Lower Respiratory Tract Infections: AECOPD, Aspiration, and Pneumonia in the COVID-19 Era (Chapter 6)

3 January, 2023

Now we’re going to detour slightly and talk about aspiration because of its importance in LRTI and antimicrobial resistance. It turns out that overt Aspirations can cause pneumonia pneumonitis via three different processes. If it’s a large volume or as large particles such as partially digested food, you can get airway obstruction which pretty much gives you symptoms immediately. Chemical irritation as from stomach acid will give you a tissue burned. This tends to become problematic within a few minutes to hours. And finally, infection is seen usually a day later. Most cases of pneumonia following aspiration are probably subclinical. That is, it’s not the ones who are observed to have emesis and aspiration, but the ones who aspirate at night or have chronic gastro esophageal reflux. The bacteriology of aspiration include oral Streptococcus and anaerobes, which are certainly present in oral secretions. However, the thinking now is that these respond well to suctioning and coughing, which clear the airways and do not necessarily need antibiotics. More difficult to treat pathogens like staphylococcus including MRSA, gram-negatives including Pseudomonas will also respond to suctioning but may require antibiotic therapy. One interesting research point that’s come up is, is the lower respiratory tract, the lower lung truly sterile? For the longest time, it was felt that it was based on lung puncture. Now, it’s thought there may be low counts of bacteria, including gram-negatives, not enough necessarily to be detectable under many circumstances, but first of all, these may constitute to the pool of pathogens that cause infection when something else happens, like a viral infection such as COVID-19. In addition, the pathogens may increase the body’s inflammatory response, making more likely to fight an infection with those pathogens in later days, so it’s an area of increased research. And finally, we’re going to turn and finish with aspiration as a problem in the elderly.

This is data from Japan over a number of years, and shows that aspiration is the primary cause of pneumonia in many elderly patients. This particular study shows that below the age of 50, no cases of pneumonia attributed aspiration. Now it can happen that a patient who suffers head trauma, or he’s in an automobile accident with unconsciousness, they can certainly ask for it and develop pneumonia, but it’s relatively uncommon compared to pneumococcal pneumonia or viruses and bacterial superinfection. On the other hand, starting at about age 50, and certainly above the age 70, more and more cases in pneumonia in these elderly patients are due to aspiration. So this is a consideration, both to look for ongoing aspiration and to think about the pathogens related to Aspiration.

So finally, we’re going to conclude with a look at gram-negative bacteria, lower respiratory tract infections. And what we’ve been able to update in looking at some of the information from not only the recent COVID 19 epidemic, which is ongoing, but also the different clinical studies and protocols that have been prepared over the past 20 to 30 years. Well, one take home is that enteric gram-negative rod bacteria can cause exacerbations of COPD, and pneumonia. These notably Pseudomonas aeruginosa seem to be more prevalent on a percentage basis in Asia than the West which is important to recall when you’re reading protocols that were for example, based in Europe or the United States. Nursing home residency or hospitalization within the past three months, as well as prior antibiotic therapy, almost any kind of antibiotic therapy, or a history of severe COPD with multiple exacerbations is a risk factor for gram-negative respiratory infection. Both gram-negative and gram-positive bacteria can be multiple antibiotic resistant. Hopefully, information will be available from your hospital or your pulmonary or Infectious Disease Society about the prevalence rates in your community. New clinical microbiology techniques allow earlier identification of potential gram-negative pathogens and or resistance determinants. So now instead of waiting a day or two, for culture results and maybe waiting an additional day for susceptibilities, gene probes and other amplification techniques in the laboratory, and tell you when you’re dealing with MRSA, or potentially a Pseudomonas or potentially ESBL-producing strain of bacteria. Fluoroquinolones are effective for moderate to severe AECOPD, and they offer advantages over other drugs for example, the oral bioavailability and the high bioavailability. They should be considered as Pseudomonas aeruginosa, or other gramme negatives are concerned, if local susceptibilities allow. A very recent publication from experts in China, looking at Pseudomonas in lower respiratory infections suggests that there would be awareness of the risk factors which we’ve covered that susceptibility testing is ideal when Pseudomonas is cultured, and in some cases, combination therapy with a beta-lactam, intermediate glycoside or carbapenem drug or one of the new combination drugs with beta lactamase inhibitors may be necessary. And finally, that’s an expert consensus –  specifically looks at three different fluoroquinolones:  levofloxacin, ciprofloxacin and sitafloxacin endorses their use in outpatients with Pseudomonas in lower respiratory infections, including a COPD. And with that, I’ll thank everyone for their attention and close.