title: Genomic characteristics of Staphylococcus aureus strains associated with high within-herd prevalence of intramammary infections in dairy cows.
abstract: Staphylococcus aureus is one of the most important causes of mastitis in dairy cattle. Based on previous research, Staph. aureus genotypes with different pathogenic and contagious properties can cause intramammary infection (IMI) and coexist in the same herd. Our study aimed to compare Staph. aureus strains from herds that differed in IMI prevalence using different molecular approaches such as ribosomal spacer (RS)-PCR, multilocus sequence typing (MLST), spa typing, ribotyping, pulsed-field gel electrophoresis (PFGE), and multiplex PCR. For this purpose, 31 dairy herds with Staph. aureus IMI were selected, and 16 of these were chosen for a comparison study: the 8 high-prevalence (HP) herds had Staph. aureus IMI prevalence >28% and the 8 low-prevalence (LP) herds had an IMI prevalence <4%. A total of 650 isolates of Staph. aureus from mammary quarters of all positive cows were genotyped with RS-PCR, a technique based on amplification of a portion of the intergenic spacer 16S-23S rRNA, and a subset of 54 strains was also analyzed by multiplex PCR, ribotyping, PFGE, MLST, and spa typing. The RS-PCR analysis revealed 12 different profiles. Staphylococcus aureus strains isolated from 5 out of 8 HP herds showed a profile identical to the genotype B (GTB), described in previous studies as being strongly associated with high within-herd prevalence of Staph. aureus mastitis and the presence of the genes coding for enterotoxins sea, sed, and sej, a long x-region of spa gene, and 3 lukE fragments. Moreover, all strains isolated in the HP herds possessed genes coding for staphylococcal enterotoxins. In LP herds, a limited number of strains of 6 genotypes, different from those isolated in HP herds, were identified and GTB was not found. Within these genotypes, 4 strains were positive for the mecA gene. Preliminary results and comparison with other genotyping methods confirmed that genotyping by RS-PCR is an accurate, rapid, and inexpensive tool for future field studies on Staph. aureus mastitis strains and generates clinically relevant results.
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, via Einstein, 26900 Lodi, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Cremonesi
authors.affiliation: Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia, Sezione di Lodi, via Einstein, 26900 Lodi, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Pozzi
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, via Einstein, 26900 Lodi, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Raschetti
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, via Einstein, 26900 Lodi, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Bignoli
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, via Einstein, 26900 Lodi, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Capra
authors.affiliation: Agroscope, Institute for Food Sciences (IFS), Schwarzenburgstrasse 161, CH-3003, Bern, Switzerland.
authors.forename: H U
authors.initials: HU
authors.lastname: Graber
authors.affiliation: Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia, Sezione di Lodi, via Einstein, 26900 Lodi, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Vezzoli
authors.affiliation: Dipartimento di Scienze Veterinarie e Sanità Pubblica, Università degli Studi di Milano, via Celoria, 20133 Milan, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Piccinini
authors.affiliation: Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia, Reparto Tecnologie Acidi Nucleici Applicate agli Alimenti, via Bianchi, 25124 Brescia, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Bertasi
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, via Einstein, 26900 Lodi, Italy; Parco Tecnologico Padano, Via Einstein, 26900 Lodi, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Biffani
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, via Einstein, 26900 Lodi, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Castiglioni
authors.affiliation: Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia, Sezione di Lodi, via Einstein, 26900 Lodi, Italy. Electronic address: mariovittorio.luini@izsler.it.
authors.forename: M
authors.initials: M
authors.lastname: Luini
mesh_terms: D000818:Animals; D002417:Cattle; D004269:DNA, Bacterial / Q000032:analysis; D005260:Female; D007558:Italy / Q000453:epidemiology; D008414:Mastitis, Bovine / Q000453:epidemiology* / Q000382:microbiology; D015995:Prevalence; D017422:Sequence Analysis, DNA / Q000662:veterinary; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial
keywords: Staphylococcus aureus; genotyping; mastitis; virulence gene