The IDSA CAP guidelines are presented here. These guidelines have been updated after almost ten years by the IDSA (Infectious disease society of America) and ATS (American thoracic Society of America). The IDSA CAP Guidelines enable physicians to appropriately diagnose and effectively treat patients with community-acquired pneumonia.

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Definition of Severe Pneumonia according to 2007 ATS/ IDSA CAP guidelines:

The validated definition includes either one major criterion or three or more minor criteria

Minor criteria [Ref]

• Respiratory rate of 30 breaths/minute or more
• PaO2/FIO2 ratio of 250 or less
• Multilobar infiltrates
• Confusion or disorientation
• Uremia (blood urea nitrogen level of 20 mg/dl or more)
• Leukopenia (white blood cell count of less than 4,000 cells/ml)
• Thrombocytopenia (platelet count of less than 100,000/ml)
• Hypothermia (core temperature below 36 C)
• Hypotension requiring aggressive fluid resuscitation

Major criteria

• Septic shock with a need for vasopressors
• Respiratory failure requiring mechanical Ventilation

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The IDSA CAP guidelines consist of 16 questions that have been answered by the IDSA/ ATS experts.

Question 1:

 In Adults with CAP, Should Gram Stain and Culture of Lower Respiratory Secretions Be Obtained at the Time of Diagnosis?

Answer:

Gram stain and culture of respiratory secretions is not recommended routinely. Except for patients who have CAP, are managed in the hospital settings and have:

1. Severe pneumonia (especially in intubated patients)
2. Are treated empirically for MRSA or pseudomonas
3. Those with a past history of respiratory infections caused by pseudomonas or MRSA
4. Patients who were hospitalized in the past 90 days and received parenteral antibiotics.

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Question 2:

In Adults with CAP, should blood cultures be obtained at the time of diagnosis?

Answer: Not routinely recommended except for patients who have CAP, are managed in the hospital settings and have:

1. Severe pneumonia (especially in intubated patients)
2. Are treated empirically for MRSA or pseudomonas
3. Those with a past history of respiratory infections caused by pseudomonas or MRSA
4. Patients who were hospitalized in the past 90 days and received parenteral antibiotics.

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Question 3:

In adults with CAP, should Legionella and Pneumococcal urinary antigen testing be performed at the time of diagnosis?

Answer:

The IDSA/ATS experts suggest not routinely testing urine for pneumococcal antigen in adults with CAP

(conditional recommendation, low quality of evidence),

except in adults with severe CAP

(conditional recommendation, low quality of evidence).

They suggest not routinely testing urine for Legionella antigen in adults with CAP

(conditional recommendation, low quality of evidence),

except

• In cases where indicated by epidemiological factors, such as association with a Legionella outbreak or recent travel

(conditional recommendation, low quality of evidence);

or

• In adults with severe CAP (as defined above)

(conditional recommendation, low quality of evidence).

They suggest testing for Legionella urinary antigen and collecting lower respiratory tract secretions for Legionella culture on selective media or Legionella nucleic acid amplification testing in adults with severe CAP

(conditional recommendation, low quality of evidence).

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Question 4:

In Adults with CAP, Should a Respiratory Sample Be Tested for Influenza Virus at the Time of Diagnosis?

Answer:

When influenza viruses are circulating in the community, they recommend testing for influenza with a rapid influenza molecular assay (i.e., influenza nucleic acid amplification test), which is preferred over a rapid influenza diagnostic test (i.e., antigen test)

(strong recommendation, moderate quality of evidence).

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Question 5:

In Adults with CAP, Should Serum Procalcitonin plus Clinical Judgment versus Clinical Judgment Alone Be Used to Withhold Initiation of Antibiotic Treatment?

Answer:

They recommend that empiric antibiotic therapy should be initiated in adults with clinically suspected and radiographically confirmed CAP regardless of initial serum procalcitonin level

(strong recommendation, moderate quality of evidence).

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Question 6:

Should a Clinical Prediction Rule for Prognosis plus Clinical Judgment versus Clinical Judgment Alone Be Used to Determine Inpatient versus Outpatient Treatment Location for Adults with CAP?

Answer:

In addition to clinical judgment, the experts recommend that clinicians use a validated clinical prediction rule for prognosis, preferentially the Pneumonia Severity Index (PSI)

(strong recommendation, moderate quality of evidence)

over the CURB-65 (tool based on confusion, urea level, respiratory rate, blood pressure, and age >65)

(conditional recommendation, low quality of evidence),

to determine the need for hospitalization in adults diagnosed with CAP.

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Question 7:

Should a Clinical Prediction Rule for Prognosis plus Clinical Judgment versus Clinical Judgment Alone Be Used to Determine Inpatient General Medical versus Higher Levels of Inpatient Treatment Intensity (ICU, Step-Down, or Telemetry Unit) for Adults with CAP?

Answer:

The IDSA experts recommend direct admission to an ICU for patients with hypotension requiring vasopressors or respiratory failure requiring mechanical ventilation

(strong recommendation, low quality of evidence).

For patients not requiring vasopressors or mechanical ventilator support, they suggest using the IDSA/ATS 2007 minor severity criteria together with clinical judgment to guide the need for higher levels of treatment intensity

(conditional recommendation, low quality of evidence).

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Question 8:

In the Outpatient Setting, Which Antibiotics Are Recommended for Empiric Treatment of CAP in Adults?

Answer:

1. For healthy outpatient adults without comorbidities listed below or risk factors for antibiotic-resistant pathogens, they recommend:

• amoxicillin 1 g three times daily

(strong recommendation, moderate quality of evidence),

or

• doxycycline 100 mg twice daily

(conditional recommendation, low quality of evidence),

or

• a macrolide (azithromycin 500 mg on the first day then 250 mg daily

or

• clarithromycin 500 mg twice daily

or

• clarithromycin extended-release 1,000 mg daily) only in areas with pneumococcal resistance to macrolides < 25%

(conditional recommendation, moderate quality of evidence).

2. For outpatient adults with comorbidities such as chronic heart, lung, liver, or renal disease, diabetes mellitus, alcoholism, malignancy, or asplenia they recommend (in no particular order of preference):

• Combination therapy:

  • amoxicillin/clavulanate 500 mg/125 mg three times daily,

or

• • amoxicillin/ clavulanate 875 mg/125 mg twice daily,

or

• • 2,000 mg/125 mg twice daily,

or

• • a cephalosporin (cefpodoxime 200 mg twice daily or cefuroxime 500 mg twice daily);

AND

• • macrolide (azithromycin 500 mg on the first day then 250 mg daily, clarithromycin [500 mg twice daily or extended-release 1,000 mg once daily])

(strong recommendation, moderate quality of evidence for combination therapy),

or

• • doxycycline 100 mg twice daily

(conditional recommendation, low quality of evidence for combination therapy);

OR

• Monotherapy:

  • respiratory fluoroquinolone
    • levofloxacin 750 mg daily,
    • moxifloxacin 400 mg daily, or
    • gemifloxacin 320 mg daily)

(strong recommendation, moderate quality of evidence).

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Question 9:

In the Inpatient Setting, Which Antibiotic Regimens Are Recommended for Empiric Treatment of CAP in Adults without Risk Factors for MRSA and P. aeruginosa?

Answer:

In inpatient adults with nonsevere CAP without risk factors for MRSA or P. aeruginosa (see Recommendation 11), they recommend the following empiric treatment regimens (in no order of preference):

• combination therapy with a b-lactam
  • ampicillin/sulbactam 1.5–3 g every 6 h,
  • cefotaxime 1–2 g every 8 h,
  • ceftriaxone 1–2 g daily, or
  • ceftaroline 600 mg every 12 h

And

• • a macrolide (azithromycin 500 mg daily or clarithromycin 500 mg twice daily)

(strong recommendation, high quality of evidence),

or

• monotherapy with a respiratory fluoroquinolone
  • levofloxacin 750 mg daily,
  • moxifloxacin 400 mg daily

(strong recommendation, high quality of evidence)

The third option for adults with CAP who have contraindications to both macrolides and fluoroquinolones is:

• combination therapy with a b-lactam (ampicillin1sulbactam, cefotaxime, ceftaroline, or ceftriaxone, doses as above) and doxycycline 100 mg twice daily

(conditional recommendation, low quality of evidence)

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Question 10:

In the Inpatient Setting, Should Patients with Suspected Aspiration Pneumonia Receive Additional Anaerobic Coverage beyond Standard Empiric Treatment for CAP?

Answer:

The experts suggest not routinely adding anaerobic coverage for suspected aspiration pneumonia unless lung abscess or empyema is suspected

(conditional recommendation, very low quality of evidence)

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Question 11:

In the Inpatient Setting, Should Adults with CAP and Risk Factors for MRSA or P. aeruginosa Be Treated with Extended-Spectrum Antibiotic Therapy Instead of Standard CAP Regimens?

Answer:

The experts recommend abandoning the use of the prior categorization of healthcare-associated pneumonia (HCAP) to guide the selection of extended antibiotic coverage in adults with CAP

(strong recommendation, moderate quality of evidence)

They recommend clinicians only cover empirically for MRSA or P. aeruginosa in adults with CAP if locally validated risk factors for either pathogen are present

(strong recommendation, moderate quality of evidence)

Empiric treatment options for MRSA include:

• vancomycin (15 mg/kg every 12 h, adjust based on levels) or
• linezolid (600 mg every 12 h).

Empiric treatment options for P. aeruginosa include:

• piperacillin-tazobactam (4.5 g every 6 h),
• cefepime (2 g every 8 h),
• ceftazidime (2 g every 8 h),
• aztreonam (2 g every 8 h),
• meropenem (1 g every 8 h), or
• imipenem (500 mg every 6 h).

If clinicians are currently covering empirically for MRSA or P. aeruginosa in adults with CAP on the basis of published risk factors but do not have local etiological data, it is recommended to continue the empiric coverage while obtaining culture data to establish if these pathogens are present to justify continued treatment for these pathogens after the first few days of empiric treatment

(strong recommendation, low quality of evidence)

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Question 12:

In the Inpatient Setting, Should Adults with CAP Be Treated with Corticosteroids?

Answer:

The experts recommend not routinely using corticosteroids in adults with nonsevere CAP

(strong recommendation, high quality of evidence)

They suggest not routinely using corticosteroids in adults with severe CAP

(conditional recommendation, moderate quality of evidence)

They suggest not routinely using corticosteroids in adults with severe influenza pneumonia

(conditional recommendation, low quality of evidence)

The experts endorse the Surviving Sepsis Campaign recommendations on the use of corticosteroids in patients with CAP and refractory septic shock.

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Question 13:

In Adults with CAP Who Test Positive for Influenza, Should the Treatment Regimen Include Antiviral Therapy?

Answer:

The ATS/ IDSA experts recommend that anti-influenza treatment, such as oseltamivir, be prescribed for adults with CAP who test positive for influenza in the inpatient setting, independent of the duration of illness before diagnosis

(strong recommendation, moderate quality of evidence)

They suggest that anti-influenza treatment be prescribed for adults with CAP who test positive for influenza in the outpatient setting, independent of the duration of illness before diagnosis.

(conditional recommendation, low quality of evidence)

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Question 14:

In Adults with CAP Who Test Positive for Influenza, Should the Treatment Regimen Include Antibacterial Therapy?

Answer:

They recommend that standard antibacterial treatment be initially prescribed for adults with clinical and radiographic evidence of CAP who test positive for influenza in the inpatient and outpatient settings

(strong recommendation, low quality of evidence)

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Question 15:

In Outpatient and Inpatient Adults with CAP Who Are Improving, What Is the Appropriate Duration of Antibiotic Treatment?

Answer:

The experts recommend that the duration of antibiotic therapy should be guided by a validated measure of clinical stability. Clinical stability is the resolution of vital sign abnormalities like heart rate, respiratory rate, blood pressure, oxygen saturation, and temperature, the ability to eat, and a normal mental status,

And

antibiotic therapy should be continued until the patient achieves stability and for no less than a total of 5 days

(strong recommendation, moderate quality of evidence)

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Question 16:

In Adults with CAP Who Are Improving, Should Follow-up Chest Imaging Be Obtained?

Answer:

In adults with CAP whose symptoms have resolved within 5 to 7 days, they suggest not routinely obtaining follow-up chest imaging

(conditional recommendation, low quality of evidence)

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Summarizing the important IDSA CAP guidelines recommendations ...

The table below shows the differences between the 2019 and 2007 American Thoracic Society/Infectious Diseases Society of America Community-acquired Pneumonia Guidelines:

Recommendations	2007 ATS/IDSA Guideline	2019 ATS/IDSA Guideline
Sputum culture	Primarily recommended in patients with severe disease	Now recommended in patients with severe disease as well as in all inpatients empirically treated for MRSA or Pseudomonas aeruginosa
Blood culture	Primarily recommended in patients with severe disease	Now recommended in patients with severe disease as well as in all inpatients empirically treated for MRSA or Pseudomonas aeruginosa
Macrolide monotherapy	Strong recommendation for outpatients	Conditional recommendation for outpatients based on resistance levels
Use of procalcitonin	Not covered	Not recommended to determine the need for initial antibacterial therapy
Use of corticosteroids	Not covered	Recommended not to use. May be considered in patients with refractory septic shock
Use of healthcare-associated pneumonia category	Accepted as introduced in 2005 ATS/IDSA hospital-acquired and ventilator-associated pneumonia guidelines	Recommend abandoning this categorization. Emphasis on local epidemiology and validated risk factors to determine the need for MRSA or P. aeruginosa coverage. Increased emphasis on de-escalation of treatment if cultures are negative
Standard empiric therapy for severe CAP	b-Lactam/macrolide and b-lactam/fluoroquinolone combinations given equal weighting	Both accepted but stronger evidence in favor of b-lactam/macrolide combination
Routine use of follow-up chest imaging	Not addressed	Recommended not to obtain. Patients may be eligible for lung cancer screening, which should be performed as clinically indicated

 

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Summary of the Initial Treatment Strategies for Outpatients with Community-acquired Pneumonia (IDSA CAP Guidelines):

	Standard regimen	Remarks
No comorbidities or risk factors for MRSA or Pseudomonas aeruginosa	Amoxicillin or doxycycline or a macrolide (if local pneumococcal resistance is < 25%)	Risk factors include prior respiratory isolation of MRSA or P. aeruginosa or recent hospitalization AND receipt of parenteral antibiotics (in the last 90 days). Drug dosages: Amoxicillin 1 g three times daily, doxycycline 100 mg twice daily, azithromycin 500 mg on the first day then 250 mg daily, clarithromycin 500 mg twice daily, or clarithromycin ER 1,000 mg daily
With comorbidities	Combination therapy with amoxicillin/clavulanate or cephalosporin AND macrolide or doxycycline OR monotherapy with respiratory fluoroquinolone	Comorbidities include: chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; or asplenia.
		Amoxicillin/clavulanate 500 mg/125 mg three times daily, amoxicillin/clavulanate 875 mg/125 mg twice daily, 2,000 mg/125 mg twice daily, cefpodoxime 200 mg twice daily, or cefuroxime 500 mg twice daily; AND azithromycin 500 mg on the first day then 250 mg daily, clarithromycin 500 mg twice daily, clarithromycin ER 1,000 mg daily, or doxycycline 100 mg twice daily. Levofloxacin 750 mg daily, moxifloxacin 400 mg daily, or gemifloxacin 320 mg daily

 

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Summary of the Initial treatment Strategies for Inpatients with Community-acquired Pneumonia by Level of Severity and Risk for Drug Resistance (IDSA CAP guidelines):

	Non-severe inpatient pneumonia	Severe inpatient pneumonia	Examples
Standard regimen	B-Lactam + macrolide or respiratory fluoroquinolone	b-Lactam1macrolide or b-lactam + fluoroquinolone	Ampicillin/ sulbactam 1.5–3 g every 6 hours, cefotaxime 1–2 g every 8 hours, ceftriaxone 1–2 g daily, or ceftaroline 600 mg every 12 hours AND azithromycin 500 mg daily or clarithromycin 500 mg twice daily. Levofloxacin 750 mg daily or moxifloxacin 400 mg daily.
Prior Respiratory Isolation of MRSA	Add MRSA coverage and obtain cultures/nasal PCR to allow de-escalation or confirmation of the need for continued therapy	Add MRSA coverage and obtain cultures/nasal PCR to allow de-escalation or confirmation of the need for continued therapy	vancomycin (15 mg/kg every 12 h, adjust based on levels) or linezolid (600 mg every 12 h).
Prior Respiratory Isolation of Pseudomonas aeruginosa	Add coverage for P. aeruginosa and obtain cultures to allow de-escalation or confirmation of the need for continued therapy	Add coverage for P. aeruginosa and obtain cultures to allow de-escalation or confirmation of the need for continued therapy	piperacillin-tazobactam (4.5 g every 6 h), cefepime (2 g every 8 h), ceftazidime (2 g every 8 h), imipenem (500 mg every 6 h), meropenem (1 g every 8 h), or aztreonam (2 g every 8 h). It does not include coverage for extended-spectrum b-lactamase–producing Enterobacteriaceae, which should be considered only on the basis of the patient or local microbiological data.)
Recent Hospitalization and Parenteral Antibiotics and Locally Validated Risk Factors for MRSA	Obtain cultures but withhold MRSA coverage unless culture results are positive. If rapid nasal PCR is available, withhold additional empiric therapy against MRSA if rapid testing is negative or add coverage if PCR is positive and obtain cultures	Add MRSA coverage and obtain nasal PCR and cultures to allow de-escalation or confirmation of the need for continued therapy	vancomycin (15 mg/kg every 12 h, adjust based on levels) or linezolid (600 mg every 12 h).
Recent Hospitalization and Parenteral Antibiotics and Locally Validated Risk Factors for P. aeruginosa	Obtain cultures but initiate coverage for P. aeruginosa only if culture results are positive	Add coverage for P. aeruginosa and obtain cultures to allow de-escalation or confirmation of the need for continued therapy	piperacillin-tazobactam (4.5 g every 6 h), cefepime (2 g every 8 h), ceftazidime (2 g every 8 h), imipenem (500 mg every 6 h), meropenem (1 g every 8 h), or aztreonam (2 g every 8 h). It does not include coverage for extended-spectrum b-lactamase–producing Enterobacteriaceae, which should be considered only on the basis of the patient or local microbiological data.

  The IDSA CAP guidelines have been endorsed by the Society of Infectious Disease Pharmacists in July 2019. It is worth mentioning here that the physicians should try to have local microbiological and antibiotic sensitivity/ antibiotic resistance data and initiate empirical treatment according to their data. The IDSA CAP guidelines primarily focus on the initial treatment strategies, however, physicians must continue to monitor their patients for the response to therapy and the development of any complications.