title: Presence of mecA-positive multidrug-resistant Staphylococcus epidermidis in bovine milk samples in Brazil.
abstract: Bacteria of the genus Staphylococcus are one of the major pathogens causing bovine mastitis. In recent decades, resistance of this genus to oxacillin (methicillin) has been a matter of concern due to the possibility of reducing the effectiveness of mastitis treatments and the transfer of resistance determinants to other bacteria. Oxacillin resistance was studied in 170 staphylococci from bovine milk samples, including 79 Staphylococcus aureus and 91 coagulase-negative staphylococci (CNS). The susceptibility profile of 10 antimicrobial agents used in veterinary practice was determined by the Etest method. In addition to the Etest, the phenotypic characterization of oxacillin resistance was tested using the cefoxitin disk diffusion test. All isolates were screened by PCR to detect the mecA gene in 2 different regions of the gene. The isolates with an oxacillin minimum inhibitory concentration ≥0.5 µg/mL or resistant to cefoxitin were identified by sequencing a 536-bp fragment of the 16S rRNA gene. This group of isolates was also evaluated for the presence of blaZ and mecC genes. Molecular analysis of the mecA gene was carried out by typing of the staphylococcal cassette chromosome mec (SCCmec). The relatedness of the mecA-positive isolates was evaluated by macrorestriction of chromosomal DNA followed by pulsed-field gel electrophoresis. With the exception of penicillin and oxacillin, 86% of the isolates showed susceptibility to cephalothin, gentamicin, erythromycin, sulfonamide, trimethoprim-sulfamethoxazole, and tetracycline. All S. aureus isolates were susceptible to oxacillin, whereas 47% (n=43) of the CNS isolates were resistant. The CNS isolates showed a higher resistance to cephalothin, erythromycin, tetracycline, and gentamicin in comparison with S. aureus. The mecA gene was only detected in 10 CNS isolates, identified as Staphylococcus epidermidis, and classified into 3 pulsotypes (A, B, and C) and 4 subtypes (A1, B1, B2, and B3). Among the isolates with an oxacillin resistance phenotype, 12 were positive for the blaZ gene, and 9 of them were mecA-positive. Two of the oxacillin-resistant isolates amplified the mecA homolog gene of Staphylococcus sciuri and none amplified mecC. Three SCCmec types, I, IV, and V, were found. Our results suggest that Staphylococcus epidermidis can be a reservoir for mecA for other Staphylococcus species. Studies investigating the molecular and phenotypic profile of antimicrobial resistance in staphylococcal species should be performed for controlling the spread of resistance and the selection of appropriate therapeutic measures.
authors.affiliation: Federal University of Juiz de Fora, Rua José Lourenço Kelmer, 36036-330 Juiz de Fora, Minas Gerais, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Fernandes Dos Santos
authors.affiliation: Embrapa Dairy Cattle Research Center, Rua Eugênio do Nascimento, 610, Bairro Dom Bosco, 36038-330 Juiz de Fora, MG, Brazil.
authors.forename: Letícia Caldas
authors.initials: LC
authors.lastname: Mendonça
authors.affiliation: Embrapa Dairy Cattle Research Center, Rua Eugênio do Nascimento, 610, Bairro Dom Bosco, 36038-330 Juiz de Fora, MG, Brazil.
authors.forename: Daniele Ribeiro de Lima
authors.initials: DRL
authors.lastname: Reis
authors.affiliation: Embrapa Dairy Cattle Research Center, Rua Eugênio do Nascimento, 610, Bairro Dom Bosco, 36038-330 Juiz de Fora, MG, Brazil.
authors.forename: Alessandro de Sá
authors.initials: AS
authors.lastname: Guimarães
authors.affiliation: Embrapa Dairy Cattle Research Center, Rua Eugênio do Nascimento, 610, Bairro Dom Bosco, 36038-330 Juiz de Fora, MG, Brazil.
authors.forename: Carla Christine
authors.initials: CC
authors.lastname: Lange
authors.affiliation: Embrapa Dairy Cattle Research Center, Rua Eugênio do Nascimento, 610, Bairro Dom Bosco, 36038-330 Juiz de Fora, MG, Brazil.
authors.forename: João Batista
authors.initials: JB
authors.lastname: Ribeiro
authors.affiliation: Embrapa Dairy Cattle Research Center, Rua Eugênio do Nascimento, 610, Bairro Dom Bosco, 36038-330 Juiz de Fora, MG, Brazil.
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Machado
authors.affiliation: Embrapa Dairy Cattle Research Center, Rua Eugênio do Nascimento, 610, Bairro Dom Bosco, 36038-330 Juiz de Fora, MG, Brazil. Electronic address: maria.brito@embrapa.br.
authors.forename: Maria Aparecida Vasconcelos Paiva
authors.initials: MAVP
authors.lastname: Brito
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001938:Brazil / Q000453:epidemiology; D002417:Cattle; D002440:Cefoxitin / Q000494:pharmacology; D005260:Female; D008414:Mastitis, Bovine / Q000453:epidemiology / Q000382:microbiology*; D016106:Methicillin Resistance / Q000235:genetics*; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D008892:Milk / Q000382:microbiology*; D010068:Oxacillin / Q000494:pharmacology; D010400:Penicillin G / Q000494:pharmacology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D013212:Staphylococcus epidermidis / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents; D012336:RNA, Ribosomal, 16S; D002440:Cefoxitin; D010400:Penicillin G; D010068:Oxacillin
keywords: SCCmec; antimicrobial resistance; mecA; methicillin-resistant staphylococci