title: Emergence of quinupristin/dalfopristin resistance among livestock-associated Staphylococcus aureus ST9 clinical isolates.
abstract: Quinupristin/dalfopristin (Q/D) is a valuable alternative to vancomycin for the treatment of meticillin-resistant Staphylococcus aureus (MRSA) infections. However, not long after Q/D was approved, bacteria with resistance to this newer antimicrobial agent were reported. To investigate the prevalence of Q/D resistance, a total of 1476 non-duplicate S. aureus isolates, including 775 MRSA, from a Chinese tertiary hospital were selected randomly from 2003 to 2013. Of the 775 MRSA, 3 (0.4%) were resistant to Q/D. All meticillin-susceptible S. aureus were susceptible to Q/D. The prevalence of Q/D resistance among S. aureus was 0.2% (3/1476). The three isolates with Q/D resistance had the same antimicrobial resistance profile, except for cefaclor and chloramphenicol. All three Q/D-resistant MRSA were positive for five streptogramin B resistance genes (ermA, ermB, ermC, msrA and msrB) and two streptogramin A resistance genes (vatC and vgaA) as determined by PCR and DNA sequencing. MRSA WZ1031 belonged to ST9-MRSA-SCCmecV-t899, whilst MRSA WZ414 and WZ480 belonged to ST9-MRSA-SCCmecNT(non-typeable)-t899. ST9 has been reported predominantly in livestock-associated (LA) MRSA in some Asian countries. The three patients with these MRSA isolates were not livestock handlers and did not keep close contact with livestock. The origin of these important LA-MRSA isolates causing human infections is not known. Taken together, Q/D resistance, which was caused by a combination of ermA-ermB-ermC-msrA-msrB-vatC-vgaA, was first found among S. aureus clinical isolates in China. The present study is the first report of the emergence of human infections caused by ST9 LA-MRSA isolates with Q/D resistance.
authors.affiliation: Department of Laboratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: Fangyou
authors.initials: F
authors.lastname: Yu
authors.affiliation: Department of Respiratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: Chaohui
authors.initials: C
authors.lastname: Lu
authors.affiliation: Department of Respiratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: Yunling
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Laboratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: He
authors.initials: H
authors.lastname: Sun
authors.affiliation: Department of Laboratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: Yongpeng
authors.initials: Y
authors.lastname: Shang
authors.affiliation: Department of Laboratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Department of Laboratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: Departments of Medicine and Microbiology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Qin
authors.affiliation: Departments of Medicine and Microbiology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Parsons
authors.affiliation: Department of Respiratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Huang
authors.affiliation: Department of Respiratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China.
authors.forename: Yuping
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Laboratory Medicine, The Second Affiliated Hospital of Nanchang University, Nanchang 336000, China.
authors.forename: Longhua
authors.initials: L
authors.lastname: Hu
authors.affiliation: Department of Respiratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, China. Electronic address: 38805@163.com.
authors.forename: Liangxing
authors.initials: L
authors.lastname: Wang
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002681:China; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D008875:Middle Aged; D058889:Molecular Typing; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D014769:Virginiamycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D014769:Virginiamycin; C062940:quinupristin-dalfopristin
keywords: Human infection; Livestock-associated; Meticillin-resistant Staphylococcus aureus; Quinupristin/dalfopristin; Resistance