Antibiotic resistance genes may be considered as environmental pollutants if anthropogenic emission
and manipulations increase their prevalence above usually occurring background levels. The prevalence
of aph(30)-IIa/nptII and aph(30)-IIIa/nptIII e frequent marker genes in plant biotechnology conferring
resistance to certain aminoglycosides e was determined in Austrian soils from 100 maize and potato
fields not yet exposed to but eligible for GMO crop cultivation. Total soil DNA extracts were analysed by
nptII/nptIII-specific TaqMan real time PCR. Of all fields 6% were positive for nptII (median: 150 copies/g
soil; range: 31e856) and 85% for nptIII (1190 copies/g soil; 13e61600). The copy-number deduced
prevalence of nptIII carriers was 14-fold higher compared to nptII. Of the cultivable kanamycin-resistant
soil bacteria 1.8% (95% confidence interval: 0e3.3%) were positive for nptIII, none for nptII (0e0.8%). The
nptII-load of the studied soils was low rendering nptII a typical candidate as environmental pollutant
upon anthropogenic release into these ecosystems.