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Frontiers in Cellular and Infection... 2013Acinetobacter baumannii is a significant contributor to intensive care unit (ICU) mortality causing numerous types of infection in this susceptible ICU population, most... (Review)
Review
Acinetobacter baumannii is a significant contributor to intensive care unit (ICU) mortality causing numerous types of infection in this susceptible ICU population, most notably ventilator-associated pneumonia. The substantial disease burden attributed to A. baumannii and the rapid acquisition of antibiotic resistance make this bacterium a serious health care threat. A. baumannii is equipped to tolerate the hostile host environment through modification of its metabolism and nutritional needs. Among these adaptations is the evolution of mechanisms to acquire nutrient metals that are sequestered by the host as a defense against infection. Although all bacteria require nutrient metals, there is diversity in the particular metal needs among species and within varying tissue types and bacterial lifecycles. A. baumannii is well-equipped with the metal homeostatic systems required for the colonization of a diverse array of tissues. Specifically, iron and zinc homeostasis is important for A. baumannii interactions with biotic surfaces and for growth within vertebrates. This review discusses what is currently known regarding the interaction of A. baumannii with vertebrate cells with a particular emphasis on the contributions of metal homeostasis systems. Overall, published research supports the utility of exploiting these systems as targets for the development of much-needed antimicrobials against this emerging infectious threat.
Topics: Acinetobacter baumannii; Animals; Biological Transport; Helicobacter Infections; Homeostasis; Humans; Metabolic Networks and Pathways; Metals; Microbial Viability; Vertebrates
PubMed: 24377089
DOI: 10.3389/fcimb.2013.00095 -
Journal of Bacteriology May 2017A critical component of bacterial pathogenesis is the ability of an invading organism to sense and adapt to the harsh environment imposed by the host's immune system....
A critical component of bacterial pathogenesis is the ability of an invading organism to sense and adapt to the harsh environment imposed by the host's immune system. This is especially important for opportunistic pathogens, such as , a nutritionally versatile environmental organism that has recently gained attention as a life-threatening human pathogen. The emergence of is closely linked to antibiotic resistance, and many contemporary isolates are multidrug resistant (MDR). Unlike many other MDR pathogens, the molecular mechanisms underlying pathogenesis remain largely unknown. We report here the characterization of two recently identified virulence determinants, GigA and GigB, which comprise a signal transduction pathway required for surviving environmental stresses, causing infection and antibiotic resistance. Through transcriptome analysis, we show that GigA and GigB coordinately regulate the expression of many genes and are required for generating an appropriate transcriptional response during antibiotic exposure. Genetic and biochemical data demonstrate a direct link between GigA and GigB and the nitrogen phosphotransferase system (PTS), establishing a novel connection between a novel stress response module and a well-conserved metabolic-sensing pathway. Based on the results presented here, we propose that GigA and GigB are master regulators of a global stress response in , and coupling this pathway with the PTS allows to integrate cellular metabolic status with external environmental cues. Opportunistic pathogens, including , encounter many harsh environments during the infection cycle, including antibiotic exposure and the hostile environment within a host. While the development of antibiotic resistance in has been well studied, how this organism senses and responds to environmental cues remain largely unknown. Herein, we investigate two previously identified virulence determinants, GigA and GigB, and report that they are required for stress resistance, likely comprising upstream elements of a global stress response pathway. Additional experiments identify a connection between GigA/GigB and a widely conserved metabolic-sensing pathway, the nitrogen phosphotransferase system. We propose that coordination of these two pathways allows to respond appropriately to changing environmental conditions, including those encountered during infection.
Topics: Acinetobacter baumannii; Drug Resistance, Bacterial; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Gene Regulatory Networks; Genes, Regulator; Metabolic Networks and Pathways; Regulon; Signal Transduction; Stress, Physiological; Virulence
PubMed: 28264991
DOI: 10.1128/JB.00066-17 -
Scientific Reports Oct 2021Acinetobacter has been frequently detected in backwater areas of the Three Gorges Reservoir (TGR) region. We here employed Caenorhabditis elegans to perform biosafety...
Acinetobacter has been frequently detected in backwater areas of the Three Gorges Reservoir (TGR) region. We here employed Caenorhabditis elegans to perform biosafety assessment of Acinetobacter strains isolated from backwater area in the TGR region. Among 21 isolates and 5 reference strains of Acinetobacter, exposure to Acinetobacter strains of AC1, AC15, AC18, AC21, A. baumannii ATCC 19606, A. junii NH88-14, and A. lwoffii DSM 2403 resulted in significant decrease in locomotion behavior and reduction in lifespan of Caenorhabditis elegans. In nematodes, exposure to Acinetobacter strains of AC1, AC15, AC18, AC21, A. baumannii, A. junii and A. lwoffii also resulted in significant reactive oxygen species (ROS) production. Moreover, exposure to Acinetobacter isolates of AC1, AC15, AC18, and AC21 led to significant increase in expressions of both SOD-3::GFP and some antimicrobial genes (lys-1, spp-12, lys-7, dod-6, spp-1, dod-22, lys-8, and/or F55G11.4) in nematodes. The Acinetobacter isolates of AC1, AC15, AC18, and AC21 had different morphological, biochemical, phylogenetical, and virulence gene properties. Our results suggested that exposure risk of some Acinetobacter strains isolated from the TGR region exists for environmental organisms and human health. In addition, C. elegans is useful to assess biosafety of Acinetobacter isolates from the environment.
Topics: Acinetobacter; Animals; Caenorhabditis elegans; Containment of Biohazards; Disease Resistance; Host Microbial Interactions; Oxidative Stress; Phylogeny; Rivers; Virulence; Water Microbiology
PubMed: 34611259
DOI: 10.1038/s41598-021-99274-0 -
Medicine Mar 2016Clinical infections caused by Acinetobacter spp. have increasing public health concerns because of their global occurrence and ability to acquire multidrug resistance....
Clinical infections caused by Acinetobacter spp. have increasing public health concerns because of their global occurrence and ability to acquire multidrug resistance. Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) complex encompasses A. calcoaceticus, A. baumannii, A. pittii (formerly genomic species 3), and A nosocomial (formerly genomic species 13TU), which are predominantly responsible for clinical pathogenesis in the Acinetobacter genus. In our previous study, a putative novel species isolated from 385 non-A. baumannii spp. strains based on the rpoB gene phylogenetic tree was reported. Here, the putative novel species was identified as A. seifertii based on the whole-genome phylogenetic tree. A. seifertii was recognized as a novel member of the ACB complex and close to A. baumannii and A. nosocomials. Furthermore, we studied the characteristics of 10 A. seifertii isolates, which were distributed widely in 6 provinces in China and mainly caused infections in the elderly or children. To define the taxonomic status and characteristics, the biochemical reactions, antimicrobial susceptibility testing, pulsed field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and whole-genome sequence analysis were performed. The phenotypic characteristics failed to distinguish A. serfertii from other species in the ACB complex. Most of the A. seifertii isolates were susceptible to antibiotics commonly used for nosocomial Acinetobacter spp. infections, but one isolate (strain A362) was resistant to ampicillin/sulbactam, ceftazidime and amikacin. The different patterns of MLST and PFGE suggested that the 10 isolates were not identical and lacked clonal relatedness. Our study reported for the first time the molecular epidemiological and genomic features of widely disseminated A. seifertii in China. These observations could enrich the knowledge of infections caused by non-A. baumannii and may provide a scientific basis for future clinical treatment.
Topics: Acinetobacter; Acinetobacter Infections; Acinetobacter baumannii; Acinetobacter calcoaceticus; Aged; Anti-Bacterial Agents; Child; China; Drug Resistance, Bacterial; Electrophoresis, Gel, Pulsed-Field; Humans; Molecular Epidemiology; Multilocus Sequence Typing; Phylogeny; Sequence Analysis
PubMed: 26945401
DOI: 10.1097/MD.0000000000002937 -
International Journal of Environmental... Jan 2019A crude oil-degrading bacterium named strain H9-3 was isolated from crude oil contaminated soil in the Northeastern area of China. Based on its morphological...
A crude oil-degrading bacterium named strain H9-3 was isolated from crude oil contaminated soil in the Northeastern area of China. Based on its morphological characteristics and 16S rDNA sequence analysis, strain H9-3 is affiliated to in the group of Gammaproteobacteria. The strain was efficient in removing 36.8% of the initial 10 g·L - 1 of crude oil within 21 days. GC-MS was performed and a preference was shown for -C10, -C11, -C14, -C17, -C34, -C12, -C13, -C14, -C27, -C32 and -C13, over -C16, -C18⁻C22, -C24⁻-C31, and -C36. This can be regarded as the specific fingerprint for crude oil degradation by strain H9-3 of . In addition to crude oil, it was shown that soybean oil and phenols can be utilized as carbon sources by strain H9-3. It was also shown that aniline and α -naphthol cannot be utilized for growth, but they can be tolerated by strain H9-3. Methylbenzene was neither utilized nor tolerated by strain H9-3. Although -hexadecane was not preferentially consumed by strain H9-3, during culture with crude oil, it could be utilized for growth when it is the sole carbon source. The degradation of some branched alkanes (-C14, -C17 and -C34) and the preferential degradation of crude oil over phenols could be used as a reference for distinguishing from . The difference in gene expression was very significant and was induced by diverse carbon sources, as shown in the qRT-PCR results. The oxidation and adhesion events occurred at high frequency during alkane degration by strain H9-3 cells.
Topics: Acinetobacter; Alkanes; Bacterial Proteins; Biodegradation, Environmental; China; DNA, Ribosomal; Gene Expression Regulation, Bacterial; Oxidoreductases; Petroleum
PubMed: 30634699
DOI: 10.3390/ijerph16020188 -
BioMed Research International 2020Metallo-beta-lactamase-producing spp. is a major challenge for therapeutic treatment of nosocomial infections. This study is aimed at determining the prevalence of...
Metallo-beta-lactamase-producing spp. is a major challenge for therapeutic treatment of nosocomial infections. This study is aimed at determining the prevalence of MBL-producing spp. among 87 clinical isolates of spp. from the Korle-Bu Teaching Hospital, Accra, between August 2014 and July 2015. spp. was identified by standard bacteriological method, and resistance to different antibiotics was assessed with the Kirby-Bauer disc diffusion method. Meropenem-resistant isolates were screened for enzyme activity using the modified Hodge test (MHT) and combined disc test (CDT). Additionally, multiplex PCR was used to determine MBL genes presence (VIM IMP, and NDM). All isolates showed high resistance to cefotaxime (90.8%), ceftazidime (75.9%), cotrimoxazole (70.1%), ciprofloxacin (64.4%), gentamicin (72.4%), levofloxacin (67.8%), and meropenem (59.8%). A total of 54 (62.1%) of isolates were multidrug-resistant. Out of 52 (59.8%) meropenem-resistant , 3 (5.8%) were carbapenemase producers by MHT, whilst, 23 (44.2%) were CDT positive. There was no significant difference between the resistance pattern of amikacin, ceftazidime, cotrimoxazole, ciprofloxacin, and meropenem amongst CDT-positive and CDT-negative isolates ( > 0.05). A total of 7/87 (8.1%) CDT-positive isolates harboured NDM; of these, 4 (57.1%) were from wound swabs, urine ( = 2) (28.6%), and ear swab ( = 1) (14.3%). The study revealed that less than 9% of spp. contained NDM encoding genes. Strict antibiotics usage plan and infection control measures are required to prevent the spread of these resistance genes.
Topics: Acinetobacter; Adolescent; Adult; Bacterial Proteins; Carbapenems; Child; Child, Preschool; Drug Resistance, Microbial; Female; Genes, Bacterial; Ghana; Humans; Infant; Infant, Newborn; Male; Microbial Sensitivity Tests; Middle Aged; Phenotype; Tertiary Care Centers; Young Adult; beta-Lactamases
PubMed: 33029505
DOI: 10.1155/2020/3852419 -
Research in Microbiology May 2011Acinetobacter genomic species (gen. sp.) 3 and gen. sp. 13TU are increasingly recognized as clinically important taxa within the Acinetobacter...
Genotypic and phenotypic characterization of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex with the proposal of Acinetobacter pittii sp. nov. (formerly Acinetobacter genomic species 3) and Acinetobacter nosocomialis sp. nov. (formerly Acinetobacter genomic species 13TU).
Acinetobacter genomic species (gen. sp.) 3 and gen. sp. 13TU are increasingly recognized as clinically important taxa within the Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) complex. To define the taxonomic position of these genomic species, we investigated 80 strains representing the known diversity of the ACB complex. All strains were characterized by AFLP analysis, amplified rDNA restriction analysis and nutritional or physiological testing, while selected strains were studied by 16S rRNA and rpoB gene sequence analysis, multilocus sequence analysis and whole-genome comparison. Results supported the genomic distinctness and monophyly of the individual species of the ACB complex. Despite the high phenotypic similarity among these species, some degree of differentiation between them could be made on the basis of growth at different temperatures and of assimilation of malonate, l-tartrate levulinate or citraconate. Considering the medical relevance of gen. sp. 3 and gen. sp. 13TU, we propose the formal names Acinetobacter pittii sp. nov. and Acinetobacter nosocomialis sp. nov. for these taxa, respectively. The type strain of A. pittii sp. nov. is LMG 1035(T) (=CIP 70.29(T)) and that of A. nosocomialis sp. nov. is LMG 10619(T) (=CCM 7791(T)).
Topics: Acinetobacter; Acinetobacter baumannii; DNA, Bacterial; Genotype; Molecular Sequence Data; Multilocus Sequence Typing; Phenotype; Phylogeny; RNA, Ribosomal, 16S
PubMed: 21320596
DOI: 10.1016/j.resmic.2011.02.006 -
Environmental Microbiology Sep 2012We evaluated the population structure and temporal dynamics of the dominant community members within sewage influent from two wastewater treatment plants (WWTPs) in...
We evaluated the population structure and temporal dynamics of the dominant community members within sewage influent from two wastewater treatment plants (WWTPs) in Milwaukee, WI. We generated > 1.1 M bacterial pyrotag sequences from the V6 hypervariable region of 16S rRNA genes from 38 influent samples and two samples taken upstream in the sanitary sewer system. Only a small fraction of pyrotags from influent samples (∼ 15%) matched sequences from human faecal samples. The faecal components of the sewage samples included enriched pyrotag populations from Lactococcus and Enterobacteriaceae relative to their fractional representation in human faecal samples. In contrast to the large number of distinct pyrotags that represent faecal bacteria such as Lachnospiraceae and Bacteroides, only one or two unique V6 sequences represented Acinetobacter, Aeromonas and Trichococcus, which collectively account for nearly 35% of the total sewage community. Two dominant Acinetobacter V6 pyrotags (designated Acineto tag 1 and Acineto tag 2) fluctuated inversely with a seasonal pattern over a 3-year period, suggesting two distinct Acinetobacter populations respond differently to ecological forcings in the system. A single nucleotide change in the V6 pyrotags accounted for the difference in these populations and corresponded to two phylogenetically distinct clades based on full-length sequences. Analysis of wavelet functions, derived from a mathematical model of temporal fluctuations, demonstrated that other abundant sewer associated populations including Trichococcus and Aeromonas had temporal patterns similar to either Acineto tag 1 or Acineto tag 2. Populations with related temporal fluctuations were found to significantly correlate with the same WWTP variables (5-day BOD, flow, ammonia, total phosphorous and suspended solids). These findings illustrate that small differences in V6 sequences can represent phylogenetically and ecologically distinct taxa. This work provides insight into microbial community composition and dynamics within the defined environment of urban sewer infrastructure.
Topics: Acinetobacter; Aeromonas; Bacteria; Bacterial Physiological Phenomena; Biodiversity; Carnobacteriaceae; Phylogeny; RNA, Ribosomal, 16S; Seasons; Sewage; Urban Population
PubMed: 22524675
DOI: 10.1111/j.1462-2920.2012.02757.x -
Applied and Environmental Microbiology Jun 2017Enzymes involved in lipid biosynthesis and metabolism play an important role in energy conversion and storage and in the function of structural components such as cell...
Enzymes involved in lipid biosynthesis and metabolism play an important role in energy conversion and storage and in the function of structural components such as cell membranes. The fatty aldehyde dehydrogenase (FAldDH) plays a central function in the metabolism of lipid intermediates, oxidizing fatty aldehydes to the corresponding fatty acid and competing with pathways that would further reduce the fatty aldehydes to fatty alcohols or require the fatty aldehydes to produce alkanes. In this report, the genes for four putative FAldDH enzymes from VT8 and an additional enzyme from were heterologously expressed in and shown to display FAldDH activity. Five enzymes (Maqu_0438, Maqu_3316, Maqu_3410, Maqu_3572, and the enzyme reported under RefSeq accession no. WP_004927398) were found to act on aldehydes ranging from acetaldehyde to hexadecanal and also acted on the unsaturated long-chain palmitoleyl and oleyl aldehydes. A comparison of the specificities of these enzymes with various aldehydes is presented. Crystallization trials yielded diffraction-quality crystals of one particular FAldDH (Maqu_3316) from VT8. Crystals were independently treated with both the NAD cofactor and the aldehyde substrate decanal, revealing specific details of the likely substrate binding pocket for this class of enzymes. A likely model for how catalysis by the enzyme is accomplished is also provided. This study provides a comparison of multiple enzymes with the ability to oxidize fatty aldehydes to fatty acids and provides a likely picture of how the fatty aldehyde and NAD are bound to the enzyme to facilitate catalysis. Based on the information obtained from this structural analysis and comparisons of specificities for the five enzymes that were characterized, correlations to the potential roles played by specific residues within the structure may be drawn.
Topics: Acinetobacter; Aldehyde Oxidoreductases; Aldehydes; Amino Acid Sequence; Bacterial Proteins; Binding Sites; Kinetics; Marinobacter; Models, Molecular; Molecular Sequence Data; Phylogeny; Sequence Alignment; Substrate Specificity
PubMed: 28389542
DOI: 10.1128/AEM.00018-17 -
Journal of Global Antimicrobial... Mar 2020Infections caused by multidrug-resistant Acinetobacter spp. have generated worldwide attention. With the increasing isolation of non-baumannii Acinetobacter, the nature...
OBJECTIVE
Infections caused by multidrug-resistant Acinetobacter spp. have generated worldwide attention. With the increasing isolation of non-baumannii Acinetobacter, the nature of associated infection and resistance needs to be explored. This study aimed to analyse the characteristics of New Delhi Metallo-Beta-Lactamase-1 (NDM-1)-producing Acinetobacter haemolyticus (named sz1652) isolated from Shenzhen city, China.
METHODS
The antibiotic spectrum was analysed after antimicrobial susceptibility testing. Combined disk test (CDT) was used to detect the metallo-beta-lactamases (MBLs). Transferability of carbapenem resistance was tested by filter mating experiments and plasmid transformation assays. Whole-genome sequencing (WGS) was performed using HiSeq 2000 and PacBio RS system.
RESULTS
The Acinetobacter haemolyticus strain sz1652 was resistant to carbapenems and other tested agents except for amikacin, tigecycline and colistin. Production of MBLs was confirmed by CDT. Transfer of carbapenem resistance was unsuccessful. WGS analysis showed that the genome of sz1652 comprised a chromosome and two plasmids; 16 genomic islands (GIs) were predicted. Genes associated with resistance were found in this strain, including the beta-lactamase genes bla, bla and bla, the fluoroquinolone resistant-related mutations [GyrA subunits (Ser81Ile) and ParC subunits (Ser84Tyr)], and efflux pump genes related to tetracycline and macrolide resistance. Analysis of the genetic environment showed that bla was embedded in Tn125 transposon. The Tn125 structure was chromosomally located and shared > 99% sequence identity with the previously reported bla carrying region.
CONCLUSION
The NDM-1-producing Acinetobacter haemolyticus coexisted with multiple drug-resistant determinants. The acquisition of the bla gene was probably facilitated by Tn125 in this strain. Non-Acinetobacter baumannii species also contained GIs.
Topics: Acinetobacter; Anti-Bacterial Agents; Base Composition; Carbapenems; China; DNA Transposable Elements; Drug Resistance, Bacterial; Genome Size; Genome, Bacterial; Genomic Islands; High-Throughput Nucleotide Sequencing; Humans; Microbial Sensitivity Tests; Urine; Whole Genome Sequencing; beta-Lactamases
PubMed: 31112806
DOI: 10.1016/j.jgar.2019.05.012