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This article was published in 1954
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Antibiotics in Veterinary Practice
T. G. HUNGERFORD, B.V.Sc., H.D.A., Penrith.
The resurrection of chemotherapy commenced with the arsenicals (neosalvarsan), continued into full life with the sulphonamides and then later, with the introduction of the antibiotics, chemotherapy has become a craze. The better known of the antibiotics at present are: Penicillin, Aureomycin (or chlortetracycline), Chloromycetin (chloramphenicol), Terramycin (or oxytetracycline), Magnamycin (or crythromycin), Streptomycin, Neomycin, Bacitracin, Tyrothricin, Streptothricin, Pyocyanase, Actinomycin, Citrinin, Gliotoxin, Fumigatin, ClaviformÃn, Patulin, Aspergillic acid, and Polymyxins.
Generally, the effectiveness of some antibiotics and sulphonamides has tempted clinicians into developing a conditioned reflex, which short circuits any tendency to think. They encounter an animal that is sick, has a high temperature, malaise and anorexia, whereupon they forthwith inject it with an antibiotic, or dose it with sulphonamides, or both. Often this is like "using a steam roller to crush an almond". In recent years it has been found that antibiotics given in full doses may kill a wide spectrum of bacteria, and leave the host animal wide open to infection by non-susceptible organisms, particularly Monilia and various fungi, which may invade the gastro-intestinal or respiratory tracts. Sometimes, damage to the kidneys, liver, or some other organ is occasioned by this violent treatment, so that the end result is the death or disability of the animal. On the other hand the great value of homely treatment often is forgotten; thus, hot fomentations, applications of blisters, and other such simple therapeutic measures are neglected. An outstanding example of this is seen in the case of Mastitis in cows. Stripping the quarter every hour, alternately with effective hot bathing and gentle deep massage, will result in the clinical recovery of many cases of Mastitis. Infusing penicillin, penicillin-streptomycin combined, aureomycin and other antibiotics into the cow for Mastitis is reputed to produce wonderful effects. These effects are more apparent in the literature than on the dairy farm, where after the continued use of antibiotics, resistant strains of pathogens are produced, which "laugh" at chemotherapy. It is by no means certain that the homely old bathing, massaging and stripping is not, by and large, a rival of the newer methods; but it is better still to make use of all procedures available.
In our practice (six clinicians) generally we use very large amounts of antibiotics and the results are most disappointing. It is surprising when one retains the critical attitude of the scientist, in appraising results how often antibiotics fail to be of real help. It is of the utmost importance that the ancillary aids to treatment be not overlooked.
Amongst these are the use of antihistaminic drugs, serum and gum saline injections, nursing procedures (warmth, shifting of position in recumbent animals, massaging,etc.), wise feeding (peptones, glucose and vitamins); and all the other clinical measures which comprised the main armamentarium of the clinician before chemotherapy came into its own.
The following comments give a thought or two about each antibiotic. Remember that full details on the susceptible organisms, dose rates of the material and mode of administration are contained, for the most part in the literature put out by the drug firm with each consignment of the drug purchased. Repetition of this information here is unnecessary. It may be mentioned that very full information is given in a book just published: "The Sulphonamides and Antibiotics in Man and Animals," second edition, 1953, by J. Stewart Lawrence and John Francis (H. K. Lewis and Company Limited, London).
PENICILLIN:
Penicillin is a crystalline powder comprising a group of substances which may be the sodium, calcium or potassium salts of at least ten (10) different penicillins. Penicillin F, also known as (1), G. also known as (2), X also known as (3), Dihydro F Flavicidin and K are some of these.
Penicillin G or (2) is usually considered the most pure penicillin and 0.000625 mg. of the sodium salt of the pure benzyl penicillin (penicillin 2 or G) is one unit of penicillin. The procaine salt of penicillin is absorbed more slowly, and the best mode of treatment is to give an initial dose of a soluble potassium salt together with procaine penicillin followed by repeated doses of the latter. A recent development is the feeding of substances that compete with penicillin for elimination from the animal body by the kidneys, and so prolong the period of concentration of penicillin in the bloodstream. Such agents are:- Para-Aminohippuric Acid, Diodrast, Iodopyracet, Carinamide, Benemid, Probenecid.
DOSE RATE:
This varies enormously between 2,000 and 50,000 units per pound of body weight intramuscularly. Generally an initial dose of 5,000 units per pound of crystalline penicillin, together with 2,000 units per pound of procaine penicillin, followed by 5,000 units per pound of procaine penicillin daily intramuscularly, can be considered adequate dosage.
Never give procaine penicillin intravenously. Sometimes penicillin is given orally in three times the dose used intramuscularly. Procaine penicillin when given in oily preparation, and more particularly when combined with aluminium monostearate, is absorbed more slowly.
Grouping of penicillin as regards synergism. It should be noted that Penicillin, Streptomycin, Bacitracin and Neomycin can be grouped together without any antagonism occurring. Aureomycin, chloromycetin and terramycin similarly can be grouped, and used together. However, members of the first group are generally antagonistic, if used in combination with the second group.
COST:
Varies from 4/- to 22/- per million units 1954. Disease conditions in which it is useful: Actinomycosis, Anthrax, Black Leg, Swine Erysipelas, Leptospirosis, Mastitis (sometimes), Strangles (sometimes), Tetanus (doubtful), Joint Ill (usually a failure), Pneumonia (sometimes).
AUREOMYCIN:
This, together with Chloromycetin and Terramycin is classed as a wide-spectrum antibiotic.
Dose: 20 mlg. per pound per mouth per day is the approximate dose rate used. Do not give intravenously as it may cause phlebitis. The dose is better if divided into three or four equal lots. Intramuscularly it may be painful. Cost: 4/- per 250 mlg. capsule.
Disease conditions in which it is useful: With Aureomycin, Chloromycetin, and Terramycin, practically all the diseases amenable to Penicillin yield to these antibiotics as well. In addition, most gram negative organisms are susceptible as well as the larger virus infection. These include Brucellosis, Mailiomyces, Psittacosis, Rickettsia, Q Fever, some distempers in cats, Cystitis, some cases of Scours, some cases of Pneumonia and Pasteurella.
CHLOROMYCETIN:
Dose rate: 25 to 50 mg, per pound, per day, divided into four doses, per mouth.
Cost: 3/- per 250 mg. capsule.
TERRAMYCIN:
Dose rate: 25 mg. per pound, per day, divided into two to four doses, per day. It may be given intramuscularly (possibly painful) with an initial dose of 3 mg. per pound; followed by 2 mg. per pound two hourly.
Cost: 1/- per 50 mg. capsule.
STREPTOMYCIN:
Dose rate: From 10 to 20,000 units per pound (1 mg. equals 1,000 units); intramuscularly, divided into two daily doses.
Cost: 6/- per gramme (per million units).
Disease conditions in which it is useful: gram negative organisms, including some enteric infection, Tuberculosis, Brucellosis, Coliform organisms.
NEOMYCIN:
Has been used a lot topically and orally and is said of recent times to be useful in mastitis.
POLYMYXIN:
Is an antibiotic which is effective against gram positive and gram negative organisms; and is stated to be useful in infections with Pseudomonas aeruginosa.
BACITRACIN:
Is a recent antibiotic stated to be of much value when used intramuscularly in enteric infection in dogs (diarrhoea) and for swine dysentery. It is used largely as wet dressings, in irrigation and in ointment bases.
ERYTHROMYCIN:
Is used orally and has much the same range of usefulness as penicillin.
MASTITIS:
In recent years a great range of antibiotic materials has been used to treat mastitis. A modern tendency is to infuse 100,000 units of penicillin, together with streptomycin. Failing this, one of the wide spectrum antibiotic preparations should be used; either aureomycin, chloromycetin or terramycin. When these have failed, one tells the owner we are still no further ahead. The clinician becomes a little cynical about the claims made in scientific articles.