As AB is an uncommon pathogen in CAP, current antibiotic guidelines are not targeted toward treating AB.’ This accounts for the inadequate empirical coverage for our group of CAP-AB patients (68.4%), especially if therapeutic combinations of salbactam-containing antibiotics are not used. Therefore, it is very important that we have increased awareness of AB as a cause of severe CAP; then we will be able to choose the appropriate antibiotics for treatment. For the treatment of patients with HAP-AB, inadequate empirical coverage (79.7%), despite adherence to the prevailing guidelines, was due to the presence of resistance to multiple antibiotics. add comment
Our study has several limitations that merit consideration. First, it was a retrospective study and is prone to missing data. A prospective study is difficult to perform for CAP-AB, given its rarity, but fortunately we were able to collect the majority of the data that were required for analysis. Second, patients with VAP-AB may not be able to experience or report symptoms such as cough, shortness of breath, or pleuritic chest pain, causing a spuriously low prevalence of these symptoms in the HAP-AB group. Third, establishing a definite diagnosis of pneumonia due to AB based on respiratory specimens, especially for nosocomial pneumonia, is difficult, given that this bacterium frequently colonizes mucosal surfaces in hospitalized patients, and that there is no specific microbiological marker for nosocomial pneumonia, even with quantitative bacterial cultures. However, in our series, we only selected patients with overt clinical symptoms and signs of pneumonia to minimize the diagnostic uncertainties. Furthermore, for all HAP-AB patients, AB was shown to be the predominant organism on direct Gram smear, and so it was a probable pathogen.
In conclusion, CAP-AB is a clinically unique entity, with a high incidence of bacteremia, ARDS, septic shock, DIC, and early death. Although it is an uncommon cause of CAP, it merits special attention as the mortality rate is very high. Further studies should be performed to explore the pathogenetic mechanisms and optimal treatment of CAP-AB.