Antibacterial chemicals bactericidal and bacteriostatic agents

include little informations about types of action of antibiotics ( Bactericidal and Bacteriostatics).

1. Antibacterial chemicals-Bactericidal and Bacteriostatic A gents SIVASANGARI SHANMUGAM

2. CON T EN T S Antibacterial Antibacterial agents Classification Bactericidal Bacteriostatic Mechanisms Advantages Disadvantages

3. ANTIBACTERIALS Antibacterial is an agent that interferes with the growth and reproduction of bacteria. These agents kill or prevent bacterial infection by fighting against bacteria. Heat, chemicals such as chlorine, and all antibiotic drugs have antibacterial properties. Antibiotics and antibacterial both attack bacteria. Antibiotics, also known as antibacterial Antibacterial can’t treat viral infections like flue,cold

4. There are some essential related terms for studying the antibacterial agents that are mentioned as following; Biocides - A widespread chemical/physical agents which inactivate microorganisms. Bacteriostatic - Property of a specific biocide agent which is able to bacterial multiplication. Bacteriocidal - A biocide able to kill bacteria . Disinfectant - To reduce only viable organisms on the inanimate object. Septic - characterized by the presence of pathogenic microbes in living tissues. Antiseptic - Which inhibit the growth of microorganisms in/on living tissues. Aseptic - To keep free of microorganisms . Antibiotics - Naturally occuring / synthetic organic compound which inhibit or destroy selective bacteria at low concentration.

5. ANTIBACTERIAL AGENTS Soaps Hand lotions Disinfectants Surface sprays Mouthwashes Toothpastes Antibiotics

6. CLASSIFICATION

7. BACTERICIDAL Those antibiotics that actually kills bacteria by any mechanism depending on the antibiotic. It inhibit cell wall synthesis . Action is irreversible. Do not work with the immune system of the host. Minimal bactericidal concentrated drug is required for kill 99.99% of bacterial population. Example : beta- lactum , daptomycin , aminoglycosides , metrnidazole , fluroquinolones and vancomycin .

8. BACTERIOSTATIC Those antibiotics that stops (or) inhibit the growth of bacteria that means no multiplication or generation of bacteria but they do not kill bacteria. Slow their growth and reproduction. Inhibits the DNA replication and protein synthesis of bacteria. Work with the immune system of the host. Minimum drug concentrated is required. For example : tetracycline and penicillin,sulfonamides , linezolid , chloramphenicol , clindamycin , macrolides .

9. MECHANISMS Inhibition /Target of bacterial cell wall biosynthesis Inhibition /Target bacterial protein biosynthesis Inhibition/ Target bacterial nucleic acid synthesis Target bacterial cell membrane function Inhibition of metabolic pathway Inhibition of ATP synthase

10. INHIBITION OF CELL WALL Antibacterials block steps in the biosynthesis of peptidoglycan , making cells more susceptible to osmotic lysis . Therefore, antibacterials that target cell wall biosynthesis are bactericidal in their action. Because human cells do not make peptidoglycan , this mode of action is an excellent example of selective toxicity. The β- Lactam antibiotics, consisting of all antibiotic agents that contains a β- lactam nucleus in their molecular structures. This includes penicillin derivatives ( penams ), cephalosporins ( cephems ), monobactams , and carbapenems . β- Lactam antibiotics are bacteriocidal and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls. The final step in the synthesis of the peptidoglycan is facilitated by penicillin-binding proteins. PBPs vary in their affinity for binding penicillin or other β- lactam antibiotics.

11. 1. Penicillin is added to the growth medium with a dividing bacterium. 2. The cell begins to grow, but is unable to synthesize new cell wall to accommdate the expanding cell. 3. As cellular growth continues, cytoplasm covered by plasma membrane begins to squeeze out through the gap(s) in the cell wall. 4. Cell wall integrity is further violated. The cell continues to increase in size, but is unable to “pinch off” the extra cytoplasmic material into two daughter cells because the formation of a division furrow depends on the ability to synthesize new cell wall. 5. The loss of the cell wall also causes its shape, so even if the original bacterium were rod-shaped, the sphereoplast is generally spherical.

12. MECHANISM OF Penicillin

13. INHIBITION OF PROTEIN SYNTHESIS Protein Synthesis Inhibitors That Bind the 30S Subunit Aminoglycosides binds to the 30S of bacterial ribosomes , impairing the proofreading ability of the ribosomal complex. This impairment causes mismatches between codons and anticodons . Resulting in the production of proteins with incorrect amino acids and shortened proteins that insert into the cytoplasmic membrane. Disruption of the cytoplasmic membrane by the faulty proteins kills the bacterial cells. The aminoglycosides , which include drugs such as streptomycin , gentamicin , neomycin , and kanamycin , effect translocation by binding to A site and are potent broad-spectrum antibacterials

14. Tetracycline is bind to the 30S subunit ,these drugs are bacteriostatic and inhibit protein synthesis by blocking the association of tRNAs with the ribosome during translation. Naturally occurring tetracyclines produced by various strains of Streptomyces were first discovered in the 1940s. Semisynthetic tetracyclines , including doxycycline and tigecycline have also been produced. Although the tetracyclines are broad spectrum in their coverage of bacterial pathogens .

15. Protein Synthesis Inhibitors That Bind the 50S Subunit There are several classes of antibacterial drugs that work through binding to the 50S subunit of bacterial ribosomes . Macrolides are broad-spectrum, bacteriostatic drugs that block elongation of proteins by inhibiting peptide bond formation between specific combinations of amino acids. The first macrolide was erythromycin . It was isolated in 1952 from Streptomyces erythreus and prevents translocation. Semisynthetic macrolides include azithromycin and telithromycin .

16. INHIBITION OF NUCLEIC ACID SYNTHESIS It interferes with DNA replication in target cells. The drug rifampin ,functions by blocking RNA polymerase activity in bacteria. The RNA polymerase enzymes in bacteria are structurally different from those in eukaryotes, providing for selective toxicity against bacterial cells. Example : Metronidazole . It is used for the treatment of a variety of infections. Inhibits the activity of DNA gyrase and blocks DNA replication, killing the cell. Example : Fluoroquinolones

17. INHIBITION OF CELL MEMBRANE FUNCTION Interacts with lipopolysaccharide in the outer membrane of gram-negative bacteria, killing the cell through the eventual disruption of the outer membrane and cytoplasmic membrane. Example : Polymyxin B Inserts into the cytoplasmic membrane of gram-positive bacteria, disrupting the membrane and killing the cell. Example : Daptomycin

18. INHIBITION OF METABOLIC PATHWAY The sulfonamides ( sulfa drugs ) are the oldest synthetic antibacterial agents and are structural analogues of para -aminobenzoic acid (PABA), an early intermediate in folic acid synthesis Inhibits the enzyme involved in production of dihydrofolic acid Ex : Sulfamethoxazole Inhibits the enzyme involved in the production of tetrahydrofolic acid Ex : Trimethoprim Interferes with the synthesis of mycolic acid Ex : Isoniazid

19. INHIBITION OF ATP SYNTHASE Diarylquinolones , that specifically inhibits mycobacterial growth. Although the specific mechanism has yet to be elucidated, this compound appears to interfere with the function of ATP synthases , perhaps by interfering with the use of the hydrogen ion gradient for ATP synthesis by oxidative phosphorylation , leading to reduced ATP production. Due to its side effects , including hepatotoxicity and potentially lethal heart arrhythmia, otherwise untreatable cases of tuberculosis .

20. Bactericidal antibacterials Function Beta – lactum and cephalosporin They work by interfering the synthesis of the bacterial cell wall Gentamycin and aminoglycosides They inhibit protein synthesis Quinolones and flouroquinolones These block bacterial DNA replication vancomycine These inhibit cell wall synthesis Polymixin B and colistin These antibiotic Bacteriostatics antibacterials Function sulphonamides They act to inhibit folate synthesis at initial stages chloramphenicol Amphenicols works as protein synthesis inhibitors spectinomycin It binds to the 30S ribosomal subunit, thereby interrupting protein synthesis trimethoprim It disturbs the tetrahydrofolate synthesis pathway

21. S.no Tested bacteria Antibacterial drug 1 Escherichia coli Cefazolin , ciprofloxacin, clindamycin , gentamicin , oxacillin , penicillin, vancomycin 2 Pseudomonas aeruginosa Cefuroxime , piperacillin , tobramycin , vancomycin 3 Staphylococus aureus Cefazolin , ciprofloxacin, clindamycin , gentamicin , oxacillin , penicillin, vancomycin 4 Staphylococus . epidermidis Ciprofloxacin, quinupristin / dalfopristin Vancomycin 5 Streptococcus pneumoniae Vancomycin , teicoplanin

22. Advantages The antibiotics do not harm other normal body cells, It is possible to treat the diseases. Macrolide antibiotics are strongly germ-killing medicines. Usually relieves symptoms in a few da y s. They are reasonably harmless to the humans.

23. Disadvantages Antibiotics can have many side effects as diarrhea . Antibiotics can kill the healthy bacteria in the body. Some antibiotics may be allergic depending on your drug allergies such as sulfa that is commonly present in many antibiotics . If the antibiotic is used long time, The bacteria will mutate to withstand the antibiotic, This is known as the antibiotic resistance.

24. References https://www.newscientist.com/article/2116448-what-are-antibacterial-agents-and-should-we-avoid-using-them/#ixzz60FTxOM7x https://www.intechopen.com/books/antimicrobials-antibiotic-resistance-antibiofilm-strategies-and-activity-methods/introductory-chapter-the-action-mechanisms-of-antibiotics-and-antibiotic-resistance https://courses.lumenlearning.com/microbiology/chapter/mechanisms-of-antibacterial-drugs/ https://www.intechopen.com/books/concepts-compounds-and-the-alternatives-of-antibacterials/antibacterial-drugs-from-basic-concepts-to-complex-therapeutic-mechanisms-of-polymer-systems https://courses.lumenlearning.com/boundless-microbiology/chapter/functions-of-antimicrobial-drugs / https://www.online-sciences.com/health/antibiotics-advantages-and-disadvantages /

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