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Acquired AmpC type beta-lactamases: an emerging problem in Italian long-term care and rehabilitation facilities

Roberta Migliavacca1, Elisabetta Nucleo, Marco M D'Andrea

  • 1Dipartimento di Scienze Morfologiche Eidologiche e Cliniche, sezione di Microbiologia, Università di Pavia, Pavia, Italy. r.miglia@unipv.it

The New Microbiologica
|September 7, 2007
PubMed

Insights

Multiple Proteus mirabilis strains resistant to key antibiotics were found in Northern Italian long-term care facilities. These strains produce a novel beta-lactamase, CMY-16, indicating concerning resistance spread in healthcare settings.

Area of Science:

  • Clinical Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • The increasing prevalence of multidrug-resistant bacteria poses a significant threat to public health, particularly in long-term care and rehabilitation facilities (LTCRFs).
  • Acquired beta-lactamases, such as ampC-like enzymes, are a major mechanism of resistance to extended-spectrum cephalosporins and cephamycins.

Purpose of the Study:

  • To investigate the emergence and characteristics of Proteus mirabilis isolates exhibiting resistance to expanded-spectrum cephalosporins and cephamycins.
  • To identify the specific resistance mechanisms, including the presence and nature of acquired beta-lactamases, in these P. mirabilis isolates.
  • To determine the genetic relatedness and dissemination patterns of the identified P. mirabilis strains across multiple LTCRFs in Northern Italy.

Main Methods:

  • Phenotypic characterization of Proteus mirabilis isolates for antibiotic susceptibility testing against extended-spectrum cephalosporins and cephamycins.
  • Molecular detection and characterization of acquired ampC-like beta-lactamase genes.
  • Genotyping using Pulse Field Gel Electrophoresis (PFGE) to assess clonal relatedness among isolates.
  • Plasmid analysis and conjugation experiments to evaluate the transferability of the resistance gene.

Main Results:

  • Multiple P. mirabilis isolates resistant to expanded-spectrum cephalosporins and cephamycins were detected in four different LTCRFs in Northern Italy.
  • These isolates produced a novel acquired ampC-like beta-lactamase, designated CMY-16.
  • PFGE analysis indicated that the isolates were clonally related, suggesting the spread of a specific P. mirabilis clone, although not identical.
  • The bla(CMY16) gene was found to be chromosomally located and not transferable by conjugation in the studied isolates.

Conclusions:

  • The findings reveal the multifocal spread of a CMY-16 producing P. mirabilis clone across LTCRFs in Northern Italy.
  • This study highlights the emergence and dissemination of acquired resistance determinants, specifically CMY-16, within the LTCRF setting.
  • Continuous surveillance and infection control measures are crucial to manage the spread of such resistant organisms in healthcare environments.

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