Actinobacillus ureae: an unusual cause of tree-in-bud pattern in a case of pneumonia on lung computed tomographic scan—first clinical case report and review of the literature from India

Abstract

A 62-year-old man with asthma sought care for intermittent fever, cough with expectoration, breathlessness and orthopnoea with grunting. Computed tomography revealed clusters of centrilobular nodules on both sides with a tree-in-bud appearance and mild diffuse bronchial wall thickening. Sputum sample grew pure colonies of Actinobacillus ureae which was confirmed by MALDI-TOF and 16SrRNA gene sequencing. A. ureae may be an additional bacteriologic causative agent of the tree-in-bud pattern on computed tomographic scan.

Actinobacillus ureae may be a critical pathogen in patients with predispositions: A case report and review of the literature

“…In our case, we not only conducted traditional phenotypic testing but also performed MALDI-TOF MS and 16S rRNA sequencing, proving the identification achieved high reliability. However, there were 2 strains confirmed by 16S rRNA sequencing in all previous reports [21,32] and only 1 strain was identified by MALDI-TOF MS. [32] Compared with gene sequencing, the MALDI-TOF MS is more common in clinical laboratories due to the advantages of being quicker and cheaper, however, it also probably makes an erroneous identification. Here, we would like to highlight the importance of molecular techniques.…”

“…[7] Similarly, alcoholism, chronic liver diseases, and immunocompromised conditions, such as receiving anti-TNF or corticosteroid therapy were also observed in non-intracranial infections. [9,32] Interestingly, among the 6 reported cases of respiratory infections due to A. ureae , 3 occurred in patients with chronic lung disease: 1 patient with emphysema, [8] 1 with chronic bronchitis, [31] and another with bronchial asthma. [32] As was the case with the patient described here, our patient had a previous history of emphysema and bilateral bullae.…”

“…[9,32] Interestingly, among the 6 reported cases of respiratory infections due to A. ureae , 3 occurred in patients with chronic lung disease: 1 patient with emphysema, [8] 1 with chronic bronchitis, [31] and another with bronchial asthma. [32] As was the case with the patient described here, our patient had a previous history of emphysema and bilateral bullae. He remained to be bedridden for more than 1 month after intracranial surgery.…”

“…Radiographic presentations of A. ureae pneumonia are not specific either, but significantly, a tree-in-bud pattern on chest CT was observed by Dawar. [32]…”

“…To date, A. ureae has been identified as the principal pathogen in only 37 cases (Table 1). The majority of cases involved meningitis or meningoencephalitis, [6,7,13,[15][16][17][18][19][20][21][22][23][24][25] bacteremia, [6,19,[23][24][25][26][27] endocarditis, [28][29][30] and respiratory infections, [8,19,26,31,32] while bone marrow infection, [12] conjunctivitis, [10,11] septic arthritis, [9] peritonitis, [13] urinogenital infection [33] and otitis media [14] was also reported. Of these patients, men accounted for the majority (n = 30, 81%).…”