Summary
Between 2002 and 2004, indicator bacteria (Enterococcus,
Escherichia coli)
isolated from 799 bulk milk samples were tested against thirty
different antibiotics for resistance. Systematic sampling over space
(every eighth Styrian cattle breeding farm on an unaligned grid) was
conducted within the scope of the bovine virus diarrhoea (BVD) control
programme. Results of resistance testing were assigned to their respective
farms by means of LFBIS (information system for agricultural and forestry
enterprises: land- und forstwirtschaftlichen Betriebsinformationssystem)
numbers. The distribution of resistance was evaluated using a geographic
information system. To show the application of spatial point pattern
analysis, results of resistance testing of Enterococcus to
tetracycline and streptomycin is presented. Kernel density estimation
and K functions were used to determine whether the distribution
of the resistant samples was clustered, relative to isolates from
samples that were sensitive to these antibiotics. Initially, spatial
clustering of resistance (tetracycline and streptomycin separately)
was investigated. The space-time scan statistic was subsequently used
to search for space-time clusters of resistance for both antibiotics
simultaneously.
Keywords
Austria,
Bovine virus diarrhoea, Escherichia coli, Geographic information
system, K function, Kernel density, Space-time scan statistics,
Spatial point pattern.
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