scholarly journals Unravelling mechanisms of meropenem induced persistence facilitates identification of GRAS compounds with anti-persister activity against Acinetobacter baumannii

2020 ◽  
Author(s):  
Timsy Bhando ◽  
Ananth Casius ◽  
Siva R. Uppalapati ◽  
Ranjana Pathania
Keyword(s):  
Acinetobacter Baumannii ◽  
Bacterial Infections ◽  
Drug Tolerance ◽  
World Health Organisation ◽  
Screening Strategy ◽  
World Health ◽  
Bacterial Cells ◽  
Nosocomial Pathogen ◽  
Compound Libraries ◽  
Mechanisms Of Persistence

ABSTRACTAcinetobacter baumannii is recognized as one of the “critical” pathogens by the World Health Organisation (WHO) due to its unprecedented ability to acquire resistance genes and undergo genetic modifications. Carbapenem classes of antibiotics are considered as the “drugs of choice” against A. baumannii infections, although increasing incidence of carbapenem resistant isolates have greatly limited their efficacy in clinical settings. Nonetheless, the phenomenon of multi-drug tolerance or persistence exhibited by A. baumannii has further led to therapeutic failure of carbapenems against chronic and recurring infections. Exploring the underlying mechanisms of persistence hosted by the nosocomial pathogen, A. baumannii can facilitate the development of effective anti-persister strategies against them. Accordingly, this study investigates the characteristics and mechanisms responsible for meropenem induced persistence in A. baumannii. Furthermore, it describes the adaptation of a screening strategy for identification of potent anti-persister compounds that cumulatively act by targeting the A. baumannii membrane, inhibiting antibiotic efflux and inducing oxidative stress mediated killing. The screen identified the phytochemical compound, thymol to display excellent activity against persisters of mechanically distinct antibiotics. While meropenem exposed A. baumannii persisters exhibited multi-drug tolerance and indicated the ability to enter a Viable But Non Culturable (VBNC) state, thymol efficiently eradicated all persister cells, irrespective of their culturability. Thymol exhibited no propensity for resistance generation and also inhibited persisters of other Gram-negative pathogens, Pseudomonas aeruginosa and Klebsiella pneumoniae. Collectively, our results establish thymol to have immense potential to act either alone or as an adjunct in combination therapies against persistent infections.IMPORTANCEApart from the global catastrophe of antibiotic resistance, the phenomenon of “antibiotic tolerance” exhibited by a subpopulation of bacterial cells known as “persisters” ensue a major clinical threat. Eradication of the persister populations holds extreme importance for an improved long-term recovery from chronic and recurring bacterial infections. This study addresses the problem of antibiotic persistence prevailing in clinics and investigates its associated mechanisms in the nosocomial pathogen, Acinetobacter baumannii in reference to the antibiotic meropenem. It further describes the use of a mechanism-based screening approach for the identification of potent multi-targeting anti-persister compounds, thereby leading to the identification of GRAS (Generally Regarded As Safe) molecules exhibiting promising activity against A. baumannii persisters. This strategy can further be utilized for repurposing of FDA approved drugs or other available compound libraries, in order to identify novel anti-persister compounds.

scholarly journals The antimicrobial activity of silver acetate against Acinetobacter baumannii in a Galleria mellonella infection model

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11196
Author(s):  
Eden Mannix-Fisher ◽  
Samantha McLean
Keyword(s):  
Acinetobacter Baumannii ◽  
Bacterial Infections ◽  
Galleria Mellonella ◽  
World Health Organisation ◽  
World Health ◽  
Infection Model ◽  
Silver Acetate ◽  
Selective Toxicity ◽  
Carbapenem Resistant

Background The increasing prevalence of bacterial infections that are resistant to antibiotic treatment has caused the scientific and medical communities to look for alternate remedies aimed at prevention and treatment. In addition to researching novel antimicrobials, there has also been much interest in revisiting some of the earliest therapies used by man. One such antimicrobial is silver; its use stretches back to the ancient Greeks but interest in its medicinal properties has increased in recent years due to the rise in antibiotic resistance. Currently antimicrobial silver is found in everything from lunch boxes to medical device implants. Though much is claimed about the antimicrobial efficacy of silver salts the research in this area is mixed. Methods Herein we investigated the efficacy of silver acetate against a carbapenem resistant strain of Acinetobacter baumannii to determine the in vitro activity of this silver salt against a World Health Organisation designated category I critical pathogen. Furthermore, we use the Galleria mellonella larvae model to assess toxicity of the compound and its efficacy in treating infections in a live host. Results We found that silver acetate can be delivered safely to Galleria at medically relevant and antimicrobial levels without detriment to the larvae and that administration of silver acetate to an infection model significantly improved survival. This demonstrates the selective toxicity of silver acetate for bacterial pathogens but also highlights the need for administration of well-defined doses of the antimicrobial to provide an efficacious treatment.

scholarly journals K2 Capsule Depolymerase Is Highly Stable, Is Refractory to Resistance, and Protects Larvae and Mice from Acinetobacter baumannii Sepsis

2019 ◽  
Vol 85 (17) ◽  
Author(s):  
Hugo Oliveira ◽  
Ana Mendes ◽  
Alexandra G. Fraga ◽  
Alice Ferreira ◽  
Andreia I. Pimenta ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Acinetobacter Baumannii ◽  
Bacterial Infections ◽  
Multidrug Resistant ◽  
Host Immune System ◽  
Dependent Manner ◽  
Bacterial Cells ◽  
Capsular Type ◽  
Nosocomial Pathogen ◽  
Content Type

ABSTRACT Acinetobacter baumannii is emerging as a major nosocomial pathogen in intensive care units. The bacterial capsules are considered major virulence factors, and the particular A. baumannii capsular type K2 has been associated with high antibiotic resistance. In this study, we identified a K2 capsule-specific depolymerase in a bacteriophage tail spike C terminus, a fragment that was heterologously expressed, and its antivirulence properties were assessed by in vivo experiments. The K2 depolymerase is active under a broad range of environmental conditions and is highly thermostable, with a melting point (Tm) at 67°C. In the caterpillar larva model, the K2 depolymerase protects larvae from bacterial infections, using either pretreatments or with single-enzyme injection after bacterial challenge, in a dose-dependent manner. In a mouse sepsis model, a single K2 depolymerase intraperitoneal injection of 50 μg is able to protect 60% of mice from an otherwise deadly infection, with a significant reduction in the proinflammatory cytokine profile. We showed that the enzyme makes bacterial cells fully susceptible to the host complement system killing effect. Moreover, the K2 depolymerase is highly refractory to resistance development, which makes these bacteriophage-derived capsular depolymerases useful antivirulence agents against multidrug-resistant A. baumannii infections. IMPORTANCE Acinetobacter baumannii is an important nosocomial pathogen resistant to many, and sometimes all, antibiotics. The A. baumannii K2 capsular type has been associated with elevated antibiotic resistance. The capsular depolymerase characterized here fits the new trend of alternative antibacterial agents needed against multidrug-resistant pathogens. They are highly specific, stable, and refractory to resistance, as they do not kill bacteria per se; instead, they remove bacterial surface polysaccharides, which diminish the bacterial virulence and expose them to the host immune system.

scholarly journals Phage φAB6-Borne Depolymerase Combats Acinetobacter baumannii Biofilm Formation and Infection

Antibiotics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 279
Author(s):  
Md. Shahed-Al-Mahmud ◽  
Rakesh Roy ◽  
Febri Gunawan Sugiokto ◽  
Md. Nazmul Islam ◽  
Ming-Der Lin ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Bacterial Infections ◽  
Capsular Polysaccharide ◽  
Foley Catheter ◽  
Inhibition Zone ◽  
Control Group ◽  
Bacterial Cells ◽  
Bacterial Lawn

Biofilm formation is one of the main causes of increased antibiotic resistance in Acinetobacter baumannii infections. Bacteriophages and their derivatives, such as tail proteins with depolymerase activity, have shown considerable potential as antibacterial or antivirulence agents against bacterial infections. Here, we gained insights into the activity of a capsular polysaccharide (CPS) depolymerase, derived from the tailspike protein (TSP) of φAB6 phage, to degrade A. baumannii biofilm in vitro. Recombinant TSP showed enzymatic activity and was able to significantly inhibit biofilm formation and degrade formed biofilms; as low as 0.78 ng, the inhibition zone can still be formed on the bacterial lawn. Additionally, TSP inhibited the colonization of A. baumannii on the surface of Foley catheter sections, indicating that it can be used to prevent the adhesion of A. baumannii to medical device surfaces. Transmission and scanning electron microscopy demonstrated membrane leakage of bacterial cells treated with TSP, resulting in cell death. The therapeutic effect of TSP in zebrafish was also evaluated and the results showed that the survival rate was significantly improved (80%) compared with that of the untreated control group (10%). Altogether, we show that TSP derived from φAB6 is expected to become a new antibiotic against multi-drug resistant A. baumannii and a biocontrol agent that prevents the formation of biofilms on medical devices.

Controversies in Sepsis Management—What is the Way Forward?

2020 ◽  
Vol 49 (9) ◽  
pp. 661-668
Author(s):  
Alvin HY Lo ◽  
Adrian CL Kee ◽  
Andrew Li ◽  
Francesca Rubulotta
Keyword(s):  
Bacterial Infections ◽  
Clinical Evidence ◽  
World Health Organisation ◽  
World Health ◽  
Surviving Sepsis Campaign ◽  
Sepsis Management ◽  
Sepsis Bundles ◽  
The Past ◽  
Key Words Critical Care ◽  
Life Threatening

Sepsis is life-threatening and might potentially progress from dysregulation to severe organ dysfunction. It is recognised by the World Health Organisation as a global health priority. The mortality rate for sepsis has decreased in many countries, and this is credited to the earlier recognition and treatment of this complex syndrome. In 2002, the Surviving Sepsis Campaign was launched, and there have been several revisions to the sepsis recommendations therefrom. The latest sepsis guidelines focus on viral as well as bacterial infections, and advise that initiating resuscitation and management should take place within one hour from when sepsis is initially suspected. Numerous studies and guidelines pertaining to sepsis management have been published over the past 2 decades. The use of novel therapies and alternative adjunctive therapies has tremendous potential in sepsis management. Debates amongst intensivists exist with the creation of updated sepsis guidelines and advances in treatment. The present review article provides both a summary and recommendations based on the latest clinical evidence and controversies around sepsis management. Key words: Critical Care Medicine, Intensive Care Medicine, Respiratory Medicine, Sepsis, Sepsis Bundles, Sepsis Management

scholarly journals Specific Interaction of Novel Friunavirus Phages Encoding Tailspike Depolymerases with Corresponding Acinetobacter baumannii Capsular Types

2020 ◽  
Author(s):  
A. V. Popova ◽  
M. M. Shneider ◽  
N. P. Arbatsky ◽  
A. A. Kasimova ◽  
S. N. Senchenkova ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Specific Interaction ◽  
World Health ◽  
High Nucleotide Sequence Identity ◽  
Resonance Spectroscopy ◽  
Ionization Mass ◽  
Capsular Polysaccharides ◽  
Aerobic Bacterium ◽  
Bacterial Cells ◽  
Nosocomial Pathogens

Acinetobacter baumannii is one of the most clinically important nosocomial pathogens. The World Health Organisation refers it to its «critical priority» category to develop new strategies for effective therapy. This microorganism is capable of producing structurally diverse capsular polysaccharides (CPSs), which serve as primary receptors for A. baumannii bacteriophages carrying polysaccharide-depolymerasing enzymes. In this study, eight novel bacterial viruses that specifically infect A. baumannii strains belonging to K2/K93, K32, K37, K44, K48, K87, K89 and K116 capsular types were isolated and characterized. The overall genomic architecture demonstrated that these viruses are representatives of the Friunavirus genus of the family Autographiviridae. The linear double-stranded DNA phage genomes of 41,105–42,402 bp share high nucleotide sequence identity, except for genes encoding structural depolymerases or tailspikes which determine the host specificity. Deletion mutants lacking N-terminal domains of tailspike proteins were cloned, expressed and purified. The structurally defined CPSs of the phage bacterial hosts were cleaved with the specific recombinant depolymerases, and the resultant oligosaccharides that corresponded to monomers or/and dimers of the CPS repeats (K-units) were isolated. Structures of the derived oligosaccharides were established by nuclear magnetic resonance spectroscopy and high-resolution electrospray ionization mass spectrometry. The data obtained showed that all depolymerases studied were glycosidases that cleave specifically the A. baumannii CPSs by the hydrolytic mechanism, in most cases, by the linkage between the K-units. IMPORTANCE Acinetobacter baumannii, a nonfermentative, Gram-negative, aerobic bacterium, is one of the most significant nosocomial pathogens. The pathogenicity of A. baumannii is based on the cooperative action of many factors, one of them being the production of capsular polysaccharides (CPSs) that surround bacterial cells with a thick protective layer. Polymorphism of the chromosomal capsule loci is responsible for the observed high structural diversity of the CPSs. In this study, we describe eight novel lytic phages which have different tailspike depolymerases (TSDs) determining the interaction of the viruses with corresponding A. baumannii capsular types (K-types). Moreover, we elucidate the structures of oligosaccharide products obtained by cleavage of the CPSs by the recombinant depolymerases. We believe that as the TSDs determine phage specificity, the diversity of their structures should be taken into consideration as selection criteria for inclusion of certain phage candidate to the cocktail designed to control A. baumannii with different K-types.

scholarly journals Controversies in Sepsis Management—What is the Way Forward?

2020 ◽  
pp. 661-668
Author(s):  
Alvin HY Lo ◽  
Adrian CL Kee ◽  
Andrew Li ◽  
Francesca Rubulotta
Keyword(s):  
Bacterial Infections ◽  
Clinical Evidence ◽  
World Health Organisation ◽  
World Health ◽  
Surviving Sepsis Campaign ◽  
Sepsis Management ◽  
Sepsis Bundles ◽  
The Past ◽  
Key Words Critical Care ◽  
Life Threatening

Sepsis is life-threatening and might potentially progress from dysregulation to severe organ dysfunction. It is recognised by the World Health Organisation as a global health priority. The mortality rate for sepsis has decreased in many countries, and this is credited to the earlier recognition and treatment of this complex syndrome. In 2002, the Surviving Sepsis Campaign was launched, and there have been several revisions to the sepsis recommendations therefrom. The latest sepsis guidelines focus on viral as well as bacterial infections, and advise that initiating resuscitation and management should take place within one hour from when sepsis is initially suspected. Numerous studies and guidelines pertaining to sepsis management have been published over the past 2 decades. The use of novel therapies and alternative adjunctive therapies has tremendous potential in sepsis management. Debates amongst intensivists exist with the creation of updated sepsis guidelines and advances in treatment. The present review article provides both a summary and recommendations based on the latest clinical evidence and controversies around sepsis management. Key words: Critical Care Medicine, Intensive Care Medicine, Respiratory Medicine, Sepsis, Sepsis Bundles, Sepsis Management

scholarly journals Virulence Potential and Treatment Options of Multidrug-Resistant (MDR) Acinetobacter baumannii

2021 ◽  
Vol 9 (10) ◽  
pp. 2104
Author(s):  
Sunil Kumar ◽  
Razique Anwer ◽  
Arezki Azzi
Keyword(s):  
Acinetobacter Baumannii ◽  
Virulence Factors ◽  
Bacterial Infections ◽  
Antimicrobial Agents ◽  
Treatment Options ◽  
Outer Membrane Proteins ◽  
Multidrug Resistant ◽  
High Rate ◽  
World Health ◽  
Tract Infections

Acinetobacter baumannii is an opportunistic pathogen which is undoubtedly known for a high rate of morbidity and mortality in hospital-acquired infections. A. baumannii causes life-threatening infections, including; ventilator-associated pneumonia (VAP), meningitis, bacteremia, and wound and urinary tract infections (UTI). In 2017, the World Health Organization listed A. baumannii as a priority-1 pathogen. The prevalence of A. baumannii infections and outbreaks emphasizes the direct need for the use of effective therapeutic agents for treating such infections. Available antimicrobials, such as; carbapenems, tigecycline, and colistins have insufficient effectiveness due to the appearance of multidrug-resistant strains, accentuating the need for alternative and novel therapeutic remedies. To understand and overcome this menace, the knowledge of recent discoveries on the virulence factors of A. baumannii is needed. Herein, we summarized the role of various virulence factors, including; outer membrane proteins, efflux pumps, biofilm, penicillin-binding proteins, and siderophores/iron acquisition systems. We reviewed the recent scientific literature on different A. baumannii virulence factors and the effective antimicrobial agents for the treatment and management of bacterial infections.

scholarly journals Phage-Derived Depolymerase as an Antibiotic Adjuvant Against Multidrug-Resistant Acinetobacter Baumannii

2021 ◽  
Author(s):  
Xi Chen ◽  
Miao Liu ◽  
Pengfei Zhang ◽  
Miao Xu ◽  
Weihao Yuan ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Bacterial Infections ◽  
Galleria Mellonella ◽  
Volume Ratio ◽  
Multidrug Resistant ◽  
Resistant Bacteria ◽  
Antibiofilm Activity ◽  
Bacterial Cells ◽  
Strain Specificity ◽  
Drug Resistant Bacteria

Bacteriophage-encoded depolymerases are responsible for degrading capsular polysaccharides (CPS), lipopolysaccharides (LPS) and exopolysachcharides (EPS) of the host bacteria during phage invasion. They have been considered as promising antivirulence agents in controlling bacterial infections, including those caused by drug-resistant bacteria. This feature inspires a hope of utilizing these enzymes to disarm the polysaccharide capsid of the bacterial cells, which then strengthens the action of antibiotics. Here we have identified, cloned, and expressed a depolymerase Dpo71 from a bacteriophage specific for the gram-negative (G-ve) bacterium Acinetobacter baumannii in the heterologous host E. coli. Dpo71 sensitizes the multidrug-resistant (MDR) A. baumannii to the host immune attack, and also acts as an adjuvant to assist or boost the action of antibiotics, for example colistin. Specifically, Dpo71 at 10 µg/ml enables a complete bacterial eradication by human serum at 50% volume ratio. Dpo71 inhibits biofilm formation and disrupts the pre-formed biofilm. Combination of Dpo71 could significantly enhance the antibiofilm activity of colistin, and improve the survival rate of A. baumannii infected Galleria mellonella. Dpo71 retains the strain-specificity of the parent phage from which Dpo71 is derived: the phage-sensitive A. baumannii strains respond to Dpo71 treatment, whereas the phage-insensitive strains do not. This indicates that Dpo71 indeed is responsible for the host specificity of bacteriophages. In summary, our work demonstrates the feasibility of using recombinant depolymerases as an antibiotic adjuvants to supplement the development of new antibacterials and to battle against MDR pathogens.

scholarly journals Phage therapy of wound-associated infections

2022 ◽  
Author(s):  
Anna Zyman ◽  
Andrzej Górski ◽  
Ryszard Międzybrodzki
Keyword(s):  
Wound Healing ◽  
Bacterial Infections ◽  
Bacterial Resistance ◽  
Phage Therapy ◽  
World Health Organisation ◽  
Good Manufacturing Practice ◽  
Modern Medicine ◽  
World Health ◽  
Therapeutic Effects ◽  
The World

AbstractPhages are viruses which can specifically infect bacteria, resulting in their destruction. Bacterial infections are a common complication of wound healing, and experimental evidence from animal models demonstrates promising potential for phage-dependent eradication of wound-associated infections. The studies discussed suggest that phage therapy may be an effective treatment, with important advantages over some current antibacterial treatments. Phage cocktails, as well as co-administration of phages and antibiotics, have been reported to minimise bacterial resistance. Further, phage-antibiotic synergism has been reported in some studies. The ideal dose of phages is still subject to debate, with evidence for both high and low doses to yield therapeutic effects. Novel delivery methods, such as hydrogels, are being explored for their advantages in topical wound healing. There are more and more Good Manufacturing Practice facilities dedicated to manufacturing phage products and phage therapy units across the world, showing the changing perception of phages which is occurring. However, further research is needed to secure the place of phages in modern medicine, with some scientists calling upon the World Health Organisation to help promote phage therapy.

A Collaborative Study to Establish the Second International Standard for Streptokinase

1990 ◽  
Vol 64 (02) ◽  
pp. 267-269 ◽  
Author(s):  
A B Heath ◽  
P J Gaffney
Keyword(s):  
High Purity ◽  
Collaborative Study ◽  
World Health Organisation ◽  
World Health ◽  
Clot Lysis ◽  
Current Standard ◽  
International Standard ◽  
Accelerated Degradation ◽  
The World ◽  
International Collaborative Study

SummaryAn International Standard for Streptokinase - Streptodomase (62/7) has been used to calibrate high purity clinical batches of SK since 1965. An international collaborative study, involving six laboratories, was undertaken to replace this standard with a high purity standard for SK. Two candidate preparations (88/826 and 88/824) were compared by a clot lysis assay with the current standard (62/7). Potencies of 671 i.u. and 461 i.u. were established for preparations A (88/826) and B (88/824), respectively.Either preparation appeared suitable to serve as a standard for SK. However, each ampoule of preparation A (88/826) contains a more appropriate amount of SK activity for potency testing, and is therefore preferred. Accelerated degradation tests indicate that preparation A (88/826) is very stable.The high purity streptokinase preparation, coded 88/826, has been established by the World Health Organisation as the 2nd International Standard for Streptokinase, with an assigned potency of 700 i.u. per ampoule.

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