Aminoglycosides

(132) These antibiotics contain sugars and include:

• Apramycin (Apralan)
• Framycetin (Framomycin)
• Gentamicin (Pangram)
• Neomycin (Neobiotic)
• Spectinomycin (Spectam)
• Streptomycin (Devomycin)]

(Examples of trade names)

They are very active against gram-negative bacteria such as E. coli and are used to treat piglet scours and to control bacteria in the digestive tract. They are bactericidal and are poorly absorbed from the intestinal tract. The use of streptomycin is banned in some countries.

Cephalosporins
Most of these medicines are poorly absorbed from the intestine and are therefore given by injection. They include:

• Cephalexin (Ceporex)
• Ceftiofur (Excenel)
• Ceftiofur has a wide range of activity and is an excellent medicine for the treatment of respiratory disease.

Macrolides Pleuromutilins and Lincosamides

This group includes:

• Erythromycin (Erythrocin) - Lincosamide
• Tiamulin (Tiamutin) - Pleuromutilin
• Tilmicosin (Pulmotil) - Macrolide
• Tylosin (Tylan) - Macrolide
• Lincomycin (Lincocin) - Lincosamide
• Valnemulin (Econor) - Pleuromutilin

They are mainly active against gram-positive bacteria and specifically act against mycoplasma such as M. hyopneumoniae the cause of enzootic pneumonia. Tiamulin, tylosin and lincomycin are active against Brachyspira hyodysenteriae the cause of swine dysentery. Chloramphenicol is also a member of this group but its use in food producing animals has been banned in some countries. Tiamulin, tilmicosin, tylosin and lincomycin are bacteriostatic.

Penicillins
There are three types:

1. Penicillin G. benzathine - This is not used orally because it is destroyed in the stomach. It is used only by injection and is very active against gram-positive bacteria including staphylococci, streptococci, erysipelothrix and clostridia and some activity against actinobacillus spp, pasteurella haemophilus and leptospira. It has a prolonged action. Penicillin G. procaine - This is slowly released giving a prolonged action.
2. Acid Resistant - Phenoxymethyl penicillin - This is the oral form, it is absorbed from the digestive system and not destroyed by gastric juices.
3. Semi-synthetic - Ampicillin, amoxycillin, cloxacillin - Ampicillin and amoxycillin have a wide range of activity against gram-positive and gram-negative bacteria. Cloxacillin has good activity against gram positive.

All the penicillins are bactericidal.

Quinolones
These medicines are new to veterinary medicine. Enrofloxacin (Baytril) is used in pigs. They are very active against gram-positive and negative organisms and thus of value in both respiratory and enteric disease.

Sulphonamides
There are approximately thirty different ones available but the common ones used in pigs are sulphadimidine (also called sulphamezathine) and sulphadiazine. The former recycles in the environment via faeces and can be responsible for tissue residue failures at slaughter particularly in the kidneys. Sulphonamides are often combined with synthetic substances called trimethoprim and baquiloprim. They are then termed potentiated sulphonamides and have a wider spectrum of activity. Sulphonamides are bacteriostatic but have a wide range of activity against both gram-positive and gram-negative organisms and they are also active against chlamydia, toxoplasma and coccidia spp.

Tetracyclines
These antibiotics are produced from streptomyces fungi and are widely used in pig medicine. Tetracyclines include oxytetracycline (OTC) and chlortetracycline (CTC). They have a wide range of activity against gram-positive and gram-negative bacteria. They are bacteriostatic at low levels but may become bactericidal at high doses and are used in respiratory diseases and secondary bacterial infections. The common ones are OTC (terramycin) and CTC (aureomycin).

Other Antibacterial Medicines
Dimetridazole (Emtryl) - This may be used either in feed or water. It acts mainly on anaerobic bacteria and it used specifically in swine dysentery and colitis.

Nitrofurans - These are mainly active against gram-negative organisms found in the intestinal tract and are available for feed medication.

• Furazolidone (Neftin) - Available for in-feed medication or oral use
• Furaltadone - Another nitrofuran used against salmonella and E. coli infections by water medication.
• Nifulidone - This is only available for water medication.

They all may be bactericidal or bacteriostatic.