Multilocus Sequence Typing of Arcobacter butzleri isolates collected from dairy plants and their products, and comparison with their PFGE types

Aims: The present study aimed to determine, by multilocus sequence type
(MLST), the heterogeneity level of Arcobacter butzleri isolates and to compare
MLST and pulsed-field gel electrophoresis (PFGE) in terms of discriminatory
power (DI) as well as unidirectional and bi-directional concordance.
Methods and Results: Arcobacter butzleri isolates (N = 133) from dairy
products and environmental samples, collected from dairy plants, were
characterized by MLST and PFGE with SacII and classified in 29 sequence
types (STs), 47 PFGE and 62 type strains (TS). Among the 119 alleles, 19 were
previously unreported and the same for all the STs but two. A significant
linkage disequilibrium was detected when the complete ST data set was
analysed The DIs of MLST, PFGE and their combination were 0937, 0953
and 0965 respectively. The adjusted Wallace coefficients between MLST and
PFGE as well as PFGE and MLST were 0535 and 0720 respectively; the
adjusted Rand coefficient was 0612.
Conclusions: The A. butzleri studied population showed recombination to
some degree. PFGE showed a DI higher than MLST. Both methods presented
good concordance. The TS analysis seems to show persistence of the same
strain on time and possible cross-contaminations between food and
environmental sites.
Significance and Impact of the Study: This study provides insights in the
A. butzleri population found in raw milk, cheese, and dairy production plants.
The data suggest that MLST and PFGE genotypes correlate reasonably well,
although their combination results in optimal resolution.