Differences in biofilm formation and transcription of biofilm-associated genes among Acinetobacter baumannii clinical strains belonging to the international clone II lineage

Background: A.baumannii is an opportunistic pathogen known for its efficient biofilm formation that is attributed for its virulence. Acinetobacter baumannii is an inhabitant of oral biofilms as well. Many gene operons are involved in the biofilm formation that need to be monitored frequently. Aim: The aim of the present study was to detect the distribution of four biofilm associated genes among A.baumannii. Materials and Methods: Four biofilm forming genes viz., bfms, ptk, pgaB, and fimH of A.baumannii were selected. Forward and reverse primers of those four genes were used for in-silico PCR amplification. 19 strains of A.baumannii set as default on the server were chosen and the amplicon bands were observed Results: The present investigation documents the distribution of four vital biofilm associated gene among 19 different strains of A.baumannii among which bfms was distributed at a higher frequency followed by pgaB and ptk Conclusion: The finding of the study suggests the presence of pgaB, bfms, ptk among the 19 different strains of A.baumannii. However further experimental validation must be done to frequently monitor the presence of the genes among the clinical strains of A.baumannii.

Download Full-text

Biocide-tolerant multidrug-resistant Acinetobacter baumannii clinical strains are associated with higher biofilm formation

Journal of Hospital Infection ◽

10.1016/j.jhin.2009.07.015 ◽

2009 ◽

Vol 73 (3) ◽

pp. 287-289 ◽

Cited By ~ 16

Author(s):

G. Rajamohan ◽

V.B. Srinivasan ◽

W.A. Gebreyes

Keyword(s):

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Multidrug Resistant ◽

Clinical Strains

Download Full-text

Analysis of virulence phenotypes and antibiotic resistance in clinical strains of Acinetobacter baumannii isolated in Nashville, Tennessee

BMC Microbiology ◽

10.1186/s12866-020-02082-1 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Ranashia L. Boone ◽

Briana Whitehead ◽

Tyra M. Avery ◽

Jacky Lu ◽

Jamisha D. Francis ◽

...

Keyword(s):

Antibiotic Resistance ◽

Antimicrobial Resistance ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Inverse Correlation ◽

Clinical Isolates ◽

Anatomical Site ◽

Inverse Association ◽

Clinical Strains ◽

Bronchial Wash

Abstract Background Acinetobacter baumannii is a gram-negative bacterium which causes opportunistic infections in immunocompromised hosts. Genome plasticity has given rise to a wide range of strain variation with respect to antimicrobial resistance profiles and expression of virulence factors which lead to altered phenotypes associated with pathogenesis. The purpose of this study was to analyze clinical strains of A. baumannii for phenotypic variation that might correlate with virulence phenotypes, antimicrobial resistance patterns, or strain isolation source. We hypothesized that individual strain virulence phenotypes might be associated with anatomical site of isolation or alterations in susceptibility to antimicrobial interventions. Methodology A cohort of 17 clinical isolates of A. baumannii isolated from diverse anatomical sites were evaluated to ascertain phenotypic patterns including biofilm formation, hemolysis, motility, and antimicrobial resistance. Antibiotic susceptibility/resistance to ampicillin-sulbactam, amikacin, ceftriaxone, ceftazidime, cefotaxime, ciprofloxacin, cefepime, gentamicin, levofloxacin, meropenem, piperacillin, trimethoprim-sulfamethoxazole, ticarcillin- K clavulanate, tetracyclin, and tobramycin was determined. Results Antibiotic resistance was prevalent in many strains including resistance to ampicillin-sulbactam, amikacin, ceftriaxone, ceftazidime, cefotaxime, ciprofloxacin, cefepime, gentamicin, levofloxacin, meropenem, piperacillin, trimethoprim-sulfamethoxazole, ticarcillin- K clavulanate, tetracyclin, and tobramycin. All strains tested induced hemolysis on agar plate detection assays. Wound-isolated strains of A. baumannii exhibited higher motility than strains isolated from blood, urine or Foley catheter, or sputum/bronchial wash. A. baumannii strains isolated from patient blood samples formed significantly more biofilm than isolates from wounds, sputum or bronchial wash samples. An inverse relationship between motility and biofilm formation was observed in the cohort of 17 clinical isolates of A. baumannii tested in this study. Motility was also inversely correlated with induction of hemolysis. An inverse correlation was observed between hemolysis and resistance to ticarcillin-k clavulanate, meropenem, and piperacillin. An inverse correlation was also observed between motility and resistance to ampicillin-sulbactam, ceftriaxone, ceftoxamine, ceftazidime, ciprofloxacin, or levofloxacin. Conclusions Strain dependent variations in biofilm and motility are associated with anatomical site of isolation. Biofilm and hemolysis production both have an inverse association with motility in the cohort of strains utilized in this study, and motility and hemolysis were inversely correlated with resistance to numerous antibiotics.

Download Full-text

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

Antibiotics ◽

10.3390/antibiotics10070833 ◽

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.

Download Full-text

High frequency of blaPER-1 gene in clinical strains of Acinetobacter baumannii and its association with quorum sensing and virulence factors

Gene Reports ◽

10.1016/j.genrep.2021.101232 ◽

2021 ◽

Vol 24 ◽

pp. 101232

Author(s):

Fariba Naeimi Mazraeh ◽

Alka Hasani ◽

Javid Sadeghi ◽

Hossein Samadi Kafil ◽

Mohammad Hossein Soroush Barhaghi ◽

...

Keyword(s):

Quorum Sensing ◽

Acinetobacter Baumannii ◽

Virulence Factors ◽

High Frequency ◽

Clinical Strains

Download Full-text

Antibiofilm and antivirulence potential of silver nanoparticles against multidrug-resistant Acinetobacter baumannii

Scientific Reports ◽

10.1038/s41598-021-90208-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Helal F. Hetta ◽

Israa M. S. Al-Kadmy ◽

Saba Saadoon Khazaal ◽

Suhad Abbas ◽

Ahmed Suhail ◽

...

Keyword(s):

Silver Nanoparticles ◽

Antibacterial Activity ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Microtiter Plate ◽

Diffusion Method ◽

Resistance Pattern ◽

Infection Model ◽

The Impact

AbstractWe aimed to isolate Acinetobacter baumannii (A. baumannii) from wound infections, determine their resistance and virulence profile, and assess the impact of Silver nanoparticles (AgNPs) on the bacterial growth, virulence and biofilm-related gene expression. AgNPs were synthesized and characterized using TEM, XRD and FTIR spectroscopy. A. baumannii (n = 200) were isolated and identified. Resistance pattern was determined and virulence genes (afa/draBC, cnf1, cnf2, csgA, cvaC, fimH, fyuA, ibeA, iutA, kpsMT II, PAI, papC, PapG II, III, sfa/focDE and traT) were screened using PCR. Biofilm formation was evaluated using Microtiter plate method. Then, the antimicrobial activity of AgNPs was evaluated by the well-diffusion method, growth kinetics and MIC determination. Inhibition of biofilm formation and the ability to disperse biofilms in exposure to AgNPs were evaluated. The effect of AgNPs on the expression of virulence and biofilm-related genes (bap, OmpA, abaI, csuA/B, A1S_2091, A1S_1510, A1S_0690, A1S_0114) were estimated using QRT-PCR. In vitro infection model for analyzing the antibacterial activity of AgNPs was done using a co-culture infection model of A. baumannii with human fibroblast skin cell line HFF-1 or Vero cell lines. A. baumannii had high level of resistance to antibiotics. Most of the isolates harbored the fimH, afa/draBC, cnf1, csgA and cnf2, and the majority of A. baumannii produced strong biofilms. AgNPs inhibited the growth of A. baumannii efficiently with MIC ranging from 4 to 25 µg/ml. A. baumannii showed a reduced growth rate in the presence of AgNPs. The inhibitory activity and the anti-biofilm activity of AgNPs were more pronounced against the weak biofilm producers. Moreover, AgNPs decreased the expression of kpsMII , afa/draBC,bap, OmpA, and csuA/B genes. The in vitro infection model revealed a significant antibacterial activity of AgNPs against extracellular and intracellular A. baumannii. AgNPs highly interrupted bacterial multiplication and biofilm formation. AgNPs downregulated the transcription level of important virulence and biofilm-related genes. Our findings provide an additional step towards understanding the mechanisms by which sliver nanoparticles interfere with the microbial spread and persistence.

Download Full-text

Lon Protease Has Multifaceted Biological Functions inAcinetobacter baumannii

Journal of Bacteriology ◽

10.1128/jb.00536-18 ◽

2018 ◽

Vol 201 (2) ◽

Cited By ~ 5

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.

Download Full-text

Growth Retardation, Reduced Invasiveness, and Impaired Colistin-Mediated Cell Death Associated with Colistin Resistance Development in Acinetobacter baumannii

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01439-13 ◽

2013 ◽

Vol 58 (2) ◽

pp. 828-832 ◽

Cited By ~ 54

Author(s):

Spyros Pournaras ◽

Aggeliki Poulou ◽

Konstantina Dafopoulou ◽

Yassine Nait Chabane ◽

Ioulia Kristo ◽

...

Keyword(s):

Cell Death ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Bloodstream Infections ◽

Single Amino Acid ◽

Colistin Resistance ◽

Resistance Development ◽

Content Type ◽

Alkyl Hydroperoxide ◽

Severe Soft Tissue

ABSTRACTTwo colistin-susceptible/colistin-resistant (Cols/Colr) pairs ofAcinetobacter baumanniistrains assigned to international clone 2, which is prevalent worldwide, were sequentially recovered from two patients after prolonged colistin administration. Compared with the respective Colsisolates (Ab248 and Ab299, both having a colistin MIC of 0.5 μg/ml), both Colrisolates (Ab249 and Ab347, with colistin MICs of 128 and 32 μg/ml, respectively) significantly overexpressedpmrCABgenes, had single-amino-acid shifts in the PmrB protein, and exhibited significantly slower growth. The Colrisolate Ab347, tested by proteomic analysis in comparison with its Colscounterpart Ab299, underexpressed the proteins CsuA/B and C from thecsuoperon (which is necessary for biofilm formation). This isolate also underexpressed aconitase B and different enzymes involved in the oxidative stress response (KatE catalase, superoxide dismutase, and alkyl hydroperoxide reductase), suggesting a reduced response to reactive oxygen species (ROS) and, consequently, impaired colistin-mediated cell death through hydroxyl radical production. Colsisolates that were indistinguishable by macrorestriction analysis from Ab299 caused six sequential bloodstream infections, and isolates indistinguishable from Ab248 caused severe soft tissue infection, while Colrisolates indistinguishable from Ab347 and Ab249 were mainly colonizers. In particular, a Colsisolate identical to Ab299 was still invading the bloodstream 90 days after the colonization of this patient by Colrisolates. These observations indicate considerably lower invasiveness ofA. baumanniiclinical isolates following the development of colistin resistance.

Download Full-text

Antimicrobial and anti-biofilm potencies of dermcidin-derived peptide DCD-1L against Acinetobacter baumannii: an in vivo wound healing model

BMC Microbiology ◽

10.1186/s12866-022-02439-8 ◽

2022 ◽

Vol 22 (1) ◽

Author(s):

Zahra Farshadzadeh ◽

Maryam Pourhajibagher ◽

Behrouz Taheri ◽

Alireza Ekrami ◽

Mohammad Hossein Modarressi ◽

...

Keyword(s):

Wound Healing ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Histopathological Examination ◽

Inhibitory Effect ◽

Bacterial Attachment ◽

Burn Wound ◽

Conventional Antibiotics

Abstract Background The global emergence of Acinetobacter baumannii resistance to most conventional antibiotics presents a major therapeutic challenge and necessitates the discovery of new antibacterial agents. The purpose of this study was to investigate in vitro and in vivo anti-biofilm potency of dermcidin-1L (DCD-1L) against extensively drug-resistant (XDR)-, pandrug-resistant (PDR)-, and ATCC19606-A. baumannii. Methods After determination of minimum inhibitory concentration (MIC) of DCD-1L, in vitro anti-adhesive and anti-biofilm activities of DCD-1L were evaluated. Cytotoxicity, hemolytic activity, and the effect of DCD-1L treatment on the expression of various biofilm-associated genes were determined. The inhibitory effect of DCD-1L on biofilm formation in the model of catheter-associated infection, as well as, histopathological examination of the burn wound sites of mice treated with DCD-1L were assessed. Results The bacterial adhesion and biofilm formation in all A. baumannii isolates were inhibited at 2 × , 4 × , and 8 × MIC of DCD-1L, while only 8 × MIC of DCD-1L was able to destroy the pre-formed biofilm in vitro. Also, reduce the expression of genes involved in biofilm formation was observed following DCD-1L treatment. DCD-1L without cytotoxic and hemolytic activities significantly reduced the biofilm formation in the model of catheter-associated infection. In vivo results showed that the count of A. baumannii in infected wounds was significantly decreased and the promotion in wound healing by the acceleration of skin re-epithelialization in mice was observed following treatment with 8 × MIC of DCD-1L. Conclusions Results of this study demonstrated that DCD-1L can inhibit bacterial attachment and biofilm formation and prevent the onset of infection. Taking these properties together, DCD-1L appears as a promising candidate for antimicrobial and anti-biofilm drug development.

Download Full-text