title: Coexistence of heavy metal and antibiotic resistance within a novel composite staphylococcal cassette chromosome in a Staphylococcus haemolyticus isolate from bovine mastitis milk.
abstract: The structure of a composite staphylococcal cassette chromosome (SCC) carried by a methicillin-resistant Staphylococcus haemolyticus (NW19A) isolated from a bovine milk sample was analyzed. The formation of the circular forms of both single SCC elements and composite SCC elements was detected in NW19A. Twenty heavy metal and antibiotic resistance-related genes coexisted in this composite SCC, suggesting that these genes might be coselected under environmental pressure. The mec gene complex in NW19A, designated type C3, is different from classic C1 or C2 gene complexes structurally and likely evolves differently. Furthermore, results from alignment of the SCC composite island of NW19A with 50 related sequences from different staphylococcal strains provided additional evidence to support the notion that coagulase-negative staphylococci (CoNS) are the original host of heavy metal resistance genes among staphylococci. Given that a SCC composite island could transfer freely among different staphylococcal species from different hosts, more attention should be paid to contamination with heavy metals and antibiotics in dairy farming environments, including wastewater, soil, feces, and feed.
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, People's Republic of China.
authors.forename: Huping
authors.initials: H
authors.lastname: Xue
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, People's Republic of China.
authors.forename: Zhaowei
authors.initials: Z
authors.lastname: Wu
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, People's Republic of China.
authors.forename: Longping
authors.initials: L
authors.lastname: Li
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, People's Republic of China.
authors.forename: Fan
authors.initials: F
authors.lastname: Li
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, People's Republic of China.
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, People's Republic of China Department of Animal Science, McGill University, Quebec, Canada xin.zhao@mcgill.ca.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhao
mesh_terms: D000818:Animals; D002417:Cattle; D002876:Chromosomes, Bacterial / Q000235:genetics; D019295:Computational Biology; D004352:Drug Resistance, Microbial; D008414:Mastitis, Bovine / Q000382:microbiology*; D019216:Metals, Heavy / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D041162:Staphylococcus haemolyticus / Q000187:drug effects* / Q000235:genetics
chemical_list: D019216:Metals, Heavy