Antibiotics Defination and classification.

Antibiotics Definition and classification.
Definition:
Antibiotics is a group of drugs or substance or compounds which inhibits or completely stops growth or kills  bacteria , fungi or yeasts or protozoa , when present in very minute concentration , these are mostly metabolites produced by microorganisms which antagonizes the microbial growth it self if present in very low concentration.
Most of the antibiotics are modified structurally to alter its pharmacokinetic or stability and antimicrobial properties so as to produce a most effective antibiotic, also most of them can be synthesized in laboratories.

See also antibiotic resistance and drug resistance mechanism

Classification of Antibiotics

Aminoglycosides :

Works against infections caused by Gram-negative bacteria, such as Escherichia coli and Klebsiella specially Pseudomonas aeruginosa. Effective against Aerobic bacteria

Mode of Action: Binding to the bacterial 30S ribosomal subunit (some work by binding to the 50S subunit), inhibiting the translocation of the peptidyl-tRNA
Amikacin
Gentamicin
Kanamycin
Neomycin
Netilmicin
Tobramycin
Paromomycin
Streptomycin

Ansamycins: Antitumor antibiotics
Geldanamycin
Herbimycin
Carbacephem:
Mode of action:prevents bacterial cell division by inhibiting cell wall synthesis.
Loracarbef
Carbapenems:Bactericidal for both Gram-positive and Gram-negative organisms and therefore useful for empiric broad-spectrum antibacterial 
Mode of action :Inhibition of cell wall synthesis
Ertapenem
Doripenem
Imipenem/Cilastatin
Meropenem
Cephalosporins:
Mode of action :Inhibits the synthesis of the peptidoglycan layer of bacterial cell walls.
Cefadroxil
Cefazolin
Cefalotin
Cefalexin
Cefaclor
Cefamandole
Cefoxitin
Cefprozil
Cefuroxime
Cefixime
Cefdinir
Cefditoren
Cefoperazone
Cefotaxime
Cefpodoxime
Ceftazidime
Ceftibuten
Ceftizoxime
Ceftriaxone
Cefepime
Ceftobiprole
Glycopeptides class of antibiotics
Mode of action : Peptidoglycan synthesis inhibition
Teicoplanin
Vancomycin
Telavancin
Lincosamides class of antibiotics
Mode of action :Blocks 50S subunit of and protein synthesis
Clindamycin
Lincomycin
Macrolides class of antibiotics
Mode of action :irreversible bloking of 50s microbial ribosome, inhibit translation of tRNA and inhibit protien synthesis.
Azithromycin
Clarithromycin
Dirithromycin
Erythromycin
Roxithromycin
Troleandomycin
Telithromycin
Spectinomycin
Monobactams class of antibioticsMode of action :inhibits synthesis of peptidoglycan and cell wall
Aztreonam
Penicillins class of antibiotics
Mode of action :inhibits synthesis of peptidoglycan and cell wall
Amoxicillin
Ampicillin
Azlocillin
Carbenicillin
Cloxacillin
Dicloxacillin
Flucloxacillin
Mezlocillin
Meticillin
Nafcillin
Oxacillin
Penicillin G
Penicillin V
Piperacillin
Temocillin
Ticarcillin
Polypeptides class of antibiotics 
Mode of action :Inhibition of isoprenyl pyrophosphate, one of the molecule responsible for building peptidoglycan synthesis of bacterial cell wall
Bacitracin
Colistin
Polymyxin B
Quinolones class of antibiotics
Mode of action :inhibit the bacterial DNA gyrase enzyme and inhibit DNA replication.
Ciprofloxacin
Enoxacin
Gatifloxacin
Levofloxacin
Lomefloxacin
Moxifloxacin
Nalidixic acid
Norfloxacin
Ofloxacin
Trovafloxacin
Grepafloxacin
Sparfloxacin
Temafloxacin

Sulfonamides class of antibiotics
Mode of action :Competitive inhibition of bacterial enzyme dihydropteroate synthetase,microbial nuclic acids synthesis is inhibited as microbial folic acid synthesis is inhibited.
Mafenide
Sulfonamidochrysoidine
Sulfacetamide
Sulfadiazine
Silver sulfadiazine
Sulfamethizole
Sulfanilimide
Sulfasalazine
Sulfisoxazole
Trimethoprim
Trimethoprim-Sulfamethoxazole (Co-trimoxazole)
Tetracyclines class of antibiotics
Mode of action :It inhibits binding of aminoacyl-tRNA to the mRNA-ribosome there by inhibiting translation process which is an inportant step in protein synthesis .
Demeclocycline
Doxycycline
Minocycline
Oxytetracycline
Tetracycline

Rifamycin

Mode of action :It inhibits DNA-dependent RNA polymerase prevents transcription and protein synthesis.
Rifampin or Rifampicin

Amphenicols class of antibiotics
Mode of action :Inhibits peptidyl transferase to 50S ribosome bacterial subunit
chloramphenicol
Thiamphenicol
Azidamfenicol
Florfenicol.
Cycloserine , is antibiotic derived from cyclisation of serin ,
Mode of action :Inhibits enzyme alanine racemase and  D-alanine ligase