The term antimicrobials encompass all agents that act against all types of microorganisms – bacteria (antibacterial), viruses (antiviral), fungi (antifungal), and protozoa (antiprotozoal). By measures to prevent the growth of unwanted microbes, antimicrobial chemicals can help keep people from getting sick. Antimicrobial additives are strikingly diverse and control microbes via many different means. In the manufacture of products, they create surfaces and materials inhospitable to microbes like bacteria and mould. Antimicrobials are the most profitable forms of chemotherapy and have been used to save the human population from the threat of infectious diseases.

A vaccine activates our immune system while not making us sick. Various dangerous infectious diseases are often prevented in this simple and effective way. Vaccination could be a simple, safe, and effective way of protecting individuals against harmful diseases, before they are available into contact with them. It uses your body’s natural defenses to make resistance to specific infections and makes your immune system stronger. Vaccines train your immune system to form antibodies, just as it does when it’s exposed to a disease. However, as a result of vaccines contain only killed or weakened varieties of germs like viruses or bacteria, they do not cause the disease or put you at risk of its complications.

Microbial physiology  and metabolism add information on sources of energy and its utilization by microorganisms. Microorganisms play vital role in environment as producers, consumers and decomposers. These are the only group of organisms that takes part in all three important stages of ecosystem. Understanding microbial physiology has larger application in industry, developing medicine and even in agriculture. Throughout earth's history, microbial metabolism has been a  thrust behind the development and maintenance of the planet's biosphere. Eukaryotic organisms such as plants and animals generally depend on organic molecules for energy, growth, and reproduction.

Pharmaceutical Microbiology is an applied branch of Microbiology. It involves the study of microorganisms related to the manufacture of pharmaceuticals like minimizing the number of microorganisms in a process environment, excluding microorganisms and microbial byproducts like exotoxin and endotoxin from water and other starting materials, and ensuring the finished pharmaceutical product is sterile. Other aspects of pharmaceutical microbiology include the research and development of anti-infective agents, the use of microorganisms to detect mutagenic and carcinogenic activity in prospective drugs, and the use of microorganisms within the manufacture of pharmaceutical products like insulin and human growth hormone.

Microorganisms  stay unrivalled in their ability to produce bioactive small molecules for drug development. Though, the core technologies used to discover microbial natural products have not evolved considerably over the past several decades, resulting in a shortage of new drug leads. Advances in DNA-sequencing and bioinformatics technologies currently build it possible to rapidly determine the clusters of genes that encode bioactive compounds and to make computer predictions of chemical structure based on gene sequence information. These structure predictions can be used to determine new chemical entities and supply necessary physicochemical “handles” that lead compound purification and structure confirmation. Industrialization of this process provides a model for rising the efficiency of natural-product discovery. The application of advanced genomics and bioinformatics technologies is  currently  poised to revolutionize natural-product discovery and lead a renaissance of interest in microorganisms as a supply of bioactive compounds for drug development.

Antibiotics are a group of medicines that are used to treat infections caused by some germs like bacteria and certain parasites). Usually, people those who need to have an antibiotic by injection are in hospital because they have a severe infection. Whereas, Antimicrobial chemotherapy is the clinical application of antimicrobial agents to treat infectious disease. It involves the administration of drugs with selective toxicity against pathogens concerned in infections, not host cells. Chemotherapeutic agents also known as synthetic antibiotics are the antimicrobial agents of synthetic origin useful in the treatment of microbial or viral disease. Few examples are sulfonilamides, isoniazid, ethambutol, AZT, nalidixic acid and chloramphenicol. Chemotherapeutic agent needs that the agent be used for antimicrobial purpose and excludes synthetic agents used for medical care against diseases that are not of microbial origin.

The immune system orchestrates a potent defense that consists of the production of specific antibody molecules and lymphocytes capable of reacting with and inactivating foreign agents, either directly or indirectly through the involvement of molecular and cellular inflammatory processes. The human immune system is necessary for our survival in a world full of potentially dangerous microbes, and high impairment of even one arm of this method can predispose to severe, even life-threatening, infections. Infection happens when a pathogen invades body cells and reproduces. Infection will generally lead to an immune response. If the response is fast and effective, the infection will be eliminated or contained so quickly that the disease will not occur. Sometimes infection leads to disease that is marked by symptoms or evidence of illness. Disease may occur when immunity is low or impaired, when virulence of the pathogen (its ability to damage host cells) is high, and when the number of pathogens in the body is great.

Infections of antibiotic-resistant pathogens cause an ever-increasing threat to mankind. The investigation of novel approaches to deal with the antimicrobial resistance crisis should be part of global response to present drawback if an untimely reversion to the pre-penicillin era of medicine is to be avoided. One such promising avenue of analysis involves so-called antibiotic resistance breakers (ARBs), capable of re-sensitising resistant bacteria to antibiotics. Multidrug-resistant bacteria are getting more common and due to their multiplicity of mechanisms, they are frequently resistant to  several if not all of the current antibiotics. This intimidating spectre has been the target of several research efforts into conventional antibiotics and alternative approaches. Bacteria have developed the capability to  supply structured communities (or cluster of cells) via adherence to surface to form biofilms that facilitate or prolong their survival beneath extreme environmental condition.

Pandemic, epidemic and endemic infectious diseases are united by a standard problem: how do we quickly and cost-effectively determine potential pharmacological arbitration to treat infections? The growing accessibility of parasite genome data provides the basis for developing methods to prioritize, a priori potential drug targets and analyze the pharmacological landscape of an infectious disease. Infectious diseases create totally different threats to different constituencies and thus are often treated as separate problems by governments, businesses, philanthropies and research funders: neglected diseases are treated as  world health problems; emerging and pandemic diseases  as public health issues; and bio-defence as a national security issue.

Antimicrobial resistance has become a serious healthcare problem, with high resistance rates of most common bacteria to clinically important antimicrobial agents. Resistance has emerged to even the newer, almost potent antimicrobial agents. Methicillin-resistant S. aureus, ESBL-producing Enterobacteriaceae and carbapenem-resistant Acinetobacter baumannii represent more than 50% of microbial isolates. Furthermore, bacterial resistance to fluoroquinolones, macrolides and third-generation cephalosporins is of serious concern. The molecular epidemiology and resistance mechanisms of the antimicrobial strains exhibited regional specificity, as well as the influence of dissemination of international clonal complexes.