effects? by chinen


									Effects of antimicrobial agents
Brief History • Pasteur and Joubert, who discovered that one type of bacteria could prevent the growth of another. They did not know at that time that the reason one bacterium failed to grow was that the other bacterium was producing an antibiotic. About antimicrobial agents • Antimicrobials include not just antibiotics, but synthetically formed compounds as well. • • • On the basis of their primary activity, they are more specifically called antibacterial, antifungal, anti parasitic , or antiviral agents Bacterial cells grow and divide. Antimicrobial agents interfere with specific processes that are essential for growth and/or division Antimicrobial agents may be either bactericidal (kills bacteria)OR bacteriostatic (inhibits microbes)

Actions of antimicrobial agents 1. Cell wall synthesis inhibitors -suppress some step in the synthesis of bacterial peptidoglycan *beta-lactams-inhibit the last step in peptidoglycan synthesis 2. Cell membrane inhibitors -inhibit the function of bacterial membranes *polymyxin – the only antibiotic that acts by this mechanism -against gram negative bacteria 3. Protein synthesis inhibitors -their attack is always at one of the events occurring in the ribosome or attachment to a particular RNA -tetracycline, chloramphenicol, macrolides(erythromycin) and the aminoglycosides (streptomycin) 4. Nucleic acid inhibitors -some chemotherapeutic agents affect the synthesis of DNA or RNA, or can bind to DNA or RNA so that their messages cannot be read. *quinolones- bind to a bacterial complex of DNA replication 5. Folate synthesis inhibitors -sulfonamides and trimethoprim= block the synthesis of folate needed for DNA replication

Classes of antimicrobial and their Effect

-used to treat bacterial infections -prolonged use of certain antibiotics can decrease the number of gut flora -The term antibiotic originally described only those formulations derived from living organisms, but is now applied also to synthetic antimicrobials, such as the sulfonamides Kinds of Antibiotics a.Penicillins *penicillin G -most useful -safest drug available b. Cephalosporin -usually effective against a broader range of bacteria than penicillin -also effective in infections such as respiratory tract infections and urinary tract infection c. Tetracycline -effective against a wide variety of bacteria and ricketssiae

-’broad spectrum’ antibiotics -doxycycline, minocycline d.Erythromycin -good alternative for people who are allergic to penicillin -used for infections such as diphtheria, pneumonia, legionnaire’s disease and whooping cough e. Aminoglycosides and polypeptides -aminoglycoside antibiotics are used almost exclusively in hospitalized patients for life threatening infections -polypeptide antibiotics are too toxic to be used generally in the body, they are not toxic if used topically, or on the surface of the body Examples. Neosporin and polysporin- combinations of amnoglycoside and polypeptide antibiotics

class of medication used specifically for treating viral infections They are relatively harmless to the host, and therefore can be used to treat infections Most of the antiviral now available are designed to help deal with HIV; herpes viruses, best known for causing cold sores and genital herpes Antiviral drugs work by inhibiting the virus before it enters the cell, stopping it from reproducing, or, in some cases, preventing it from exiting the cell. Other types of antiviral drugs, such as amantadine (Symmetrel) and rimantadine (Flumadine) are used to prevent or treat certain kinds of influenza (flu) Acyclovir (Zovirax) is used to treat chickenpox, shingles, and the symptoms of herpes virus infections of the genitals, lips, mouth, skin, and brain. The medicine does not cure the infections, but it relieves the discomfort and speeds healing of sores, when they are present.

-An antifungal drug is medication used to treat fungal infections such as athlete's foot, ringworm, candidiasis, cryptococcal meningitis -Thus, fungal and human cells are similar at the molecular level, making it more difficult to find a target for an antifungal drug to attack that does not also exist in the infected organism -Example. Natamycin- used to treat fungal infections

class of medications which are indicated for the treatment of infection by parasites, such as nematodes, cestodes, trematodes, infectious protozoa, and amoebae They must kill the infecting pest without serious damage to the host. Example. Mebendazole- used to treat infestations by worms including pinworms ,roundworms, tape worms, hookworms and whipworms

USES • only a small number are safe chemotherapeutic agents, effective in controlling infectious diseases in plants, animals, and humans • A much larger number are used in almost every phase of human activity: in agriculture, food preservation, and water, skin, and air disinfection. Adverse Effects of Antimicrobial Agents -Many antibiotics are toxic to the host. -Alterations of the normal intestinal flora caused by antibiotics may result in diarrhea or in super infection with opportunistic pathogens

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