Carbapenem resistance in Acinetobacter baumannii is a public health issue globally, mainly due to the production of carbapenem hydrolyzing class D ß-lactamases (CHDLs). In Brazil, OXA-23 and OXA-143 CHDLs have been prevalent in A. baumannii from clinical settings, with some OXA-23 reports in the environmental samples, whereas OXA-72 has begun to be increasingly reported. This study aims to perform the genomic and microbiological characterization of carbapenem-resistant A. baumannii isolates recovered from migratory birds and captive birds inhabiting a lake within a Brazilian Zoo. Four hundred and eighty-one gram-negative bacilli were recovered from choanal and cloacal swabs obtained from 50 migratory birds and 37 captive birds present at the zoo’s lake between July and August of 2012. Among all GNB, nine OXA-72-producing A. baumannii were detected from the microbiota of four migratory and five captive aquatic birds. The OXA-72-producing A. baumannii isolates were submitted to antimicrobial susceptibility test and PFGE, exhibiting a multidrug-resistant profile and clonal relatedness with OXA-72-positive human isolates circulating for eighteen years in a hospital setting. MLST, plasmid analysis and whole-genome sequencing revealed which all carbapenem-resistant A. baumannii from bird and human hosts belonged to clonal complex 79, and harboured a small plasmid (~16.6-kb in size), named pAC1-BRL, which carried blaOXA-72 gene, macrolide resistance genes msrE and mphE, and the toxinantitoxin system AbkAB. To determine the impact of pAC1-BRL acquisition in the the capacity of a microorganism to survive in a competitive environment (in the following called fitness), the laboratory strain A. baumannii ATCC 19606 was used in the fitness experiments and suggested an increase of its relative fitness after the pAC1-BRL acquisition. In summary, the detection of OXA-72-producing A. baumannii strains belonging to CC79 in aquatic birds is a piece of epidemiological evidence demonstrating that dissemination of high-risk bacteria is extending beyond the hospital.

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Author: Ana Clara Narciso, Ana Cristina Gales, Ana Tereza R. Vasconcelos, Luiz G.P. Almeida, Nilton Lincopan, Patricia Locosque Ramos, Rodrigo Cayô, Stéfanie Vanessa Santos, Willames M.B.S. Martins