The American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA) yesterday published updated guidelines on the diagnosis and treatment of adults with community-acquired pneumonia (CAP), and certain changes could prove antibiotic-sparing.

The new guidelines, published in the American Journal of Respiratory and Critical Care Medicine, were produced by a multidisciplinary panel of 15 experts from the United States, Australia, and Canada and reflect new and relevant research that's been published since the last CAP guidelines were issued by ATS and IDSA in 2007. They cover diagnosis and treatment of one of the most common infectious diseases in the world and a significant cause of morbidity and mortality.

"CAP remains one of the leading causes of deaths in the world," Grant Waterer, MBBS, PhD, co-chair of the guideline committee and a professor of medicine at the University of Western Australia, said in an ATS press release. "Not only has there been new data in the past decade, but there is now a strong national and international focus on antibiotic stewardship. It was time to update the guideline so that clinicians could be certain they were still practicing evidence-based care."

While CAP—defined as pneumonia acquired outside of the hospital—can be caused by either bacteria or viruses, distinguishing between viral and bacterial is challenging. It is commonly treated empirically with antibiotics upon diagnosis, and the choice of antibiotic is based on severity of illness, comorbidities, and other risk factors.

Notable changes

Although the updated guidelines contain several recommendations that remain unchanged from the 2007 guidelines, there are some notable changes. One of them is a recommendation to obtain sputum cultures in patients with severe CAP and those who are being treated empirically for CAP caused by methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa. The previous guidelines recommended sputum cultures primarily in patients with severe illness.

The rationale for this recommendation is that sputum culture results can help guide appropriate antibiotic therapy by either ruling out or confirming infection with MRSA or P aeruginosa, which require broader-spectrum antibiotics like vancomycin and piperacillin-tazobactam.

"These recommendations are not based on high-grade evidence but reflect the committee's desire to improve antibiotic use as well as improve clinicians' understanding of their local pathogen prevalences and resistance patterns, which we believe are key to selecting appropriate empiric antibiotic therapy," the authors write.

Using the same rationale, the new guidelines also recommend obtaining blood cultures from patients who have severe CAP and those being empirically treated for MRSA or P aeruginosa.

Another significant change is the elimination of the term healthcare-associated pneumonia (HCAP), which was initially introduced in 2005 to guide selection of extended antibiotic coverage in certain CAP patients. Previously, patients who acquired pneumonia in the community but lived in a nursing home or had been in a healthcare facility in the last 90 days were given the HCAP label, and the guidelines recommended treating those patients with antibiotics that cover for MRSA or Pseudomonas. The theory was that prior healthcare exposure was a risk factor for antibiotic-resistant pathogens.

The new guidelines recommend that these patients be given the CAP label, and that clinicians treat empirically for MRSA or P aeruginosa in these patients only if locally validated risk factors for either pathogen are present.

Valerie Vaughn, MD, a hospitalist at the University of Michigan's academic medical center who was not involved in crafting the guidelines, said this is a big change—with positive implications for antibiotic stewardship.

"The biggest change is that it's going to reduce the amount of MRSA and Pseudomonal coverage that occurs automatically, especially in patients that aren't that sick," Vaughn said. "Now, the guidelines are saying that you should really look at the patient's risk factors, you should look at the disease severity, and think before you give all those patients anti-MRSA and Pseudomonal coverage."

Under the previous guidelines, Vaughn said, "we were treating a whole bunch of patients for resistant organisms when they really weren't at high risk for it."

Revised therapy recommendations

The guidelines also revise empiric therapy recommendations. For healthy outpatients without comorbidities or risk factors for resistant pathogens, the new guidelines recommend amoxicillin as the first option, doxycycline as the second option, and a macrolide (azithromycin or clarithromycin) as the third option, depending on resistance levels; the previous guidelines strongly recommended macrolides for outpatients.

For inpatients who have severe CAP and no risk factors for MRSA or P aeruginosa, the new guidelines recommend that either a beta-lactam antibiotic plus a macrolide or a beta-lactam plus a respiratory fluoroquinolone should be the treatment of choice. While the 2007 guidelines also made this recommendation, the authors note there is now stronger evidence in favor of the beta-lactam/macrolide combination.

In addition, the guidelines recommend against using corticosteroids in CAP patients and against routine use of follow-up chest x-rays in patients who are improving. They also advise that procalcitonin levels should not be used to guide initial antibiotic therapy. These topics were not addressed in the 2007 guidelines.

The authors note that while the new guidelines should result in better care and better outcomes for patients, they're disappointed that many key questions have not been studied adequately enough to allow for strong recommendations. They also say that rapid diagnostic tests are needed to help clinicians quickly identify the causative pathogens and provide more targeted antibiotic therapy.

"Until we have such widely available (and affordable) tests, therapy for many or most patients with CAP will remain empiric," they write.

See also:

Oct 1 Am J Respir Crit Care Med CAP guidelines

Oct 1 AST press release