Preface

Pathogens have historically affected human populations worldwide, resulting in epidemics and pandemics of different origins and epidemiology, as well as high mortality rates. Despite advancements in detection mechanisms and treatment of many known diseases through the development of novel drugs, the increase in the pace of evolution of drug resistance remains the greatest obstacle in drug design and discovery. The most recent threat to mankind is the SARS-coronavirus-2 (COVID-19), a viral zoonosis, which is difficult to diagnose due to many symptomatic similarities to influenza. Approaching the virus via a standardised treatment protocol has been inefficacious due to its rapid mutation, either being more virulent or becoming drug-resistant. The viral infection has engulfed the world in a fight response, in search of an appropriate vaccine or treatment to reduce the risk of infection and loss of human life. Biomolecular engineering and molecular bio-computing have been our greatest tools in drug discovery and development. It has enabled the repurposing of existing drugs by understanding the structure-activity relationship and pharmacokinetic properties against new targets or biological systems.

The book offers an insightful perspective on the most up-to-date developments and research engaged in the combat against pathogens and COVID-19. The contributions from distinguished researchers and leaders in their field are a critical analysis of vaccine development strategies, novel heterocyclic drug scaffolds, the history and biology of infection, and natural products as quorum sensors.

The chapter by Arindam Mitra emphasises reverse vaccinology approaches in vaccine design, intuitively targeting multiple pathogens, including the novel coronavirus, to combat the current pandemic of COVID-19. It also highlights the major advantages of reverse vaccinology for the discovery of novel vaccines with reduced time and cost in development. The second chapter by N. Ramalakshmi et al. is a critical review of leptospirosis and its treatment. The current remedies for milder cases of leptospirosis involve antibiotic administration viz penicillin, ampicillin, cefmetazole, oxalactam, ceftizoxime, and cefotaxime. This review summarizes the most recent literature on synthetic lead molecules, natural product chemotherapies, and drug targets. The third chapter by Nachimuthu Ramesh et al. sheds light on phage therapy and its evolution from lab to bedside endpoints in treating patients. The history and fundamentals of phage biology and its significance in treating infectious diseases have been provided, with commercialization strategies undertaken by the pharmaceutical industry. The fourth chapter by Debaprasad Parai et al. focuses on quorum sensing inhibitors (QSIs) from natural products. Quorum sensing is a signalling process, which regulates the expression of several virulence factors in both gram-negative and gram-positive bacteria via an autoinducing loop. When a critical bacterial cell density is reached, a complex of regulatory proteins and specific signalling molecules enable the autoinduction of the quorum sensor and the expression of the target genes. This chapter provides a literature review describing the various QSIs obtained from natural sources and their role as anti-infective agents. The fifth chapter by Shaik Baji Baba et al. reveals the importance of nitrogen and oxygen-based heterocycles as potential anti-infective agents. It details the development of 1,2,4-triazoles, isatin, and coumarin-based anti-infective agents. Structure-activity relationship studies provide scope for future researchers to develop the most effective and least toxic anti-infective agents.

We would like to acknowledge the expert contributions of the authors mentioned in the review articles in accomplishing this book, which forms an updated base platform for novel drug discovery and development against infective agents. Each author has been recognised as a dynamic leader in their field and we wish them well for their future research. We reserve a special recognition for the Bentham Science Publishing team, particularly Mrs. Fariya Zulfiqar (Manager Publications) and Mr. Mahmood Alam (Editorial Director), for the timely production of the 6^th volume and promotion of this scientific collaboration.