Emergence of multidrug-resistant Proteus mirabilis in a long-term care facility in Croatia

• Published in: Wiener Klinische Wochenschrift Vol. 128; no. 11-12; pp. 404 - 413
• Main Authors: Bedenić, Branka, Firis, Nataša, Elveđi-Gašparović, Vesna, Krilanović, Marija, Matanović, Krešimir, Štimac, Iva, Luxner, Josefa, Vraneš, Jasmina, Meštrović, Tomislav, Zarfel, Gernot, Grisold, Andrea
• Format: Journal Article
• Language: English
• Published: Austria 01.06.2016
• Subjects: Anti-Bacterial Agents - administration & dosage; Bacterial Proteins - metabolism; beta-Lactamases - metabolism; Communicable Diseases, Emerging - microbiology; Croatia; Disease Susceptibility - microbiology; Drug Resistance, Multiple, Bacterial - drug effects; Humans; Long-Term Care - statistics & numerical data; Nursing Homes - statistics & numerical data; Proteus Infections - microbiology; Proteus mirabilis - classification; Proteus mirabilis - enzymology; Proteus mirabilis - genetics; Species Specificity; CMY-16; Clonal dissemination; Proteus mirabilis; AmpC β-lactamases; Conjugative plasmid
• ISSN: 0043-5325; 1613-7671
• DOI: 10.1007/s00508-016-1005-x

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. 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). 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. 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.