title: Bovine mastitis Staphylococcus aureus: antibiotic susceptibility profile, resistance genes and molecular typing of methicillin-resistant and methicillin-sensitive strains in China.
abstract: The emergence of methicillin-resistant Staphylococcus aureus (MRSA) infection in dairy animals is of great concern for livestock and public health. The aim of present study was to detect new trends of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) towards antibiotic susceptibility, resistance genes and molecular typing by methods of disc diffusion, multiplex PCR assay and multilocus sequence typing (MLST). A total of 219 S. aureus strains were isolated from bovine mastitis cases from six provinces of China, including 34 MRSA strains. The results revealed that more than 70% isolated strains showed resistance to various antibiotics, and multiple-drugs resistance to more than five categories of antibiotics was found more common. The ermC was the most prevalent resistance gene, followed by other genes; however, ermA was the least frequently detected gene. Twenty-eight mecA-negative MRSA and six mecA-positive MRSA strains were detected, and in which three strains were ST97-MRSA-IV, others were ST965-MRSA-IV, ST6-MRSA-IV and ST9-MRSA-SCCmec-NT. The mecA-negative MRSA strains were found resistant to most of the antibiotics, and harbored aac(6')/aph(2''), aph(3')-III and tetM genes higher than MSSA strains. The resistance to most of the antibiotics was significantly higher in MRSA than in MSSA strains. The MLST profiles showed that these strains mainly belonged to CC5, CC398, CC121 and CC50 lineage, especially within ST97 and ST398, while some novel sequence types (ST2154, ST2165 and ST2166) were identified and deposited in the MLST database. This indicates that the resistance of S. aureus is becoming more complicated by changes in multi-drug resistance mechanism and appearance of mecA-negative MRSA isolates, and importantly, MRSA-IV strains in different MLST types are emerging.
authors.affiliation: College of Veterinary Medicine, China Agricultural University, Beijing 100193, China; Institute of Veterinary Medicine, Xinjiang Academy of Animal Science, Xinjiang Uyghur Autonomous Region, Urumqi 830000, China.
authors.forename: Dengfeng
authors.initials: D
authors.lastname: Wang
authors.affiliation: Institute of Veterinary Medicine, Xinjiang Academy of Animal Science, Xinjiang Uyghur Autonomous Region, Urumqi 830000, China.
authors.forename: Zhicai
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Lanzhou Institute of Husbandry and Pharmaceutical Science of CAAS, Lanzhou 730050, China.
authors.forename: Zuoting
authors.initials: Z
authors.lastname: Yan
authors.affiliation: Institute of Veterinary Medicine, Xinjiang Academy of Animal Science, Xinjiang Uyghur Autonomous Region, Urumqi 830000, China.
authors.forename: Jianyong
authors.initials: J
authors.lastname: Wu
authors.affiliation: College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
authors.forename: Tariq
authors.initials: T
authors.lastname: Ali
authors.affiliation: Institute of Veterinary Medicine, Xinjiang Academy of Animal Science, Xinjiang Uyghur Autonomous Region, Urumqi 830000, China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.affiliation: College of Veterinary Medicine, China Agricultural University, Beijing 100193, China. Electronic address: luyanli@cau.edu.cn.
authors.forename: Yanli
authors.initials: Y
authors.lastname: Lv
authors.affiliation: College of Veterinary Medicine, China Agricultural University, Beijing 100193, China. Electronic address: hanbo@cau.edu.cn.
authors.forename: Bo
authors.initials: B
authors.lastname: Han
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents; D002417:Cattle; D002681:China; D005260:Female; D005843:Geography; D008414:Mastitis, Bovine / Q000382:microbiology*; D016106:Methicillin Resistance / Q000235:genetics; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents
keywords: Bovine mastitis; MLST; MRSA; Resistance gene; SCCmec type; Staphylococcus aureus