planktonic bacteria
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2021 ◽  
Author(s):  
Kexin Liu ◽  
Shuang Tan ◽  
Weiyuan Ye ◽  
Limin Hou ◽  
Binghu Fang

Abstract Background: Klebsiella pneumoniae is widely distributed in water and plays a major role in both human and animal infections. Many K. pneumoniae strains form biofilms on various surfaces, enhancing their pathogenicity and resistance to antibiotics. New ways of inhibiting biofilm formation are needed. Iron is vital to the growth of microorganisms and the formation of biofilms due to its participation in various metabolic processes and its roles as an enzyme and protein cofactor. It is also present in groundwater. The aim of this study was to examine the effects of iron on K. pneumoniae biofilm formation and any associated metabolic changes.Results: Biofilm formation was enhanced to the greatest extent by the presence of 0.16 mM FeCl2, producing a denser structure under electron microscopy. The number of biofilm-forming and planktonic bacteria did not change, but protein and polysaccharide concentrations in the bacterial extracellular polymeric substances (EPS) were significantly increased by iron supplementation. To clarify this mechanism, intracellular metabolomic analysis was carried out, showing that the differential, down-regulated metabolites included succinic acid. Addition of succinic acid counteracted the biofilm-forming effect of iron, with no bactericidal side effects.Conclusion: This study demonstrates the importance of succinic acid and iron in Klebsiella pneumoniae biofilms, and provides insight into the formation of K. pneumoniae biofilms and direction for the development of new antibacterial agents.


2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Tova Wasserman-Bruck ◽  
Boger-May Boger-May ◽  
Derek Rubadeux ◽  
Katelyn Ruley-Haase ◽  
David L. Boone

Background and Objectives: Gastrokine-1 (Gkn1) is a protein produced solely in the stomach and secreted into the lumen of the gut. Gkn1 has a BRICHOS domain which is anti-amyloidogenic. While the exact function of Gkn1 is not yet completely understood, Gkn1 has a protective role against IBD in induced models of colitis. Since microbes secrete amyloid to facilitate biofilm formation, we hypothesized that Gkn1 may play a protective role against IBD by inhibiting amyloid formation by biofilm forming microbes in the gut. We examined the effects of varying concentrations of Gkn1 on known biofilm forming microbes to determine if there was a dose responsive inhibitory effect of Gkn1 on biofilm formation.  Methods: Bacterial colonies from Adherent Invasive E. coli and E. faecalis were cultured and incubated at 37 degrees Celsius overnight. The samples were then diluted 1:100 and inoculated into 96-well costar microassay plates with concentrations of Gkn1 ranging from 0.00075 to 0.025 mg/ml. At 8, 24, or 48 hour time points the plates were then washed to remove planktonic bacteria, and adherent biofilms were stained with crystal violet. Biofilm formation was analyzed by comparing the OD590/OD600 against a control.   Results:  Using a one-way ANOVA, we determined that there is dose response inhibition of biofilm formation with Gkn1, with the greatest inhibition of biofilm formation at concentrations of Gkn1 between 0.00312 and 0.0125 mg/ml.  Conclusions:  A dose response inhibition of Gkn1 on biofilm formation was identified. Since Gkn1 has demonstrated a protective role against IBD in induced colitis, targeting intestinal luminal amyloids may be a potential therapeutic approach for IBD.


Author(s):  
Ibrahim Alkhaibari ◽  
Hansa Raj KC ◽  
Duminduni H Angappulige ◽  
David Gilmore ◽  
Mohammad A Alam

Background: Methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci and Acinetobacter baumannii cause serious antibiotic-resistant infections. Finding new antibiotics to treat these infections is imperative for combating this worldwide menace. Methods & Results: In this study, the authors designed and synthesized potent antimicrobial agents using 4-trifluoromethylphenyl-substituted pyrazole derivatives. In addition to their potency against planktonic bacteria, potent compounds effectively eradicated S. aureus and Enterococcus faecalis biofilms. Human cells tolerated these compounds with good selectivity factors. Furthermore, the authors provide evidence for the mode of action of compounds based on time-kill kinetics, flow cytometry analysis of propidium iodide-treated bacteria and oxygen uptake studies. Conclusion: This study demonstrated 20 novel compounds with potent antibacterial activity that are tolerated by human cell lines.


Biomedicines ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1677
Author(s):  
Pei-Chun Wong ◽  
Ren-Yi Wang ◽  
Long-Sheng Lu ◽  
Wei-Ru Wang ◽  
Jason Shian-Ching Jang ◽  
...  

Bacterial infection remains a great risk in medical implantation surgery. In this paper, we found that degradable metals may be a feasible alternative option of antibacterial implantation materials. It is known that the spalling mechanism of magnesium (Mg) during degradation leads to Mg ions-induced alkaline environment, which is harmful to planktonic bacteria. In this study, we showed that alkaline pH environment is almost harmless to those adhesive bacteria protected in well-formed biofilms. Moreover, experimental results demonstrated that the biofilm formed in the place where Mg spalls are destroyed, releasing the covered bacteria to be planktonic in the alkaline environment. As a result, the colonization of biofilms continues to shrink during the degradation of Mg. It implies that if degradable metal is employed as implantation material, even if bacterial infection occurs, it may be possibly cured without second surgery.


Pharmaceutics ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1840
Author(s):  
Miriam E. van Gent ◽  
Muhanad Ali ◽  
Peter H. Nibbering ◽  
Sylvia N. Kłodzińska

Bacterial infections constitute a threat to public health as antibiotics are becoming less effective due to the emergence of antimicrobial resistant strains and biofilm and persister formation. Antimicrobial peptides (AMPs) are considered excellent alternatives to antibiotics; however, they suffer from limitations related to their peptidic nature and possible toxicity. The present review critically evaluates the chemical characteristics and antibacterial effects of lipid and polymeric AMP delivery systems and coatings that offer the promise of enhancing the efficacy of AMPs, reducing their limitations and prolonging their half-life. Unfortunately, the antibacterial activities of these systems and coatings have mainly been evaluated in vitro against planktonic bacteria in less biologically relevant conditions, with only some studies focusing on the antibiofilm activities of the formulated AMPs and on the antibacterial effects in animal models. Further improvements of lipid and polymeric AMP delivery systems and coatings may involve the functionalization of these systems to better target the infections and an analysis of the antibacterial activities in biologically relevant environments. Based on the available data we proposed which polymeric AMP delivery system or coatings could be profitable for the treatment of the different hard-to-treat infections, such as bloodstream infections and catheter- or implant-related infections.


PLoS Biology ◽  
2021 ◽  
Vol 19 (10) ◽  
pp. e3001406
Author(s):  
Erin L. Attrill ◽  
Rory Claydon ◽  
Urszula Łapińska ◽  
Mario Recker ◽  
Sean Meaden ◽  
...  

Bacteriophages represent an avenue to overcome the current antibiotic resistance crisis, but evolution of genetic resistance to phages remains a concern. In vitro, bacteria evolve genetic resistance, preventing phage adsorption or degrading phage DNA. In natural environments, evolved resistance is lower possibly because the spatial heterogeneity within biofilms, microcolonies, or wall populations favours phenotypic survival to lytic phages. However, it is also possible that the persistence of genetically sensitive bacteria is due to less efficient phage amplification in natural environments, the existence of refuges where bacteria can hide, and a reduced spread of resistant genotypes. Here, we monitor the interactions between individual planktonic bacteria in isolation in ephemeral refuges and bacteriophage by tracking the survival of individual cells. We find that in these transient spatial refuges, phenotypic resistance due to reduced expression of the phage receptor is a key determinant of bacterial survival. This survival strategy is in contrast with the emergence of genetic resistance in the absence of ephemeral refuges in well-mixed environments. Predictions generated via a mathematical modelling framework to track bacterial response to phages reveal that the presence of spatial refuges leads to fundamentally different population dynamics that should be considered in order to predict and manipulate the evolutionary and ecological dynamics of bacteria–phage interactions in naturally structured environments.


Author(s):  
Mostafa Dadashi Firouzjaei ◽  
Mehdi Pejman ◽  
Mohammad Sharifian Gh ◽  
Sadegh Aghapour Aktij ◽  
Ehsan Zolghadr ◽  
...  

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