title: Molecular basis of rifampicin resistance in methicillin-resistant Staphylococcus pseudintermedius isolates from dogs.
abstract: BACKGROUND
  Methicillin-resistant Staphylococcus pseudintermedius (MRSP) often display resistance to almost all classes of antimicrobial agents used in veterinary medicine. In the present study, we investigated the emergence of rifampicin resistance in MRSP, the persistence of these isolates and identified the corresponding mutations in the rpoB gene.
  
  
  METHODS
  In addition to two rifampicin-resistant MRSP isolates from a multicentre study, consecutive MRSP isolates collected prior to and after rifampicin therapy from nine dogs at five Dutch veterinary hospitals were included in this study. The isolates were tested for resistance to rifampicin and other antimicrobial agents. The rifampicin resistance-determining region (RRDR) within the rpoB gene of the rifampicin-resistant and -susceptible isolates was amplified by PCR and sequenced. PFGE served to determine the genetic relationships of the MRSP isolates.
  
  
  RESULTS
  Two MRSP isolates of the multicentre study showed mutations at position 513 or 522 in the RRDR of the rpoB gene. In contrast to the rifampicin-susceptible isolates, all rifampicin-resistant MRSP isolates showed mutations at one or two of the amino acid positions 508, 509, 513, 516, 522, 526 and 531. In most strains, a single amino acid exchange was observed. PFGE analysis confirmed that the rifampicin-resistant MRSP isolates were indistinguishable from or closely related to the rifampicin-susceptible isolate obtained from the same dog prior to rifampicin application.
  
  
  CONCLUSIONS
  Therapy of MRSP infections with rifampicin results in the rapid emergence of rifampicin resistance and these isolates can persist for months. As a consequence, single therapy with rifampicin is not recommended.
authors: Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut (FLI), Neustadt-Mariensee, Germany.
authors: Kristina
authors: K
authors: Kadlec
authors: Engeline
authors: E
authors: van Duijkeren
authors: Jaap A
authors: JA
authors: Wagenaar
authors: Stefan
authors: S
authors: Schwarz
mesh_terms: D000818:Animals; D015373:Bacterial Typing Techniques; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D004283:Dog Diseases / Q000188:drug therapy / Q000382:microbiology*; D004285:Dogs; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D058889:Molecular Typing; D020125:Mutation, Missense; D016133:Polymerase Chain Reaction; D012293:Rifampin / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D013210:Staphylococcus / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D004269:DNA, Bacterial; D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit; D012293:Rifampin