Introduction to Biofilms in Family Medicine:

Antibiofilm Effect of Biogenic Silver Nanoparticles Combined with Oregano Derivatives against Carbapenem-Resistant Klebsiella pneumoniae

Resistant bacteria may kill more people than COVID-19, so the development of new antibacterials is essential, especially against microbial biofilms that are reservoirs of resistant cells. Silver nanoparticles (bioAgNP), biogenically synthesized using Fusarium oxysporum, combined with oregano derivatives, present a strategic antibacterial mechanism and prevent the emergence of resistance against planktonic microorganisms. Antibiofilm activity of four binary combinations was tested against enteroaggregative Escherichia coli (EAEC) and Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC): oregano essential oil (OEO) plus bioAgNP, carvacrol (Car) plus bioAgNP, thymol (Thy) plus bioAgNP, and Car plus Thy. The antibiofilm effect was accessed using crystal violet, MTT, scanning electron microscopy, and Chromobacterium violaceum anti-quorum-sensing assays. All binary combinations acted against preformed biofilm and prevented its formation; they showed improved antibiofilm activity compared to antimicrobials individually by reducing sessile minimal inhibitory concentration up to 87.5% or further decreasing biofilm metabolic activity and total biomass. Thy plus bioAgNP extensively inhibited the growth of biofilm in polystyrene and glass surfaces, disrupted three-dimensional biofilm structure, and quorum-sensing inhibition may be involved in its antibiofilm activity. For the first time, it is shown that bioAgNP combined with oregano has antibiofilm effect against bacteria for which antimicrobials are urgently needed, such as KPC.

The vermiform cecal appendix, expendable or essential? A narrative review

PURPOSE OF REVIEW

The vermiform cecal appendix is a small thin pouch-like tube of intestinal tissue situated in the lower right abdomen. It is attached at the junction of the large intestine between the ascending colon and small intestine. Historically, the appendix has been labeled redundant with no significant function, a remnant of evolution. This idea was thought to represent a function that may have been critical for survival that became nonsignificant over time. Evolutionary biologists deemed it to be a vestigial organ that early in human evolution was a dedicated organ that was useful and exploited by herbivorous ancestors.

RECENT FINDINGS

Currently, the vermiform cecal appendix has generated significant renewed research interest. As such it has been reported to present a site with a high concentration of lymphoid tissue and a biofilm microbiome that approximately mirrors that which is found in the large bowel.

SUMMARY

Research suggests that the vermiform cecal appendix may be the site of a safe-house biofilm that could re-inoculate the large bowel. Given that the appendix has no known role in digestion, the network of lymphoid tissue and microbiome could constitute an initial site of bacterial translocations that can influence early life ontology and immunological tolerance. A dysbiotic microbiome in the appendix is posited to trigger inflammatory sequelae.

The vermiform appendix: an immunological organ sustaining a microbiome inoculum

The hominoid vermiform appendix has been characterized as a diverticulum of the caecum and describes an entity at the juxtaposition of the colon in the confluence of tanias. The independent development of the lymphoid follicle centres of the appendix is progressed at birth in the presence of the intestinal commensal microbiome, an obligatory prompt for the diversification of intestinal and extra-intestinal mucosal immunological tissue. In the vermiform appendix, this activity is centred on further developing the inventory of primary antibodies and the maturation of T- and B-lymphocyte cells in the follicles within the lymphoid tissue. Furthermore, the columnar epithelia, enterocytes and goblet cells comprise the complement of cells that occupy the lamina propria and muscularis mucosae of the vermiform appendix's mucosa, while macrophages and an abundance of immunoglobulin A and immunoglobulin G generating plasma cells seed the lamina propria Intraepithelial immune cells consisting predominantly of specific CD8⁺ T regulatory lymphocytes occupy sites in the appendix analogous to those present in the intestinal epithelia of the caecal colon. The complement of bacterial genera concealed in the vermiform appendix is posited extant as a biofilm inoculum of the intestinal commensal microbiome. This facilitates re-inoculation of the proximal colon and to a lesser degree the terminal ilium post an intestinal perturbation such as occurs with daily lifestyle stressors, dietary choices and the short-term administration of antibiotics rather than an infectious fulminant colitis. A plausible appreciation results of the importance of multiple immunological aspects of a healthy vermiform appendix and the provision of a commensal biofilm to the gut that repairs a dysbiotic microbiome contributing to balancing intestinal pro- and anti-inflammatory activity for maintaining homeostasis in the gut. Since the composition of the gut microbiome can vary over the short-term and long-term, it is plausible that the appendix inoculum may be instrumental in maintaining the intestinal microbiome.

Spectroscopic identification and anti-biofilm properties of polar metabolites from the medicinal plant Helichrysum italicum against Pseudomonas aeruginosa

Two new acylated styrylpyrones, one 5-methoxy-1(3H)-isobenzofuranone glucoside and a hydroxymethyl-orcinol derivative, along with sixteen known aromatic metabolites, including lignans, quinic acid derivatives low-molecular weight phenol glucosides, have been isolated from the methanol extract of Helichrysum italicum, a medicinal plant typical of the Mediterranean vegetation. The structures of these compounds have been elucidated on the basis of extensive 2D-NMR spectroscopic analyses, including COSY, TOCSY, HSQC, CIGAR-HMBC, H2BC and HSQC-TOCSY, along with Q-TOF HRMS(2) analysis. Selected compounds were evaluated for their anti-biofilm properties against Pseudomonas aeruginosa.

In vitro determination of the antibiotic susceptibility of biofilm-forming Pseudomonas aeruginosa and Staphylococcus aureus: possible role of proteolytic activity and membrane lipopolysaccharide

We carried out a comprehensive overview of inhibitory effects of selected antibiotics on planktonic and biofilm cells of Staphylococcus aureus (ATCC 29213) and Pseudomonas aeruginosa (ATCC 27853) strains. The possible involvement of protease activity and the lipopolysaccharide (LPS) profile of P. aeruginosa were also analyzed. Biofilm cells of both strains were more resistant to antibiotics than their planktonic counterparts. Protease activity was increased in both strains in the biofilm forms. Challenge with sublethal doses of antibiotics also increased proteolytic activity of biofilm cells. Additionally, the LPS profile of P. aeruginosa showed pattern alterations of the biofilm that can contribute to biofilm resistance and survival. These observations provide evidence for the involvement of bacterial proteolytic activity and LPS profile in the resistance of biofilm bacteria to antibiotics compared to their planktonic counterparts.