Veterinary antibiotics in the aquatic and terrestrial environment

The fate of antibiotics in the environment, and especially antibiotics used in animal husbandry, is subject to recent studies and the issue of this review. The assumed quantity of antibiotics excreted by animal husbandry adds up to thousands of tonnes per year. Administered medicines, their metabolites or degradation products reach the terrestrial and aquatic environment by the application of manure or slurry to areas used agriculturally, or by pasture-reared animals excreting directly on the land, followed by surface run-off, driftage or leaching in deeper layers of the earth. The scientific interest in antimicrobially active compounds in manure and soil, but also in surface and ground water, has increased during the last decade. On the one side, scientific interest has focused on the behaviour of antibiotics and their fate in the environment, on the other hand, their impact on environmental and other bacteria has become an issue of research. Analytical methods have now been developed appropriately and studies using these new techniques provide accurate data on concentrations of antimicrobial compounds and their residues in different organic matters. Some antibiotics seem to persist a long time in the environment, especially in soil, while others degrade very fast. Not only the fate of these pharmaceuticals but their origin as well is an object of scientific interest. Besides human input via wastewater and other effluents, livestock production has been recognised as a source of contamination. One main concern with regard to the excessive use of antibiotics in livestock production is the potential promotion of resistance and the resulting disadvantages in the therapeutic use of antimicrobials. Since the beginning of antibiotic therapy, more and more resistant bacterial strains have been isolated from environmental sources showing one or multiple resistance. There have been several attempts to use antibiotic resistance patterns in different bacteria as indicators for various sources of faecal pollution. This review gives an overview of the available data on the present use of veterinary antibiotics in agriculture, on the occurrence of antibiotic compounds and resistant bacteria in soil and water and demonstrates the need for further studies.     

Veterinary use and antibiotic resistance

Globally, an estimated 50% of all antimicrobials serve veterinary purposes. Bacteria that inevitably develop antibiotic resistance in animals comprise food-borne pathogens, opportunistic pathogens and commensal bacteria. The same antibiotic resistance genes and gene transfer mechanisms can be found in the microfloras of animals and humans. Direct contact, food and water link animal and human habitats. The accumulation of resistant bacteria by the use of antibiotics in agriculture and veterinary medicine and the spread of such bacteria via agriculture and direct contamination are documented.     

Consequences of the widespread use of antibiotics

The cancer problem is increasing as life expectancy increases and greater portions of the populace live to the age at which cancer is more likely. Early diagnosis still is difficult. Even with modern methods and with considerable public education with regard to cancer, the disease is often not diagnosed until it is beyond the stage at which cure might be effected. The need for a serodiagnostic test for general screening purposes for cancer detection is tremendous. The major objective of cancer serodiagnostic test methods is to discover a general test that will detect cancer in a high percentage of cases while it is in an early stage; that will give few "false positive" results; that can be done in any laboratory; and that is simple and inexpensive. Many serodiagnostic tests for cancer have been published but none has proven worthy of being a good general test to detect cancer. Yet unless some serodiagnostic test which will be suitable for general screening purposes is developed, it is difficult to see how there can be much improvement in the early diagnosis of cancer, particularly internal cancer. It is hoped that an open-minded attitude will be maintained by physicians on this subject. Recent reports of such a test being developed are encouraging and it is hoped that continued investigations will be confirmatory.     

Inappropriate use of antibiotics in croup at three types of hospital.

Despite recent suggestions that bacterial infection is an increasingly important cause of serious croup, most authorities still consider croup a viral disease in which antibiotic therapy is unnecessary. To assess the frequency of antibiotic use in croup among children in hospital, we reviewed the records at three types of hospital in Ontario. Children with evidence of a concurrent infection that might be bacterial were considered to have received antibiotics appropriately. Whereas only 6% of cases at a university-affiliated children''s hospital were inappropriately treated with antibiotics, the proportions at a small rural community hospital staffed by general practitioners and a general hospital staffed by both pediatricians and general practitioners in a medium-sized city were 63% and 38%. Possible reasons for these differences are discussed.     

Rational and irrational use of antibiotics in a Canadian teaching hospital.

Parenteral therapy with gentamicin, cloxacillin, ampicillin and cephalothin was surveyed on a surgical, a gynecologic and medical ward of a teaching hospital. During a 3-month period 219 patients (12.9% of the total number admitted to the three wards) received at least one of the four antibiotics parenterally. Ampicillin and gentamicin were used most frequently on the three wards when the indication for therapy was either infection or empirical use. Cephalothin was used most frequently for prophylaxis in the gynecologic and surgical patients; no medical patient received this drug. Overall, therapy was assessed to be irrational in 42.0, 50.0 and 12.0% of the surgical, gynecologic and medical patients, respectively. Prophylaxis was the indication for therapy in 76.9 and 86.8% of the surgical and gynecologic patients, respectively, for whom the therapy was assessed to be irrational.     

The prophylactic use of antibiotics in cell culture

This article describes the historical development of the prophylactic use of antibiotics in cell culture as well as their effects on cells. The influence of antibiotics on cell morphology, cellular degeneration and cell death and cellular function is summarized. Cellular DNA as well as protein synthesis are affected which can lead to interference with, or even changes in, metabolic processes. Such effects must be considered in cell culture research. As antibiotics are used in multifold ways, the otherwise standardized conditions in cell culture are no longer comparable. The prophylactic use of antibiotics is rejected for scientific reasons.