Antimicrobials Lecture Notes PDF

Level (1) - Semester (1) MICROBIOLOGY D R Z I A D M A LECTURE (5) H A N ANTIMICROBIALS A -  Antibiotics  Antifungal  Antiviral  Antiprotozoal  Antihelminth  A naturally occurring & synt...

Level (1) - Semester (1) MICROBIOLOGY D R Z I A D M A LECTURE (5) H A N ANTIMICROBIALS A -  Antibiotics  Antifungal  Antiviral  Antiprotozoal  Antihelminth  A naturally occurring & synthetically derived compounds that inhibit or destroy selective bacteria.  Selective toxicity.  Bactericidal rather than bacteriostatic.  Do not develop antibacterial resistance.  Non-allergic.  Water soluble & stable.  Good tissue distribution (BBB).  Kill bacteria.  Examples:  Aminoglycosides  Vancomycin  Rifampin  Beta-lactams  Quinolones  Metronidazole  Inhibit growth of susceptible bacteria, rather than killing them immediately; will eventually lead to bacterial death.  Examples:  Chloramphenicol  Clindamycin  Trimethoprim  Erythromycin  Sulfonamides  Tetracyclines - ① Natural Penicillins (Penicillin G): for Gram +ve cocci except Staphylococcus aureus. ② Penicillinase-Resistant Penicillins (Methicillin??): for Staphylococci aureus. ③ Extended-Spectrum Penicillins (Amoxycillin): for many strains of Gram -ve bacteria. ④ Carpenicillin: more active against P. aeruginosa. ⑤ Pipracillin: Greater activity against P. aeruginosa.  Bacteria produce enzymes capable of destroying penicillins.  These enzymes are known as beta-lactamases.  As a result, the medication is not effective.  Chemicals have been developed to inhibit these enzymes → clavulanic acid.  These chemicals bind with beta-lactamase and prevent the enzyme from breaking down the penicillin → amoxicillin clavulanic acid = Augmentin. +ve > -ve +ve = -ve -ve > +ve +ve = -ve MRSA Pseudomonas ✓ Cephalothin Cefuroxime Cefotaxime Cefipime Ceftaroline - Gram -ve Gram +ve Gram +ve Salmonella Retapamulin Gentamicin Oxytetracycline Erythromycin Chloramphenicol Retapamulin Amikacin  Polymyxin B → topical.  Amphotericin B → antifungal.  Bactericidal.  Active against Gram positive Bacteria, MRSA, VRSA.  Inhibit folate synthesis.  Treatment of UTI.  Sulphamethoxazole (sulphonamides) + Trimethoprim.  Target DNA gyrase.  Ciprofloxacin & Levofloxacin.  Inhibits RNA polymerase (inhibit mRNA synthesis).  Antituberculous.  - ① Prevents emergence of resistant organisms. ② Polymicrobial infection. ③ Decreased toxicity. ④ Synergism. ① Antagonism. ② Increased cost. ③ Adverse effects.  1 + 1 = 2; β lactam + β lactam.  1+1=>2  One drug inhibits enzymes produced by bacteria (?).  1 + 1 = 0. ① Prophylaxis in persons of normal susceptibility exposed to specific pathogen;  From Rheumatic fever (long-acting Penicillin). ② Prophylaxis in persons of increased susceptibility:  Respiratory diseases (Chronic).  Immunosuppressed host. ③ Surgical Prophylaxis. -  Viral infection or mixed bacterial infection.  Wrong choice of antibiotics.  Inadequate doses of the suitable antibiotics.  Inadequate duration of treatment.  Wrong route of administration.  Use of antagonistic antibiotic combination.  Development of antimicrobial resistance.  Misuse (Abuse, Overuse) of Antibiotics.  Leading to emergency of multidrug resistant bacteria (Super bugs) cause life threaten infections. ① Methicillin resistant Staphylococcus aureus (MRSA). ② Vancomycin resistant Staphylococcus aureus (VRSA). ③ Pan-resistant Gram-negative Bacilli.  Def.: Unresponsiveness of the microorganism to administrated antibiotics. ① Reduction of intracellular antibiotic accumulation by decreasing permeability. ② Active efflux of antibiotic (efflux pump). ③ Enzymatic inactivation: Penicillinase, β- lactamases. ④ Alteration of target site: alteration of the target receptors of antibiotic, metabolic pathway, enzymes. a. Non- Genetic. b. Genetic:  Chromosomal.  Extra- Chromosomal; Plasmid. -  Live, nonpathogenic bacteria (or yeasts) effective in the treatment or prevention of certain human diseases.  The nonpathogen excludes the pathogen from binding sites on the mucosa. ① Enhance the immune response against the pathogen. ② Reduce the inflammatory response against the pathogen. ③ Oral live Lactobacillus strain reduces nosocomial diarrhea in young children. ④ Yeast Saccharomyces reduces antibiotic-associated diarrhea caused by C. difficile.  Serious complications in:  Highly immunosuppressed patients  Patients with indwelling vascular catheters.  - Clinical Case  A 45 years old female visited the outpatient clinics suffering from fever & burning urination. On Examination her body temperature was 38.8°C. She had frequency & dysuria. The physician asked her to do microbiological examination for her urine which recovered Gram negative bacilli & prescribe her Nitrofurantoin. Questions ① Inhibitors of protein synthesis include: a. Tetracyclines. b. Quinolones. c. Penicillins. d. Vancomycin. ② Aminoglycosides: a. Inhibit DNA synthesis. b. Disturb cytoplasmic membrane functions. C. Inhibit Protein synthesis. d. Inhibit Cell wall synthesis. ③ List 4 mechanisms of antibiotic resistance. ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ……………………………………………………………………………..………….. ……………………………………………………………………………..…………..