Prevalence and molecular characterisation of highlevel gentamicin resistant enterococci isolated from animal sources and food in Germany

Alemán. Enterococcal strains isolated from materials of animal origin and food were examined with regardto their resistance behaviour against gentamicin. The minimal inhibition concentration(MIC) wasdetermined by the microdilution method (Sensititre®-system) and particularly for high-levelresistant strains with the Etest®. Four genes responsible for this kind of resistance ( aac(6')-Ieaph(2")-Ia, aph(2")-Ib, aph(2")-Ic, aph(2")-Id ) were investigated by PCR. All high-level gentamicinresistant strains (n = 9 with MIC values >500ìg/ml) only possessed the first mentioned gene. Theremaining three genes were neither detected for these strains nor for strains with MIC valuesfrom 32 - 256ìg/ml against gentamicin. Furthermore, a link to vancomycin resistance genes( vanA, vanB ) could not be seen by PCR examinations. The majority of the examined strainsshowed MIC values from 1ìg/ml to <64ìg/ml (n=754 of a total of 862 strains). The ninementioned high-level gentamicin resistant strains were subsequently well-investigated bymolecular biological methods. Their species affiliation were determined by both microbiologicaland biochemical test schemes and by PCR. Due to the results the strains were classified as E.gallinarum and E. faecalis. Dependent on their species they carried the same resistance patternsagainst 16 selected antimicrobial agents. Fingerprint examinations using PFGE showedcomparable fragment patterns for all E. faecalis strains independently from material (minced meatfrom cattle, pig, and ham from pork) and from the region. However only one high-level resistant E. gallinarum strain from poultry showed a distinguished fragment pattern. For all other high-levelresistant E. gallinarum strains a fragment pattern could neither be generated by the restrictionenzyme Sma I nor by Apa I. The results of this study revealed a minor frequency of gentamicinhigh-level resistant strains.