Resistance, Virulence and Social Behavior as Leading Factors of Microbial Pathogens Fitness

A special issue of Pathogens (ISSN 2076-0817).

Deadline for manuscript submissions: closed (29 February 2024) | Viewed by 3359

Special Issue Editors


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Guest Editor
Microbiology & Immunology Department, Faculty of Biology, University of Bucharest, Soseaua Panduri nr. 90-92, Sector 5, 050663 Bucharest, Romania
Interests: biofilms and tolerance of biofilm-embedded cells; QS mechanism and QS inhibitors; antipathogenic strategies; human microbiota; probiotics
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
Microbiology & Immunology Department, Faculty of Biology, University of Bucharest, Soseaua Panduri nr. 90-92, Sector 5, 050663 Bucharest, Romania
Interests: human microbiota; probiotics and prebiotics; antimicrobial strategies; surfaces with anti-biofilm properties
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Antibiotic resistance (AR) is a major form of antimicrobial resistance (AMR) which is known to be caused mainly by overuse (or misuse) of antibiotics. Currently, AR of strictly or opportunistic pathogens is one of the biggest challenges. The burden of resistant and multidrug-resistant bacterial strains is felt not only in the medical field, but also in the natural environment, because antibiotics are also used in agriculture and animal husbandry, and thus reach the water bodies. 

AMR is caused by both inherited and acquired genes, as well as phenotypical or behavioral resistance of microbial biofilms, both of which contribute to bacterial virulence. Virulence is a driving force in host–pathogen interaction and evolution of the infectious process, as it leads to a high rate of pathogen multiplication/ reproductive fitness, colonization and evolution of infection. However, the mobile genetic elements of virulence genes are often recombined with AR genes; in this way, the microbial fitness is increased and these superbug-resistant/multi-resistant and virulent pathogens represent a huge challenge for the medical field.

The biofilm-embedded cells manifest tolerance towards high concentrations of antimicrobials, as well as towards host defense mechanisms. This is great cause for concern within the medical field, as biofilm-associated infections are predominant (~80% of total infections) and develop on intact or damaged tissues, as well as medical devices. Moreover, resistance genes are easily exchanged among biofilm cells by horizontal transfer, due to their proximity. 

Biofilm formation caused by pathogens is correlated with the colonization step of the infectious process. Inside these dense populations, the cells communicate with one another or with their host. Quorum sensing (QS) is a communication mechanism mediated by chemical signals synthesized by bacteria/microorganisms, which accumulates inside cells but secretes extracellularly. These QS molecules modulate the expression of some target genes when they reach a critical concentration, and consequently induce changes in cell population behavior or phenotype, with a greater adaptive value. The QS mechanism controls different physiological processes such as biofilm formation, motility, cellular division, as well as expression of virulence factors (adhesins, enzymes, exotoxins, siderophores), etc. Thus, QS circuits are intensely studied as a potential target for fighting microbial infections, including those produced by genetically resistant or tolerant cells.

It has been shown that QS inhibitors and QS quenching molecules, which are produced by many organisms as innate defense mechanisms, including the normal microbiota members or eukaryotic hosts, can represent anti-pathogenic strategies, interfering with virulence/resistance gene expression. Use of these molecules as alternative or complementary antimicrobial treatments will slow down the selection of resistant and virulent strains, because they inhibit the expression of virulence genes without killing pathogens or selecting for AR genes.

For this special issue, both original research and review articles are welcomed. Potential topics include, but are not limited to:

  • MDR pathogens;
  • Virulence factors, fitness and their influence on bacterial and fungal pathogenesis;
  • Biofilms and their tolerance to antimicrobials—means of recovering cell sensitivity;
  • Anti-pathogenic strategies;
  • In vitro and in vivo evaluation of novel antibacterial and anti-biofilm agents.

Prof. Dr. Veronica Lazar
Dr. Lia Mara Diţu
Guest Editors

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Published Papers (2 papers)

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Research

8 pages, 1020 KiB  
Communication
Pathogenic Biofilm Removal Potential of Wild-Type Lacticaseibacillus rhamnosus Strains
by Gregoria Mitropoulou, Vasiliki Kompoura, Grigorios Nelios and Yiannis Kourkoutas
Pathogens 2023, 12(12), 1449; https://doi.org/10.3390/pathogens12121449 - 14 Dec 2023
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Abstract
The emergence of antimicrobial resistance remains one of the greatest public health concerns. Biofilm formation has been postulated as a mechanism of microbial pathogens to resist antimicrobial agents. Lactic Acid Bacteria (LAB) and their metabolites have been proposed to combat bacterial biofilms due [...] Read more.
The emergence of antimicrobial resistance remains one of the greatest public health concerns. Biofilm formation has been postulated as a mechanism of microbial pathogens to resist antimicrobial agents. Lactic Acid Bacteria (LAB) and their metabolites have been proposed to combat bacterial biofilms due to their antimicrobial activity. In this vein, the aim of the present study was to investigate the biofilm removal potential of cell-free supernatants (CFSs) of five wild-type Lacticaseibacillus rhamnosus strains, isolated from Greek natural products, in comparison to the commercially available L. rhamnosus GG strain, against biofilms formed by common foodborne pathogens (Salmonella Enteritidis, Salmonella Typhimurium, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus). The biofilm removal activity of LAB was assessed on a two-day-old mature biofilm using a microtiter plate-based procedure. Both non-neutralized and neutralized CFSs removed biofilms in a concentration-dependent manner. The biofilm removal activity of the non-neutralized CFSs was significantly higher compared to the neutralized CFSs, as expected, with ranges of 60–89% and 30–80%, respectively. The biofilm removal efficiency of L. rhamnosus OLXAL-3 was significantly higher among the wild-type L. rhamnosus strains tested (20–100% v/v). In conclusion, our results suggest the great potential of the application of wild-type L. rhamnosus strain’ CFSs as effective natural agents against pathogenic bacterial biofilms. Full article
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15 pages, 705 KiB  
Article
Snapshot of Phenotypic and Molecular Virulence and Resistance Profiles in Multidrug-Resistant Strains Isolated in a Tertiary Hospital in Romania
by Bianca Simona Truşcă, Irina Gheorghe-Barbu, Marina Manea, Elvira Ianculescu, Ilda Czobor Barbu, Luminița Gabriela Măruțescu, Lia-Mara Dițu, Mariana-Carmen Chifiriuc and Veronica Lazăr
Pathogens 2023, 12(4), 609; https://doi.org/10.3390/pathogens12040609 - 17 Apr 2023
Cited by 4 | Viewed by 1674
Abstract
A current major healthcare problem is represented by antibiotic resistance, mainly due to multidrug resistant (MDR) Gram negative bacilli (GNB), because of their extended spread both in hospital facilities and in the community’s environment. The aim of this study was to investigate the [...] Read more.
A current major healthcare problem is represented by antibiotic resistance, mainly due to multidrug resistant (MDR) Gram negative bacilli (GNB), because of their extended spread both in hospital facilities and in the community’s environment. The aim of this study was to investigate the virulence traits of Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa MDR, XDR, and PDR strains isolated from various hospitalized patients. These GNB strains were investigated for the presence of soluble virulence factors (VF), such as hemolysins, lecithinase, amylase, lipase, caseinase, gelatinase, and esculin hydrolysis, as well as for the presence of virulence genes encoding for VF involved in adherence (TC, fimH, and fimA), biofilm formation (algD, ecpRAB, mrkA, mrkD, ompA, and epsA), tissue destruction (plcH and plcN), and in toxin production (cnfI, hlyA, hlyD, and exo complex). All P. aeruginosa strains produced hemolysins; 90% produced lecithinase; and 80% harbored algD, plcH, and plcN genes. The esculin hydrolysis was detected in 96.1% of the K. pneumoniae strains, whereas 86% of them were positive for the mrkA gene. All of the A. baumannii strains produced lecithinase and 80% presented the ompA gene. A significant association was found between the number of VF and the XDR strains, regardless of the isolation sources. This study opens new research perspectives related to bacterial fitness and pathogenicity, and it provides new insights regarding the connection between biofilm formation, other virulence factors, and antibiotic resistance. Full article
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