BIOE 402. Medical Technology Assessment. 2 or 3 hours. Bioentrepreneur course. Assessment of medical technology in the context of commercialization. Objectives, competition, market share, funding, pricing, manufacturing, growth, and intellectual property; many issues unique to biomedical products. Course Information: 2 undergraduate hours. 3 graduate hours. Prerequisite(s): Junior standing or above and consent of the instructor.

“Bioinformatics” 특집을 내면서

In this Review, Schwechheimer and Kuehn describe recent developments in elucidating the mechanisms of biogenesis and cargo selection of the outer-membrane vesicles (OMVs) produced by Gram-negative bacteria. They also discuss the functions of OMVs in bacterial physiology and during pathogenesis. Outer-membrane vesicles (OMVs) are spherical buds of the outer membrane filled with periplasmic content and are commonly produced by Gram-negative bacteria. The production of OMVs allows bacteria to interact with their environment, and OMVs have been found to mediate diverse functions, including promoting pathogenesis, enabling bacterial survival during stress conditions and regulating microbial interactions within bacterial communities. Additionally, because of this functional versatility, researchers have begun to explore OMVs as a platform for bioengineering applications. In this Review, we discuss recent advances in the study of OMVs, focusing on new insights into the mechanisms of biogenesis and the functions of these vesicles.

Outer-membrane vesicles from Gram-negative bacteria: biogenesis and functions

Use of silver and silver salts is as old as human civilization but the fabrication of silver nanoparticles (Ag NPs) has only recently been recognized. They have been specifically used in agriculture and medicine as antibacterial, antifungal and antioxidants. It has been demonstrated that Ag NPs arrest the growth and multiplication of many bacteria such as Bacillus cereus, Staphylococcus aureus, Citrobacter koseri, Salmonella typhii, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, Vibrio parahaemolyticus and fungus Candida albicans by binding Ag/Ag+ with the biomolecules present in the microbial cells. It has been suggested that Ag NPs produce reactive oxygen species and free radicals which cause apoptosis leading to cell death preventing their replication. Since Ag NPs are smaller than the microorganisms, they diffuse into cell and rupture the cell wall which has been shown from SEM and TEM images of the suspension containing nanoparticles and pathogens. It has also been shown that smaller nanoparticles are more toxic than the bigger ones. Ag NPs are also used in packaging to prevent damage of food products by pathogens. The toxicity of Ag NPs is dependent on the size, concentration, pH of the medium and exposure time to pathogens.

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A review on biosynthesis of silver nanoparticles and their biocidal properties.

The significance of extracellular DNA (eDNA) in biofilms was overlooked until researchers added DNAse to a Pseudomonas aeruginosa biofilm and watched the biofilm disappear. Now, a decade later, the widespread importance of eDNA in biofilm formation is undisputed, but detailed knowledge about how it promotes biofilm formation and conveys antimicrobial resistance is only just starting to emerge. In this review, we discuss how eDNA is produced, how it aids bacterial adhesion, secures the structural stability of biofilms and contributes to antimicrobial resistance. The appearance of eDNA in biofilms is no accident: It is produced by active secretion or controlled cell lysis - sometimes linked to competence development. eDNA adsorbs to and extends from the cell surface, promoting adhesion to abiotic surfaces through acid-base interactions. In the biofilm, is it less clear how eDNA interacts with cells and matrix components. A few eDNA-binding biomolecules have been identified, revealing new concepts in biofilm formation. Being anionic, eDNA chelates cations and restricts diffusion of cationic antimicrobials. Furthermore, chelation of Mg(2+) triggers a genetic response that further increases resistance. The multifaceted role of eDNA makes it an attractive target to sensitize biofilms to conventional antimicrobial treatment or development of new strategies to combat biofilms.

The role of extracellular DNA in the establishment, maintenance and perpetuation of bacterial biofilms

Co-selection of multi-antibiotic resistance in bacterial pathogens in metal and microplastic contaminated environments: An emerging health threat.

Release of extracellular DNA (eDNA) was observed during in vitro growth of a clinical strain of Acinetobacter baumannii. Membrane vesicles (MV) of varying diameter (20–200 nm) containing DNA were found to be released by transmission electron microscopy (TEM) and atomic force microscopy (AFM). An assessment of the characteristics of the eDNA with respect to size, digestion pattern by DNase I/restriction enzymes, and PCR-sequencing, indicates a high similarity with genomic DNA. Role of eDNA in static biofilm formed on polystyrene surface was evaluated by biofilm augmentation assay using eDNA available in different preparations, for example, whole cell lysate, cell-free supernatant, MV suspension, and purified eDNA. Biofilm augmentation was seen up to 224.64%, whereas biofilm inhibition was 59.41% after DNase I treatment: confirming that eDNA facilitates biofilm formation in A. baumannii. This is the first paper elucidating the characteristics and role of eDNA in A. baumannii biofilm, which may provide new insights into its pathogenesis.

https://downloads.hindawi.com/journals/tswj/2012/973436.pdf

Characterization of eDNA from the clinical strain Acinetobacter baumannii AIIMS 7 and its role in biofilm formation.

Acinetobacter baumannii infections are difficult to treat due to biofilm formation. The literature shows paucity of data on A. baumannii bacteriophages and their application in biofilm control. In this report, we have isolated a new lytic bacteriophage, AB7-IBB1, infecting A. baumannii. Transmission electron microscopy revealed its resemblance to members of the family Siphoviridae, with a tail size of 240 × 10 nm and an icosahedral head 50 nm in diameter. Plaques were 3-5 mm in diameter after 24 h, increasing to 7-9 mm in three days. The phage genome size was determined to be ~75 kb. AB7-IBB1 could lyse 23 of 39 (59 %) clinical isolates of A. baumannii. It exhibited rapid adsorption (>99 % adsorbed in 5 min), a latency period of 30 min and a burst size of 125 PFU/infected cell. The phage affected A. baumannii biofilm formation on an abiotic surface (polystyrene) and a biotic surface (human embryonic kidney 293 cell line). It also showed biofilm control ability on an abiotic surface (polystyrene). FESEM visualization studies confirmed the detrimental effect of phage AB7-IBB1 on host biofilm. In conclusion, this study reports a novel lytic bacteriophage, AB7-IBB1, belonging to family Siphoviridae, with promising anti-biofilm properties.

Novel lytic bacteriophage AB7-IBB1 of Acinetobacter baumannii: isolation, characterization and its effect on biofilm

A major facilitator superfamily (MFS) transporter-like open reading frame (ORF) of 453&#x2009;bp was identified in a pathogenic strain Acinetobacter baumannii AIIMS 7, and its association with adherence and biofilm formation was investigated. Reverse transcription PCR (RT-PCR) showed differential expression in surface-attached biofilm cells than nonadherent cells. In vitro translation showed synthesis of a ∼17 kDa protein, further confirmed by cloning and heterologous expression in E. coli DH5𝛼. Up to 2.1-, 3.1-, and 4.1- fold biofilm augmentation was observed on abiotic (polystyrene) and biotic (S. cerevisiae/HeLa) surface, respectively. Scanning electron microscopy (SEM) and gfp-tagged fluorescence microscopy revealed increased adherence to abiotic (glass) and biotic (S. cerevisiae) surface. Extracellular DNA(eDNA) was found significantly during active growth; due to probable involvement of the protein in DNA export, strong sequence homology with MFS transporter proteins, and presence of transmembrane helices. In summary, our findings show that the putative MFS transporter-like ORF (pmt) is associated with adherence, biofilm formation, and probable eDNA release in A. baumannii AIIMS 7.

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An MFS Transporter-Like ORF from MDR Acinetobacter baumannii AIIMS 7 Is Associated with Adherence and Biofilm Formation on Biotic/Abiotic Surface.

Background & objectives: Available literature shows paucity of reports describing antibiotic and metal resistance profile of biofilm forming clinical isolates of Acinetobacter haemolyticus. The present study was undertaken to evaluate the antibiotic and metal resistance profile of Indian clinical isolate of A. haemolyticus MMC 8 isolated from human pus sample in planktonic and biofilm form. Methods: Antibiotic susceptibility and minimum inhibitory concentration were determined employing broth and agar dilution techniques. Biofilm formation was evaluated quantitatively by microtiter plate method and variation in complex architecture was determined by scanning electron microscopy. Minimum biofilm inhibiting concentration was checked by Calgary biofilm device. Results: Planktonic A. haemolyticus MMC 8 was sensitive to 14 antibiotics, AgNO 3 and HgC1 2 resistant to streptomycin and intermediately resistant to netilmycin and kanamycin. MMC 8 exhibited temporal variation in amount and structure of biofilm. There was 32 - 4000 and 4 - 256 fold increase in antibiotic and metal salt concentration, respectively to inhibit biofilm over a period of 72 h as against susceptible planktonic counterparts. Total viable count in the range of 10 5 -10 6 cfu / ml was observed on plating minimum biofilm inhibiting concentration on Muller-Hinton Agar plate without antimicrobial agents. Biofilm forming cells were several folds more resistant to antibiotics and metal salts in comparison to planktonic cells. Presence of unaffected residual cell population indicated presence of persister cells. Interpretation & conclusions: The results indicate that biofilm formation causes enhanced resistance against antibiotics and metal salts in otherwise susceptible planktonic A. haemolyticus MMC 8.

Time dependent enhanced resistance against antibiotics & metal salts by planktonic & biofilm form of Acinetobacter haemolyticus MMC 8 clinical isolate

Biofilm formation in Acinetobacter baumannii is a common cause of nosocomial infections in humans. Clinical devices and abiotic surfaces are important sites of colonization leading to formation of biofilms. Such infections are often resistant to multiple antibiotic therapies, and hence there is need for an effective mode of control. Herein, we describe the isolation, characterization of a new lytic bacteriophage of A. baumannii and its effect on biofilm. The phage AB7-IBB2, with a genome size of about 170 kb was identified to be of family Podoviridae as revealed by transmission electron microscopy. It had an isometric head (35 nm) and a short tail (7 nm). It lysed 19/39 (49 %) clinical isolates of A. baumannii. Rapid adsorption (>99 % adsorbed in 4 min), a latency period of 25 min and a burst size 22 PFU/infected cell was observed. The phage could inhibit A. baumannii biofilm formation and disrupt preformed biofilm as well. The phage has promising potential to be considered as a candidate biocontrol agent for A. baumannii infections.

Praveen K. Sahu

Papers

Characterization of eDNA from the clinical strain Acinetobacter baumannii AIIMS 7 and its role in biofilm formation.

Novel lytic bacteriophage AB7-IBB1 of Acinetobacter baumannii: isolation, characterization and its effect on biofilm

An MFS Transporter-Like ORF from MDR Acinetobacter baumannii AIIMS 7 Is Associated with Adherence and Biofilm Formation on Biotic/Abiotic Surface.

Time dependent enhanced resistance against antibiotics & metal salts by planktonic & biofilm form of Acinetobacter haemolyticus MMC 8 clinical isolate

Effect of a Novel Podophage AB7-IBB2 on Acinetobacter baumannii Biofilm