S 20

CHRONICAL VIRAL HEPATITIS

M. Peck-Radosavljevic
Associate Professor of Medicine, Dept. of Gastroenterology and Hepatology, Medical University of Vienna, Austria

With over 500 million infected people worldwide, chronic viral hepatitis B and C are among the most prevalent chronic viral infections today, causing cirrhosis, liver failure, and hepatocellular carcinoma.
Interferon (IFN)-based drug therapy has been the preferred treatment for most of the last decade with variable efficacy. For treatment of chronic hepatitis B, the advent of the nucleoside analogue lamivudine marked a significant change in the antiviral strategy but rapid emergence of mutant HBV-strains has dampened enthusiasm lately. With the advent of the new nucleoside analogues adefovir dipivoxil and tenofovir among others with a markedly improved resistance profile, effective antiviral therapy is again available.
IFN-alpha / ribavirin combination therapy is still the standard treatment for chronic hepatitis C. Conventional IFN’s have been substituted completely in the last two years by pegylated IFN’s for reasons of efficacy and patient preference. Marked progress has been achieved in early identification of potential non-responders to therapy and with tailoring treatment dose and duration to viral subtype. Still, for the most prevalent viral subtype in the western world, the lasting success rate after one year of combination antiviral therapy barely reaches 50%. This could maybe be improved to 60% by better patient adherence to therapy, which would also require improved drug formulations with less side effects but prospective studies are lacking.
Other novel therapies like serine protease inhibitors for HCV have been shown to exhibit excellent short-term antiviral activity in early clinical studies but no efficacy and resistance data have been presented so far. With the recent development of an HCV-replicon system, new antiviral agents like helicase- or polymerase-inhibitors or specific antisense strategies can finally be tested in vitro. Another approach in early clinical development is therapeutic vaccination against HCV. With several clinical trials in early stages, the verdict on these strategies is still out.

S 21

SCIENTIFIC EVIDENCE: PROOF AGAINST USE OF ANTIBIOTICS AS FEED ADDITIVES

W. Witte, I. Klare and G. Werner
Wernigerode, Germany

Antibiotics had been used for nearly 40 years as feed additives in animal husbandry and exerted an instant selective pressure in favour of antibiotic resistant bacteria and their transferable resistance genes. When oxytetracycline was replaced as feed additive (growth promoter) by the streptothricine antibiotic nourseothricine by 1983 in East Germany, we performed a large prospective study on emergence and spread of sat-genes (streptothricine acetyl transferase).
Resistant E. coli possessing this gene on transposons of the Tn7 family were first seen in pigs, then in the intestinal flora of healthy humans in urban communities, in uropathogenic E. coli and even in Shigella sonnei.
In the mid 1990s glycopeptide resistant E. faecium was detected in animal faeces from pigs and chicken receiving avoparcin as feed additive. The same resistance gene (vanA) and type of transferable elements was also found in E. faecium from meat products from healthy nonhospitalized humans and from nosocomial infections which indicates to the route of transfer. The same results were obtained for streptogramin resistance and spread of vatD and vatE genes even before any clinical use of streptogramin antibiotics in humans.

S 22

FEED ADDITIVES AND ANTIBIOTIC USE IN HORTICULTURE: SITUATION IN AUSTRIA

F. Allerberger, P. Fida, R. Grossgut, H. Würzner
Institute for Hygiene and Social Medicine, University of Innsbruck, Austria
Austrian Agency for Health and Food Safety, Vienna, Austria

In 2002 the EU Agricultural Council agreed to phase out all antibiotics as growth promoters by 2006. In Austria, the overall use of growth-promoting antibiotics has already decreased by 26% as compared to 1997. The amount of antimicrobials (active ingredients in kg) used as growth promoters totaled 12,030 kg in 2002 (salinomycin sodium 9,612 kg; avilamycin 2,180 kg; flavophospholipol 208 kg; monensin sodium
30 kg). In the same year 36,325 kg antibiotics were employed for human medicine. According to FEDESA, in 1999 farm animals consumed 4,700 tonnes (35%) of all the antibiotics administered in the European Union, while humans consumed 8,500 tonnes (65%). Austria is one of those countries where antibiotics are not generally approved for use against plant disease in forestry, agronomy or horticulture. So far, antibiotics were employed only once: in 1998 12 kg Plantomycin® (active ingredient of streptomycin-sulfate: 212 g/kg) were imported into the province of Vorarlberg, with 8 kg being actually used for the treatment of apple tree cultures against fire blight, a major disease of apples and pears caused by Erwinia amylovora. In Austria 11.54 kg streptomycin (as its sulfate) were legally imported in 2002 for use in human medicine. While it is widely agreed that antibiotics used for therapeutic purposes in human or veterinary medicine should not be generally approved for use in agronomy or horticulture, there is also a need for mechanisms to be put in place whereby streptomycin is available with adequate safeguards for the control of fire blight.