Faculty of medicine

Antibacterial By

Asmaa Mohamed Abdel-Azizlecturer of Pharmacology,

Faculty of Medicine, Minia University

Classification of antimicrobials

antivirals

Antihelminthics antiprotozoals

antifungals

antibacterials

antimicrobials

Classification of Antibacterial agents:

There are FOUR systems of classification:

1- Spectrum against bacteria

2- Effect on bacterial growth

3- Mechanism of action

4- Time-dependant or concentration-dependant.

Classification according to the mechanism of

action

.Inhibitors of

Cell wall

synthesis

ß-lactam antibiotics

penicillins cephalosporins monobactams carbapenems

β-lactam Antibiotics

-Bactericidal by inhibiting bacterial cell wall synthesis

-Bacteria become resistant by producing β-lactamase

enzymes

-β-lactamase enzymes destroy the antibiotic

PenicillinsNarrow spectrum:

➢ Penicillin G

➢ Penicillin V

Penicillinase resistant:

➢ Cloxacillin, Dicloxacillin, Nafcillin, Methicillin

Broad spectrum:

➢ Ampicillin

➢ Amoxicillin

Antipseudomonal:

➢ Ticarcillin, Piperacillin, Mezlocillin

Uses

Urinary tract infection

Respiratory infections

Gastro-intestinal (GI) infections

Genital (venereal) infections

Bacterial endocarditis

Adverse effects

-Diarrhea with ampicillin

-Nephrotoxicity with cephalosporins

-Hypersensitivity reaction (anaphylactic shock):With

penicillin injections

-Prevented by skin sensitivity test

Intra-dermal hypersensitivity skin test

Skin hypersensitivity

Cephalosporins

First generation:

➢ Cefadroxil, Cefazolin, Cephaliexin, Cephalothin

Second generation:

Cefaclor, cefoxitin, cefotetan, cefurexime.

Third generation:

Cefotaxime, cefoperazone, ceftriaxone, ceftizoxime.

Fourth generation:

Cefepime.

Clinical uses

-The drugs of choice for serious infections

caused by Klebsiella, Enterobacter, Proteus,

Serratia, and Haemophilus spp

-Cefotaxime, ceftriaxone are approved for

treatment of meningitis

-Cefixime can be given orally in respiratory and

urinary tract infections.

-Ceftriaxone is the therapy of choice for all

forms of gonorrhea.

adverse effects of cephalosporins

Generally, the cephalosporins have an excellent safety record.

However, they my cause:

-Allergy (ranges from skin rash, anaphylaxis, nephritis,

granulocytopenia, hemolytic anemia).

-Local irritation & thrombophelebitis at site of injections

-Renal toxicity (interstitial nephritis, tubular necrosis) caused

withdrawal of cephaloridine.

-Hypoprothrombinemia and bleeding disorders

-Alcohol intolerance (Disulfiram like reaction) with some

drugs. (e.g cefoperazone, cefamandole).

Monobactams

Aztreonam

Act by inhibiting cell wall synthesis.

Active against only gram-negative rods.

Including P. aeruginosa.

Used as alternative to penicillin in allergic

patients.

Given IV, eliminated by the kidney.

May cause skin rash and raise liver enzymes.

Carbapenems

Imipenem

-Broad spectrum

-Stable to most Beta-lactamase producing

bacteria.

-Given only parentrally & is distributed to all

tissues including CSF.

-Eliminated by the kidney (dose is adjusted in

renal patients).

Other cell wall inhibitors (Non Beta-Lactam group)

Vancomycin

Kinetics

Poorly absorbed orally.

It distributes widely in the body.

the dose must be adjusted in renal impairment.

Clinical uses

Particularly useful in the management of infections due to

methicillin-resistant staphylococci (e.g. osteomyelitis,

pneumonia, endocarditis).

Vancomycin can be administered orally to patients with

pseudomembranous colitis (antibiotic-associated enterocolitis

caused by C difficile), although metronidazole is preferred

Adverse effects

1- Phlebitis at the site of injection.

2- Hypersensitivity. "Red-man" syndrome

is not an allergic reaction but a direct toxic

effect of vancomycin on mast cells, causing

them to release histamine.

3- Ototoxicity and nephrotoxicity

Fosfomycin

-Inhibits a very early stage of bacterial cell wall

synthesis.

-Active against both gram-positive and gram-

negative organisms.

-Available in both oral and pareteral

formulation.

-Eliminated by renal execretion.

-Used as a single 3-g dose for treatment of

uncomplicated UTI.

-It appears to be safe for use in pregnancy.

Fluoroquinolones

Bactericidal by inhibiting bacterial DNA

synthesis by targeting bacterial DNA gyrase

(topoisomerase II) and topoisomerase IV.

e.g.: Ciprofloxacin, norfloxacin, Gemifloxacin,

gatifloxacin, moxifloxacin, sparafloxacin

Uses

-Mainly to treat urinary tract infection

-Respiratory infections

-Gastro-intestinal infections

-Genital (venereal) infections

Adverse effects

-Gastro-intestinal disturbances: most common

-Gatifloxacin: has been associated Hyperglycemia in

diabetic patients and hypoglycemia in patients

receiving oral hypoglycemic drugs

Damaging growing cartilage and causing arthropathy

(so, it is not routinely recommended in patients below

18 years).

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