Multilocus sequence typing of Arcobacter butzleri isolates collected from dairy plants and their products, and comparison with their PFGE types.
OBJECTIVE
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.


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 0·937, 0·953 and 0·965 respectively. The adjusted Wallace coefficients between MLST and PFGE as well as PFGE and MLST were 0·535 and 0·720 respectively; the adjusted Rand coefficient was 0·612.


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.


CONCLUSIONS
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.
Department of Agricultural and Food Sciences, University of Bologna, Ozzano dell'Emilia, Italy.
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De Cesare
Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata, Putignano, Italy.
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Parisi
Department of Veterinary Medical Sciences, University of Bologna, Ozzano dell'Emilia, Italy.
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Giacometti
Department of Veterinary Medical Sciences, University of Bologna, Ozzano dell'Emilia, Italy.
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Serraino
Department of Veterinary Medical Sciences, University of Bologna, Ozzano dell'Emilia, Italy.
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Piva
Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata, Putignano, Italy.
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Caruso
Department of Veterinary Medicine, University of Sassari, Sassari, Italy.
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De Santis
Department of Agricultural and Food Sciences, University of Bologna, Ozzano dell'Emilia, Italy.
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Manfreda
D000483:Alleles; D020640:Arcobacter / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D015373:Bacterial Typing Techniques / Q000379:methods*; D003611:Dairy Products / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods*; D005511:Food Handling / Q000295:instrumentation; D005838:Genotype; D058885:Multilocus Sequence Typing / Q000379:methods*
Arcobacter butzleri; concordance between genotyping methods; dairy products and dairy plants; multi locus sequence typing; pulsed-field gel electrophoresis