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Drees, Nathalie (2012): Untersuchung auf antimikrobielle Resistenzen und Vorkommen von Extended‐Spectrum‐Beta‐Lactamasen bei Shigatoxin‐Gen tragenden Escherichia coli. Dissertation, LMU München: Faculty of Veterinary Medicine
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Abstract

Shiga toxin producing E. coli (STEC) can occur either as part of the normal intestinal gut flora or as pathogenic agents in animals and humans causing serious disease in humans. In the present study we determined the frequencies of resistance against 14 different antimicrobial agents of in total 235 STEC isolates from farm cattles, wild ruminants and food products. This susceptibility testing was performed using broth microdilution method. Overall, the most frequent resistances were detected against streptomycin, sulfonamides, and tetracycline. Furthermore, 30 of the 36 resistant isolates detected in this study were multi drug resistant against two or more antimicrobial agents. Another focus of this study was the detection of potential ESBL producing isolates, which show resistance to the enlarged spectrum of β‐lactam antibiotics such as cephalosporins of the 3rd and 4th generation. Therefore, all STEC isolates were examined both phenotypically and genotypically using microdilution method and PCR, respectively. Performing a sequential analysis the majority (8/10) of those isolates were non‐ESBL blaTEM‐1. However, using microdilution method detectably minor susceptibility to 3rd and 4th generation cephalo‐sporins in five (2.1%) out of the 235 studied STEC isolates was observed. Overall, antimicrobial susceptibility of STEC isolates could be detected in isolates from domestic ruminants as well as in a very small proportion of wild ruminant isolates.