Abstract
BACKGROUND Acinetobacter baumannii outbreaks have been associated with pandemic International Clones (ICs), but the virulence factors involved with their pathogenicity are sparsely understood. Pigment production has been linked with bacterial pathogenicity, however, this phenotype is rarely observed in A. baumannii.OBJECTIVES This study aimed to characterise the reddish-brown pigment produced by A. baumannii strains, and to determine its biosynthetic pathway by genomic approaches.METHODS Pigment characterisation and antimicrobial susceptibility were conducted by phenotypic tests. The clonal relationship was obtained by pulsed field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). The genome of an A. baumannii was obtained for characterisation of genes involved with pigment production.FINDINGS The pyomelanin was the pigment produced by A. baumannii. Strains were extensively drug resistant and belonged to the IC-5/ST79. The pyomelanin biosynthetic pathway was determined and presented a particular architecture concerning the peripheral (tyrB, phhB and hpd) and central (hmgB, hmgC and hmgR) metabolic pathway genes. The identification of a distant HmgA homologue, probably without dioxygenase activity, could explain pyomelanin production. Virulence determinants involved with adherence (csuA/BABCDE and a T5bSS-carrying genomic island), and iron uptake (basABCDEFGHIJ, bauABCDEF and barAB) were characterised.MAIN CONCLUSION There is a biosynthetic pathway compatible with the pyomelanin production observed in persistent A. baumannii IC-5 strains.
Highlights
Acinetobacter baumannii outbreaks have been associated with pandemic International Clones (ICs), but the virulence factors involved with their pathogenicity are sparsely understood
Acinetobacter baumannii is one of the most relevant pathogens associated with nosocomial infections that presents the long-term ability to survive on inanimate surfaces, contributing to national and international clonal dissemination.[1]. The A. baumannii outbreaks have been associated with high-risk pandemic lineages, named International Clones (ICs), characterised by a high capacity to persist in clinical environments and by presenting a broad antimicrobial resistance profile.[2,3] in spite of A. baumannii association with nosocomial and persistent infections, the role of virulence factors in its pathogenesis remains largely obscure
This study reports the occurrence of persistent A. baumannii strains producing a brown diffusible pigment resembling the pyomelanin, which caused an outbreak in a hospital of the Amazon Basin, Brazil
Summary
Acinetobacter baumannii outbreaks have been associated with pandemic International Clones (ICs), but the virulence factors involved with their pathogenicity are sparsely understood. Pigment production has been linked with bacterial pathogenicity, this phenotype is rarely observed in A. baumannii
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