scholarly journals Bacterial behavior in human blood reveals complement evaders with some persister-like features

2020 ◽  
Vol 16 (12) ◽  
pp. e1008893
Author(s):  
Stéphane Pont ◽  
Nathan Fraikin ◽  
Yvan Caspar ◽  
Laurence Van Melderen ◽  
Ina Attrée ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Human Blood ◽  
Immune Cells ◽  
Bacterial Load ◽  
Survival Rates ◽  
Bloodstream Infections ◽  
Health Concern ◽  
Bacterial Cells ◽  
Human Pathogens ◽  
Different Strains

Bacterial bloodstream infections (BSI) are a major health concern and can cause up to 40% mortality. Pseudomonas aeruginosa BSI is often of nosocomial origin and is associated with a particularly poor prognosis. The mechanism of bacterial persistence in blood is still largely unknown. Here, we analyzed the behavior of a cohort of clinical and laboratory Pseudomonas aeruginosa strains in human blood. In this specific environment, complement was the main defensive mechanism, acting either by direct bacterial lysis or by opsonophagocytosis, which required recognition by immune cells. We found highly variable survival rates for different strains in blood, whatever their origin, serotype, or the nature of their secreted toxins (ExoS, ExoU or ExlA) and despite their detection by immune cells. We identified and characterized a complement-tolerant subpopulation of bacterial cells that we named “evaders”. Evaders shared some features with bacterial persisters, which tolerate antibiotic treatment. Notably, in bi-phasic killing curves, the evaders represented 0.1–0.001% of the initial bacterial load and displayed transient tolerance. However, the evaders are not dormant and require active metabolism to persist in blood. We detected the evaders for five other major human pathogens: Acinetobacter baumannii, Burkholderia multivorans, enteroaggregative Escherichia coli, Klebsiella pneumoniae, and Yersinia enterocolitica. Thus, the evaders could allow the pathogen to persist within the bloodstream, and may be the cause of fatal bacteremia or dissemination, in particular in the absence of effective antibiotic treatments.

scholarly journals Bacterial behavior in human blood reveals complement evaders with persister-like features

2020 ◽  
Author(s):  
Stéphane Pont ◽  
Nathan Fraikin ◽  
Yvan Caspar ◽  
Laurence Van Melderen ◽  
Ina Attrée ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Human Blood ◽  
Immune Cells ◽  
Bacterial Load ◽  
Phenotypic Heterogeneity ◽  
Health Concern ◽  
Resistant Bacteria ◽  
Bacterial Cells ◽  
Human Pathogens ◽  
Bacterial Strains

AbstractsBacterial bloodstream infections (BSI) are a major health concern and can cause up to 40% mortality. Pseudomonas aeruginosa BSI is often of nosocomial origin and is associated with a particularly poor prognosis. The mechanism of bacterial persistence in blood is still largely unknown. Here, we analyzed the behavior of a cohort of clinical and laboratory Pseudomonas aeruginosa strains in human blood. In this specific environment, complement was the main defensive mechanism, acting either by direct bacterial lysis or by opsonophagocytosis, which required recognition by immune cells. We found highly variable survival rates for different strains in blood, whatever their origin, serotype, or the nature of their secreted toxins and despite their detection by immune cells. We identified and characterized a complement-tolerant subpopulation of bacterial cells that we named “evaders”. Evaders represented 0.1-0.001% of the initial bacterial load and displayed transient tolerance. Although evaders shared some features with bacterial persisters, which tolerate antibiotic treatment, they appear to have evolved distinct strategies to escape complement. We detected the evaders for five other major human pathogens: Acinetobacter baumannii, Burkholderia multivorans, enteroaggregative Escherichia coli, Klebsiella pneumoniae, and Yersinia enterocolitica. Thus, the evaders could allow the pathogen to persist within the bloodstream, and may be the cause of fatal bacteremia or dissemination, notably in the absence of effective antibiotic treatments.Author summary for “Complement evaders”Blood infections by antibiotic resistant bacteria, notably Pseudomonas aeruginosa, are major concerns in hospital settings. The complex interplay between P. aeruginosa and the innate immune system in the context of human blood is still poorly understood. By studying the behavior of various P. aeruginosa strains in human whole blood and plasma, we showed that bacterial strains display different rate of tolerance to the complement system. Despite the complement microbicide activity, most bacteria withstand elimination through phenotypic heterogeneity creating a tiny (<0.1%) subpopulation of transiently tolerant evaders. While genetically identical to the rest of the complement-sensitive population, evaders allow the bacteria to persist in plasma. This phenotypic heterogeneity thus prevents total elimination of the pathogen from the circulation, and represent a new strategy to disseminate within the organism.

Bioactivity of Phenolic Compounds Extracted from Strawberry against Formation of Pseudomonas aeruginosa Biofilm

2019 ◽  
Vol 10 (01) ◽  
Author(s):  
Baydaa Hussein ◽  
Zainab A. Aldhaher ◽  
Shahrazad Najem Abdu-Allah ◽  
Adel Hamdan
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Phenolic Compounds ◽  
Biofilm Formation ◽  
Opportunistic Infections ◽  
Formation Rate ◽  
Hydrocarbon Chain ◽  
Health Concern ◽  
Gas Chromatography Mass Spectrometry ◽  
Phenolic Contents

Background: Biofilm is a bacterial way of life prevalent in the world of microbes; in addition to that it is a source of alarm in the field of health concern. Pseudomonas aeruginosa is a pathogenic bacterium responsible for all opportunistic infections such as chronic and severe. Aim of this study: This paper aims to provide an overview of the promotion of isolates to produce a biofilm in vitro under special circumstances, to expose certain antibiotics to produce phenotypic evaluation of biofilm bacteria. Methods and Materials: Three diverse ways were used to inhibited biofilm formation of P.aeruginosa by effect of phenolic compounds extracts from strawberries. Isolates produced biofilm on agar MacConkey under certain circumstances. Results: The results showed that all isolates were resistant to antibiotics except sensitive to azithromycin (AZM, 15μg), and in this study was conducted on three ways to detect the biofilm produced, has been detected by the biofilm like Tissue culture plate (TCP), Tube method (TM), Congo Red Agar (CRA). These methods gave a clear result of these isolates under study. Active compounds were analyzed in both extracts by Gas Chromatography-mass Spectrometry which indicate High molecular weight compound with a long hydrocarbon chain. Conclusion: Phenolic compounds could behave as bioactive material and can be useful to be used in pharmaceutical synthesis. Phenolic contents which found in leaves and fruits extracts of strawberries shows antibacterial activity against all strains tested by the ability to reduce the production of biofilm formation rate.

scholarly journals CO0005 C-C CHEMOKINE RECEPTOR TYPE 5 AND ITS LIGANDS CCL4, 8 AND 11 CAN LINK COVID-19, RHEUMATOID ARTHRITIS AND HYDROXYCHLOROQUINE

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 213.3-214
Author(s):  
M. Y. Hachim ◽  
S. Hannawi
Keyword(s):  
Rheumatoid Arthritis ◽  
Mechanism Of Action ◽  
Immune Cells ◽  
Health Concern ◽  
Healthy Controls ◽  
Global Public Health ◽  
Ccr5 Expression ◽  
Disease Modifying Drugs ◽  
Link Type ◽  
Disease Modifying

Background:Coronavirus disease (COVID-19) caused by SARS-COV2 represents an unprecedented global public health concern with a particular burden on patients with chronic diseases and those on immune-modulating drugs. It is especially worrisome to patients with rheumatoid arthritis (RA) who are on immune suppression regimens[1]. On the other side, many reports showed and recommended the use of some Disease-Modifying Drugs commonly used to treat rheumatic diseases like hydroxychloroquine. However, the general understanding of COVID-19 characteristics in this population and the mechanism of action of these drugs in COVID-19 is still unknown[2].Objectives:Explore publicly available transcriptomic dataset of patients infected with SARS-COV2 compared to uninfected to identify differentially expressed genes (DEGs) related to the immune system that might be pathogenic in RA synovium. Then explore the effect of Disease-Modifying Drugs on their local expression that might give hints about their possible mechanism of action.Methods:RNAseq dataset (GSE147507) were retrieved using the Gene Expression Omnibus (GEO) and used to identify DEGs between infected and uninfected lung samples using BioJupies tools [3]. The DEGs were explored for common pathways using Metascape online tool (http://metascape.org) [10], as shown in figure (1). The chemokines genes were filtered out, and their common receptor (CR) was identified. The immune cells that express a higher level of the identified receptor were explored using DICE project tool (https://dice-database.org/). The expression of CR was searched in a microarray dataset (GSE77298) of synovial biopsies of RA and healthy controls. RNAseq dataset (GSE97165) of synovial biopsies taken from 19 early RA patients at baseline and after six months of Triple Disease-Modifying Anti-rheumatic drugs (tDMARD; methotrexate, sulfasalazine, and hydroxychloroquine) treatment.Results:84 DEGs were identified between uninfected and COVID-19 infected lung samples. These DEGs were enriched in pathways specific to (response to the virus, response to interferon, leukocyte activation, and chemotaxis). Interestingly, SARS-COV-2 infected lungs express more CCL4, CCL8, and CCL11; the three ligands shared the same receptor, which is CCR5. Top immune cells that express CCR5 were CD4 T memory T reg cells, Th17, Th1, and monocytes. CCR5 was significantly upregulated in RA compared to healthy controls synovium (p=0.04) and was dramatically downregulated after six months of tDMARD treatment (p=0.004), as shown in figure (2).Conclusion:Using publicly available transcriptomic datasets properly highlighted the possible beneficiary effect of DMARDs in patients with COVID-19, which can block CCR5 rich immune cells recruitment.References:[1]Favalli, E.G., et al.,COVID-19 infection and rheumatoid arthritis: Faraway, so close!Autoimmun Rev, 2020. 19(5): p. 102523.[2]Gianfrancesco, M.A., et al.,Rheumatic disease and COVID-19: initial data from the COVID-19 Global Rheumatology Alliance provider registries.The Lancet Rheumatology, 2020. 2(5): p. e250-e253.[3]Torre, D., A. Lachmann, and A. Ma’ayan,BioJupies: Automated Generation of Interactive Notebooks for RNA-Seq Data Analysis in the Cloud.Cell Systems, 2018. 7(5): p. 556-561.e3.Figure 1.Flowchart of transcriptomic analysisFigure 2.(A) Top immune cells that express CCR5 (B) CCR5 expression in synovial biopsies of RA and control (C) CCR5 expression at baseline and after 6 months of tDMARD treatment.Disclosure of Interests:None declared

scholarly journals Microbial Associations with Pancreatic Cancer: A New Frontier in Biomarkers

Cancers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 3784
Author(s):  
Mark Stasiewicz ◽  
Marek Kwaśniewski ◽  
Tomasz M. Karpiński
Keyword(s):  
Pancreatic Cancer ◽  
Helicobacter Pylori ◽  
Survival Rates ◽  
Health Concern ◽  
Current State ◽  
Increased Risk ◽  
Microbial Biomarkers ◽  
New Frontier ◽  
Microbial Associations ◽  
Fungal Genus

Pancreatic cancer (PC) remains a global health concern with high mortality and is expected to increase as a proportion of overall cancer cases in the coming years. Most patients are diagnosed at a late stage of disease progression, which contributes to the extremely low 5-year survival rates. Presently, screening for PC remains costly and time consuming, precluding the use of widespread testing. Biomarkers have been explored as an option by which to ameliorate this situation. The authors conducted a search of available literature on PubMed to present the current state of understanding as it pertains to the use of microbial biomarkers and their associations with PC. Carriage of certain bacteria in the oral cavity (e.g., Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Streptococcus sp.), gut (e.g., Helicobacter pylori, Synergistetes, Proteobacteria), and pancreas (e.g., Fusobacterium sp., Enterobacteriaceae, Pseudomonadaceae) has been associated with an increased risk of developing PC. Additionally, the fungal genus Malassezia has likewise been associated with PC development. This review further outlines potential oncogenic mechanisms involved in the microbial-associated development of PC.

scholarly journals A novel application of bubble-eye strain of Carassius auratus for ex vivo fish immunological studies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hiroto Nakajima ◽  
Atsushi Miyashita ◽  
Hiroshi Hamamoto ◽  
Kazuhisa Sekimizu
Keyword(s):  
Inflammatory Cytokines ◽  
Immune Cells ◽  
Ex Vivo ◽  
Large Bubble ◽  
Suitable Model ◽  
Bacterial Cells ◽  
Functional Impairments ◽  
Gene Expressions ◽  
Pro Inflammatory Cytokines

AbstractIn this study, we investigated a new application of bubble-eye goldfish (commercially available strain with large bubble-shaped eye sacs) for immunological studies in fishes utilizing the technical advantage of examining immune cells in the eye sac fluid ex vivo without sacrificing animals. As known in many aquatic species, the common goldfish strain showed an increased infection sensitivity at elevated temperature, which we demonstrate may be due to an immune impairment using the bubble-eye goldfish model. Injection of heat-killed bacterial cells into the eye sac resulted in an inflammatory symptom (surface reddening) and increased gene expression of pro-inflammatory cytokines observed in vivo, and elevated rearing temperature suppressed the induction of pro-inflammatory gene expressions. We further conducted ex vivo experiments using the immune cells harvested from the eye sac and found that the induced expression of pro-inflammatory cytokines was suppressed when we increased the temperature of ex vivo culture, suggesting that the temperature response of the eye-sac immune cells is a cell autonomous function. These results indicate that the bubble-eye goldfish is a suitable model for ex vivo investigation of fish immune cells and that the temperature-induced infection susceptibility in the goldfish may be due to functional impairments of immune cells.

scholarly journals Carbon Nanotubes—Potent Carriers for Targeted Drug Delivery in Rheumatoid Arthritis

Pharmaceutics ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 453
Author(s):  
Camilla Kofoed Andersen ◽  
Sangita Khatri ◽  
Jonas Hansen ◽  
Sofie Slott ◽  
Rohith Pavan Parvathaneni ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Carbon Nanotubes ◽  
B Cells ◽  
Human Blood ◽  
Immune Cells ◽  
Bone Marrow Cells ◽  
Coupling Efficiency ◽  
Drug Carriers ◽  
Whole Body ◽  
Whole Body Imaging

Two types of single-walled carbon nanotubes (SWCNTs), HiPco- and carboxyl-SWCNT, are evaluated as drug carriers for the traditional anti-inflammatory drug methotrexate (MTX) and a small interfering RNA (siRNA) targeting NOTCH1 gene. The nanotubes are solubilized by PEGylation and covalently loaded with MTX. The coupling efficiency (CE%) of MTX is 77–79% for HiPco-SWCNT and 71–83% for carboxyl-SWCNT. siRNA is noncovalently attached to the nanotubes with efficiency of 90–97% for HiPco-SWCNT and 87–98% for carboxyl-SWCNT. Through whole body imaging in the second near-infrared window (NIR-II window, 1000–1700 nm), SWCNTs were found to be selectively accumulated in inflamed joints in a serum transfer mouse model. We further investigated the interactions of the siRNA/MTX loaded nanotubes with human blood and mice bone marrow cells. In human blood, both types of unloaded SWCNTs were associated with B cells, monocytes and neutrophils. Interestingly, loading with MTX suppressed SWCNTs targeting specificity to immune cells, especially B cells; in contrast, loading siRNA alone enhanced the targeting specificity. Loading both MTX and siRNA to carboxyl-SWCNT enhanced targeting specificity to neutrophils and monocytes but not B cells. The targeting specificity of SWCNTs can potentially be adjusted by altering the ratio of MTX and siRNA loaded. The combined results show that carbon nanotubes have the potential for delivery of cargo drugs specifically to immune cells involved in rheumatoid arthritis.

Otitis media in Indigenous Australian children: review of epidemiology and risk factors

2013 ◽  
Vol 128 (S1) ◽  
pp. S16-S27 ◽  
Author(s):  
Jake Jervis-Bardy ◽  
L Sanchez ◽  
A S Carney
Keyword(s):  
Public Health ◽  
Risk Factors ◽  
Otitis Media ◽  
Bacterial Load ◽  
Grey Literature ◽  
Acute Otitis Media ◽  
Chronic Otitis Media ◽  
Health Concern ◽  
Indigenous Australian ◽  
Indigenous Children

AbstractBackground:Otitis media represents a major health concern in Australian Indigenous children (‘Indigenous children’), which has persisted, despite public health measures, for over 30 years.Methods:Global searches were performed to retrieve peer-reviewed and ‘grey’ literature investigating the epidemiology of and risk factors for otitis media in Indigenous children, published between 1985 and 2012.Results:In Indigenous children, the prevalence of otitis media subtypes is 7.1–12.8 per cent for acute otitis media, 10.5–30.3 per cent for active chronic otitis media and 31–50 per cent for tympanic membrane perforation. The initial onset of otitis media in Indigenous children occurs earlier and persists for longer after the first year of life, compared with non-Indigenous children. Indigenous children are colonised by otopathogens more frequently, at younger ages and with a higher bacterial load. Poor community and domestic infrastructure, overcrowding and exposure to tobacco smoke increase the risk of otitis media in Indigenous children; however, the availability of swimming pools plays no role in the prevention or management of otitis media.Conclusion:Despite awareness of the epidemiological burden of otitis media and its risk factors in Indigenous children, studies undertaken since 1985 demonstrate that otitis media remains a significant public health concern in this population.

Implication of bats in the transmission of zoonotic strains of Salmonella in Benin

2021 ◽  
Vol 11 (5) ◽  
pp. 583-587
Author(s):  
Kouengoua Armelle ◽  
Deguenon Esther ◽  
Dougnon T. Victorien ◽  
Farougou Souaïbou ◽  
Kpodékon Tchokponhoué Tchégninougbo Marc ◽  
...  
Keyword(s):  
Virulence Gene ◽  
Positive Control ◽  
Health Concern ◽  
Public Health Concern ◽  
Salmonella Spp ◽  
Amoxicillin Clavulanic Acid ◽  
Different Strains ◽  
Specific Virulence ◽  
Zoonotic Strains ◽  
Do So

Bats play a very important role in the transmission of zoonosis, including Salmonella. Salmonella are responsible for salmonellosis, which is a major public health concern. They are the cause of many hospitalizations and deaths worldwide. The objective of this study was to contribute to the im-provement of the control of zoonotic strains of Salmonella in Benin. To do so, a collection of 400 bats was made and after slaughter and dissection, bacteriological analyses were made on the gut to isolate and identify the different strains of Salmonella carried by these bats. The resistance profile and the presence of specific virulence gene such invA, spvR, spvC and stn were studied. The strain Salmonella Typhimurium ATCC 14028 was used as a positive control. Of the 400 bats slaughtered, 14 isolate of Salmonella spp were identified by API gallery. Therefore, the prevalence of Salmonella strains in bats was 3.5%. Salmonella spp strains isolated showed total re-sistance to amoxicillin, clavulanic acid and also to first and second genera-tions of cephalosporins. The stn and invA genes have been found in the DNA of all strains of Salmonella isolated. The consumption of bats being a com-mon practice in Benin, the risk of virulent Salmonella strains transmission must be taken very seriously and people must be sensitized to this in order to slow down the risk of infection.

REACTIVE CHANGES OF LIVER AND KIDNEY HISTOLOGICAL ELEMENTS IN MURINE MODELS OF SEPSIS CAUSED BY ADMINISTRATION OF DIFFERENT STRAINS TO MICE

2020 ◽  
pp. 66-71
Author(s):  
Татьяна Геннадьевна Боровая ◽  
Владимир Григорьевич Жуховицкий ◽  
Мария Николаевна Черкасова
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Morphological Changes ◽  
Blood Stasis ◽  
Intraperitoneal Administration ◽  
Liver Parenchyma ◽  
Experimental Models ◽  
Control Group ◽  
Reactive Changes ◽  
Liver And Kidney ◽  
Different Strains

Цель - выявление реактивных изменений гистологических элементов печени и почек у мышей в экспериментальных моделях сепсиса, вызванного штаммами 1840 и 1623 Pseudomonas aeruginosa (PsA1840, 1623). Материал и методы. Сепсис моделировали на двух группах половозрелых самцов мышей линии C57Bl/6 интраперитонеальным введением Pseudomonas aeruginosa. Животным 1-й группы (8 особей) вводили штамм 1840, животным 2-й группы (12 особей) - штамм 1623. Контрольная группа состояла из 3 животных. Перед началом опыта штаммы тестировали на присутствие генов экзотоксинов U, S, T, Y (ExoU, ExoS, ExoT, ExoY) с помощью полимеразной цепной реакции (ПЦР). Для визуализации продуктов ПЦР применяли электрофорез в горизонтальном 1,5 % агарозном геле. Животных вскрывали на терминальной стадии сепсиса. Серийные парафиновые срезы печени и почек толщиной 4 мкм окрашивали гематоксилином - эозином, анализировали особенности гистоструктуры органов и фотографировали в световом микроскопе «AxioPlus» (фирма Zeiss, Германия). Результаты. Штамм PsA 1840, имеющий ген exoU, вызывал выраженные деструктивные изменения пластинок гепатоцитов и замещение участков паренхимы печени гомогенным эозинофильным веществом. Присутствовали признаки стаза крови в синусоидных капиллярах, расширение и тромбоз центральных вен, немногочисленные скопления лейкоцитов. Морфологические изменения нефронов состояли в локальных деструктивных изменениях проксимальных канальцев на периферии коркового вещества почек. При введении PsA1623, имеющего ген exoS, возникали массовая гибель почечных телец и дегенерация канальцев нефронов. В печени дольковая гистоархитектура в основном сохранялась. Выводы. Предполагается связь выявленных различий в реактивных изменениях гистологических элементов печени и почек в подопытных группах с особенностями геномов штаммов PsA, использованных для моделирования сепсиса. Objective - to identify reactive changes of liver and kidney histological elements in experimental models of sepsis in mice caused by 1840 and 1623 Pseudomonas aeruginosa strains (PsA1840, 1623). Material and methods. Sepsis was modeled in two groups of mature male C57Bl/6 mice by intraperitoneal administration of Pseudomonas aeruginosa. Strain 1840 was administered to animals of the first group (n=8), animals of the second group (n=12) were administered strain 1623; the control group consisted of 3 animals. Before the experiment, the strains were tested for the presence of genes of exotoxins U, S, T, Y (ExoU, ExoS, ExoT, ExoY) using polymerase chain reaction (PCR). Electrophoresis in horizontal 1,5 % agarose gel was used to visualize PCR products. The animals were euthanized at the terminal stage of sepsis. The extracted liver and kidneys were fixed according to the generally accepted histological method, and embedded into paraffin blocks. Serial 4 μm thick sections of organs were stained with hematoxylin and eosin, analyzed and photographed using «AxioPlus» light microscope (Zeiss, Germany). Results. Strain PsA 1840, carrying the gene of exotoxin U (ExoU), caused severe destructive changes of hepatocytes plates and the replacement of the liver parenchyma with homogeneous eosinophilic substance. There were signs of blood stasis in sinusoidal capillaries, expansion and thrombosis of central veins, a few accumulations of leukocytes. Morphological changes of nephrons consisted of local destructive changes in the proximal tubules at the periphery of kidney cortical substance. After the introduction of PsA1623, carrying the gene of exotoxin S (ExoS), the massive death of renal corpuscles and degeneration of nephron tubules were registered. However, the lobular histoarchitecture in the liver remained mostly unaltered. Conclusions. It is supposed that there is a possible connection of the observed differences in reactive changes of liver and kidney histological elements in two experimental groups with genome features of PsA strains used for the sepsis modeling.

Pseudomonas aeruginosa Oligoribonuclease Controls Susceptibility to Polymyxin B by Regulating Pel Exopolysaccharide Production

2022 ◽  
Author(s):  
Baopeng Yang ◽  
Yujun Jiang ◽  
Yongxin Jin ◽  
Fang Bai ◽  
Zhihui Cheng ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Bacterial Resistance ◽  
Defense Mechanism ◽  
Extracellular Polysaccharide ◽  
Opportunistic Pathogen ◽  
Polymyxin B ◽  
Guanosine Monophosphate ◽  
Extracellular Dna ◽  
Bacterial Cells ◽  
Bacterial Survival

Polymyxins are considered as the last resort antibiotics to treat infections caused by multidrug-resistant Gram negative pathogens. Pseudomonas aeruginosa is an opportunistic pathogen that causes various infections in humans. Proteins involved in lipopolysaccharide modification and maintaining inner and outer membrane integrities have been found to contribute to the bacterial resistance to polymyxins. Oligoribonuclease (Orn) is an exonuclease that regulates the homeostasis of intracellular (3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP), thereby regulating the production of extracellular polysaccharide in P. aeruginosa . Previously, we demonstrated that Orn affects the bacterial resistance to fluoroquinolone, β-lactam and aminoglycoside antibiotics. In this study, we found that mutation of orn increased the bacterial survival following polymyxin B treatment in a wild type P. aeruginosa strain PA14. Overexpression of c-di-GMP degradation enzymes in the orn mutant reduced the bacterial survival. By using a fluorescence labeled polymyxin B, we found that mutation of orn increased the bacterial surface bound polymyxin B. Deletion of the Pel synthesis genes or treatment with a Pel hydrolase reduced the surface bound polymyxin B and bacterial survival. We further demonstrated that Pel binds to extracellular DNA (eDNA), which traps polymyxin B and thus protects the bacterial cells. Collectively, our results revealed a novel defense mechanism against polymyxin in P. aeruginosa .

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