Spread of multidrug-resistant Proteus mirabilis isolates producing an AmpC-type beta-lactamase: epidemiology and clinical management

Int J Antimicrob Agents. 2009 Apr;33(4):328-33. doi: 10.1016/j.ijantimicag.2008.09.007. Epub 2008 Dec 17.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Anti-Bacterial Agents / therapeutic use
  • Bacterial Proteins / biosynthesis*
  • Bacterial Typing Techniques
  • Cluster Analysis
  • DNA Fingerprinting
  • DNA, Bacterial / genetics
  • Drug Resistance, Multiple, Bacterial*
  • Electrophoresis, Gel, Pulsed-Field
  • Female
  • Genotype
  • Humans
  • Italy / epidemiology
  • Male
  • Middle Aged
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • Prevalence
  • Proteus Infections / epidemiology*
  • Proteus Infections / microbiology*
  • Proteus mirabilis / classification
  • Proteus mirabilis / drug effects*
  • Proteus mirabilis / genetics
  • Proteus mirabilis / isolation & purification*
  • Sequence Analysis, DNA
  • Young Adult
  • beta-Lactamases / biosynthesis*

Substances

  • Anti-Bacterial Agents
  • Bacterial Proteins
  • DNA, Bacterial
  • AmpC beta-lactamases
  • beta-Lactamases