An antimicrobial is a substance that kills or slows the growth of microbes like bacteria (antibacterial activity), fungi (antifungal activity), viruses (antiviral activity), or parasites (antiparasitic activity).

Main classes

---

Antibiotics

Antibiotics are one class of antibacterial and antifungal antimicrobials that can potentially be used as medicinal drugs to treat infections because of their low toxicity for humans or animals.

The term originally described only those formulations derived from living organisms but is now applied also to synthetic antimicrobials, such as the sulfonamides.

The discovery, development, and clinical use of antibiotics during the 20th century have decreased substantially the morbidity and mortality from bacterial infections. The antibiotic era began with the therapeutic application of sulfonamide drugs in 1936, followed by a “golden” period of discovery from approximately 1945 to 1970, when a number of structurally diverse, highly effective agents were discovered and developed. However, since 1980 the introduction of new antimicrobial agents for clinical use has declined. Paralleled to this there has been an alarming increase in bacterial resistance to existing agents . Antimicrobials are among the most commonly used drugs. For example, 30% or more hospitalized patients are treated with one or more courses of antimicrobial therapy. However, antimicrobials are also among the drugs commonly misused by physicians, e.g. using of antibacterial agent in viral respiratory tract infection. The inevitable consequence of widespread and injudicious use of antimicrobials has been the emergence of antibiotic- resistant pathogens, resulting in the emergence of a serious threat to global public health. The resistance problem demands that a renewed effort be made to seek antibacterial agents effective against pathogenic bacteria resistant to current antibiotics. One of the possible strategies towards this objective is the rational localization of bioactive phytochemicals.

Traditional healers have long used plants to prevent or cure infectious conditions. Many of these plants have been investigated scientifically for antimicrobial activity and a large number of plant products have been shown to inhibit growth of pathogenic bacteria. A number of these agents appear to have structures and modes of action that are distinct from those of the antibiotics in current use, suggesting that cross-resistance with agents already in use may be minimal. So, it is worthwhile to study plants and plant products for activity against resistant bacteria.

Essential oils

Many essential oils have topical (external) antimicrobial activity, including:

• Tea tree oil - in cosmetic, medicine
• Mint oil - in medicine, cosmetic (tooth paste etc.)
• Leleshwa oil
• Sandalwood oil - in cosmetic
• Clove oil - stomatology etc.
• Lavender oil
• Nigella sativa (Black cumin) oil
• Onion (Allium cepe) - phytoncides, in phytotherapy

Some essential oils included to national Pharmacopoeias and much more of it now use in Aromatherapy.

Nitrofuranes

Inorganic cations

• Hg²⁺ and Hg₂²⁺
• Ag+

Organic surfactants

See also

---

• Antibiotic
• Antiseptic
• Disinfectant

Pharmacologic agents

Antimicrobien