Relatedness of wildlife and livestock avian isolates of the nosocomial pathogen Acinetobacter baumannii to lineages spread in hospitals worldwide

Abstract

SummaryThe natural habitats and potential reservoirs of the nosocomial pathogen Acinetobacter baumannii are poorly defined. Here, we put forth and tested the hypothesis of avian reservoirs of A. baumannii. We screened tracheal and rectal swab samples from livestock (chicken, geese) and wild birds (white stork nestlings) and isolated A. baumannii from 3% of sampled chicken (n 5 220), 8% of geese (n 5 40) and 25% of white stork nestlings (n 5 661). Virulence of selected avian A. baumannii isolates was comparable to that of clinical isolates in the Galleria mellonella infection model. Whole genome sequencing revealed the close relationship of an antibiotic-susceptible chicken isolate from Germany with a multidrug-resistant human clinical isolate from China and additional linkages between livestock isolates and human clinical isolates related to international clonal lineages. Moreover, we identified stork isolates related to human clinical isolates from the United States. Multilocus sequence typing disclosed further kinship between avian and human isolates. Avian isolates do not form a distinct clade within the phylogeny of A. baumannii, instead they diverge into different lineages. Further, we provide evidence that A. baumannii is constantly present in the habitats occupied by storks. Collectively, our study suggests A. baumannii could be a zoonotic organism that may disseminate into livestock.

Fluorescence-based detection of natural transformation in drug resistant Acinetobacter baumannii

“…Taking advantage of avian strain genome availability (32), we confirmed that the HU gene and the flanking regions are highly conserved with at least 99,1% identity between the avian strains' sequences and AB5075 strain sequence. Previously, five of these nine strains were found transformable in a qualitative transformation assay using the antibiotic-selection based method (32). All of the five strains were also found transformable using the fluorescencebased method but their ability to undergo transformation spreads over a range of three orders of magnitude ( Fig.…”

“…Acinetobacter baumannii is now an established member of the growing list of bacteria capable of undergoing natural genetic transformation (13,32). Together with genomic evidence of high recombination rates and multiple horizontal gene transfer events, natural transformation should be considered as a major contributor of antibiotic resistance genes acquisition in A. baumannii.…”

“…Indeed, sensing pili retraction was involved in induction of virulence genes expression and holdfast synthesis respectively in Pseudomonas aeruginosa and Vibrio cholera (38,39). Also, and intriguingly, agarose is a necessary component of semi-solid media required to natural transform A. baumannii or closelyrelated species (13,32,40). One hypothesis could be that the competent state for natural transformation is induced by the presence of agarose itself.…”

“…To further validate the cytometry-based method and to gain insight into the transformation ability of non-clinical strains isolated from wild animals, we sought to estimate the transformation ability of nine fully sequenced strains isolated from wild storks, some of them related to human clinical isolates (32). Taking advantage of avian strain genome availability (32), we confirmed that the HU gene and the flanking regions are highly conserved with at least 99,1% identity between the avian strains' sequences and AB5075 strain sequence.…”

“…6A). Remarkably, the fluorescence based-method allowed us to detect transformation in one isolate that was not identified as transformable using the antibioticselection method (32) (Fig. 6A, strain 280/1C).…”