title: Spread of multidrug-resistant Proteus mirabilis isolates producing an AmpC-type beta-lactamase: epidemiology and clinical management.
abstract: A remarkable increase in Proteus mirabilis strains producing acquired AmpC-type beta-lactamases (CBLs) has been observed at Ospedale di Circolo e Fondazione Macchi (Varese, Italy) over the last few years. The epidemiology and treatment outcome of infections associated with this unprecedented spread are reported. From 2004-2006, 2070 P. mirabilis isolates were investigated. Extended-spectrum beta-lactamases (ESBLs) and CBL resistance determinants were identified by gene amplification and direct sequencing. Clonal relatedness was evaluated by macrorestriction analysis. Overall, 43 CBL-positive isolates were obtained from hospitalised (n=22) and non-hospitalised (n=21) patients (median age 78.8 years). The prevalence of CBL-positive isolates increased from 0.3% in 2004 to 4.6% in 2006, whereas that of ESBL-positive isolates remained constant (ca. 10%). CBL-positive isolates were multidrug-resistant and carried the CMY-16 determinant. All but two isolates were genetically identical or closely related. Retrospective analysis of clinical records revealed that the majority of CMY-16-positive isolates were associated with urinary tract infections. Treatment with amikacin or carbapenems was consistently effective, whereas piperacillin/tazobactam produced a clinical response in seven of nine cases. This is the first report of a rapid spread of CBL-positive P. mirabilis strains endowed with remarkable antimicrobial resistance. Practical methods for CBL detection are needed for the appropriate management of related infections.
authors.affiliation: Laboratory of Medical Microbiology, Ospedale di Circolo, University of Insubria, Varese, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Luzzaro
authors.forename: Gioconda
authors.initials: G
authors.lastname: Brigante
authors.forename: Marco Maria
authors.initials: MM
authors.lastname: D'Andrea
authors.forename: Beatrice
authors.initials: B
authors.lastname: Pini
authors.forename: Tommaso
authors.initials: T
authors.lastname: Giani
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Mantengoli
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: Rossolini
authors.forename: Antonio
authors.initials: A
authors.lastname: Toniolo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001426:Bacterial Proteins / Q000096:biosynthesis*; D015373:Bacterial Typing Techniques; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005838:Genotype; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D015995:Prevalence; D011512:Proteus Infections / Q000453:epidemiology* / Q000382:microbiology*; D011513:Proteus mirabilis / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D017422:Sequence Analysis, DNA; D055815:Young Adult; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C048795:AmpC beta-lactamases; D001618:beta-Lactamases