Clinically useful families of beta- lactam compounds include penicillins , cephalosporins ,

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Clinically useful families of beta- lactam compounds include penicillins , cephalosporins , monobactams carbapenems. The Action of Antimicrobial Drugs. The mechanism of action of penicillins and cephalosporins . - PowerPoint PPT Presentation

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Clinically useful families of beta-lactam compounds include penicillins, cephalosporins, monobactamscarbapenems

The Action of Antimicrobial Drugs

The mechanism of action of penicillins and cephalosporins.

-Lactam antibiotics bind to and competitively inhibiting the transpeptidase enzyme that cross-links PG layers.Pharmacokinetics- Orally, IM or IV- Absorption dependant on stability in acid and absorption to food- Widely distributed in body fluids- Lipid insoluble- Do not cross blood-brain barrier- Elimination via kidneys- 90% tubular secretion- Short plasma half-life- Intermittent exposure advantageous

Penicillin

5Retention of Penicillin G

What are the side-effects of antibiotics?

Most common side-effects of antibiotics:

Diarrhoea

Feeling and being sick

Fungal infections of the mouth, digestive tract and vagina

Rare side-effects of antibiotics:

Formation of kidney stones (when taking sulphonamides) Abnormal blood clotting (when taking some cephalosporins) Sensitivity to sun (when taking tetracyclines) Blood disorders (when taking trimethoprim) Deafness (when taking erythromycin and the aminoglycosides)

Side Effects and Contraindications- Hypersensitivity- rashes, fever- GI disturbances- Thrush- Renal Impaired patientsAllergic reactions to antibiotics

Some patients may develop an allergic reaction to antibiotics - especially penicillins.

Side effects might include a rash, swelling of the tongue and face, and difficulty breathing.

Reactions to antibiotics can be very serious, and sometimes fatal - they are called anaphylactic reactions. Bacterial resistance:

It is important to complete the whole course of the medication to prevent the infection from coming back.

If you do not complete the course, there is a higher chance the bacteria may become resistant to future treatments - because the ones that survive when you did not complete the course have had some exposure to the antibiotic and may consequently have built up a resistance to it. Antimicrobial ResistanceRelative or complete lack of effect of antimicrobial against a previously susceptible microbe

11Antibiotic ResistanceA variety of mutations can lead to antibiotic resistanceMechanisms of antibiotic resistanceEnzymatic destruction of drugPrevention of penetration of drugAlteration of drug's target siteRapid ejection of the drugResistance genes are often on plasmids or transposons that can be transferred between bacteria. Resistance to Antibiotics

Penicillin resistancevia penicillinase ( Lactamase)

Some penicillin resistant organisms produce Penicillinase which degrades penicillin.14

Broad vs. narrow spectrum drugsAntisepticsAntiseptics- Anti (against) Septic (putrefactive)- substance applied to living tissue to prevent sepsis

- Disinfectant- substance applied to non-living materials to prevent microbial growthHistory of Antiseptics- 1867, Joseph Lister

Common antiseptics used during the last 150 years include alcohol, boric acid, hydrogen peroxide, iodine, carbolic acid and other phenol compounds, chlorohexadine, sodium chloride, sodium hypochlorite and calcium hypochlorite.

- Broad spectrum antimicrobials

- Multiple targets

Chemical structures and uses of biocides in antiseptics and disinfectants

Chemical structures and uses of biocides in antiseptics and disinfectants

Mode of ActionSavlonManufactured by Novartis Consumer Health, UK

- Cholorohexidine gluconate

- Cetrimide

The active ingredients in Savlon creamMode of Action of Chlorhexidine

Antiseptic like Chlorhexidine (CHX) contains a positively charged hydrophobic and lipophilic molecule which can combine with the molecules of phospholipids and lipo-polysaccharides on the cell membrane of microorganism.Due to this interaction, CHX enters in the cell through active or passive transport mechanism. This interaction affects the osmotic equilibrium of cell, hence increase the permeability of membrane which further allowing the reactant molecule in cell and cause damage of cell. The presence of antiseptic inside the microbe cell directly affects the intracellular constituents like nucleic acid and collapse the bacterial cell. This antiseptic shows its activity in acidic medium at pH 5.5 - 0.7.25Mechanism of Action- Used topically- Chlorohexidine- Bacteriocidal to Gram positive and Gram negative - Membrane disrupting- Cetrimide- cationic surfactant

Side Effects and Contraindications- Localised sensitivity- Incompatible with anionic substances- Nausea/ Vomiting- Depression of CNS- No known contraindications