Molecular characterization and clonal diversity of methicillin-susceptible Staphylococcus aureus in milk of cows with mastitis in Brazil.
Mastitis is an important disease for the dairy industry worldwide, causing economic losses and reducing milk quality and production. Staphylococcus aureus is a worldwide agent of this intramammary infection, which also causes foodborne diseases. The objective of this study was to determine the frequency of methicillin-susceptible Staphylococcus aureus (MSSA) isolates in milk of mastitis cows in Brazil and to analyze the genetic lineages and the content of antimicrobial resistance genes and virulence factors among these isolates. Fifty-six MSSA isolates were recovered from 1,484 milk samples (positive for the California mastitis test) of 518 cows from 11 different farms in Brazil (representing 51% of total Staph. aureus obtained), and they were further characterized. Methicillin-susceptible Staphylococcus aureus were isolated from 3.7% of California mastitis test-positive tested milk samples and from 6.2% of tested mastitic cows. Methicillin-susceptible Staphylococcus aureus isolates were characterized by spa typing, agr typing, and multilocus sequence typing, and resistance and virulence traits were investigated by PCR. Seven spa types were identified among MSSA (% of isolates): t127 (44.6), t605 (37.5), t002, t1784, t2066 (1.8), and 2 new ones: t10856 (10.7) and t10852 (1.8). Five distinct sequence types (ST) were detected (% of isolates): ST1 (46.4), ST126 (37.5), ST133 (10.7), ST5 (3.6), and a novel ST registered as ST2493 (1.8). Resistances were detected for streptomycin, chloramphenicol, and tetracycline. One strain contained the chloramphenicol resistance gene (fexA; included within transposon Tn558) and 3 strains contained the tetracycline resistance gene [tet(K)]. Methicillin-susceptible Staphylococcus aureus strains were susceptible to most of the antibiotics studied and lacked the virulence genes of Panton-Valentine leukocidin (lukF/S-PV), toxic shock syndrome toxin 1 (tst), exfoliative toxin A (eta), and exfoliative toxin B (etb), as well as the genes of the immune evasion cluster. Methicillin-susceptible Staphylococcus aureus isolates were detected in a relatively low proportion of cows with mastitis (6.2%) and recovered isolates presented high diversity of genetic lineages, with CC1 and CC126 the predominant clonal complexes, and CC133 also being detected. Larger epidemiological studies with molecular characterization of isolates are required to deepen the knowledge on the circulating genetic lineages among the cow population with mastitis.
Department of Microbiology and Immunology, SP, Brazil.
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Silva
Department of Hygiene Veterinary and Public Health, Universidade Estadual Paulista (UNESP), Botucatu 18.618-970, SP, Brazil.
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Guimarães
Department of Hygiene Veterinary and Public Health, Universidade Estadual Paulista (UNESP), Botucatu 18.618-970, SP, Brazil.
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Manzi
Department of Microbiology and Immunology, SP, Brazil.
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Budri
Department of Food and Agriculture, University of La Rioja, 26006 Logroño, Spain.
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Gómez-Sanz
Department of Food and Agriculture, University of La Rioja, 26006 Logroño, Spain.
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Benito
Department of Hygiene Veterinary and Public Health, Universidade Estadual Paulista (UNESP), Botucatu 18.618-970, SP, Brazil.
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Langoni
Department of Microbiology and Immunology, SP, Brazil.
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Rall
Department of Food and Agriculture, University of La Rioja, 26006 Logroño, Spain. Electronic address: carmen.torres@unirioja.es.
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Torres
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015373:Bacterial Typing Techniques; D001938:Brazil; D002417:Cattle; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005260:Female; D014644:Genetic Variation; D008414:Mastitis, Bovine / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D058885:Multilocus Sequence Typing; D013203:Staphylococcal Infections / Q000382:microbiology / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D037521:Virulence Factors / Q000235:genetics
D000900:Anti-Bacterial Agents; D037521:Virulence Factors
Staphylococcus aureus; mastitis; methicillin susceptibility; spa typing