By :Lecturer Nabeel Ahmed Al anbagi nabeela.alambaki@uokufa.edu.iq Antimicrobial By :Lecturer Nabeel Ahmed Al anbagi nabeela.alambaki@uokufa.edu.iq

Definitions • Antibiotic—antimicrobials of microbial origin, most of which are produced by molds ,fungi or by bacteria of the genus Streptomyces. • Antimicrobial, antimicrobic—any substance with sufficient antimicrobial activity that it can be used in the treatment of infectious diseases.

Sources of Antimicrobial Agents 1-living source 2-Synthesis source 3- asemisynthetic source

several molds of the genus Penicillium, produce pencillin and cephalosporin Gram-positive bacteria as Streptomyces found in soils and freshwater sediments, which produce several antibiotic as Streptomycin tetracyclines chloramphenicol erythromycin.

Chemically synthesized is compounds synthesized for other purposes and tested for their therapeutic effectiveness in animals. The as sulfonamides,

Classification Antimicrobial according mechanism of action 1-Antimicrobics that act on cell wall synthesis. 2-Affect the Cell Membrane. 3-Inhibitors of Protein Synthesis 4-Inhibitors of Nucleic Acid Synthesis 5-Folate Inhibitors

Antimicrobial that act on cell wall synthesis. This group act on The peptidoglycan (murein sac) component of the bacterial cell wall gives it its shape and rigidity. Most important groups are :- B-lactams and the glycopeptides

B-Lactams groups Their name derives from the presence of a B- lactam ring in their structure; this ring is essentialfor antibacterial activity. This group composed from 1-penicillins 2-cephalosporins 3-carbapenems 4-monobactams

Penicillins Act on Gram-positive organisms, Gram-negative cocci 1- Penicillin G (benzylpenicillin) 2- Penicillin V (phenoxymethylpenicillin) 3- semi synthetic penicilins ,The penicillinase- resistant penicillins (methicillin, nafcillin, oxacillin)

Cephalosporins Cephalosporins The structure of the cephalosporins confers resistance to hydrolysis by staphylococcal penicillinase and to the B- lactamases of groups of Gram-negative bacilli, which vary with each cephalosporin. The cephalosporins are classified by generation— first, second, third, or fourth.

Example for cephalosporin cefoxitin cefaclor ceftriaxone cefotaxime ceftazidime

Carbapenems broadest spectrum of all B-lactam antibiotics. penetration of Gram- and Gram+ bacterial cells and high level of resistance to Blactamases Monobactams.

Glycopeptide Antimicrobics Two agents, vancomycin and teicoplanin, belong to this group

Polypeptide Antibiotics Affect the Cell Membrane 2 Polypeptide Antibiotics Affect the Cell Membrane

Polypeptide Antibiotics Both bacitracin and polymyxin B are polypeptide antibiotics produced by Bacillus species. These antibiotics are quite toxic internally and can cause kidney damage. Therefore, they generally are restricted to topical use, such as on the skin.

Antimicrobial Inhibitors of Protein Synthesis 3 Antimicrobial Inhibitors of Protein Synthesis

1-Aminoglycosides. 2.Tetracyclines. 3-Chloramphenicol. 4-Macrolides. 5-Clindamycin 6-Streptogramins

Aminoglycosides The aminoglycosides are a group of bactericidal antibiotic compounds that attach irreversibly to the 30S subunit of bacterial ribosomes, Gentamicin Tobramycin Neomycin, Kanamycin

Tetracyclines The tetracyclines are a group of broadspectrum bacteriostatic antibiotics that act on 30S subunit Oxytetracycline Chlortetracyclines doxycycline

3.Chloramphenicol. An antibiotic with a broad spectrum acts on 50s subunit .Its discovery from Streptomyces

Macrolides. erythromycin, azithromycin, and clarithromycin, tylosin .They affect protein synthesis at the ribosomal level by binding to the 50S subunit

Clindamycin Clindamycin is chemically unrelated to the macrolides acts on 50s subunit but has a similar mode of action and spectrum. It has greater activity than the macrolides against Gram-negative anaerobes

Inhibitors of Nucleic Acid Synthesis

1-Quinolones The primary target of all quinolones is DNA topoisomerase (gyrase), the enzyme responsible for nicking, supercoiling, and sealing bacterial DNA during replication. Among the fluoroquinolones, ciprofloxacin, norfloxacin, levoafloxacin andofloxacin. .

2-Rifampin asemisynthetic bactericidal drug derived from Streptomyces . interferes with RNA synthesis. This agent is active against most Gram-positive bacteria and selected Gram-negative organisms, including Neisseria and Haemophilus antimycobacterial activity, which includes Mycobacterium tuberculosis.

3- Metronidazole  is an antibiotic and antiprotzol medication .

Folate Inhibitors

Agents that interfere with synthesis of folic acid by bacteria .such as Sulfonamides. Trimethoprim-Sulfamethoxazole.