The correct answer is:

Linezolid

Educational Objective:

Discuss the diagnosis and treatment of MRSA pneumonia.

Key Point:

The treatment of choice for MRSA pneumonia is intravenous vancomycin or linezolid.

Explanation:

Community-acquired pneumonia due to MRSA (MRSA pneumonia) should be suspected in patients who are colonized with MRSA or who have other MRSA risk factors such as living in prison/jail and participating in contact sports. MRSA pneumonia may also occur in association with influenza.

A patient with MRSA risk factors, who presents with pneumonia, rapid clinical deterioration with sepsis, acute respiratory distress syndrome, and necrotizing pneumonia requires empiric coverage for MRSA, which typically consists of adding either vancomycin or linezolid to a regular pneumonia regimen (a third-generation cephalosporin or beta-lactam or beta-lactamase inhibitor PLUS a macrolide or fluoroquinolone)

Linezolid has been approved for the treatment of infections caused by vancomycin-resistant Enterococcus faecium, hospital-acquired pneumonia caused by Staphylococcus aureus, complicated skin and skin structure infections (SSSIs), uncomplicated SSSIs caused by methicillin-susceptible S. aureus or Streptococcus pyogenes, and community-acquired pneumonia caused by Streptococcus pneumoniae.

The methicillin-resistant S. aureus and vancomycin-resistant enterococci are considered the most common Gram-positive bacteria found in intensive care units (ICUs), and linezolid, as an antimicrobial drug, is commonly utilized to treat infected ICU patients.

Linezolid is very well absorbed orally with a bioavailability of 100%. The presence of food does not affect its absorption. Therefore, the administration route of antibiotic can be changed from intravenous (IV) to oral in clinically stable patients. Moreover, co-administration with antacids like magnesium hydroxide and aluminum hydroxide had no effect on oral absorption.

Daptomycin penetrates poorly into the lungs and is not indicated for MRSA pneumonia treatment, although it can be quite effective and bactericidal in nonpulmonary MRSA infections and vancomycin-resistant Enterococcus faecalis.

Ceftaroline is a fifth-generation cephalosporin with coverage against MRSA; however, it has not been approved for use in MRSA pneumonia.

Tigecycline has been associated with increased mortality in severely ill patients and it is chosen only if other alternatives are contraindicated.

There is no role for quinolones (such as Levofloxacin) in the treatment of MRSA infections, even when in vitro susceptibility is present, because of the risk of developing resistance.

Additional Figures:

Bacterial Infections: Community-acquired Pneumonia with Methicillin-resistant Staphylococcus Aureus in a Patient Admitted to the Intensive Care Unit

Bacterial Infections: Emergence of community-acquired meticillin-resistant Staphylococcus aureus strain USA300 as a cause of necrotising community-onset pneumonia - bacterial infections

References:

Moran GJ, Waxman MA. Pneumonia. (Chapter 66) In: Walls R, et al. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 9th ed., 2018: 871-880.e2

Hashemian SMR, Farhadi T, Ganjparvar M. Linezolid: a review of its properties, function, and use in critical care. Drug Des Devel Ther. 2018 Jun 18;12:1759-1767. doi: 10.2147/DDDT.S164515. PMID: 29950810; PMCID: PMC6014438.

Rodvold KA, McConeghy KW. Methicillin-resistant Staphylococcus aureus therapy: past, present, and future. Clin Infect Dis. 2014;58(suppl 1):S20-S27.

Wunderink RG. How important is methicillin-resistant Staphylococcus aureus as a cause of community-acquired pneumonia and what is best antimicrobial therapy? Infect Dis Clin North Am. 2013;27(1):177-188.