Deciphering Multifactorial Resistance Phenotypes in by Genomics and Targeted Label-free Proteomics.

Resistance to β-lactams in involves various mechanisms. To decipher them, whole genome sequencing (WGS) and real-time quantitative polymerase chain reaction (RT-qPCR) were complemented by mass spectrometry (MS) in selected reaction monitoring mode (SRM) in 39 clinical isolates. The targeted label-free proteomic approach enabled, in one hour and using a single method, the quantitative detection of 16 proteins associated with antibiotic resistance: eight acquired β-lactamases ( GES, NDM-1, OXA-23, OXA-24, OXA-58, PER, TEM-1, and VEB), two resident β-lactamases ( ADC and OXA-51-like) and six components of the two major efflux systems ( AdeABC and AdeIJK).

New aminoglycoside-modifying enzymes APH(3')-VIII and APH(3')-IX in Acinetobacter rudis and Acinetobacter gerneri.

Analysis of whole-genome sequences of 133 strains of Acinetobacter detected two genes for new types of aminoglycoside 3'-O-phosphotransferase [APH(3')], type VIII in Acinetobacter rudis and IX in A. gerneri. The enzymes were related to each other (49% identity) and to APH(3')-VI (61% and 51% identity, respectively), which is intrinsic to A.

Contribution of the Ade Resistance-Nodulation-Cell Division-Type Efflux Pumps to Fitness and Pathogenesis of Acinetobacter baumannii.

Unlabelled: Overexpression of chromosomal resistance-nodulation-cell division (RND)-type efflux systems with broad substrate specificity contributes to multidrug resistance (MDR) in Acinetobacter baumannii We have shown that modulation of expression of the structural genes for the efflux systems AdeABC and AdeIJK confers MDR and results in numerous alterations of membrane-associated cellular functions, in particular biofilm formation. However, the contribution of these RND pumps to cell fitness and virulence has not yet been studied. The biological cost of an antibiotic resistance mechanism is a key parameter in determining its stability and dissemination.

Origin in Acinetobacter gyllenbergii and dissemination of aminoglycoside-modifying enzyme AAC(6')-Ih.

Objectives: The aac(6')-Ih gene encoding aminoglycoside 6'-N-acetyltransferase type I subtype h [AAC(6')-Ih] is plasmid-borne in Acinetobacter baumannii where it confers high-level amikacin resistance, but its origin remains unknown. We searched for the gene in the genomes of a collection of 133 Acinetobacter spp. and studied its species specificity, expression and dissemination.

Contribution of resistance-nodulation-cell division efflux systems to antibiotic resistance and biofilm formation in Acinetobacter baumannii.

Unlabelled: Acinetobacter baumannii is a nosocomial pathogen of increasing importance due to its multiple resistance to antibiotics and ability to survive in the hospital environment linked to its capacity to form biofilms. To fully characterize the contribution of AdeABC, AdeFGH, and AdeIJK resistance-nodulation-cell division (RND)-type efflux systems to acquired and intrinsic resistance, we constructed, from an entirely sequenced susceptible A. baumannii strain, a set of isogenic mutants overexpressing each system following introduction of a point mutation in their cognate regulator or a deletion for the pump by allelic replacement.