Effects of sub-inhibitory concentrations of meropenem and tigecycline on the expression of genes regulating pili, efflux pumps and virulence factors involved in biofilm formation by Acinetobacter baumannii

AbstractIn a recent report by the Centers for Disease Control and Prevention (CDC), multidrug resistant (MDR) Acinetobacter baumannii is a pathogen described as an “urgent threat.” Infection with this bacterium manifests as different diseases such as community and nosocomial pneumonia, bloodstream infections, endocarditis, infections of the urinary tract, wound infections, burn infections, skin and soft tissue infections, and meningitis. In particular, nosocomial meningitis, an unwelcome complication of neurosurgery caused by extensively-drug resistant (XDR) A. baumannii, is extremely challenging to manage. Therefore, understanding how A. baumannii adapts to different host environments, such as cerebrospinal fluid (CSF) that may trigger changes in expression of virulence factors that are associated with the successful establishment and progress of this infection is necessary. The present in-vitro work describes, the genetic changes that occur during A. baumannii infiltration into CSF and displays A. baumannii’s expansive versatility to persist in a nutrient limited environment while enhancing several virulence factors to survive and persist. While a hypervirulent A. baumannii strain did not show changes in its transcriptome when incubated in the presence of CSF, a low-virulence isolate showed significant differences in gene expression and phenotypic traits. Exposure to 4% CSF caused increased expression of virulence factors such as fimbriae, pilins, and iron chelators, and other virulence determinants that was confirmed in various model systems. Furthermore, although CSF's presence did not enhance bacterial growth, an increase of expression of genes encoding transcription, translation, and the ATP synthesis machinery was observed. This work also explores A. baumannii’s response to an essential component, human serum albumin (HSA), within CSF to trigger the differential expression of genes associated with its pathoadaptibility in this environment.

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Genome-Wide Identification of Acinetobacter baumannii Genes Necessary for Persistence in the Lung

mBio ◽

10.1128/mbio.01163-14 ◽

2014 ◽

Vol 5 (3) ◽

Cited By ~ 107

Author(s):

Nengding Wang ◽

Egon A. Ozer ◽

Mark J. Mandel ◽

Alan R. Hauser

Keyword(s):

Amino Acid ◽

Stress Response ◽

Acinetobacter Baumannii ◽

Virulence Factors ◽

Efflux Pumps ◽

Integration Host Factor ◽

Nucleotide Metabolism ◽

Massively Parallel ◽

Rich Medium ◽

Content Type

ABSTRACTAcinetobacter baumanniiis a Gram-negative bacterium that causes diseases such as pneumonia, bacteremia, and soft tissue infections in hospitalized patients. Relatively little is known about howA. baumanniicauses these infections. Thus, we used insertion sequencing (INSeq), a combination of transposon mutagenesis and massively parallel next-generation sequencing, to identify novel virulence factors ofA. baumannii. To this end, we generated a random transposon mutant library containing 150,000 unique insertions inA. baumanniistrain ATCC 17978. The INSeq analysis identified 453 genes required for growth in rich medium. The library was then used in a murine pneumonia model, and the relative levels of abundance of mutants before and after selection in the mouse were compared. When genes required for growth in rich medium were removed from the analysis, 157 genes were identified as necessary for persistence in the mouse lung. Several of these encode known virulence factors ofA. baumannii, such as OmpA and ZnuB, which validated our approach. A large number of the genes identified were predicted to be involved in amino acid and nucleotide metabolism and transport. Other genes were predicted to encode an integration host factor, a transmembrane lipoprotein, and proteins involved in stress response and efflux pumps. Very few genes, when disrupted, resulted in an increase inA. baumanniinumbers during host infection. The INSeq approach identified a number of novel virulence determinants ofA. baumannii, which are candidate targets for therapeutic interventions.IMPORTANCEA. baumanniihas emerged as a frequent cause of serious infections in hospitals and community settings. Due to increasing antibiotic resistance, alternative approaches, such as antivirulence strategies, are desperately needed to fightA. baumanniiinfections. Thorough knowledge ofA. baumanniipathogenicity is essential for such approaches but is currently lacking. With the increasingly widespread use of massively parallel sequencing, a class of techniques known as transposon insertion sequencing has been developed to perform comprehensive virulence screens of bacterial genomesin vivo. We have applied one of these approaches (INSeq) to uncover novel virulence factors inA. baumannii. We identified several such factors, including those predicted to encode amino acid and nucleotide metabolism proteins, an integration host factor protein, stress response factors, and efflux pumps. These results greatly expand the number ofA. baumanniivirulence factors and uncover potential targets for antivirulence treatments.

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The immune response in Acinetobacter baumannii pneumonia

Romanian Journal of Infectious Diseases ◽

10.37897/rjid.2016.1.3 ◽

2016 ◽

Vol 19 (1) ◽

pp. 16-21 ◽

Cited By ~ 1

Author(s):

Cristina Anca Tudor ◽

◽

Cristian Boros ◽

Raluca Petre ◽

Adriana Elena Nica ◽

...

Keyword(s):

Immune Response ◽

Respiratory Tract ◽

Acinetobacter Baumannii ◽

Virulence Factors ◽

Biofilm Formation ◽

Lower Respiratory Tract ◽

Defense Mechanism ◽

Immunocompromised Patients ◽

Common Site ◽

Acinetobacter Baumanii

Acinetobacter baumannii is a bacterium that is commonly causes of nosocomial infections, the most common site of infection and colonization is the lower respiratory tract. Although it is present more often in immunocompromised patients, the defense mechanism against infection with Acinetobacter baumanii remains incomplete elucidated. Among the virulence factors involved in infection with Acinetobacter baumanii are production and release of exopolysaccharide, and ability to biofilm formation in tissues. Understanding of virulence mechanisms is important for early initiation of treatment.

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Comparative analysis of carbapenemases, RND family efflux pumps and biofilm formation potential among Acinetobacter baumannii strains with different carbapenem susceptibility

BMC Infectious Diseases ◽

10.1186/s12879-021-06529-2 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Yanpeng Zhang ◽

Bing Fan ◽

Yong Luo ◽

Zhiyuan Tao ◽

Yongbo Nie ◽

...

Keyword(s):

Cell Division ◽

Comparative Analysis ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Carbapenem Resistance ◽

Efflux Pumps ◽

Relative Expression ◽

Formation Potential ◽

Tertiary Hospitals

Abstract Aim This study has conducted a comparative analysis of common carbapenemases harboring, the expression of resistance-nodulation-cell division (RND) family efflux pumps, and biofilm formation potential associated with carbapenem resistance among Acinetobacter baumannii (A. baumannii) strains with different carbapenem susceptibility. Methods: A total of 90 isolates of A. baumannii from two tertiary hospitals of China were identified and grouped as carbapenem susceptible A. baumannii (CSAB) strains and carbapenem non-susceptible A. baumannii (CnSAB) strains based on the susceptibility to imipenem. Harboring of carbapenemase genes, relative expression of RND family efflux pumps and biofilm formation potential were compared between the two groups. Result: Among these strains, 12 (13.3 %) strains were divided into the CSAB group, and 78 (86.7 %) strains into the CnSAB group. Compared with CSAB strains, CnSAB strains increased distribution of blaOXA−23 (p < 0.001) and ISAba1/blaOXA−51−like (p = 0.034) carbapenemase genes, and a 6.1-fold relative expression of adeB (p = 0.002), while CSAB strains led to biofilm formation by 1.3-fold than CnSAB strains (p = 0.021). Conclusions Clinically, harboring more blaOXA−23−like and ISAba1/blaOXA−51−like complex genes and overproduction of adeABC are relevant with carbapenem resistance, while carbapenem susceptible strains might survive the stress of antibiotic through their ability of higher biofilm formation.

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Impact of a Cross-Kingdom Signaling Molecule of Candida albicans on Acinetobacter baumannii Physiology

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01540-15 ◽

2015 ◽

Vol 60 (1) ◽

pp. 161-167 ◽

Cited By ~ 19

Author(s):

Xenia Kostoulias ◽

Gerald L. Murray ◽

Gustavo M. Cerqueira ◽

Jason B. Kong ◽

Farkad Bantun ◽

...

Keyword(s):

Candida Albicans ◽

Cell Membrane ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Defense Mechanism ◽

Membrane Integrity ◽

Efflux Pumps ◽

Signaling Molecule ◽

Content Type ◽

Antagonistic Interactions

ABSTRACTMultidrug-resistant (MDR)Acinetobacter baumanniiis an opportunistic human pathogen that has become highly problematic in the clinical environment. Novel therapies are desperately required. To assist in identifying new therapeutic targets, the antagonistic interactions betweenA. baumanniiand the most common human fungal pathogen,Candida albicans, were studied. We have observed that theC. albicansquorum-sensing molecule, farnesol, has cross-kingdom interactions, affecting the viability ofA. baumannii. To gain an understanding of its mechanism, the transcriptional profile ofA. baumanniiexposed to farnesol was examined. Farnesol caused dysregulation of a large number of genes involved in cell membrane biogenesis, multidrug efflux pumps (AcrAB-like and AdeIJK-like), andA. baumanniivirulence traits such as biofilm formation (csuA,csuB, andompA) and motility (pilZandpilH). We also observed a strong induction in genes involved in cell division (minD,minE,ftsK,ftsB, andftsL). These transcriptional data were supported by functional assays showing that farnesol disruptsA. baumanniicell membrane integrity, alters cell morphology, and impairs virulence characteristics such as biofilm formation and twitching motility. Moreover, we showed thatA. baumanniiuses efflux pumps as a defense mechanism against this eukaryotic signaling molecule. Owing to its effects on membrane integrity, farnesol was tested to see if it potentiated the activity of the membrane-acting polymyxin antibiotic colistin. When coadministered, farnesol increased sensitivity to colistin for otherwise resistant strains. These data provide mechanistic understanding of the antagonistic interactions between diverse pathogens and may provide important insights into novel therapeutic strategies.

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Mucin acts as a nutrient source and a signal for the differential expression of genes coding for cellular processes and virulence factors in Acinetobacter baumannii

PLoS ONE ◽

10.1371/journal.pone.0190599 ◽

2018 ◽

Vol 13 (1) ◽

pp. e0190599 ◽

Cited By ~ 18

Author(s):

Emily J. Ohneck ◽

Brock A. Arivett ◽

Steven E. Fiester ◽

Cecily R. Wood ◽

Maeva L. Metz ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Differential Expression ◽

Virulence Factors ◽

Nutrient Source ◽

Cellular Processes ◽

Expression Of Genes ◽

Differential Expression Of Genes

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Cerebrospinal fluid (CSF) boosts metabolism and virulence expression factors in Acinetobacter baumannii

10.1101/2020.07.13.201848 ◽

2020 ◽

Author(s):

Jasmine Martinez ◽

Chelsea Razo-Gutierrez ◽

Casin Le ◽

Robert Courville ◽

Camila Pimentel ◽

...

Keyword(s):

Cerebrospinal Fluid ◽

Acinetobacter Baumannii ◽

Virulence Factors ◽

Respiratory Infections ◽

Atp Synthesis ◽

Bloodstream Infections ◽

Multidrug Resistant ◽

Model Systems ◽

Phenotypic Traits ◽

Expression Of Genes

AbstractIn a recent report by the Centers for Disease Control and Prevention (CDC), multidrug resistant (MDR) Acinetobacter baumannii is a pathogen described as an “urgent threat”. Infection with this bacterium manifests as different diseases such as community and nosocomial pneumonia, bloodstream infections, endocarditis, urinary tract, wound infections, burn infections, skin and soft tissue infections, and meningitis. In particular, nosocomial meningitis, a common complication of neurosurgery caused by extensively-drug resistant (XDR) A. baumannii, is extremely challenging to manage. Therefore, it is necessary to identify signals, such as exposure to cerebrospinal fluid (CSF), that trigger expression of virulence factors that are associated with the successful establishment and progress of this infection. While a hypervirulent A. baumannii strain did not show changes in its transcriptome when incubated in the presence of CSF, a low-virulence isolate showed significant differences in gene expression and phenotypic traits. Exposure to 4% CSF caused increased expression of virulence factors such as fimbriae, pilins, and iron chelators, and virulence as determined in various model systems. Furthermore, although CSF’s presence did not enhance bacterial growth, it was associated with an increase of expression of genes encoding transcription, translation, and the ATP synthesis machinery. Experiments to identify the active CSF component pointed to human serum albumin (HSA).ImportanceAcinetobacter baumannii, notorious for its multidrug resistant phenotype, overcomes nutrient deprived and desiccated conditions through its metabolic flexibility, pathogenic and physiological adaptability. Although this pathogen is commonly associated with respiratory infections, there have been a considerable amount of cases of A. baumannii bacterial meningitis. These infections are usually post-neurological surgery complications associated with high mortality rates ranging from 40 to 70%. This work describes interactions that may occur during A. baumannii infection of human cerebrospinal fluid (CSF). A. baumannii’s displays capabilities to persist and thrive in a nutrient-limited environment, which also triggers the expression of virulence factors. This work also further explores A. baumannii’s utilization of an essential component within CSF to trigger enhanced expression of genes associated with its pathoadaptibility in this environment.

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Biofilm Formation Restrained by Subinhibitory Concentrations of Tigecyclin in Acinetobacter baumannii Is Associated with Downregulation of Efflux Pumps

Chemotherapy ◽

10.1159/000450537 ◽

2016 ◽

Vol 62 (2) ◽

pp. 128-133 ◽

Cited By ~ 5

Author(s):

Huale Chen ◽

Jianming Cao ◽

Cui Zhou ◽

Haiyang Liu ◽

Xiaoxiao Zhang ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Real Time ◽

Biofilm Formation ◽

Efflux Pump ◽

Efflux Pumps ◽

Extracellular Dna ◽

Proteinase K ◽

Quantitative Detection ◽

Rt Pcr ◽

Subinhibitory Concentrations

Background: Tigecycline, one of the few therapeutic options against multidrug-resistant Acinetobacter baumannii, reaches subinhibitory serum concentrations only with cautious clinical dosing and pharmacokinetics. Subinhibitory concentrations of tigecycline might induce an A. baumannii biofilm. Methods: Biofilm formation was assessed via the crystal violet staining method. We further analyzed the main biofilm components with NaIO4, proteinase K, and DNase. Real-time RT-PCR was applied for quantitative detection of biofilm potential-associated genes. Results: In this study, A. baumannii proved to be a strong biofilm producer, and we found that proteins and extracellular DNA are crucial components of the A. baumannii biofilm. Quantitative real-time RT-PCR revealed positive correlations between biofilm formation restrained by subinhibitory concentrations of tigecycline and the expression of biofilm potential-associated genes, especially the AdeFGH efflux pump gene. Conclusion: Our results suggest that downregulation of efflux pumps, especially the AdeFGH efflux pump, is probably responsible for the decline in biofilm formation in A. baumannii treated with subinhibitory concentrations of tigecyclin.

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Inhibition of Virulence Factors and Biofilm Formation of Acinetobacter Baumannii by Naturally-derived and Synthetic Drugs

Current Drug Targets ◽

10.2174/1389450121666201023122355 ◽

2020 ◽

Vol 21 ◽

Author(s):

Nilushi Indika Bamunuar Achchi ◽

Fazlurrahman Khan ◽

Young-Mog Kim

Keyword(s):

Acinetobacter Baumannii ◽

Virulence Factors ◽

Biofilm Formation ◽

Resistance Mechanisms ◽

Initial Surface ◽

Surface Attachment ◽

Synthetic Compounds ◽

Mortality And Morbidity ◽

Synthetic Drugs ◽

Host Cell Surface

: Acinetobacter baumannii is a Gram-negative, aerobic, non-motile, and pleomorphic bacillus. A. baumanii is also a highly-infectious pathogen causing high mortality and morbidity rates in intensive care units. The discovery of novel agents against A. baumanii infections is urgently needed due to the emergence of drug-resistant A. baumannii strains and the limited number of efficacious antibiotics available for treatment. In addition to the production of several virulence factors, A. baumannii forms biofilms on the host cell surface as well. Formation of biofilms occurs through initial surface attachment, microcolony formation, biofilm maturation, and detachment stages, and is one of the major drug resistance mechanisms employed by A. baumanii. Several studies have previously reported the efficacy of naturally-derived and synthetic compounds as anti-biofilm and anti-virulence agents against A. baumannii. Here, inhibition of biofilm formation and virulence factors of A. baumannii using naturally-derived and synthetic compounds are reviewed.

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