Antimicrobial resistance poses a serious public health threat and is an especially challenging issue when treating respiratory infections. Research shows that the number of pneumonia cases caused by antibiotic-resistant bacteria has risen substantially in recent years. These cases have been linked to higher mortality and morbidity, longer stays in intensive care, and increased costs due to inadequate therapy when compared with pneumonia caused by non-resistant pathogens.
“We’re in the middle of an antimicrobial resistance crisis in the United States,” says Helen W. Boucher, MD, FACP, FIDSA. “One of the biggest contributors to this issue is the overuse of antibiotics. Some clinicians are treating infections too broadly and prescribing unwarranted antibiotics. Although many respiratory infections are caused by viruses, antibiotics are often prescribed inappropriately to treat these infections.”
As with any infection, respiratory infections should be treated as narrowly as possible, according to Dr. Boucher, who co-authored a review article summarizing the current state of antimicrobial-resistant bacterial respiratory tract pathogens (Table) that was published in Current Opinion in Pulmonary Medicine. “The goal is to treat the exact pathogen that’s causing the infection, and nothing more. Treating beyond a specific pathogen can lead to overuse of antibiotics, resistance, and adverse effects for patients,” she says.
Dr. Boucher says strong, accurate diagnostic testing is required in order to appropriately prescribe antibiotics. “For pneumonia,” she says, “there are several new tools that are highly accurate in diagnosing the pathogen causing the infection. This allows for appropriate, pathogen-directed therapy. Pathogen-directed therapy also includes recognizing if the bacterium is susceptible or resistant to certain antibiotics.” Even when these factors are known, targeting antimicrobial-resistant bacteria can still be challenging because there are few therapeutic options available for treating respiratory infections.
For healthcare- and ventilator-associated pneumonia, pseudomonas and MRSA are often the cause. “Interventions have been put in place to prevent pneumonia in most hospitals in the U.S.,” says Dr. Boucher, “but when it does occur, it is important to treat it quickly with powerful antibiotics that are meant to treat resistant organisms. In most cases, the cause is not immediately known, so most hospitals follow protocols that start therapy based on the statistically most common causes—typically MRSA and pseudomonas—and then perform diagnostic tests to narrow treatment to one or two drugs that treat the specific pathogen. If a certain pathogen like pseudomonas is known to be the cause, treatment should include agents that target that pathogen, not those that treat many other bacteria at the same time. Doing so provides the best treatment for a given infection and causes less damage to the rest of the patient’s body. It also helps in our global fight against antibiotic resistance.”
Before initiating empirical antibiotics for a respiratory infection caused by an unknown pathogen, clinicians should take into consideration a patient’s risk of having resistant pathogens and their institution’s susceptibility to such pathogens, according to Dr. Boucher. “This data should be used to determine the most appropriate antibiotics to use first, while awaiting diagnostic testing results,” she says. “Patients should then be followed daily to determine if diagnostic testing has provided any answers that allow for de-escalation of therapy.”
The Ultimate Goal
The successful use of targeted therapy relies on the accurate, rapid identification of pathogens and the recognition of susceptibility patterns, says Dr. Boucher. “While there has been progress in recent years, the current gold-standard technique of Gram stain and cultures or respiratory specimens takes 48 to 72 hours to process,” she says. Diagnostic techniques using molecular assays or mass spectrometry may provide accurate identification of pathogens within a few hours, but most research in this area has focused on detecting viral respiratory infections. Studies are needed to determine the validity of such diagnostics in detecting bacterial respiratory infections.
In the meantime, Dr. Boucher says clinicians should ask themselves the following questions when treating patients with a respiratory infection:
- Do I know what the pathogen is?
- Can I reduce antibiotic exposure?
- Have I performed the right diagnostic tests?
- Is there information that will allow me to stop using any of these antibiotics?
- Are any of these antibiotics hurting the patient?
“Routinely asking these questions will help clinicians work toward the ultimate goal, which is treating patients with the most appropriate drugs for their infection,” Dr. Boucher says.
Lee B, Boucher H. Targeting antimicrobial-resistant bacterial respiratory tract pathogens: it is time to ‘get smart’. Curr Opin Pulm Med. 2015;21:293-303. Available at
Zumla A, Memish Z, Maeurer M, et al. Emerging novel and antimicrobial-resistant respiratory tract infections: new drug development and therapeutic options. Lancet Infect Dis. 2014;14:1136-1149.
Kuti E, Patel A, Coleman C. Impact of inappropriate antibiotic therapy on mortality in patients with ventilator-associated pneumonia and blood stream infection: a meta-analysis. J Crit Care. 2008;23:91-100.
Saravu K, Preethi V, Kumar R, et al. Determinants of ventilator associated pneumonia and its impact on prognosis. J Crit Care. 2012;27:322.e7-e14.