First report of cavitary pneumonia due to community-acquired Acinetobacter pittii, study of virulence and overview of pathogenesis and treatment

Abstract

Background Acinetobacter pittii is a nosocomial pathogen rarely involved in community-acquired infections. We report for the first time that A. pittii can be responsible for cavitary community-acquired pneumonia and study its virulence, and discuss its pathogenesis and treatment options.Case presentationA 45-year-old woman with a history of smoking and systemic lupus was admitted to Nimes University Hospital (France) with coughing and sputum lasting for three weeks. Thoracic CT scanner showed cavitary pneumonia. Broncho-alveolar lavage cultures found community-acquired Acinetobacter calcoaceticus-baumannii complex. The clinical outcome was favourable after twenty-one days of antimicrobial treatment by piperacillin/tazobactam and amikacin then cefepime. Multilocus sequence typing (MLST) analyses identified an A. pittii ST249. Despite the atypical clinical presentation with an unexpected partial destruction of lung parenchyma, we found very low virulence potential of the A. pittii strain with nematode killing assays and biofilm formation test. The median time required to kill 50% of the nematodes was 7 ± 0.3 days for A. pittii ST249, 7 ± 0.2 days for A. baumanii NAB ST2 and 8 ± 0.2 days for E. coli OP50, (p > 0,05). A. pittii ST249 showed significantly slower biofilm formation than A. baumanii NAB ST2: BFI = 8.83 ± 0.59 vs 3.93 ± 0.27 at 2 h (p < 0.0001), BFI = 6.3 ± 0.17 vs 1.87 ± 0.12 at 3 h (p < 0.0001) and BFI = 3.67 ± 0.41 vs 1.7 ± 0.06 after 4 h of incubation (p < 0.01).ConclusionsCommunity-acquired A. pittii should be considered as possible cause of sub-acute cavitary pneumonia particularly in a smoking and/or immunocompromised patient despite its low virulence potential.

In vitro and in vivo Virulence Potential of the Emergent Species of the Acinetobacter baumannii (Ab) Group

“…Nevertheless, it is important to acknowledge that the results provided in our study arise from the usage of in vitro and nematode infection models that do not entirely reflect more complex clinical scenarios and, thus, the extrapolation of these results to infer virulence in the human host must be taken with extreme caution. For instance, respiratory tract infections and in particular both community-acquired as well as nosocomial pneumonia are mainly attributed to A. baumannii and A. nosocomialis while there is little evidence that the other species are capable of causing such infections in humans (Wang et al, 2013; Larcher et al, 2017).…”

Alert Germ Infections: Chest X-ray and CT Findings in Hospitalized Patients Affected by Multidrug-Resistant Acinetobacter baumannii Pneumonia

“…Nodules (10 patients), bronchial wall thickening (5 patients), interlobular septal thickening (17 patients), bronchiectasis (10 patients), and air bronchogram (40 patients) were also observed. Cavitary lesions were found in only four cases [26]. Pleural effusion was found in 43 patients and was bilateral in 34 (79.1%) cases.…”

Characterization of co-metabolic biodegradation of methyl tert-butyl ether by a Acinetobacter sp. strain

“…50 Acinetobacter pittii, formerly known as Acinetobacter genomospecies 3, is an aerobic Gram-negative bacillus that can be found in various settings, including soil, foods, sewage, and animals, as well as on human skin and ora. 51,52 As a nosocomial opportunistic pathogen which mainly invades patients with immunosuppression and serious diseases, A. pittii is commonly considered less virulent than Acinetobacter baumannii within the Acinetobacter calcoaceticusbaumannii complex. 53 Based on the results above, bioaugmentation of MTBEcontaminated environment with strain SL3 signicantly improved the removal rate of MTBE from the contaminated water.…”