Systems Involved in Antimicrobial Resistance and Virulence of Clinically Important Pathogens

Dear Colleagues,

The spread of multidrug resistant (MDR) microbes has caused a public health crisis of global dimensions. MDR bacteria, and more specifically the carbapenemase-producing Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii, have already been detected all over the globe. Genes encoding carbapenemases are usually associated with mobile genetic elements (MGEs) such as integrons, insertion sequences, transposons, and plasmids. Plasmids play an important role in the epidemiology of antibiotic resistance, since acquisition of various resistance genes on a replicon can result in resistance to multiple antibiotics of the host bacterial cell. Additionally, plasmids harbor various genes encoding virulence or adhesion factors, which offer an advantage to the bacterium for successful invasion and survival within the infected host.

Furthermore, bacteria like A. baumannii and P. aeruginosa show a great propensity to form biofilms on medical devices. It is widely accepted that pathogens within biofilm communities have increased tolerance to extracellular stress. Biofilms have become important virulence factors for A. baumannii, as they provide an insulation that allows bacteria to survive under harsh environmental conditions. Eventually, this makes the organisms tolerant to multiple antimicrobials, giving them multidrug resistance. Additionally, P. aeruginosa is known to produce a variety of cell-associated factors and secreted toxins such as exoenzymes, toxins, and secondary metabolites. These factors help the bacterium to facilitate successful infection and colonization across a wide range of environments. The synthesis of these factors is regulated by a cell-to-cell signaling mechanism referred to as quorum-sensing. Quorum sensing signifies the mode of communication among bacteria to maintain the population density via signal molecules called ‘auto-inducers’. Such cell-to-cell communication has been associated with processes such as bioluminescence, swarming, twitching, antibiotic production, conjugative DNA transfer, sporulation, production of virulence markers, biofilm formation, and biosurfactant production.

Finally, many clones of bacterial strains process a CRISPR/Cas system, which is an adaptive immune system that allows bacteria to limit the entry of genetic elements such as bacteriophages and plasmids. Interestingly, several recent studies have pointed at direct links of CRISPR/Cas systems to regulation of stress-related phenomena. Thus, exploring the role of those systems in bacterial infections is important for fighting MDR pathogens.

The scope of this Special Issue is to collect original contributions on the systems involved in antimicrobial resistance and virulence of clinically important pathogens. It is our pleasure to invite you to submit research articles, short communications, or review articles related to these topics.

Dr. Costas C. Papagiannitsis
Dr. Ibrahim Bitar
Guest Editors

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