The causes of adult bacterial community-acquired pneumonia (CAP) include S. pneumoniae, Heamophilus influenza, as well as atypical bacteria, Mycoplasma, Chlamydophila, and Legionella.
It is not possible to predict the pathogen from the clinical presentation of the pneumonia.
Therefore, your antibiotic must cover the above possibilities.
Although the guideline diagnosis of adult CAP requires a chest x-ray for diagnosis, there is no need to defer antibiotic treatment until after the chest x-ray. And in fact, patients do better if they receive the initial dose of antibiotics within 8 hours of diagnosis.
In treating community-acquired pneumonia (CAP), it is important to ask, what antibiotics have you been on in the last three months. The key is to choose an antibiotic in a different class from what the patient has been on in the past three months.
There is no way to clinically differentiate between typical and atypical pneumonia so you need to cover for both in treating CAP.
The guidelines suggest for a person with an outpatient CAP and no history of antibiotic use in the last three months, use a macrolide (azithromycin), doxycycline, or a respiratory floroquinolone (levofloxacin, moxifloxacin). The trouble with doxycycline is that it causes photosensitivity (so maybe not in the summer).
For an inpatient non-ICU admission for CAP, choose levofloxacin or moxifloxacin, or ceftriaxone (an antipneumococcal beta-lactam) plus a macrolide.
See references for recommended antibiotic therapy of the CAP patient admitted to the ICU and for the patient with COPD admitted for pneumonia.
The latest guidelines state that five days of antibiotic therapy is adequate. If they aren’t better in five days, you need to do a lot more evaluation. Dr. Koenig says that it can be helpful to know that you are dealing with legionella (via a urinary antigen test) because you might want to treat it for a little longer, up to fourteen or twenty-one days. But even so, most legionella will respond to five days of azithromycin.
Dr. Koenig strongly endorses use of bedside physician performed ultrasound in the critical care patient with lung disease. He states it is much better than chest x-ray for the evaluation of alveolar consolidation, pleural effusion, and congestive heart failure.
[Dr. Koenig and his associates have an excellent website, Critical Care Ultrasonography Forum, which may be useful to any physician dealing with inpatients or emergency department patients. The site has an excellent and extensive collection of ultrasound interpretation practice clips. These clips cover lung, cardiac, abdomen, and vascular cases.]
[The best brief teaching videos for a physician to get started with bedside ultrasound are by critical care specialist Dr. Liz Turner. Her 2012 lecture, on YouTube, Quality Improvement Technology and Medical Education: Bedside Ultrasound with Elizabeth Turner, explains the need for and rationale for the technique. A list of her YouTube ultrasound teaching videos are here.]
On average, it takes 2.5 to 4 days of treatment of CAP for the patient to start to feel better. So if after five or six days the patient is not feeling better, something else is going on–so just giving a different antibiotic might not be the way to go.
What should you be thinking about when there is delayed resolution of the CAP? Does the patient have COPD, bronchiectasis, alcoholism, immunodeficiency, neurologic disease, or Congestive Heart Failure? Maybe the patient has tuberculosis or a fungal infection.
When the CAP is not improving, reconsider the diagnosis.
Perhaps the problem is a non-infectious etiology such as eg, malignancy, vasculitis, collagen vascular disease, eosinophilic disease, bronchiolitis obliterans organizing PNA, pulmonary embolism, or pulmonary hemorrhage.
Maybe you are treating the wrong pathogen (but Dr. Koenig says that if you are following the guidelines, probably not although it could be mycobacterium or a fungus).
If the patient isn’t getting better, perhaps there is a post obstructive process (an endobronchial lesion) or an empyema.
So here is what to do when you have a non-resolving pneumonia. Now is the time to get sputum for gram stain and culture and to get blood cultures. Now is the time to do a chest CT (and Dr. Koenig says you do not need IV contrast unless you are worried about a pulmonary embolus). And if you haven’t come up with an answer then you need to move towards more invasive diagnosis with fiberoptic bronchoscopy or open lung biopsy.
INFECTIOUS DISEASES OF THE AIRWAY
Audio-Digest Family Practice
Volume 62, Issue 09, March 7, 2014 Community-Acquired Pneumonia (Summary) George C. Mejicano, MD, MS, Professor of Medicine and Senior Associate Dean for Education, Oregon Health and Science University, Portland
TOPICS IN PNEUMONIA
Audio-Digest Internal Medicine
Volume 61, Issue 05, February 7, 2014 Community-Acquired Pneumonia + Nonresolving Pneumonia (Summary) Seth Koenig, MD, Associate Professor of Medicine, Division of Pulmonary, Critical Care, and Hospital Medicine, Hofstra North Shore Long Island Jewish School of Medicine at Hofstra University, Hempstead, NY
Infectious Diseases Society of America/American Thoracic Society Consensus Guidelines on the Management of Community-Acquired Pneumonia in Adults (Full Text PDF) Clinical Infectious Diseases 2007; 44:S27–72.