The reducing effects of Flavophospholipol on antibiotic resistance and plasmid transfer – an
overview about recent findindings. (Die reduzierende Wirkung von Flavophospholipol auf die
Entstehung von Antibiotikaresistenzen sowie auf die Übertragung von Plasmiden – ein Überblick
über die neuesten Erkenntnisse.)

P. Ader *, P.J.G. Oostenbach – Unterschleißheim / Boxmeer

The demand for pork and poultry products is strongly influenced by the consumers concern for healthy and safe food. The topic of food safety mainly concentrates on Salmonella contamination and is recently joined by the topic of antimicrobial resistance due to the use of antimicrobial growth promoters (AMGP´s) in animal feed. Latest findings on Flavophospholipol, registered as AMGP for pigs, poultry and several other species, describe a reducing effect on the development of antibiotic resistance and on the frequency of plasmid transfer.

Method:

For the first investigation, conducted at the University of Maastricht (The Netherlands) by van den Boogard (2001), 168 piglets were infected per oral administration with non-pathogenic E. coli strains, with a known multi-resistance pattern. Four weeks later the animals feces were analysed for the occurence of E. coli and vancomycin resistant enterococci (VRE). Furthermore the isolated E. coli strains were tested for their sensitivity to various antibiotics (ampicilline, oxytetracycline, trimethoprime, sulphamethoxazole, ampicilline + oxytetracycline). After that the piglets were divided into three groups. Feed of group I was supplemented with 9 ppm Flavomycinä, feed of group II was supplemented with 15 ppm avoparcin and group III served as control. Just before being slaughtered animals feces was analysed again in the same manner as descrided above.
The other trial was conducted by Riedl et al. 2001. Three Vancomycin A resistant field strains of Enterococcus faecium were co-cultivated with some Enterococcus faecium strains which were still sensible to Vancomycin A. The transfer frequency of Vancomycin A resistance encoding plasmids was examined after giving various concentrations of flavophospholipol to the nutrient solutions. For control Vancomycin A itself was mixed into the cultivated solution in different concentrations.

Results:

The first study clearly shows an increase of antibiotic resistance of the isolated E. coli strains to all tested antibiotics in the control and in the avoparcin group. In the Flavomycinä group the occurence of antibiotic resistances was unchanged or slightly diminuished. The prevalence of VRE in the vancomycin-group increased significantly during the trial as compared to the control and flavophospholipol group.
The other experiment resulted in an decrease of the transfer of Vancomycin A resistance encoding plasmids in an dose dependent manner in the presence of flavophospholipol. In the presence of Vancomycin A this effect lacked.

Conclusion:

Flavophospholipol does not induce an antibiotic resistance to antibiotics used for veterinary or human therapy as it is not related to any antibiotic used for these purposes. Furthermore it is capable of reducing antibiotic resistance to other antibiotics. This effect seems to be yielded by interfering in the biosynthesis of the plasmid bridge (pylus) which is a prerequisite for the genetic transfer from one bacteria to another.

*Fa. Intervet Deutschland GmbH, Feldstr. 1a, D – 85716 Unterschleißheim