Pulmonology Advisor: What are some key considerations in choosing the right antibiotics for pneumonia or TB?

Dr Cohen: Providing certain empiric antibiotics for bacterial pneumonia could decrease the likelihood of diagnosing active TB. For example, the use of fluoroquinolone antibiotics (such as levofloxacin), which are second-line agents for TB, may have a partial effect against TB. Decreasing the bacterial load may delay the diagnosis of TB

However, with the advent of molecular testing – which are non-culture-based techniques – the diagnosis of TB is changing. The use of molecular diagnostic tests, such as the Hain line probe assay or the GeneXpert, can allow for more rapid diagnosis. However, in a low-burden setting such as the United States, we do not typically run these tests routinely unless we have a high degree of clinical suspicion of TB. 

Dr Deresinski: Cases of pneumonia acquired in the community can be treated with a number of different antibiotics. If patients fail to respond to first-line antibiotics, it may be because the illness is not due to a bacterial infection or that it is caused by a bacterium that is resistant to the prescribed antibiotics. This may be determined by microbiologic testing and testing the ability of various antibiotics to inhibit the growth of bacteria recovered in culture of respiratory secretions. This allows selection of the antibiotics best suited to treat the infection. In some cases, the infection may be due, as suggested, to viruses or even to fungi or Mycobacterium tuberculosis.


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Dr Rogers: Bacterial pneumonia can become deadly very quickly, and so we tend to treat it empirically. If we can get a sputum or blood culture that tells us the specific bacteria involved, that is a huge help and allows for more targeted treatment, but that is often not possible. So, a lot of times, you base your treatment regimen on the history, appearance on chest X-ray, the patient’s own risk factors and baseline health, and knowledge of the common bacterial resistance patterns in your hospital or area.

With TB, it is usually, although not always, a more indolent course, meaning that people have had it for weeks or months rather than days. That gives you a chance to make sure you have the diagnosis right, often with multiple sputums or invasive bronchoscopy for a sample if you cannot make the diagnosis otherwise. Because TB takes a while to culture, it can take some time to get resistance patterns, so you still need to choose a regimen empirically based on your knowledge of whether TB in your area or where the patient traveled is sensitive to standard therapy. So, you still try to treat quickly, both for the patient and to limit any exposure to others.

TB is quite rare in most regions of the United States. At a pulmonary review course 2 years ago, people raised their hands if they had ever seen a case of TB, and less than half of the room had seen it. That means it is not on clinicians’ radars, so we need to keep a high index of suspicion.

Pulmonology Advisor: In considering whether to delay antibiotics in patients with TB or pneumonia, and in choosing which ones to give, are there more problems with certain classes?

Dr Cohen: There is really no debate about whether antibiotics should be delayed for pneumonia with sepsis or septic shock – they should always be given immediately. But in terms of which antibiotics to give, you have to think about where the patient came from – for example, if they haven’t been in the health care system very much, they are less likely to have been exposed to drug-resistant bacteria

Some antibiotics, including newer agents such as ceftazidime/avibactam, are reserved for known drug-resistant infections. Overuse and unnecessary exposure to these reserved antibiotics may allow drug-resistance to develop and circulate in communities, which would squander their usefulness. 

Dr Deresinski: TB may occasionally mimic other more common bacterial pneumonias, but more often presents with more prolonged symptoms. Treatment, which differs from that for other causes of pneumonia, is not usually initiated until the diagnosis is confirmed. Unfortunately, the diagnosis is often not initially considered, and antibiotics are administered, and one of the antibiotic types that may be administered are fluoroquinolones, such as levofloxacin. Because the fluoroquinolones are partly effective against Mycobacterium tuberculosis, their administration may actually delay the ability to diagnose this infection.

When the diagnosis of TB is confirmed, treatment is initiated immediately not only to improve the patient’s clinical status but also to reduce the risk of transmission to others. Treatment may have to be altered when the infection is caused by drug-resistant strains.

Dr Rogers: In general, on a patient-by-patient basis, I do not think this is such an issue. On a societal level, a lot of patients with viral illness receive treatment with antibiotics, which has no benefit, exposes them to risk, and can increase the risk for antibiotic resistance to the entire community. On an individual level, we know that treating with antibiotics, even if you do not experience drug-related adverse effects, wipes out your good bacteria and puts patients at risk for things such as Clostridium difficile diarrhea, so each decision to treat with antibiotics should not be taken lightly.

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Pulmonology Advisor: What is recommended for patients who do not appear to be responding to the first round of antibiotics?

Dr Cohen: Monitoring an individual’s response to treatment is important. If a patient being treated for infection is doing poorly, then it is possible that the infection is not contained, the particular antibiotics are not effective, or they have not been given a long enough time to work. Drug resistance may be one reason that the antibiotics are ineffective. The clinician may wish to broaden the antibiotics and continue to make similar adjustments based on how the patients respond.

Pulmonology Advisor: Are there any additional points you would like to mention?

Dr Cohen: When patients are admitted to the ICU with sepsis or septic shock, it is important to obtain appropriate culture data so that the source of the infection can be identified, and antibiotics can be narrowed appropriately. 

References

1. Kim RY, Ng AM, Persaud AK, et al. Antibiotic timing and outcomes in sepsis. Am J Med Sci. 2018;355(6):524-529.

2. Sherwin R, Winters ME, Vilke GM, Wardi G. Does early and appropriate antibiotic administration improve mortality in emergency department patients with severe sepsis or septic shock? J Emerg Med. 2017;53(4):588-595.