foul smelling relevant? Why or why not?

Type 2 Diabetes

Not as severe

yes; foul smelling means anaerobic organisms.

O.M.'s WBC count was 15 x 103/mm3 (normal ~5 - 10 x 103/mm3)

O.M.'s fasting blood glucose, was 350 mg/dL (normal ~70-110), and ESR was 55 mm/hour (normal ~ 0 -15)

What estimations can be made about O.M.'s T2DM therapy?

What other laboratory marker also evaluates non-specific inflammation?

Are there any other laboratory assessments that you would like to have to better manage O.M.'s therapy?

May need insulin

CRP level

ABX culture

O.M.'s wound is derided, and contents obtained from a deep wound swab is sent to the microbiology laboratory for cultures.

He is hospitalized to receive wound care and to begin antibiotics.

What are some common organisms that the antimicrobial regimen should cover?

What antibiotic(s) should be initiated in O.M.?

What laboratory parameters should be used to monitor the therapy's effectiveness?

Gram(+) & Gram (-) organisms

Something with gram (+) and gram (-) coverage

WBC count, Temperature, SCr, BUN

WBC count -> biggest consideration to see if antibiotic is working

What are differences between cefazolin and ceftriaxone?

Cefazolin (1st gen.) -> gram (+) coverage

Ceftriaxone (3rd gen) -> gram (-) coverage (may also do gram(+))

Compare and contrast vancomycin, daptomycin, and linezolid

All gram (+) ONLY

Vancomycin -> nephrotoxicity

Daptomycin -> not good to use in pulmonary disease; causes muscle pain

Linezolid -> bone marrow suppression (Decrease WBCs, platelets, RBCs)

Why are levofloxacin & rifampin being used together?

Synergistic effects -> different MOAs

What are key points about levofloxacin and rifampin therapy?

Rifampin -> CYP inducer

Levofloxacin -> tendonitis, tendon rupture, chelation, not good in pregnancy

What is the catalase designation for B-hemolytic strep?

Catalase negative

Possible rationale for why organisms lyse blood agar

They want the iron that comes from RBC. Iron is important in bacterial growth.

What organisms have this hemolysis pattern? (B-hemolytic)

GAS -> S. pyogenes

GBS -> S. agalactiae

State an advantage of ceftriaxone use over penicillin

Ceftriaxone (3rd gen) -> broader coverage than penicillin

Which class of antibiotics should be used as last line of therapy to treat Pseudomonoas aeruginosa?

Carbapenems -> except ertapenem (Q24H, no PA coverage)

Doripenem (Q8H)

Meropenem (Q8H)

Imipenem/ cilastatin (Q6H)

What may explain why imipenem/cilastatin is not listed as possible options for Pseudomonas aeruginosa?

Seizure potential with imipenem

How is aztreonam therapy different from the other medications listed as possible treatment options?

Only gram (-) coverage

Which class of antibiotics should be avoided, if possible, when treating Pseudomonas aeruginosa in a patient on valproic acid therapy?

Prevent valproic acid activation

Valproic acid -> used for seizure control