The use of many rapid detection technologies could be expanded if the bacteria were separated, concentrated, and purified from the sample matrix before detection. Specific advantages of bacterial concentration might include facilitating the detection of multiple bacterial strains; removal of matrix-associated assay inhibitors; and provision of adequate sample size reduction to allow for the use of representative food sample sizes and/or small media volumes. Furthermore, bacterial concentration could aid in improving sampling techniques needed to detect low levels of pathogens or sporadic contamination, which may perhaps reduce or even eliminate the need for cultural enrichment prior to detection. Although bacterial concentration methods such as centrifugation, filtration, and immunomagnetic separation have been reported for food systems, none of these is ideal and in many cases a technique optimized for one food system or microorganism is not readily adaptable to others. Indeed, the separation and subsequent concentration of bacterial cells from a food sample during sample preparation continues to be a stumbling block in the advancement of molecular methods for the detection of foodborne pathogens. The purpose of this review is to provide a detailed understanding of the science, possibilities, and limitations of separating and concentrating bacterial cells from the food matrix in an effort to further improve our ability to harness molecular methods for the rapid detection of foodborne pathogens.

Bacterial Separation and Concentration from Complex Sample Matrices: A Review

Dental implants have 89% plus survival rates at 10-15 years, but peri-implantitis or dental implant infections may be as high as 14%. Peri-implantitis can limit clinical success and impose health and financial burdens to patients and health providers. The pathogenic species associated with periodontitis (e.g., Fusobacterium ssp, A. actinomycetemcomitans, P. gingivalis) are also associated with peri-implantitis. Incidence of peri-implantitis is highest within the first 12 months after implantation, and is higher in patients who smoke or have poor oral health as well as with calcium-phosphate-coated or surface-roughened implants. Biomaterial therapies using fibers, gels, and beads to deliver antibiotics have been used in the treatment of Peri-implantitis though clinical efficacy is not well documented. Guided tissue regeneration membranes (e.g., collagen, poly-lactic/glycolic acid, chitosan, ePTFE) loaded with antimicrobials have shown success in reosseointegrating infected implants in animal models but have not been proven in humans. Experimental approaches include the development of anti-bioadhesion coatings, coating surfaces with antimicrobial agents (e.g., vancomycin, Ag, Zn) or antimicrobial releasing coatings (e.g., calcium phosphate, polylactic acid, chitosan). Future strategies include the development of surfaces that become antibacterial in response to infection, and improvements in the permucosal seal. Research is still needed to identify strategies to prevent bacterial attachment and enhance normal cell/tissue attachment to implant surfaces.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/jbm.b.31152

Biomaterial and antibiotic strategies for peri-implantitis: a review

Over the last fifty years, microbiologists have developed reliable culture-based techniques to detect food borne pathogens. Although these are considered to be the "gold-standard," they remain cumbersome and time consuming. Despite the advent of rapid detection methods such as ELISA and PCR, it is clear that reduction and/or elimination of cultural enrichment will be essential in the quest for truly real-time detection methods. As such, there is an important role for bacterial concentration and purification from the sample matrix as a step preceding detection, so-called pre-analytical sample processing. This article reviews recent advancements in food borne pathogen detection and discusses future methods with a focus on pre-analytical sample processing, culture independent methods, and biosensors.

Detection of pathogens in foods: the current state-of-the-art and future directions

In aquatic environments, microorganisms attach to metals and colonise the surface to form biofilms producing an environment at the biofilm/metal interface that is radically different from that of the bulk medium in terms of pH, dissolved oxygen, and organic and inorganic species and leading to electrochemical reactions that control corrosion rates. The term microbiologically influenced corrosion is used to designate corrosion resulting from the presence and activities of microorganisms within biofilms at metal surfaces. Microorganisms can accelerate rates of partial reactions in corrosion processes and shift the mechanism for corrosion. Microbiologically influenced corrosion has received increased attention by corrosion scientists and engineers in recent years with the development of surface analytical and electrochemical techniques that can quantify the impact of microbes on electrochemical phenomena and provide details of corrosion mechanisms. Microbiologically influenced corrosion has been docu...

Microbiologically influenced corrosion of metals and alloys

A metal in living tissue is prone to corrosion. The interaction of the foreign body with the tissue involves the redox reaction (an electron exchange) at the interface, the hydrolysis (a proton exchange) of oxidehydrates as products of corrosion, and the formation of metal-organic complexes in the electrolyte. Denatured tissue in contact with the foreign body is the consequence. But behaviour of metals is variable; gold, stainless steel and most other metals react as described while few others like titanium and tantalum do not. The absence of a foreign body effect of a chemical kind is, without doubt, favorable in terms of tissue susceptibility to infection in the presence of titanium.

Metal implants and surface reactions

THE immobilisation of enzymes by attachment to water-insoluble materials has received considerable attention recently1, both for academic reasons and for possible industrial applications. A logical extension of this approach, especially where multi-stage enzymic reactions are being considered, is the immobilisation of microorganisms, which are often the source of many enzyme preparations. The advantages of such an approach are immediately obvious. The tedious and time consuming procedures for enzyme extraction and purification are instantly eliminated, cofactors and coenzymes are readily at hand, the cellular enzymes are often organised into the requisite metabolic pathways and problems associated with enzyme instability may also be avoided. Furthermore, the use of immobilised cells would avoid the problem in industrial processes of separating the product from the enzyme. The immobilisation of cells by the standard glutaraldehyde procedure, however, causes their decease, and entrapment in polyacrylamide gel is commonly used instead to achieve immobilisation2,3. This method produces a minimum of interaction between the microbial cell and the insoluble matrix, thus maximising the probability of the cell's survival. On the other hand, the availability of the cell to any intended substrate is seriously reduced, since it can reach the cell only by diffusion. An alternative approach of immobilising cells on collagen, by the formation of a stable network of multiple ionic (salt) linkages, hydrogen bonds and Van der Waals' interactions has been successful4. We have now pursued an independent approach and report here the successful immobilisation of cells on the hydroxides (hydroxyoxides) of titanium (IV) and zirconium (IV) by a chelation process.

Microbial cells living immobilised on metal hydroxides.

Application of living immobilized cells to the acceleration of the continuous conversions of ethanol (wort) to acetic acid (vinegar)—Hydrous titanium(IV) oxide-immobilized Acetobacter species

Investigation of a number of gelatinous metal hydroxides has established that several (e.g. those formed from TiIV, ZrIV, FeIII, VIII, and SnII) are capable of forming with enzymes insoluble complexes which are enzymically active. From the practical viewpoint TiIV and ZrIV proved the most satisfactory. Comparatively high retentions of enzyme specific activity may be achieved. Complexes of these metal hydroxides may also be formed with peptides and amino-acids. All these complexes are considered to be formed by the re-occupation of ligand sites on the metal ions by the incoming molecules. The metal hydroxide–amino-acid complexes can also subsequently bind an enzyme molecule, to give a product the pH–activity profile of which may differ from that of the soluble form of the enzyme. Thus by this technique it may be possible to alter the pH optimum of an enzyme. The peptide ligand can be displaced from the complex by phosphate or fluoride ions, or by any other such entity capable of forming a more stable complex with the metal ion involved.

Insoluble complexes of amino-acids, peptides, and enzymes with metal hydroxides

The water-insoluble hydroxides of zirconium (IV), titanium (IV), titanium (III), iron (II), vanadium (III), and tin (II) have been used to prepare insoluble derivatives of a cyclic peptide antibiotic by a facile chelation process. Testing of the antibacterial activities of the products against two gram-positive and two gram-negative bacteria showed that in the majority of cases the water-insoluble antibiotics remained active against those bacteria susceptible to the parent antibiotic. The power of the assay system has been extended by the novel use of colored organisms to aid determinations where the growth of normal organisms could not be distinguished from the appearance of the supporting material. Insoluble derivatives of neomycin, polymyxin B, streptomycin, ampicillin, penicillin G, and chloramphenicol were prepared by chelation with zirconium hydroxide, and these derivatives similarly reflected the antibacterial activities of the parent compounds. Several of the metal hydroxides themselves possess antibacterial activity due to complex formation with the bacteria. However, the use of selected metal hydroxides can afford a simple, inexpensive, and inert matrix for antibiotic immobilization, resulting in an antibacterial product that may possess slow-release properties. The mechanisms by which the metal hydroxide-antibiotic association-dissociation may occur are discussed.

Active Immobilized Antibiotics Based on Metal Hydroxides

Further facile immobilization of enzymes on hydrous metal oxides and use of their immobilization reversibility phenomena for the recovery of peptide antibiotics

John D. Humphreys

Papers

Microbial cells living immobilised on metal hydroxides.

Application of living immobilized cells to the acceleration of the continuous conversions of ethanol (wort) to acetic acid (vinegar)—Hydrous titanium(IV) oxide-immobilized Acetobacter species

Insoluble complexes of amino-acids, peptides, and enzymes with metal hydroxides

Active Immobilized Antibiotics Based on Metal Hydroxides

Further facile immobilization of enzymes on hydrous metal oxides and use of their immobilization reversibility phenomena for the recovery of peptide antibiotics