Practical 1: Antibiotics

for small test week 2, based on presentation, finished

the 3 groups of antiiinfectives are?

1. antibacterics - against bacteria

2. antimycotics - against moulds and yeasts

3. antivirotics - against viruses

the 2 groups of antibacterics?

antibacterics acc. to chemical structure:

1. antibiotics - products of metabolism of microorganisms (like bacteria and fungi)

   • kills other microorganism or stop their growing

   • replaced by semi-synthetic and synthetic substances (due to effect, availability + price)

2. chemotherapeutics

   • sulfonamides

   • quinolones

   • nitrofurans

Beta lactams Antibiotic include?

a type of antibiotic - characterized by beta-lactam ring in their structure. incl:

• penicillins

  1. narrow spectrum: benzylpenicillin

  2. broader spectrum: ampicillin, amoxicilin

  3. beta lactamase resistant penicillins: dicloxacilin, cloxacilin, nafcilin

• cephalosporins - cephalexin, ceftiofur ex.

PENICILLINS - narrow spectrum include?

benzylpenicillin

PENICILLINS- broader spectrum include?

ampicillin, amoxicillin

beta-lactamase resistant PENICILLINS include?

dicloxacilin, cloxacilin, nafcilin

CEPHALOSPORINS, 1st generation?

• cefacetrile

• cefaspirin

• cephalexin

• cefadroxil

CEPHALOSPORINS 2nd generation?

cefoxitin

cefotetan

CEPHALOSPORINS 3rd generation?

cefoperazone

ceftiofur

cefovecin

CEPHALOSPORINS 4th generation include?

cefquinone

Classification of antibiotics into which 11 groups according to chemical structure? (overview)

1. Penicillins

2. Cefalosporins

3. tetracyclins

4. amfenicols

5. polypeptids and glycopeptids

6. aminoglycosides

7. macrolids

8. lincosamids

9. ansamycins

10. dieterpens

11. antibiotics with different structure, such as fusidic acid

what is MIC of penicillin?

MIC: minimum inhibitory concentration, it is the lowest conc. of penicillin that prevents visible growth of bacteria.

• 0.03 IU/ml

TETRACYCLINS include?

1st gen: Chlortetacycline, oxytetracycline, tetracycline

2nd gen: doxycycline

AMFENICOLS include?

Florfenicol

POLYPEPTIDES & GLYCOPEPTIDES incl?

1. polypeptides: colistin, polymyxin B

2. glycopeptides: Vankomycin, teikoplanin

AMINOGLYCOSIDES & AMINOCYCLITOLS include?

1. Aminoglycosides:

   • 1st gen: streptomycin, dihydrostreptomycin, neomycin, kanamycin

   • 2nd gen: gentamicin

   • 3rd gen: amikacin, netilmicin

   • 4th gen: isepamycin, dactinomycin

2. Aminocyclitols:

   • spectinomycin

MACROLIDES include?

1. gen: erythromycin, spiramycin, tylosin

2. gen: tilmikosin, tylvalosin, tildipirosin

Azalides (under macrolides) include?

gamithromycin

Triamilides (under macrolides) include?

Tulathromycin

LINCOSAMIDES include?

lincomycin, clindamycin

ANSAMYCINS include?

rifaximin

DITERPENES include?

tiamulin, valnemulin

Antibiotics with different structure?

1. novobiocin

2. fusidic acid

what is the classification of ATBs according to mechanism of action?

1. cell envelope ATB - cell wall synthesis inhibitors

   • ex. beta-lactams, glycopeptides

2. protein synthesis inhibitors

   • ex. tetracyclines, amphenicols, aminoglycosides, macrolides

3. nucleic acids synthesis inhibitors

   • rifamycins

classification of ATBs acc. to the effect on microorganisms?

1. bacteriostatic (stops growth of bacteria)

   • ex. tetracyclines, macrolides, amphenicols

2. bactericidal (kills bacteria)

   • ex. beta lactams, polypeptides

classification of ATBs according to the spectrum of action?

1. broad spectrum - effective against wide range of bacteria (both G+ and G-) ex. tetracyclines

2. slightly broad - ex. ampicillin, neomycin

3. narrow spectrum - effective only against specific families of bacteria ex. penicillin G.

Classification acc. to adverse effects of antibiotics?

3 groups of adverse effects:

1. animals: allergic reaction, salivation, emesis, disruption of intestinal flora, diarrhea, reduction of vit. B synthesis, resistancy development

2. products of animal origin causes: depreciation meat, difficulties in processing milk fermented products

3. human: occurrence of residues in meat, eggs, milk, resistance development.

classification of ATB according to resistance of microorganisms?

1. Primary - natural, microorganism to the antibiotic completely unresponsive ex. penicillin not acting on mycobacterium tuberculosis.

2. Secondary - obtained a property that is subject to various genetic changes

testing the effectiveness of ATBs by which 2 methods?

1. Diffusion:

   • disc diffusion method (qualitative)

   • E-test (quantitative)

2. Dilution:

   • microdilution

   • macrodilution

explain method of disc diffusion.

• disc diffusion method (qualitative)

  • involve placing ATB impregnated discs on an agar plate inoculated with bacteria. As the antibiotic diffuses into the agar, it creates a conc. gradient.

  • clear zones of inhibition around the discs indicate the effectiveness of ATB

explain the method of E-test.

• another method is E-test (quantitative)

  • determines MIC of ATB, using plastic strip with a gradient of ATB conc., placed on agar plate already inoculated with bacteria.

  • The ATB diffuses into agar → gradient made → MIC determined by point where there is no bacterial growth

Dilution methods are?

quantitative method for MIC determination

1. Macrodilution method: liquid medium in tubes

   • larger volumes of liquid medium

   • observes turbidity, clear tubes indicate effective inhibition.

2. Microdilution method: liquid medium in microplates

   • smaller volumes

We observe turbidity, where clear tubes/wells indicate effective inhibition.