Specific Organisms and Therapeutic Regimens

Organism-specific therapeutic regimens for community-acquired pneumonia (CAP) are provided below, including those for Streptococcus pneumoniae, Haemophilus influenzae, methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible S aureus (MSSA), Pseudomonas aeruginosa, Legionella pneumophila, Mycoplasma pneumoniae, Chlamydia pneumoniae, anaerobes, influenza A/B, histoplasmosis, and blastomycosis.^{[1, 2]}

It is important to note that the most commonly observed bacterial etiology in CAP is S pneumoniae. The listed empiric regimens (see Community-Acquired Pneumonia Empiric Therapy) consider but cannot predict the details of particular resistance patterns observed in specific geographic locations; thus, attention to the results of resistance testing should be acted on as soon as possible.

Point-of-care testing that informs antibiotic coverage and narrows the spectrum will arguably improve outcomes and minimize overuse of antibiotics. This approach with more careful and rapid diagnostics may also open the way for more directed use of antiviral agents.^[3]In addition, identifying a specific pathogen within the first 24-72 hours can still be useful for continued therapy. For example, this information may be used to select specific antimicrobial therapy when considering a switch from parenteral to oral therapy.^[1]

Organisms of bioterrorism must be considered in the context of mass presentations or suspected exposure events. These organisms or agents may include anthrax (inhalation), Yersinia pestis (pneumonic plague), tularemia, Legionella, influenza, and ricin (inhalation).

Management “bundles” (activity sets) applied to the care of patients with community-acquired pneumonia and those who are at risk for pneumonia have proven important in reducing mortality and improving outcomes (hospital length of stay and complication rates) by ensuring optimal care of patients admitted to the hospital setting by using checklists of proven strategies. These practices include such interventions as administering twice-daily oral hygiene with chlorhexidine, elevating the head of the bed (HOB) to 30°, and sitting the patient upright for all meals and oral intake.

Other important considerations in managing patients admitted with CAP include vaccinating patients appropriately to prevent recurrent infections with both pneumococcal vaccines (Prevnar and then Pneumovax) and influenza vaccines. In addition, counselling about smoking cessation strategies is essential to minimize future pneumonia risk.

The organism-specific recommendations below are adapted from the Infectious Diseases Society of America/American Thoracic Society Consensus Guidelines.^[1]

It is of interest that the types of observed pneumonia vary by region and community; however, the most common etiology is generally S pneumoniae (approximately 40%); the etiology is viral in approximately 30% of cases.^[4]

The duration of treatment for community-acquired pneumonia has decreased from 2 weeks to 10 days to, currently, a minimum of 5 days. With this minimal duration of antibiotic therapy (5 days), patients should be afebrile for 48-72 hours and have no more than one abnormal vital sign before antibiotic therapy is discontinued.^[5]

Streptococcus pneumoniae community-acquired pneumonia

S pneumoniae CAP is treated as follows:

Amoxicillin 500 mg PO q8h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign
Cefotaxime 1 g IV q8h for a minimum of 5 days and until the patient is afebrile for 48-72 hours and has no more than one abnormal vital sign
Ceftriaxone 1 g IV q24h for a minimum of 5 days and until the patient is afebrile for 48-72 hours and has no more than one abnormal vital sign

Penicillin–intermediately resistant or -resistant strains are treated as follows:

Ceftaroline 600 mg IV q12h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign
Ceftriaxone 2 g IV q24h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign

Haemophilus influenzae community-acquired pneumonia

H influenzae CAP is treated as follows:

Amoxicillin 500 mg PO q8h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign
Amoxicillin-clavulanate 2 g PO q12h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign
Ceftriaxone 1 g IV q24h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign

Methicillin-resistant Staphylococcus aureus community-acquired pneumonia

MRSA CAP is treated as follows:

Vancomycin 15 mg/kg IV q12h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign or
Linezolid 600 mg IV or PO q12h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign

Methicillin-susceptible Staphylococcus aureus community-acquired pneumonia

MSSA CAP is treated as follows:

Oxacillin 1g IV q4-6h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign or
Nafcillin 1-2g IV q6h for a minimum of 5 days and until patient is afebrile for 48-72 hours and has no more than one abnormal vital sign

Pseudomonas aeruginosa community-acquired pneumonia

P aeruginosa CAP requires combination treatment until the specific susceptibilities of the pathogen are known.

Option 1 for P aeruginosa CAP is as follows (with a therapy duration of 10-14 days):

Piperacillin-tazobactam 4.5 g IV q6h or 3.375 g IV q4h or
Cefepime 2 g IV q8h or
Imipenem 1 g q6-8h or
Meropenem 2 g IV q8h
If penicillin allergic, substitute aztreonam 2g IV q6-8h
PLUS
Ciprofloxacin 400 mg IV q8h or
Levofloxacin 750 mg IV q24h

Option 2 for P aeruginosa CAP is as follows (with a therapy duration of 10-14 days):

Piperacillin-tazobactam 4.5 g IV q6h or 3.375 g IV q4h or
Cefepime 2 g IV q8h or
Imipenem 1 g q6-8h or
Meropenem 2 g IV q8h
If penicillin allergic, substitute aztreonam 2g IV q6-8h
PLUS
Gentamicin 7 mg/kg/day IV or
Tobramycin 7 mg/kg/day IV or
Amikacin 20 mg/kg/day IV
PLUS
Azithromycin 500 mg IV q24h

Option 3 for P aeruginosa CAP is as follows (with a therapy duration of 10-14 days):

Piperacillin-tazobactam 4.5 g IV q6h or 3.375 g IV q4h or
Cefepime 2 g IV q8h or
Imipenem 1 g q6-8h or
Meropenem 2 g IV q8h
If penicillin allergic, substitute aztreonam 2g IV q6-8h
PLUS
Gentamicin 7 mg/kg/day IV or
Tobramycin 7 mg/kg/day IV or
Amikacin 20 mg/kg/day IV
PLUS
Levofloxacin 500 mg IV or PO q24h or
Moxifloxacin 400 mg IV/PO q24h

Legionella pneumophila community-acquired pneumonia

L pneumophila CAP is treated as follows:

Levofloxacin 750 mg IV q24h, then 750 mg PO daily for 7-10 days or
Moxifloxacin 400 mg IV q24h, then 400 mg PO daily for 7-10 days or
Azithromycin 500 mg IV, then 500 mg PO daily for 7-10 days (second line after fluoroquinolones ^[6])

Mycoplasma pneumoniae community-acquired pneumonia

M pneumoniae CAP is treated as follows:

Doxycycline 100 mg IV/PO BID for 7-10 days
Azithromycin 500 mg PO q24h for 3 days or 1 g PO as a single dose, then 500 mg PO q24h for 2 days or 2 g PO as a single dose or
Clarithromycin extended-release 1000 mg PO q24h or 500 mg PO q12h for 7 days or
Erythromycin 500 mg PO q8h for 7-14 days

Chlamydia pneumoniae community-acquired pneumonia

C pneumoniae CAP is treated as follows:

Azithromycin 500 mg PO q24h for 3 days or 1 g PO as a single dose, then 500 mg PO q24h for 2 days or 2 g PO as a single dose or
Clarithromycin extended-release 1000 mg PO q24h or 500 mg PO q12h for 7-14 days or
Erythromycin 500 mg PO q8h for 7-14 days

Anaerobes community-acquired pneumonia

Anaerobes CAP is treated as follows: