Direct examination and cultures of bronchoalveolar lavage in pneumonia diagnosis: a comparative experimental study

Evaluation of the diagnostic value of fluorescent in situ hybridization in a rat model of bacterial pneumonia

In severe nosocomial pneumonia, the pathogenic responsibility of bacteria isolated from airways is far from certain, and a lung biopsy is sometimes performed. However, detection and identification of pathogens are frequently unachieved. Here, we developed a protocol for direct visualization of bacteria within the lung tissue using fluorescent in situ hybridization (FISH) in a rat model of Acinetobacter baumannii pneumonia. The reference positive diagnosis of bacterial pneumonia was the presence of pathological signs of pneumonia associated with the proof of bacteria or bacterial PCR products into the parenchyma. By analysis of 122 sets of slices from 26 rats and using the eubacterial probe EUB-338, our results show that FISH reached a sensitivity and a diagnostic accuracy higher than that of optic microscopy (sensitivity: 96% versus 55.4% and diagnostic accuracy: 96.7% versus 66.4%), whereas both approaches had 100% specificity. FISH could be useful especially on negative biopsies from patients with suspected infectious pneumonia.

Pneumonia pathogen detection and microbial interactions in polymicrobial episodes

Recent reports show that microbial communities associated with respiratory infections, such as pneumonia and cystic fibrosis, are more complex than expected. Most of these communities are polymicrobial and might comprise microorganisms originating from several diverse biological and ecological sources. Moreover, unexpected bacteria in the etiology of these respiratory infections have been increasingly identified. These findings were established with the use of efficient microbiological diagnostic tools, particularly molecular tools based on common gene amplification, followed by cloning and sequencing approaches, which facilitated the identification of the polymicrobial flora. Similarly, recent investigations reported that microbial interactions might exist between species in polymicrobial communities, including typical pneumonia pathogens, such as Pseudomonas aeruginosa and Candida albicans. Here, we review recent tools for microbial diagnosis, in particular, of intensive care unit pneumonia and the reported interactions between microbial species that have primarily been identified in the etiology of these infections.