title: Emergence of multidrug-resistant Proteus mirabilis in a long-term care facility in Croatia.
abstract: BACKGROUND
  An increased frequency of Proteus mirabilis isolates resistant to expanded-spectrum cephalosporins was observed recently in a long-term care facility in Zagreb (Godan). The aim of this study was the molecular characterization of resistance mechanisms to new cephalosporins in P. mirabilis isolates from this nursing home.
  
  
  METHODS
  Thirty-eight isolates collected from 2013-2015 showing reduced susceptibility to ceftazidime were investigated. Antibiotic susceptibilities were determined by broth microdilution method. Inhibitor-based tests were performed to detect extended-spectrum (ESBLs) and AmpC β-lactamases. AmpC β-lactamases were characterized by polymerase chain reaction (PCR) followed by sequencing of bla ampC genes. Quinolone resistance determinants (qnr genes) were characterized by PCR. Genotyping of the isolates was performed by repetitive element sequence (rep)-PCR and pulsed-field gel electrophoresis (PFGE).
  
  
  RESULTS
  Presence of an AmpC β-lactamase was confirmed in all isolates by combined-disk test with phenylboronic acid. All isolates were resistant to amoxicillin alone and combined with clavulanate, cefotaxime, ceftriaxone, cefoxitin, and ciprofloxacin; but susceptible to cefepime, imipenem, and meropenem. PCR followed by sequencing using primers targeting bla ampc genes revealed CMY-16 β-lactamase in all but one strain. Bla cmy-16 was carried by a non-conjugative plasmid which did not belong to any known plasmid-based replicon typing (PBRT) group. Rep-PCR identified one large clone consisting of 15 isolates, three pairs or related isolates, one triplet, and four singletons. PFGE confirmed the clonality of the isolates.
  
  
  CONCLUSIONS
  This is the first report of multidrug resistant P. mirabilis in a nursing home in Croatia. Cephalosporin resistance was due to plasmid-mediated AmpC β-lactamase CMY-16.
authors.affiliation: Department of Microbiology, School of Medicine, University of Zagreb, Šalata 3, Zagreb, Croatia. branka.bedenic@kbc-zagreb.hr.|Clinical Department for Clinical and Molecular Microbiology, Clinical Hospital Centre Zagreb, Kišpatićeva 12, 10000, Zagreb, Croatia. branka.bedenic@kbc-zagreb.hr.
authors.forename: Branka
authors.initials: B
authors.lastname: Bedenić
authors.affiliation: Clinical Department for Clinical and Molecular Microbiology, Clinical Hospital Centre Zagreb, Kišpatićeva 12, 10000, Zagreb, Croatia.
authors.forename: Nataša
authors.initials: N
authors.lastname: Firis
authors.affiliation: Department for Gynecology and Obstetrics, School of Medicine, University of Zagreb, University Hospital Center Zagreb, Zagreb, Croatia.
authors.forename: Vesna
authors.initials: V
authors.lastname: Elveđi-Gašparović
authors.affiliation: Department for Microbiology, Public Health Institute of Dubrovnik-Neretva County, Dubrovnik, Croatia.
authors.forename: Marija
authors.initials: M
authors.lastname: Krilanović
authors.affiliation: Department of Microbiology and Infectious Diseases with Clinic, Faculty of Veterinary Medicine, University of Zagreb, Zagreb, Croatia.
authors.forename: Krešimir
authors.initials: K
authors.lastname: Matanović
authors.affiliation: Department of Microbiology and Infectious Diseases with Clinic, Faculty of Veterinary Medicine, University of Zagreb, Zagreb, Croatia.
authors.forename: Iva
authors.initials: I
authors.lastname: Štimac
authors.affiliation: Institute for Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Josefa
authors.initials: J
authors.lastname: Luxner
authors.affiliation: Zagreb Institute of Public Health "Andrija Štampar", School of Medicine, University of Zagreb, Zagreb, Croatia.
authors.forename: Jasmina
authors.initials: J
authors.lastname: Vraneš
authors.affiliation: Polyclinic "Dr Zora Profozić", Zagreb, Croatia.
authors.forename: Tomislav
authors.initials: T
authors.lastname: Meštrović
authors.affiliation: Institute for Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Gernot
authors.initials: G
authors.lastname: Zarfel
authors.affiliation: Institute for Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Andrea
authors.initials: A
authors.lastname: Grisold
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage; D001426:Bacterial Proteins / Q000378:metabolism*; D021821:Communicable Diseases, Emerging / Q000382:microbiology*; D017523:Croatia; D004198:Disease Susceptibility / Q000382:microbiology; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D006801:Humans; D008134:Long-Term Care / Q000706:statistics & numerical data; D009735:Nursing Homes / Q000706:statistics & numerical data; D011512:Proteus Infections / Q000382:microbiology*; D011513:Proteus mirabilis / Q000145:classification / Q000201:enzymology* / Q000235:genetics*; D013045:Species Specificity; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C048795:AmpC beta-lactamases; D001618:beta-Lactamases
keywords: AmpC β-lactamases; CMY-16; Clonal dissemination; Conjugative plasmid; Proteus mirabilis