scholarly journals Insights into Background of Microbial Aggregations (Acinetobacter baumannii): A Century of Challenges

2021 ◽  
Vol 1 (4) ◽  
Author(s):  
Mohammad Motamedifar ◽  
Nafiseh Hosseinzadeh Shakib ◽  
Yeganeh Sadeghi Asl
Keyword(s):  
Quorum Sensing ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Drug Targets ◽  
Signaling Molecules ◽  
Worldwide Distribution ◽  
Structural Details ◽  
Alternative Drug ◽  
Biofilm Structure ◽  
Hospital Acquired

: In recent years, Acinetobacter baumannii has attracted the research community’s attention since they are turned into the leading cause of both community- and hospital-acquired infections. The emergence of MDR-Acinetobacter baumannii strains threatens hospitalized patients since antibiotics fail to withdraw the bacterial infectious agents. Despite its worldwide distribution, health settings fail to combat limitations in therapeutic regions against Acinetobacter baumannii. The capability of biofilm formation in Acinetobacter baumannii strengthens their virulence and also survival. Understanding the fundamental virulence mechanisms beyond the microbial aggregations leads to exploring alternative drug targets such as signaling molecules and Quorum sensing systems to block bacterial communication and antimicrobial resistance. The significance of examining the biofilm's structural details and the relationship between Quorum sensing networks and related signaling molecules has been explicitly highlighted. Accordingly, this review study aimed to explain the general biofilm structure, the mechanisms beyond biofilm formation, quorum sensing system, and the generation of signaling molecules in Acinetobacter baumannii.

scholarly journals Interaction of Acinetobacter baumannii with Human Serum Albumin: Does the Host Determines the Outcome?

Antibiotics ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 833
Author(s):  
Camila Pimentel ◽  
Casin Le ◽  
Marisel R. Tuttobene ◽  
Tomas Subils ◽  
Krisztina M. Papp-Wallace ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Human Serum Albumin ◽  
Quorum Sensing ◽  
Serum Albumin ◽  
Human Serum ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Model Systems ◽  
Expression Levels ◽  
Multiple Drugs

Acinetobacter baumannii has become a serious threat to human health due to its extreme antibiotic resistance, environmental persistence, and capacity to survive within the host. Two A. baumannii strains, A118 and AB5075, commonly used as model systems, and three carbapenem-resistant strains, which are becoming ever more dangerous due to the multiple drugs they can resist, were exposed to 3.5% human serum albumin (HSA) and human serum (HS) to evaluate their response with respect to antimicrobial resistance, biofilm formation, and quorum sensing, all features responsible for increasing survival and persistence in the environment and human body. Expression levels of antibiotic resistance genes were modified differently when examined in different strains. The cmlA gene was upregulated or downregulated in conditions of exposure to 3.5% HSA or HS depending on the strain. Expression levels of pbp1 and pbp3 tended to be increased by the presence of HSA and HS, but the effect was not seen in all strains. A. baumannii A118 growing in the presence of HS did not experience increased expression of these genes. Aminoglycoside-modifying enzymes were also expressed at higher or lower levels in the presence of HSA or HS. Still, the response was not uniform; in some cases, expression was enhanced, and in other cases, it was tapered. While A. baumannii AB5075 became more susceptible to rifampicin in the presence of 3.5% HSA or HS, strain A118 did not show any changes. Expression of arr2, a gene involved in resistance to rifampicin present in A. baumannii AMA16, was expressed at higher levels when HS was present in the culture medium. HSA and HS reduced biofilm formation and production of N-Acyl Homoserine Lactone, a compound intimately associated with quorum sensing. In conclusion, HSA, the main component of HS, stimulates a variety of adaptative responses in infecting A. baumannii strains.

scholarly journals Lon Protease Has Multifaceted Biological Functions inAcinetobacter baumannii

2018 ◽  
Vol 201 (2) ◽  
Author(s):  
Carly Ching ◽  
Brendan Yang ◽  
Chineme Onwubueke ◽  
David Lazinski ◽  
Andrew Camilli ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Developmental Process ◽  
Cell Envelope ◽  
Opportunistic Pathogen ◽  
Lon Protease ◽  
Content Type ◽  
Hospital Acquired Infections ◽  
Biofilm Development ◽  
Hospital Acquired

ABSTRACTAcinetobacter baumanniiis a Gram-negative opportunistic pathogen that is known to survive harsh environmental conditions and is a leading cause of hospital-acquired infections. Specifically, multicellular communities (known as biofilms) ofA. baumanniican withstand desiccation and survive on hospital surfaces and equipment. Biofilms are bacteria embedded in a self-produced extracellular matrix composed of proteins, sugars, and/or DNA. Bacteria in a biofilm are protected from environmental stresses, including antibiotics, which provides the bacteria with selective advantage for survival. Although some gene products are known to play roles in this developmental process inA. baumannii, mechanisms and signaling remain mostly unknown. Here, we find that Lon protease inA. baumanniiaffects biofilm development and has other important physiological roles, including motility and the cell envelope. Lon proteases are found in all domains of life, participating in regulatory processes and maintaining cellular homeostasis. These data reveal the importance of Lon protease in influencing keyA. baumanniiprocesses to survive stress and to maintain viability.IMPORTANCEAcinetobacter baumanniiis an opportunistic pathogen and is a leading cause of hospital-acquired infections.A. baumanniiis difficult to eradicate and to manage, because this bacterium is known to robustly survive desiccation and to quickly gain antibiotic resistance. We sought to investigate biofilm formation inA. baumannii, since much remains unknown about biofilm formation in this bacterium. Biofilms, which are multicellular communities of bacteria, are surface attached and difficult to eliminate from hospital equipment and implanted devices. Our research identifies multifaceted physiological roles for the conserved bacterial protease Lon inA. baumannii. These roles include biofilm formation, motility, and viability. This work broadly affects and expands understanding of the biology ofA. baumannii, which will permit us to find effective ways to eliminate the bacterium.

scholarly journals Effect of Coriander Oil (Coriandrum sativum) on Planktonic and Biofilm Cells of Acinetobacter baumannii

2013 ◽  
Vol 8 (5) ◽  
pp. 1934578X1300800 ◽  
Author(s):  
Andreia F. Duarte ◽  
Susana Ferreira ◽  
Rosário Oliveira ◽  
Fernanda C. Domingues
Keyword(s):  
Essential Oil ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Antimicrobial Properties ◽  
Hospital Acquired Infections ◽  
Microtiter Plates ◽  
Crystal Violet Assay ◽  
Hospital Acquired ◽  
Microdilution Broth ◽  
Susceptibility Assay

The increasing incidence of hospital-acquired infections caused by multi-drug resistant pathogens, such as Acinetobacter baumannii, coupled with the low efficacy of drugs and rising treatment costs has created interest in the potential antimicrobial properties of natural products. The main objective of this work was to determine the effect of coriander essential oil on Acinetobacter baumannii in different growth phases, as well as its ability to inhibit the formation or eradication of biofilms. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of coriander oil using a microdilution broth susceptibility assay was determined. The effects of different concentrations of coriander oil (ranging from 0.125 to 4×MIC) on biofilm formation and on established biofilm were tested using 96-well microtiter plates. Crystal violet assay was used as indicator of total biofilm biomass and the biofilm viability was assessed with a XTT staining method. It was found that coriander oil presented significant antibacterial activity against all tested strains of A. baumannii, with MIC values between 1 and 4 μL/mL. The MBC values were the same as the MIC, being an indicator of the bactericidal activity of this essential oil. In what concerns the effect of this essential oil on biofilm formation inhibition was observed of at least 85% of biomass formation by all A. baumannii strains using 2×MIC of coriander oil, in addition to a decrease in the metabolic activity of the cells. After exposure to coriander oil, a decrease in 24 h and 48 h-old biofilm biomass and metabolism was seen for all tested concentrations, even with sub-inhibitory concentrations. Coriander essential oil proved to have a significant antibacterial and anti-biofilm activity and should be considered in the development of future disinfectants to control A. baumannii dissemination.

scholarly journals AbaM Regulates Quorum Sensing, Biofilm Formation and Virulence in Acinetobacter baumannii

2021 ◽  
Author(s):  
Mario López-Martín ◽  
Jean-Frédéric Dubern ◽  
Morgan R. Alexander ◽  
Paul Williams
Keyword(s):  
Quorum Sensing ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Plant Pathogens ◽  
Galleria Mellonella ◽  
Homoserine Lactone ◽  
Infection Model ◽  
Wild Type ◽  
Surface Motility ◽  
Biofilm Development

Acinetobacter baumannii possesses a single divergent luxR/luxI-type quorum sensing (QS) locus named abaR/abaI. This locus also contains a third gene located between abaR and abaI which we term abaM that codes for an uncharacterized member of the RsaM protein family known to regulate N-acylhomoserine lactone (AHL) dependent QS in other β- and γ-proteobacteria. Here we show that disruption of abaM via a T26 insertion in A. baumannii strain AB5075 resulted in increased production of N-(3-hydroxydodecanoyl)-L-homoserine lactone (OHC12) and enhanced surface motility and biofilm formation. In contrast to the wild type and abaI::T26 mutant, the virulence of the abaM::T26 mutant was completely attenuated in a Galleria mellonella infection model. Transcriptomic analysis of the abaM::T26 mutant revealed that AbaM differentially regulates at least 76 genes including the csu pilus operon and the acinetin 505 lipopeptide biosynthetic operon, that are involved in surface adherence, biofilm formation and virulence. A comparison of the wild type, abaM::T26 and abaI::T26 transcriptomes, indicates that AbaM regulates ∼21% of the QS regulon including the csu operon. Moreover, the QS genes (abaI/abaR) were among the most upregulated in the abaM::T26 mutant. A. baumannii lux-based abaM reporter gene fusions revealed that abaM expression is positively regulated by QS but negatively auto-regulated. Overall, the data presented in this work demonstrates that AbaM plays a central role in regulating A. baumannii QS, virulence, surface motility and biofilm formation. Importance Acinetobacter baumanni is a multi-antibiotic resistant pathogen of global healthcare importance. Understanding Acinetobacter virulence gene regulation could aid the development of novel anti-infective strategies. In A. baumannii, the abaR and abaI genes that code for the receptor and synthase components of an N-acylhomoserine (AHL) lactone-dependent quorum sensing system (QS) are separated by abaM. Here we show that although mutation of abaM increased AHL production, surface motility and biofilm development, it resulted in the attenuation of virulence. AbaM was found to control both QS-dependent and QS-independent genes. The significance of this work lies in the identification of AbaM, an RsaM ortholog known to control virulence in plant pathogens, as a modulator of virulence in a human pathogen.

scholarly journals Assessment of Antibiofilm Potencies of Nervonic and Oleic Acid against Acinetobacter baumannii Using In Vitro and Computational Approaches

Biomedicines ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1133
Author(s):  
Sagar Kiran Khadke ◽  
Jin-Hyung Lee ◽  
Yong-Guy Kim ◽  
Vinit Raj ◽  
Jintae Lee
Keyword(s):  
Fatty Acids ◽  
Oleic Acid ◽  
Quorum Sensing ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Unsaturated Fatty Acids ◽  
Homoserine Lactone ◽  
Antimicrobial Treatment ◽  
Dynamic Simulations

Acinetobacter baumannii is a nosocomial pathogen, and its biofilms are tolerant to desiccation, nutrient starvation, and antimicrobial treatment on biotic and abiotic surfaces, tissues, and medical devices. Biofilm formation by A. baumannii is triggered by a quorum sensing cascade, and we hypothesized that fatty acids might inhibit its biofilm formation by interfering with quorum sensing. Initially, we investigated the antibiofilm activities of 24 fatty acids against A. baumannii ATCC 17978 and two clinical isolates. Among these fatty acids, two unsaturated fatty acids, nervonic and oleic acid, at 20 μg/mL significantly inhibited A. baumannii biofilm formation without affecting its planktonic cell growth (MICs were >500 μg/mL) and markedly decreased the motility of A. baumannii but had no toxic effect on the nematode Caenorhabditis elegans. Interestingly, molecular dynamic simulations showed that both fatty acids bind to the quorum sensing acyl homoserine lactone synthase (AbaI), and decent conformational stabilities of interactions between the fatty acids and AbaI were exhibited. Our results demonstrate that nervonic and oleic acid inhibit biofilm formation by A. baumannii strains and may be used as lead molecules for the control of persistent A. baumannii infections.

scholarly journals Specific quorum sensing molecules are possibly associated with responses to herbicide toxicity in a Pseudomonas strain

2020 ◽  
Author(s):  
Paloma Nathane Nunes de Freitas ◽  
Amanda Flávia da Silva Rovida ◽  
Caroline Rosa Silva ◽  
Sônia Alvim Veiga Pileggi ◽  
Luiz Ricardo Olchanheski ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Agricultural Production ◽  
Biofilm Formation ◽  
Structural Changes ◽  
Bacterial Species ◽  
Signaling Molecules ◽  
Oxygen Species ◽  
Physiological Plasticity ◽  
Response System ◽  
Generating System

AbstractPesticides contribute to pest control and increased agricultural production; however, they are toxic to non-target organisms and they contaminate the environment. The exposure of bacteria to these substances can lead to the need for physiological and structural changes for survival, which can be determined by genes whose expression is regulated by quorum sensing (QS). However, it is not yet clear whether these processes can be induced by herbicides. Thus, the aim of this work was to determine whether there is a QS response system in a Pseudomonas fluorescens strain that is modulated by herbicides. This strain was isolated from water storage tanks used for washing pesticide packaging and was tested against herbicides containing saflufenacil, glyphosate, sulfentrazone, 2,4-D, and dicamba as active molecules. We found that this strain possibly uses QS signaling molecules to control the production of reactive oxygen species, whether those produced by the bacterium’s energy generating system or by molecules induced by the presence of saflufenacil and glyphosate. This strain used other signaling molecules for various stages of biofilm formation in the presence of herbicides containing sulfentrazone, 2,4-D, and dicamba. These findings, as an initial screening which will guide new studies, suggest that this strain has a flexibility in gene expression that allows survival in the presence of several stress-inducing molecules, regardless of previous exposure. This represents a model of metabolic and physiological plasticity. Biofilms made up of several bacterial species can use this model in agricultural environments, increasing the potential for degradation of xenobiotics, but with impacts on diversity and functionality of microbiotas in these environments.

scholarly journals The CpAL Quorum Sensing System Regulates Production of Hemolysins CPA and PFO To Build Clostridium perfringens Biofilms

2015 ◽  
Vol 83 (6) ◽  
pp. 2430-2442 ◽  
Author(s):  
Jorge E. Vidal ◽  
Joshua R. Shak ◽  
Adrian Canizalez-Roman
Keyword(s):  
Quorum Sensing ◽  
Clostridium Perfringens ◽  
Biofilm Formation ◽  
Extracellular Dna ◽  
Wild Type ◽  
Content Type ◽  
Type C ◽  
Enteritis Necroticans ◽  
Biofilm Structure

Clostridium perfringensstrains produce severe diseases, including myonecrosis and enteritis necroticans, in humans and animals. Diseases are mediated by the production of potent toxins that often damage the site of infection, e.g., skin epithelium during myonecrosis. In planktonic cultures, the regulation of important toxins, such as CPA, CPB, and PFO, is controlled by theC. perfringensAgr-like (CpAL) quorum sensing (QS) system. Strains also encode a functional LuxS/AI-2 system. AlthoughC. perfringensstrains form biofilm-like structures, the regulation of biofilm formation is poorly understood. Therefore, our studies investigated the role of CpAL and LuxS/AI-2 QS systems and of QS-regulated factors in controlling the formation of biofilms. We first demonstrate that biofilm production by reference strains differs depending on the culture medium. Increased biomass correlated with the presence of extracellular DNA in the supernatant, which was released by lysis of a fraction of the biofilm population and planktonic cells. Whereas ΔagrBmutant strains were not able to produce biofilms, a ΔluxSmutant produced wild-type levels. The transcript levels of CpAL-regulatedcpaandpfoAgenes, but notcpb, were upregulated in biofilms compared to planktonic cultures. Accordingly, Δcpaand ΔpfoAmutants, in type A (S13) or type C (CN3685) backgrounds, were unable to produce biofilms, whereas CN3685Δcpbmade wild-type levels. Biofilm formation was restored in complemented Δcpa/cpaand ΔpfoA/pfoAstrains. Confocal microscopy studies further detected CPA partially colocalizing with eDNA on the biofilm structure. Thus, CpAL regulates biofilm formation inC. perfringensby increasing levels of certain toxins required to build biofilms.

scholarly journals Defining Gene-Phenotype Relationships in Acinetobacter baumannii through One-Step Chromosomal Gene Inactivation

mBio ◽  
2014 ◽  
Vol 5 (4) ◽  
Author(s):  
Ashley T. Tucker ◽  
Emily M. Nowicki ◽  
Joseph M. Boll ◽  
Gregory A. Knauf ◽  
Nora C. Burdis ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Antibiotic Resistance ◽  
Acinetobacter Baumannii ◽  
Genome Editing ◽  
Biofilm Formation ◽  
Content Type ◽  
Stress Protection ◽  
Biocide Resistance ◽  
Hospital Acquired ◽  
Oxidative Stress Protection

ABSTRACTRates of infection with hospital-acquiredAcinetobacter baumanniihave exploded over the past decade due to our inability to limit persistence and effectively treat disease.A. baumanniiquickly acquires antibiotic resistance, and its genome encodes mechanisms to tolerate biocides and desiccation, which enhance its persistence in hospital settings. With depleted antibiotic options, new methods to treatA. baumanniiinfections are desperately needed. A comprehensive understanding detailingA. baumanniicellular factors that contribute to its resiliency at genetic and mechanistic levels is vital to the development of new treatment options. Tools to rapidly dissect theA. baumanniigenome will facilitate this goal by quickly advancing our understanding ofA. baumanniigene-phenotype relationships. We describe here a recombination-mediated genetic engineering (recombineering) system for targeted genome editing ofA. baumannii. We have demonstrated that this system can perform directed mutagenesis on wide-ranging genes and operons and is functional in various strains ofA. baumannii, indicating its broad application. We utilized this system to investigate key gene-phenotype relationships inA. baumanniibiology important to infection and persistence in hospitals, including oxidative stress protection, biocide resistance mechanisms, and biofilm formation. In addition, we have demonstrated that both the formation and movement of type IV pili play an important role inA. baumanniibiofilm.IMPORTANCEAcinetobacter baumanniiis the causative agent of hospital-acquired infections, including pneumonia and serious blood and wound infections.A. baumanniiis an emerging pathogen and has become a threat to public health because it quickly develops antibiotic resistance, making treatment difficult or impossible. While the threat ofA. baumanniiis well recognized, our understanding of even its most basic biology lags behind. Analysis ofA. baumanniicellular functions to identify potential targets for drug development has stalled due in part to laborious genetic techniques. Here we have pioneered a novel recombineering system that facilitates efficient genome editing inA. baumanniiby single PCR products. This technology allows for rapid genome editing to quickly ascertain gene-phenotype relationships. To demonstrate the power of recombineering in dissectingA. baumanniibiology, we use this system to establish key gene-phenotype relationships important to infection and persistence in hospitals, including oxidative stress protection, biocide resistance, and biofilm formation.

Physicochemical parameters influencing the formation of biofilms compared in mutant and wild-type cells of Pseudomonas chlororaphis O6

2005 ◽  
Vol 52 (7) ◽  
pp. 21-25 ◽  
Author(s):  
A.J. Anderson ◽  
D.W. Britt ◽  
J. Johnson ◽  
G. Narasimhan ◽  
A. Rodriguez
Keyword(s):  
Quorum Sensing ◽  
Biofilm Formation ◽  
Cell Structure ◽  
Strong Interactions ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Small Colony Variant ◽  
Force Microscopy ◽  
Force Mode ◽  
Biofilm Structure

Bacteria colonize surfaces as heterogeneous structures called biofilms. Intercellular communication using acyl homoserine lactones has been implicated in biofilm formation in some systems. Here, we investigate cell structure in biofilms and associated physiochemical properties of wild type and quorum sensing mutants of Pseudomonas chlororaphis O6 (PcO6), a root-colonizing bacterium. The wild type strain generates multilayered biofilms under conditions where the quorum sensing mutant, deficient in the GacS sensor kinase, does not mature beyond a monolayer structure. However, this gacS mutant rapidly evolves to form a small colony variant (gacS-SCV) that again produces a multilayered biofilm structure although AHSL production is not restored to wild type level. Biofilms formed by the gacS-SCV (114±12°) mutant were the most hydrophobic displaying a higher average ethylene glycol contact angle than those formed by the wild type (28±7°) and gacS (18±6°). Tapping mode atomic force microscopy revealed elongated cell structure in both of the mutant biofilm cells. Digital pulsed force mode adhesion mapping showed that the average adhesion followed the order gacS>gacS-SCV, wild-type. Certain of these gacS mutant cells displayed strong interactions of the AFM tip with cell boundaries, the role of which in biofilm formation is currently under investigation.

Evaluation of type II toxin-antitoxin systems, antibiotic resistance profiles, and biofilm quorum sensing genes in Acinetobacter baumannii isolates in Iraq

2020 ◽  
Vol 20 ◽  
Author(s):  
Mohammed F. Al Marjania ◽  
Ebrahim Kouhsari ◽  
Fatima S. Ali ◽  
Sawsan H. Authman
Keyword(s):  
Antibiotic Resistance ◽  
Quorum Sensing ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Bacterial Genome ◽  
Bacterial Toxin ◽  
Clinical Samples ◽  
Disk Diffusion Test ◽  
Molecular Determinants ◽  
Imipenem Resistance

Background: Bacterial Toxin-Antitoxin (TAs) systems are extensive two-component elements in the bacterial genome, which involved in many key biological functions including growth arrest, survival, biofilm formation, plasmid maintenance, defense against phages, persistence and virulence. Aim: This study aimed to assess the molecular determinants involved in TAs, biofilm quorum sensing, and antibiotic resistance profiles in Acinetobacter baumannii isolated from Baghdad`s hospitals in Iraq. Methods: A total of 127 A. baumannii isolates were collected from 2160 different clinical samples. The antimicrobial susceptibility test was performed using disk diffusion test. All isolates were characterized for molecular determinants involved in TAs and biofilm formation using the well-known PCR-based sequencing assay. Results: A high multi-drug resistant (MDR) (96.06%; 122/127 ) and imipenem resistance (84.25%; 107/127 ) rates were observed from A.baumannii isolates. Results showed the presence of rhlIR gene in three isolates (2.36%), and lasIR gene appeared in two isolates (1.57%) isolates, whilst, mazEF, ccdAB, and relBE genes have not detected among isolates. Conclusion: A high MDR and imipenem resistance rates within a low prevalence of rhlIR, and lasIR genes could be found in clinical A. baumannii isolates from some of Iraqi hospitals.

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