Acinetobacter baumannii DSM30011: an environmental strain isolated at the onset of the antibiotic era reveals clues into the origins of an opportunistic nosocomial pathogen

VIALE AM; TAIB, NAJWA; GOMES JP; BORGES V; ESPARIZ M.; SALCEDO SP; REPIZO GD; CAMERANESI MM; BROCHIER-ARMANET, CÉLINE

Simposio; Acinetobacter 2017; 2017

Acinetobacter baumannii represents nowadays an important nosocomial opportunistic pathogen whose reservoirs outside the clinical setting are obscure. Here we traced the origins of the collection strain A. baumannii DSM30011 to an isolate first reported in 1944, obtained from the enriched microbiota responsible of the aerobic decomposition of the resinous desert shrub guayule. Whole-genome sequencing and phylogenetic analyses based on core genes confirmed DSM30011 affiliation to A. baumannii. Comparative genomic studies with 32 complete A. baumannii revealed the presence of 12 unique accessory chromosomal regions in DSM30011, among which five encompassed phage-related genes, five contained toxin genes associated to the type 6 secretion system and one bore an atypical CRISPRs/cas cluster. No antimicrobial resistance islands were identified in agreement with its general antimicrobials susceptibility including the folate synthesis inhibitors sulfamethoxazole/trimethoprim. Marginal ampicillin resistance was detected inDSM30011, most likely due to chromosomal ADC-type ampC and blaOXA-51-type genes. Searching for catabolic pathways genes revealed several clusters involved in the degradation of plant defenses including woody tissues and a previously unreported atu locus responsible of aliphatic terpenes degradation, suggesting that resinous plants may provide effective niches for this organism. DSM30011 also harboured most genes and regulatory mechanisms linked to persistence and virulence in pathogenic Acinetobacter species. This strain, which was isolated from environmental sources before the introduction of massive antibiotic use last century, may thus provides important clues into the genomic diversity, virulence potential, and evolutionary processes that led to the leap of A. baumannii towards an opportunistic pathogen of humans.