eChapters

1. Introduction

Nothing in the universe is non medicinal everything has its value in its own way. Infectious diseases are an important health hazard all over the world, both in developing and developed countries. Several synthetic antibiotics are employed in the treatment of infectious and communicable diseases. A number of researchers nowadays are working seriously to find out substitutes for antibiotics as they cause side effects on the functioning of different parts of the body organs and systems. Antibiotics are also known to disturb the natural intestinal micro flora, thus depriving the benefits of these microbes to human body. Medicinal plants exhibit antimicrobial activity since they contain innumerable biologically active chemical constituents. The medicinal plant wealth, the strong and time tested traditional medicare systems like ayurveda and the human resource base are the strengths of India. Over the last forty years intensive efforts have been made to discover clinically useful antibacterial/ antifungal drugs (Sashikumar et al., 2003). Over 50% of all modern clinical drugs are of natural product origin (Ates, 2003). Higher plants as sources of medicinal compounds have continued to play a dominant role in the maintenance of human health since ancient times (Farombi, 2003).

ABSTRACT

Indole alkaloids gramine, tyramine and tryptamine were isolated from the aerial part of Cynodon dactylon (L.) Pers. for the first time and their antimicrobial properties agains microbial pathogens were studied. Structures of the compounds were elucidated base upon the spectroscopic data such as ¹H-NMR, ¹³C- NMR and MS. The evaluations o the crude extract and the alkaloids for their efficacy in inhibiting the growth of huma pathogenic bacteria and dermatophytes were carried out in vitro. The crude extrac was effective in inhibiting the growth of all the tested microorganisms. Tryptamin and tyramine did not inhibit microbial growth when tested individually, but in combination the growth inhibition of Klebsiella pneumoniae was prominent. Gramin was the most effective one in inhibiting the growth of all the tested microbial pathogens

Introduction

In the past few decades, the shrimp aquaculture industry has become an increasing disease challenge, impacting huge economic losses and sustainable development. Viruses, bacteria, and microsporidian parasites are major pathogens that threaten shrimp healthcare and currently, antimicrobial resistance (AMR) pathogens, and fungi have emerging diseases in the shrimp industry worldwide.

Naturally, invertebrate crustaceans, including shrimp, depend on nonspecific immune responses mainly involved by haemolymph and hemocytic cells. A cellular immune process involving phagocytosis, encapsulation, nodulation, and prophenol oxidase leads to melanin synthesis and humoral responses such as secretion of clotting protein, enzyme inhibitors, antioxidant enzymes and antimicrobial peptides for killing or resistance against invading pathogens. Antimicrobial peptides (AMPs) are evolutionary conserved small peptide molecules ubiquitously found in all living organisms. AMPs are an integral part of the innate immune system in various organisms. These peptides have a broad spectrum of inhibitory effects against bacteria, viruses, fungi, and parasites. Shrimp AMPs are short, molecular weight of less than 13 kDa, possess diverse structures, sizes, and biochemical features, and have an amphipathic structure with cationic or anionic properties that selectively target the negatively charged membranes of microbes.

ABSTRACT

In this study, different concentrations of acetone, alcohol, benzene and chloroform extract of Wedelia chinensis were carried out against human pathogenic bacterial and fungal strains. High frequency of anti-bacterial activity was observed on the Escherichia coli. Moderate amount of antibacterial activity was observed on Staphylococcus aureus. Highly resistant bacterium to this plant was screened through antibacterial pour plate method, which showed on the following organisms Citrobacter diversens, Serratia marcescens and Streptococcus pyogenes. The aim of this study is main evaluation of antimicrobial activity of plant. The ethanolic extracts demonstrating antibacterial and antifungal activity could result in the discovery of antibacterial and antifungal agents.

Fisheries sector plays an important role in food security and fish is now traded internationally. Shift in the trading policies (import and export) of seafood/aquatic products are happening at a rapid pace and consumption of seafood increased globally in substantial quantum. It is estimated that aquatic products export from Asian countries outcompetes earlier contributions to their importing partners year after year. Aquatic products include chordates, mollusc and arthropods from freshwater, brackish and marine system. They are nutrient rich diet and perishable too in nature and this prompted the industry to process the seafood in to different forms such as frozen, canned, cured and dried to extend its shelf life and recently value addition step being followed to improve the customer satisfaction. Nevertheless, the risk associated with the transboundary exchange of pathogens of seafood importance and its antibiotic resistance cannot be disregarded. Majority of the pathogens are not a native flora of fish. Each step in the aquatic products production chain either in the captured or cultured fisheries involves the contact of the seafood to the environment where they are grown, various implements used, contact surfaces, handlers, water etc. This post harvest handling makes the seafood contaminated with the pathogens of seafood importance such as Escherichia coli, Salmonella spp, Clostridium botulinum, Listeria monocytogenes, Staphylococcus aureus, Vibrio cholerae, Vibrio parahaemolyticus, Shigella sp, Aeromonas hydrophila, Plesiomonas shigelloides and viral pathogens such as hepatitis A virus etc. Among these pathogens, Escherichia coli, Salmonella spp, Staphylococcus aureus and Shigella spp are non-indigenous to the aquatic environment and others are indigenous to the aquatic environment. Depending on the nature of the environment (contaminated water source), feeding habits (filter feeders), season of harvest (summer season) are very crucial factors which cause seafood inherently contaminated in nature.

Introduction 
Antimicrobial resistance (AMR) is one of the most significant global health challenges of the 21st century. Defined as the ability of microorganisms— including bacteria, viruses, fungi, and parasites—to resist the effects of antimicrobial drugs, AMR undermines the progress of modern medicine. Antimicrobials—including antibiotics, antivirals, antifungals, and antiparasitics—are the cornerstone of modern medicine. Their discovery transformed the treatment of infectious diseases and enabled surgical advances, chemotherapy, and organ transplantation. However, Alexander Fleming, the discoverer of penicillin, warned that misuse could render these drugs ineffective. Antibiotics, since their discovery in the 20th century, revolutionized healthcare, saving millions of lives and enabling complex medical procedures. Yet, the misuse and overuse of antimicrobials in human health, veterinary practices, and agriculture have rapidly accelerated the emergence of resistant organisms. Today, this warning has materialized as a global crisis. Antimicrobial resistance (AMR) is now considered one of the top ten public health threats by the World Health Organization (WHO). It is not only a biomedical issue but also a socio-economic and developmental challenge. This chapter aims to provide an in-depth overview of AMR, focusing on definitions, history, mechanisms, causes, global status, impacts, and the urgency of mitigation efforts. It also explores national and global responses and future directions to curb the spread of AMR. AMR is estimated to cause 700,000 deaths annually worldwide, with projections of 10 million deaths annually by 2050 if urgent interventions are not implemented. In addition to health impacts, AMR poses grave threats to food security, sustainable agriculture, economic stability, and global development. This chapter provides a comprehensive overview of AMR, including definitions and conceptual frameworks, historical background, mechanisms of

Introduction
Antimicrobial resistance (AMR) is one of the top global public health threats. It is estimated that bacterial AMR was directly responsible for 1.27 million global deaths in 2019 and contributed to 4.95 million deaths (Murray et al., 2019).Despite its magnitude, public awareness of AMR remains low. Unlike tobacco smoke, antibiotics are potentially life-saving medications, but it is just as vital to understand the risks of overuse and their impact on future effectiveness in society as a whole (Langfordet al., 2019). Effective risk communication is essential to addressing AMR because it not only informs professional and community stakeholders but also nurturesbehaviour change across sectors. Within a One Health framework, risk communication connects human medicine, veterinary practice, agriculture, and environmental management, ensuring coordinated responses to reduce misuse and overuse of antimicrobials. This article explores the role of risk communication in combating AMR, highlighting global lessons, challenges, and strategies to strengthen communication systems for sustainable containment.
The Growing Threat of AMR
AMR occurs when microorganisms such as bacteria, viruses, fungi, and parasites evolve mechanisms to resist drugs that once effectively treated them. Misuse and overuse of antimicrobials in human health, livestock, aquaculture, and crop production accelerate resistance. According to WHO, AMR is projected to cause 10 million deaths annually by 2050 if left unaddressed (O’Neill, 2016). In countries like India, with high infectious disease burdens and large-scale antimicrobial consumption, the risks are particularly acute. Communicating these risks clearly and effectively is critical for influencing prescribing practices, agricultural use, and community awareness.Persistent misconceptions include beliefs that antibiotics are effective against viral illnesses and the mistaken notion that it is the human body, rather than bacteria, that develops resistance (Muflihet al., 2021). These knowledge gaps are often linked to insufficient or ineffective health communication (Krockowet al., 2023), sparse media coverage compared to threats like sepsis (Fitzpatrick et al., 2019).
Challenges in AMR Risk Communication
1. Low Public Awareness: Despite the global severity ofAMR, public awareness remains critically low. Surveys have found that a mere fraction of the population grasp its implications, with some reporting only ~8–11% demonstrating adequate understanding and many feeling powerless to contribute (Goshaet al., 2024).
2. Ineffective understanding of Terminology: It is recognized that AMR has a ‘language problem’ and the way in which healthcare professionals communicate about AMR may not always resonate with patients (Langford et al., 2019). Technical labels like “AMR” or “antimicrobial resistance” fall short in public communication. Experiments reveal that phrases such as “Antibiotic Resistance” or “Antibiotic Crisis” are more memorable and better at promoting critical behaviors—like completing prescribed antibiotic courses—than more formal terminology.
3. Misconceptions about Antibiotics: Widespread misunderstandings persist regarding antibiotics’ purpose and effect. Many incorrectly believe antibiotics treat viruses—common colds, flu, or even are effective painkillers (Gunasekara et al., 2022).Some think AMR occurs because the body becomes resistant, rather than bacteria evolving resistance(Muflihet al., 2021).
4. Complexity of the Issue: AMR is inherently multifaceted—spanning interactions among humans, animals, and the environment—which makes it challenging to distill into clear, actionable messages. Understanding Risk

Introduction
India has been making steady progress in the livestock sector with significant rise of meat, egg and milk production and a sustained annual growth rate of more than 5%. This growth trajectory is anticipated to accelerate further due to rising middle-class incomes combined with high income elasticity of demand for livestock products. However, despite having huge livestock resource, protein deficiency in rural India remains widespread. Recent data shows that two third of the Indian households are deficient in protein intake1. Looking at the growth potential in the sector, Govt. of India has put special focus on this sector and have undertaken many initiatives to boost animal health productivity and to increase farmer’s income. However, a major limiting factor in profitable livestock production in India is the high prevalence of infectious diseases. These livestock diseases cause great socioeconomic impact and are often exacerbated by inadequate biosecurity measures both in intensive and open production systems. Consequently, the use of antimicrobials for disease treatment has become an essential aspect of livestock management. Antibiotics usage in Animal Healthcare Antibiotics are an essential part of therapeutic management of infectious diseases in both farm and companion animals, ensuring better animal health and life; thereby also assures healthy food from the animal sources. In India a wide range of antibiotics are available in the veterinary practice viz. Penicillin, Semi-synthetic penicillin like Ampicillin, Amoxycillin, Aminoglycosides like Streptomycin, Gentamicin, Neomycin; Tetracycline, Kanamycin, Erythromycin; Fluoroquinolones like Enrofloxacin, Norfloxacin, Ciprofloxacin,

Introduction
Aquaculture is one of the sunrise sectors contributing a significant quantity to the global supply of fish for human consumption. Fish is a superior source of highquality animal protein and highly digestible energy. Disease problems in farmed fishes are one of the main barriers, resulting in significant financial losses up to a tune of US$2.48 B, 14.95% of the annual aquaculture production value in Indian aquaculture. In the aquatic environment, bacteria are quite prevalent and the majority of bacterial pathogens are found in the water’s natural flora. They only spread illness when poor husbandry practices, inadequate nutrition, and unfavourable environmental circumstances contribute to fish stress. Pathogenic bacteria, including Aeromonas spp, Escherichia coli, Staphylococcus spp, Salmonella spp., Shigella spp., Yersinia enterocolitica, Clostridium botulinum, Plesiomonas shigelloides, and Listeria monocytogenes, can be either naturally present in fish or introduced to them during handling, processing, and storage. Antimicrobial resistance (AMR) in Indian aquaculture presents a multifaceted and growing challenge at the intersection of public health, environmental sustainability, and food security. As aquaculture expands to meet rising global demands for protein, the sector has increasingly relied on antimicrobials to prevent and treat bacterial infections. However, due to some indiscriminate and unregulated use of these agents as well as the householdsewage, hospital effluents, contamination from agricultural wastes andinadequately treated urban waters that enter the aquaculture through drains and rivers,creates strong selective pressure and accelerate the development and dissemination of resistant pathogens in aquatic environments posing a serious threat not only to farmed fish but also to human health through environmental contamination and the broader food chain. Resistant bacteria and resistance genes can spread through water systems, biofilms, and aquaculture products, creating reservoirs that contribute to the broader One Health AMR crisis. Food borne pathogens (Aeromonas spp., Vibrio spp., and Streptococcus spp.) from aquatic animals were found resistant to antimicrobial agents that are relevant for therapeutic usage in human clinical settings. E. coliwas found to be resistant as a sign of possible human and terrestrial animal effects. Distinguishing resistance that has been selected in different sectors is extremely difficult and caution is needed while trying to attribute the source of antibiotic resistance in bacteria in the aquatic environment. Understanding the drivers, mechanisms, and impacts of AMR in aquaculture is essential for developing effective mitigation strategies and sustainable management practices that safeguard both aquatic and human health.

Introduction
Antimicrobial resistance (AMR) is regarded as a silent pandemic that is responsible for causing the majorityof deaths every year and has become a major healthcare challenge and a significant public health issue. It has been reported that AMR alone has caused more fatalities than road accidents and cancer. It is among the top ten global health threats and has been recognized as a part of the multisector One Health approach. It has been predicted that by the year 2050, the burden of AMR will decrease the gross domestic product (GDP) by 2 to 3.5%, causing a loss of USD100 trillion to the world, with the annual death rate reaching 10 million. India faces one of the world’s highest antimicrobial resistance (AMR) rates, driven by high antibiotic consumption in humans, widespread non-prescription use, and unregulated application in livestock, aquaculture, and agriculture. Surveillance data show alarming resistance in major pathogens E. coli and Klebsiella,which now exhibit very low susceptibility to key antibiotics such as cefotaxime, ciprofloxacin, and carbapenems. Factors exacerbating the burden include inadequate infection prevention, limited laboratory capacity, poor enforcement of regulations, environmental contamination from pharmaceutical and hospital waste, and low public awareness. The combined impact threatens public health, food safety, and the economy. In general terms, AMR is defined as the ability of the microorganisms to withstand the action of an antimicrobial agent,i.e. Antibacterial agents, antifungal agents, potentially toxic metals, and disinfectants. AMR is known to be a natural process that occurs over time due to genetic changes in the pathogens under selective pressure, where a pathogen undergoes mutations and is often linked to indiscriminate use of antimicrobial agents.
Indefinite and improper use of antimicrobial agentshas been a major factor in the emergence of AMR. AMR affects both animals and humans alike, and resistant pathogens pose a challenge in treating infections. One of the crucial factors responsible for AMR is theenvironment, which is regarded as both a vehicle for spreading AMR microbes as well is a culprit of AMR pollutants, which severely impact the ecosystems. AMR is a multifaceted problem and to control it effectively, meticulous measures have been implemented for monitoring and surveillance of AMR in clinical settings, in both human and veterinary fields. However, the environmental surveillance dealing with the environmental AMR has yet to be established. The implementation of comprehensive monitoring of AMR in environment will vastly improve our understanding of the various dissemination routes and propagation of the resistant microbes in environment and their role in spreading AMR. In this chapter, we will discuss the environmental spread of AMR, drivers of AMR in the environment, factors influencing AMR, challenges faced, measures to tackle AMR, and future trends in curbing the burden of AMR.

Introduction
Antimicrobial resistance (AMR) is a global concern that poses a significant threat to contemporary healthcare systems, potentially hindering the management and treatment of various diseases. Microorganisms can act as reservoirs for AMR across various ecological niches; thus, a “one health” proposal is essential for coordinating a multisectoral strategy aimed at investigating and tackling this alarming issue. This method seems to be an effective strategy for addressing and alleviating the challenges posed by AMR; however, it demands the collaborative efforts and assets that are consistently and efficiently executed by health practitioners. Horses have been pivotal in human history; they have served in wars, provided transportation, and even aided in mining operations. In contemporary society, horses are significant as sport animals and in therapeutic settings involving animals. Given these close interactions between humans and equines, it becomes essential to effectively identify infectious diseases and antimicrobial resistance (AMR) impacting both species, particularly in instances of highly contagious diseases. Resistant bacteria represent a significant threat to the health of both equines and humans. Horses may obtain resistant bacteria through several avenues, such as interaction with other animals, exposure to contaminated materials, or to antibiotic uses. The responsible utilization of antibiotics and the implementation of antimicrobial stewardship programs are essential in reducing the transmission of antimicrobial resistance (AMR) within equine populations. A variety of zoonotic pathogens that exhibit resistance to antibiotics has been identified in equines. This includes Extended-Spectrum Beta-Lactamases (ESBL) which produces E. coli, Methicillin-Resistant Staphylococcus Aureus (MRSA), and Multidrug-Resistant (MDR) Salmonella. Horses can develop AMR through various channels like:

AMR has been prevalent in almost all European countries from past decades. A 2021-2022 report published by the European Food Safety Authority (EFSA) and the European Centre for Disease Prevention and Control (ECDC) on AMR in zoonotic and indicator bacteria from humans, animals and food origin reported vast differences in antimicrobials resistance levels among the European countries, with comparatively higher AMR percentages in the southern and eastern parts of Europe (ECDC, 2022, 2023). The resistance levels ranged from very high for tetracyclines, sulfonamides and ampicillin, moderate for ciprofloxacin to low levels for third-generation cephalosporins (cefotaxime and ceftazidime) in human cases infected with Salmonella spp. in 2022 (ECDC, 2023). The trends are dynamic and over a decade of 2013 2022, the human isolates from 12 and 15 countries reported a statistically significant reduction in tetracycline and ampicillin resistance, particularly for S. typhimurium (ECDC, 2023). The ciprofloxacin and cefotaxime combination, a highest priority critically important antimicrobials (CIA), had very low and rare resistance levels for Salmonella isolates of humans and animal and their derived meat.

Livestock species wise variation was also observed in the resistance pattern in imported meat, being higher in poultry meat isolates compared to pig or cattle meat for Escherichia coli (ECDC, 2023). High to extremely high levels of f luoroquinolone resistance from Campylobacter jejuni and C. coli of both human and animal origin isolates exist, due to which the fluoroquinolones can no more be used as a treatment option for human Campylobacter infections (ECDC 2023). The combined occurrence of erythromycin resistance and ciprofloxacin in Campylobacter spp is considered of high public health importance, and the report mentioned that the combined resistance for these antimicrobials was higher in C. coli compared to C. jejuni from food-producing animals and humans. However, while the ciprofloxacin resistance showed an increase in over 13 study countries, seven countries reported reduced erythromycin resistance for C. jejuni. Overall, resistance to conventional antimicrobials was frequent in Campylobacter and Salmonella from humans and animals. Increasing trend in resistance to one of two CIA for treatment in humans has been observed in poultry-originated Salmonella serovars and Campylobacter while combined resistance was is low in few Salmonella serovars and C. coli isolates from humans and animals in some countries (ECDC, 2023).

Introduction
 Antibiotic therapy is one of the mainapproaches of modern medicine used tofight bacterial diseases worldwide.Antibiotics comprise of any natural, synthetic, or semi-synthetic substances which interfereswith the growth and development of microbes or have killing effect onmicrobes, specifically bacteria. The availability of these antibiotics for treating various bacterial infectious diseases significantly improved the quality of life of humans as well as animals.The period from1930s to 1960s is considered as the ‘golden era’ of antibiotics during whichmost of the antibiotics available today werediscovered. Antibiotics, once known as the magic bullets of modern-day medicine, are now an “endangered species” facing the danger of extinction due to the worldwide emergence of antibiotic resistance (ABR)/antimicrobial resistance (AMR) among microbes. In general, AMR is the capacity of a microbes (bacteria, fungi, and viruses) to resist the growthinhibitory or killing activity of an antimicrobial beyond its normal susceptibility by altering their physiologyor genetic makeup. AMR has emerged as one of the most critical and complicated global public health threat due to its multi-faceted nature.World Health Organization (WHO) has declared AMR as one of the top 10 global public health threats. The emergence of AMR is closely related to the extensive use and misuse of existingantibiotics in the human and animal fields without properguidelines as well as failure to developor discover new antibiotics. AMR leads to a significant health burden worldwide as it is estimated that bacterial AMR alone attributesto 1.14 million deaths globally in the year 2021 and if left unchecked, it may contribute to 10 million deaths annually by 2050.This prediction was recently updated with the data from 2019 and reported that the deaths of 4.95 million people were related to drug-resistant bacterial infections and 1.27 million deaths were directly attributable to AMR.In addition to the health burden, AMR also increases the healthcare costs and imposes significant indirect economic burdens.Increasing reports of treatment failures in patients with infections caused by multi-, extensive-, and pan-drugresistant bacteriahave been documented in literature from different part of the world. Antibiotics once normally used to treat bacterial infections are no longer effective, and it becomes vital to use “reserve” or “last resort” antimicrobials that are often more expensive. Furthermore, WHO has also emphasized that AMR not only makes infections harder to treat but also jeopardizes ancillary medical procedures such as surgeries and cancer treatments. Food may act as a carrier for the transfer of antimicrobialresistant bacteria (AMRB) and antimicrobial resistance genes (ARGs) to humans.Many scientific reports establish a link between the extensive use of antibiotics duringagricultural production and the increase in AMRamong human pathogens, in which food is one of thepossible transmission routes. Antibiotics are regularly added to feed as additives in intensive animal production systems at sub-therapeutic doses to stimulate growth, improve feed efficiency and avoid infections. The extensive use of antibiotics in human treatment, animal therapy and agricultural use as growth promoters are further causes of bacterial resistance to antibiotics. In recent years, the prevalence of AMR among microorganisms isolated from animal source foods (milk, meat, eggs etc) has increased. The increasing demand for quality animal protein has driven intensive farming, leading to increased antimicrobial usage. In the year 2020, global antimicrobial consumption in food-producing animals was estimated around 99,502 tonnes.Antibiotics are commonly used prophylactically infoodproducing animals and it is projected that by 2030 such usewill increase by approximately 67% globally.Despite efforts to reduce antibiotic use, many countries still rely heavily on antimicrobials for growth promotion and disease prevention. The Food and Drug Administration (FDA) has emphasized the need for better monitoring of antimicrobial use in animals. The emergence and spread of AMR in the food chain is considered as a multisectoral issue, because (i) antibiotics are widely used in livestock production systems (cattle, poultry etc), (ii) AMRB and ARGs can easily spread at each stage of the food production chain, and (iii) these AMRB can cause infections in humans.Thus, the emergence of AMR along the food chain is a major

Use of Antimicrobial Agents

The most frequently used classes of antimicrobial drugs in animals include tetracyclines, sulfonamides alone or in combination with potentiators, quinolones particularly fluoroquinolones, aminopenicillins alone as well as in combination with potentiators, first- and second-generation cephalosporins and also third- and fourth-generation cephalosporins, macrolides, and glycopeptides [1]. The “Terrestrial Animal Code”, issued by the Office International des Epizooties (OIE) in 2022 represents recent guidance for the responsible and prudent use of antimicrobials in veterinary medicine [2]. It describes the respective responsibilities of the competent authority and stakeholders in all processes pertaining to veterinary antimicrobial agents ranging from authorization to the administration to the animals.

ABSTRACT

Serious infections caused by bacteria that have become resistant to commonly used antibiotics have become a major global healthcare problem in the 21^st century. Antibiotic resistance, initially a problem of the hospital setting associated with an increased number of hospitals acquired infections usually in critically ill and immuno-suppressed patients, has now extended into the community causing severe infections difficult to diagnose and treat. In hospitals, most common resistant bacteria include methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci and gram-negative rods including Enterobacteriaceae and Pseudomonas aeruginosa. Vancomycin intermediate and resistant S. aureus, represent a new treatment challenge. In the community, penicillin and macrolide-resistant pneumococci developed several decades ago and are now present all over the world. More recently, communityacquired methicillin-resistant S. aureus has become a problem in several countries causing skin infections but also severe diseases. The molecular mechanisms by which bacteria have become resistant to antibiotics are diverse and complex. Bacteria have developed resistance to all different classes of antibiotics discovered to date. The most frequent type of resistance is acquired and transmitted horizontally via the conjugation of a plasmid. In recent times new mechanisms of resistance have resulted in the simultaneous development of resistance to several antibiotic classes creating very dangerous multidrug-resistant (MDR) bacterial strains, some also known as ‘‘superbugs’’. In many cases the use of antibiotics is unnecessary or questionable. The indiscriminate and inappropriate use of antibiotics in outpatient clinics, hospitalized patients and in the food industry is the single largest factor leading to

AMR is undoubtedly the most serious challenge ever faced by the world health community because of its multifaceted complex nature and its overwhelming impact over the human and veterinary communities. Livestock sector is no exception to have the serious and devastating impact from the emergence and spread of AMR. Because of a steady shift towards intensive farming and increased stocking density there has been increase occurrence of infectious diseases. Growing world population, rapid urbanization, and deforestation, shrinkage of grazing land all aided to this process. This leads to increased usage of antimicrobials in food animals – cause of concern for the scientific community as AMU is known the single most important driver of AMR.

Introduction

Antimicrobials, viz. antibiotics, antivirals, antifungals and anthelmintics are substances widely used to prevent and treat infections in humans, fish & prawn, livestock animals, and crops. In a situation where microorganisms such as bacteria, viruses, parasites or fungi become resistant to antimicrobial treatments to which they were previously susceptible, it is apprehended that antimicrobial resistance in the microbes has evolved. In fact, antibiotic resistant bacteria evade the effects of antibiotics and multiply in their own way leading to severe health consequences in human and animals. The menace is such that antimicrobial resistance (AMR) hinders treatment modalities targeted for infectious diseases. The hazards of antimicrobial resistance is frequently observed in various pathogenic and non-pathogenic organisms, viz. Salmonella spp., Campylobacter spp., Yersinia sp., E. coli serotype O157:H7, enterococci, Pasteurella sp., Actinobacillus sp. with varying severity (McEwen and Fedorka-Cray, 2002). Microorganisms that develop resistance to commonly used antimicrobials are referred to as superbugs. Globally it is a matter of great concern that it spreads rapidly and threatening the ability to treat common infectious diseases, resulting in prolonged illness, disability and death. Without any effective antimicrobial agent, treatment of infectious diseases, many medical procedures like cancer therapy, diabetes management, organ transplantation, and major surgery will not be possible. The microbes showing resistance to multiple antimicrobials are commonly known as multidrug resistance (MDR) organisms (Magiorakos et al., 2012).

Antimicrobial Resistance abbreviated as AMR is defined as the process by which microorganisms like bacteria, fungi, viruses, and parasites change over a period and become resistant to a drug to which they were earlier susceptible to. This makes the medicines ineffective for treatment overtime, thus making infections difficult to treat thereby increasing the risk of spread of diseases caused by them and severe illness which may lead to death. This in turn necessitates the need for development of newer antibiotics. However, there has been a sharp decline in the development and manufacture of new antibiotics in the recent years resulting in development of only few antibiotics in the past two decades. The increase in emergence of antibiotic resistance concurrent with decline in development of newer antibiotics poses a serious threat to health of both humans and animals. Every year about 700,000 deaths have been reported to occur due to resistant infections and this rate is likely to increase further with estimated infections due to resistant pathogens expected to reach over 50 million globally by 2050 (O’Neill, 2016). The worrisome trends of increasing antimicrobial resistance across the globe poses a serious threat to both animal and human health as AMR not only increases the morbidity and mortality rates but also increases the economic burden on health care (Zhu et al., 2022). This presents an extremely grave situation as the supply of new antibiotics is inadequate to cope with the increase of AMR pathogens. The unnecessary use of antibiotics globally especially in the livestock sector as growth promoter further helps in selective enrichment of AMR pathogens which further increases health risks. It is well known that resistant pathogenic and commensal bacteria can persist and spread within and between premises despite zero antimicrobial drug use. This may be explained due to maintenance, replication, and further dissemination of resistance genes by horizontal transfer of genes via natural ecosystem and can occur either by conjugation, transformation and transduction; and these mechanisms can rapidly spread AMR genes among microbial community in natural environment and human microbiome, where these resistant bacterial species may be selected due to presence of antimicrobial drugs (Zhu et al., 2022). The physical transfer of bacteria via movement of animals, workers, and equipment and ineffective cleaning and disinfection may also be responsible for increasing the AMR pathogens in the natural environments.

Introduction

Discovery of the antimicrobial agents in the early twentieth century was a breakthrough to safeguard the public health from the microbial infection. Propensity of these compounds to kill pathogens influenced the discovery of novel antimicrobials. However, since the 1970s, soon after the discovery of the fluoroquinolones, no major antibiotics have been introduced. The prevalent issue is largely attributed to the repercussions of antibiotic overuse or irresponsible utilization across diverse contexts, predominantly in clinical treatment, agricultural practices, animal healthcare, war crisis and the food system. Moreover, the accessibility and availability of antibiotics results in antimicrobial resistance (AMR). Nonprudent use of antibiotics accompanied by genetic plasticity allows microorganisms to adapt to the effect of antimicrobials causing a rapid surge of antimicrobial resistance. Extensive use of antimicrobials in animal husbandry is a major driver of AMR selection and the emergence of antimicrobial-resistant bacteria (ARBs) (World Health Organization, 2014).

Introduction to Antibiotic Discovery

Antibiotics are the drugs that are used to treat illnesses caused by bacteria in humans and animals. These act by killing or inhibiting the growth and multiplication of bacteria. Antibiotics were considered as “magic bullets” that selectively kills microbes responsible for disease causation, but at the same time would not affect the host (Zaman et al., 2017).

Louis Pasteur in 1877, first discovered the properties of antibacterial compounds with the inhibition of anthrax by saprophytic bacteria. In 1928, Alexander Fleming observed that the growth of Staphylococcus aureus in petri dishes was inhibited by substances produced by the fungus Penicillium chrysogenum, which led to the discovery of the first antibiotic, penicillin (Aminov, 2017). Selman Waksman, discovered multiple antibiotics from filamentous actinomycetes living in the soil and defined an antibiotic as “a compound made by a microbe to destroy other microbes”. Following the discovery of Penicillin, various antimicrobial compounds such as sulphonamides, aminoglycosides, tetracyclines, lipopeptides, oxazolidinones, glycopeptides, streptogramins, and quinolones were discovered in the “Golden era” of antibiotics during the period from the 1940s to the 1960s and most of the antibiotics still in current use were discovered during that period (Salam et al., 2023). Millions of metric tons of newer classes of antibiotics have been produced in last 60 years since its inception.