Introduction: Pneumonia in an immunocompromised host is unique with respect to the organisms involved. The emergence of new pathogens has significant impact on therapy. Achromobacter xylosoxidans (A.xylosoxidans) is an uncommon pathogen known to cause serious infections in immunocompromised hosts. Despite its ubiquitous existence, community acquired infections are rare. We report a case of A.xylosoxidans causing invasive cavitary pneumonia.
Case Presentation: A 53 year-old male with a history of HIV (unknown CD4 count, viral load) presented with ethanol intoxication. He denied any fevers, chills, cough, recent travel or sick contacts. Exam was significant for temperature of 101.9 F , sinus tachycardia, cachexia, and bronchial breath sound over the left upper lobe of the lung. Laboratory results showed a white blood cell count of 6.6k/ul, positive drug screen for cocaine and cannabis and elevated blood alcohol level. Computed tomography (CT) of the head was unremarkable and CT scan of the chest demonstrated an apical cavitary lesion with patchy opacity in the left upper lobe (Figure 1). His CD4 count was 2 cells/ul and a viral load of 9058 copies/ml. Infectious work up including blood cultures, AFB smears, pneumocystis smear, aspergillus antibody and lumbar puncture were negative. Deep tracheal aspirate culture grew A.xylosoxidans. He was treated with cefepime for 14 days with clinical and radiological improvement.
Discussion: A.xylosoxidans, isolated by Yabucci and Ohyama is an aerobic, gram-negative, catalase and oxidase positive bacilli. It is an opportunistic bacteria with low virulence but immunocompromised hosts with HIV or malignancy can experience significant morbidity and mortality.A.xylosoxidans is rarely isolated from clinical material and can be confused with other gram negative rods, like Pseudomonas and Burkholderia underestimating its role as a significant pathogen. A.xylosoxidans pneumonia is associated with a high case-fatality rate of 67% and complications include empyema, adult respiratory distress syndrome, chronic scarring and recurrent pneumonia . It is inherently resistant to many antibiotics but most isolates are susceptible to carbapenems and antipseudomonal penicillin. Due to the multidrug resistance and high case fatality, a drug sensitivity pattern is crucial to optimise therapy. Being so uncommonly isolated, A.xylosoxidans is either overlooked or discarded as a contaminant. In light of the propensity for misidentification, sequencing offers a more reliable method of definitive diagnosis, though its utility in clinical practice is unknown.
Conclusions: Although A.xylosoxidans is routinely regarded as a contaminant, it can be a clinically significant pathogen causing invasive pneumonia in immunocompromised hosts with very high morbidity and mortality.
