Journal of Fisheries & Livestock Production
Open Access

Antibiotics; Boost animal performance; Immune modulating drugs; Veterinary treatment

Introduction

Antibiotics have played unmatched roles in the prevention, control, and treatment of infectious diseases in both humans and animals since the discovery and use of penicillin in the 1940s. Additionally, it has been demonstrated that including antibiotics in animal feeds helps to increase feed effectiveness, encourage animal growth, and raise the standard of animal products [1, 2]. Recent research revealed a link between antibiotics’ ability to promote growth and the bile salt hydrolase activity, an enzyme produced by intestinal bacteria that has a negative impact on the consumption and digestion of host fat. Antibiotics are therefore useful tools for ensuring the growth of an industrialised, intensive farming sector. Antibiotics are being overused, which has led to concerns about the emergence of resistant bacteria and the possibility that they could spread from animals to humans through the transfer of resistant bacteria and their resistant components [3, 4]. There is a connection between non-therapeutic antimicrobial applications and the spread of multidrug resistance, including resistance to medications that were never used on farms. Because of this worry, Sweden first forbade the use of some antibiotics in animal feeds in 1986, and then as a result of European Union member states’ adoption of European Parliament and Council Regulation EC No. 1831/2003 in 2006, all antibiotic growth boosters were outlawed.

Antibiotic use in feed has been prohibited, but this has had unforeseen consequences on the EU’s animal production businesses, including an increase in animal illnesses and a decline in animal production. When the ban was implemented, a high incidence of infections emerged, which led to a considerable increase in the use of disinfectants and therapeutic antibiotics, which led to an increase in the overall amount of antibiotics used in animals [5]. Contrary to its “golden age,” when many antibiotics were developed and sold, the discovery and development of novel antibiotics significantly slowed for many years. Between 2006 and 2010, there were 283% more antimicrobial shortages. Due to the significant expense and danger involved in the development and use of such drugs, the absence of novel core antibiotic moieties may serve as a compensatory mechanism for the resistance to currently available antibiotics.

Numerous alternatives and replacements have been proposed in order to reduce the higher mortality and morbidity rates brought on by the restriction on antibiotics used in feed. They include feed enzymes, bacteriophages and their lysis, antimicrobial peptides, pro- , pre-, and symbiotic, plant extracts, inhibitors for bacterial quorum sensing, biofilm and pathogenicity, antibacterial vaccinations, immunomodulatory drugs, and more [6]. Are these antibiotic substitutes truly as successful at treating animal ailments as antibiotics? In this research, the development and use of antibiotic alternatives were examined, and the potential for such alternatives was highlighted.

Perspectives

Alternatives to antibiotics should have the following qualities: I be non-toxic or have no negative effects on animals; (ii) be simple to remove from the body or only leave short-term residues; (iii) not cause bacterial resistance; (iv) be stable in feed and animal gastrointestinal tracts; (v) be easily decomposed and have no negative effects on the environment; (vi) not affect palatability; (vii) not disrupt the normal intestinal flora of animals; In actuality, there are currently no antibiotic alternatives that satisfy all of the aforementioned criteria [7].

When it comes to the efficiency of preventing sickness and promoting growth, antibiotic alternatives still fall well short of antibiotics. Only a few bacterial infectious diseases may currently be controlled by vaccines, and antibacterial vaccines are often used to prevent bacterial infections. Animal health is mostly preserved through immune-modulatory and feed enzymes, which do not directly harm or inhibit germs. Currently, bacteriophages are exclusively utilised in food, and their safety is still debatable [8]. Plant extracts and probiotics have complicated chemical makeups and poor stability, which can have a variety of effects and safety issues. Since most QSIs are hazardous to eukaryotic cells, research on inhibitors that target bacteria’s QS and pathogenicity is on-going. Only when used in conjunction with antibiotics do biofilm inhibitors have positive outcomes. The high price and limited antibacterial spectrum of AMPs prevent them from being widely used, despite the fact that they can still cause bacterial resistance [9, 10]. AMPs can treat bacterial illnesses. Proteinaceous substances, however, such as feed enzymes, AMPs, bacteriophage lysins, QS quenching enzymes, and enzymatic biofilm inhibitors under research, are inherently unstable and easily broken down in the gastrointestinal tract. Contrarily, antibiotics have a better antibacterial effect than all other antibiotic alternatives and can directly suppress or kill germs. Additionally, the production of antibiotics uses a single, relatively pure active ingredient that is highly stable, consistent, and of high quality thanks to good manufacturing practises. Humans have not yet discovered a method that is more clinically effective than choosing the right medications to treat the targeted bacterium.

The main justification behind the EU’s restriction on low dose antibiotics as feed additives is antimicrobial resistance. Penicillium, the bacterium that makes penicillin, has actually coexisted with other bacteria for tens of thousands of years. Penicillin resistance was first identified after penicillin had been used extensively. Although antibiotic alternatives have not yet been linked to bacterial resistance, with so many of these alternatives in use, bacteria may eventually change to develop resistance [11]. Drug pressure is proportionate to the likelihood of drug resistance developing and spreading. The irregular and unlawful use of antibiotic substitutes may have the same detrimental effects as the conventional usage of antibiotics.

However, we must always remember that prevention is always preferable to treatment. Antibiotics continue to be a useful tool in the prevention and control of animal diseases for many developing nations due to the unfavourable farming environment and high frequency of disease. It has been established that an improvement in farm hygiene is necessary in light of the EU’s ban on growth boosters [12]. The prevalence of bacterial illnesses in the target animals would probably rise without a significant improvement in the production environment when the amount of “old” antibiotics used in feed decreases as a result of the ban. Advanced antibiotics may be used more therapeutically as a result, which could have unforeseen consequences that provide new problems for public health [13]. Furthermore, there is no scientific data that distinguishes between the use of antibiotics for treatment and prevention in terms of the emergence of resistance. Political and social pressure may cause the implementation of such a policy, but bacteria may not always “listen” to the policy-makers, thus it is important to weigh the benefits and risks before doing so. Therefore, the choice to employ in-feed antibiotics should be based on sound scientific principles. It is impossible to replicate the ban on using antibiotics as growth promoters everywhere in the world.

Traditional antibiotics’ effectiveness still has room for improvement. Some “ancient” antibiotics are still effective against some MDR bacteria by identifying novel bacterial targets. It has been shown that extendedspectrum- lactamase-producing E. coli infections can often be treated without the use of carbapenems. The association of molecules can also strengthen the antibacterial activity of antibiotics, and novel formulations can enable targeted medication delivery via nanoparticles. Additionally, it is preferable to utilise broad-spectrum bactericidal drugs in empirical therapy to destroy the assumed infectious bacteria, which may or may not be MDR. It is crucial to switch to the most appropriate narrow-spectrum agent once an infection is under control and the results of the culture and susceptibility tests have been reported [14, 15]. This will reduce the possibility of negative drug effects and the risk of the emergence of antibiotic-induced resistance.

Conclusion

To guarantee the long-term sustainable development of animal agriculture, prudent antibiotic use and ongoing antibiotic substitute development are required. For responsible use of antibiotics and the creation of regulations and policies governing their use, we must firmly specify the target animals, the length of the treatment, and the withdrawal time. In order to keep antibiotic resistance and foodchain residues within predetermined safe levels, we must also strengthen the oversight and enforcement of legislation. Additionally, since recent developments in Europe demonstrated a distinctly more positive outcome of the prohibition of antibiotic growth promoters than was anticipated during the first years after the prohibition due to an improvement in animal welfare, we must improve the management of animal nutrition and production hygiene. Alternatives to antibiotics will require much investigation. We should expand our research into the impacts of combining the use of antibiotics and their alternatives in order to preserve powerful antibiotics for effective human therapy in addition to doing research and developing innovative, safe, and effective substitutes.

https://www.frontiersin.org/articles/10.3389/fmicb.2014.00217/full

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