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MBio Oct 2014The amikacin resistance gene aphA6 was first detected in the nosocomial pathogen Acinetobacter baumannii and subsequently in other genera. Analysis of 133 whole-genome...
The amikacin resistance gene aphA6 was first detected in the nosocomial pathogen Acinetobacter baumannii and subsequently in other genera. Analysis of 133 whole-genome sequences covering the taxonomic diversity of Acinetobacter spp. detected aphA6 in the chromosome of 2 isolates of A. guillouiae, which is an environmental species, 1 of 8 A. parvus isolates, and 5 of 34 A. baumannii isolates. The gene was also present in 29 out of 36 A. guillouiae isolates screened by PCR, indicating that it is ancestral to this species. The Pnative promoter for aphA6 in A. guillouiae and A. parvus was replaced in A. baumannii by PaphA6, which was generated by use of the insertion sequence ISAba125, which brought a -35 sequence. Study of promoter strength in Escherichia coli and A. baumannii indicated that PaphA6 was four times more potent than Pnative. There was a good correlation between aminoglycoside MICs and aphA6 transcription in A. guillouiae isolates that remained susceptible to amikacin. The marked topology differences of the phylogenetic trees of aphA6 and of the hosts strongly support its recent direct transfer within Acinetobacter spp. and also to evolutionarily remote bacterial genera. Concomitant expression of aphA6 must have occurred because, contrary to the donors, it can confer resistance to the new hosts. Mobilization and expression of aphA6 via composite transposons and the upstream IS-generating hybrid PaphA6, followed by conjugation, seems the most plausible mechanism. This is in agreement with the observation that, in the recipients, aphA6 is carried by conjugative plasmids and flanked by IS that are common in Acinetobacter spp. Our data indicate that resistance genes can also be found in susceptible environmental bacteria. Importance: We speculated that the aphA6 gene for an enzyme that confers resistance to amikacin, the most active aminoglycoside for the treatment of nosocomial infections due to Acinetobacter spp., originated in this genus before disseminating to phylogenetically distant genera pathogenic for humans. Using a combination of whole-genome sequencing of a collection of Acinetobacter spp. covering the breadth of the known taxonomic diversity of the genus, gene cloning, detailed promoter analysis, study of heterologous gene expression, and comparative analysis of the phylogenetic trees of aphA6 and of the bacterial hosts, we found that aphA6 originated in Acinetobacter guillouiae, an amikacin-susceptible environmental species. The gene conferred, upon mobilization, high-level resistance to the new hosts. This work stresses that nonpathogenic bacteria can act as reservoirs of resistance determinants, and it provides an example of the use of a genomic library to study the origin and dissemination of an antibiotic resistance gene to human pathogens.
Topics: Acinetobacter; Amino Acid Sequence; Aminoglycosides; Anti-Bacterial Agents; Base Sequence; Cluster Analysis; Conjugation, Genetic; Drug Resistance, Bacterial; Environmental Microbiology; Escherichia coli; Evolution, Molecular; Gene Transfer, Horizontal; Interspersed Repetitive Sequences; Kanamycin Kinase; Microbial Sensitivity Tests; Molecular Sequence Data; Phylogeny; Promoter Regions, Genetic; Sequence Homology
PubMed: 25336457
DOI: 10.1128/mBio.01972-14 -
Genome Announcements Oct 2015Here, we report three genome sequences of bacteria isolated from murine proximal colonic tissue and identified as Acinetobacter parvus CM11, Acinetobacter radioresistens...
Draft Genome Sequences of Acinetobacter parvus CM11, Acinetobacter radioresistens CM38, and Stenotrophomonas maltophilia BR12, Isolated from Murine Proximal Colonic Tissue.
Here, we report three genome sequences of bacteria isolated from murine proximal colonic tissue and identified as Acinetobacter parvus CM11, Acinetobacter radioresistens CM38, and Stenotrophomonas maltophilia BR12.
PubMed: 26472823
DOI: 10.1128/genomeA.01089-15 -
Antimicrobial Agents and Chemotherapy 2014Whole-genome sequencing of a collection of 103 Acinetobacter strains belonging to 22 validly named species and another 16 putative species allowed detection of genes for...
Whole-genome sequencing of a collection of 103 Acinetobacter strains belonging to 22 validly named species and another 16 putative species allowed detection of genes for 50 new class D β-lactamases and 65 new Acinetobacter-derived cephalosporinases (ADC). All oxacillinases (OXA) contained the three typical motifs of class D β-lactamases, STFK, (F/Y)GN, and K(S/T)G. The phylogenetic tree drawn from the OXA sequences led to an increase in the number of OXA groups from 7 to 18. The topologies of the OXA and RpoB phylogenetic trees were similar, supporting the ancient acquisition of blaOXA genes by Acinetobacter species. The class D β-lactamase genes appeared to be intrinsic to several species, such as Acinetobacter baumannii, Acinetobacter pittii, Acinetobacter calcoaceticus, and Acinetobacter lwoffii. Neither blaOXA-40/143- nor blaOXA-58-like genes were detected, and their origin remains therefore unknown. The phylogenetic tree analysis based on the alignment of the sequences deduced from blaADC revealed five main clusters, one containing ADC belonging to species closely related to A. baumannii and the others composed of cephalosporinases from the remaining species. No indication of blaOXA or blaADC transfer was observed between distantly related species, except for blaOXA-279, possibly transferred from Acinetobacter genomic species 6 to Acinetobacter parvus. Analysis of β-lactam susceptibility of seven strains harboring new oxacillinases and cloning of the corresponding genes in Escherichia coli and in a susceptible A. baumannii strain indicated very weak hydrolysis of carbapenems. Overall, this study reveals a large pool of β-lactamases in different Acinetobacter spp., potentially transferable to pathogenic strains of the genus.
Topics: Acinetobacter; Amino Acid Motifs; Anti-Bacterial Agents; Cephalosporinase; Escherichia coli; Gene Expression; Molecular Sequence Data; Phylogeny; Plasmids; Recombinant Proteins; Sequence Alignment; beta-Lactams
PubMed: 24277043
DOI: 10.1128/AAC.01261-13 -
Biotechnology For Biofuels 2017-acetyl-β-d-glucosamine (GlcNAc) is extensively used as an important bio-agent and a functional food additive. The traditional chemical process for GlcNAc production...
BACKGROUND
-acetyl-β-d-glucosamine (GlcNAc) is extensively used as an important bio-agent and a functional food additive. The traditional chemical process for GlcNAc production has some problems such as high production cost, low yield, and acidic pollution. Therefore, to discover a novel chitinase that is suitable for bioconversion of chitin to GlcNAc would be of great value.
RESULTS
Here, we describe the complete isolation and functional characterization of a novel exo-chitinase from HANDI 309 for the conversion of chitin. The identified exo-chitinase mainly produced -acetyl-d-glucosamine, using chitin as a substrate by submerged fermentation. The HANDI 309 biofuels producing exo-chitinase were characterized by TLC, and was further validated and quantified by HPLC. Furthermore, the optimal temperature and pH for the exo-chitinase activity was obtained in the culture conditions of 30 °C and 7.0, respectively. The maximum growth of the stationary phase was reached in 24 h after incubation. These results suggest that HANDI 309 biofuels producing exo-chitinases may have great potential in chitin to -acetyl-d-glucosamine conversion.
CONCLUSIONS
The excellent thermostability and hydrolytic properties may give the exo-chitinase great potential in chitin to GlcNAc conversion in industry. This is the first report that HANDI 309 is a novel bacterial strain that has the ability to produce an enormous amount of exo-chitinase-producing bio-agents in a short time on an industrial scale without any pretreatment, as well as being potentially valuable in the food and pharmaceutical industries.
PubMed: 28293289
DOI: 10.1186/s13068-017-0740-1 -
Microorganisms Jun 2019is an ocular bacterial pathogen isolated in cases of keratitis, conjunctivitis, and endophthalmitis. Gram-negative brick-shaped diplobacilli from ocular specimens, and...
is an ocular bacterial pathogen isolated in cases of keratitis, conjunctivitis, and endophthalmitis. Gram-negative brick-shaped diplobacilli from ocular specimens, and slow growth in culture, are early indications of ocular infection; however, identifying to species can be complex and inconsistent. In this study, bacteria consistent with were identified to species using: (1) DNA sequencing coupled with vancomycin susceptibility, (2) MALDI-TOF mass spectrometry, and (3) the Biolog ID system. Study samples consisted of nine ATCC controls, 82 isolates from keratitis, 21 isolates from conjunctivitis, and 4 isolates from endophthalmitis. The ATCC controls were correctly identified. For keratitis, 66 (80.5%) were identified as , 7 (9.0%) as , 5 (6%) as , 2 (2.5%) as , 1 (1.0%) as , and 1 (1.0%) as . For conjunctivitis, 9 (43.0%) were identified as , 6 (29.0%) as , 3 (14.3%) as , 2 (9.5%) as (), and 1 (4.5%) as . From endophthalmitis, 3 of 4 of the isolates were . Overall, . and were identified in 70% (75 of 107) and 13% (14 of 107) of cases, respectively, totaling 83% (89 of 107). and are important bacterial pathogens of the eye as determined by DNA sequencing, MALDI-TOF MS, and Biolog. Although is a clinical pathogen, other species of appear to have a prominent role in eye infections.
PubMed: 31167433
DOI: 10.3390/microorganisms7060163