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Molecular epidemiology of a nosocomial outbreak due to SHV-4-producing strains of Citrobacter diversus
Z El Harrif-Heraud1, C Arpin, S Benliman
1Laboratoire de Microbiologie, Hôpital Robert Boulin, Libourne, France.
Abstract:
Over a 6-month period, eight strains of Citrobacter diversus (Citrobacter koseri) resistant to extended-spectrum cephalosporins and monobactams were isolated from seven colonized and/or infected patients from the same intensive care unit. All strains harbored a single large conjugative plasmid which mediated an extended-spectrum beta-lactamase of the SHV-4 type (ceftazidimase phenotype; enzyme pI, 7.8; plasmid DNA hybridization with a blaSHV-specific probe). All strains were characterized by antibiotic resistance pattern analysis, beta-lactamase content analysis, plasmid profiling, ribotyping with EcoRI, and arbitrarily primed (AP)-PCR with primers O8 and O12. Among the eight C. diversus strains, strains Cd5 to Cd12, six isolates (isolates Cd6 to Cd11) were identical by all markers; one strain (strain Cd5) differed by two markers (antibiotype and AP-PCR pattern with primer O8), and the remaining strain (strain Cd12) differed by two other markers (ribotype and AP-PCR pattern with primer O12). Our results suggest that six of the eight SHV-4-producing C. diversus strains studied (strains Cd6 to Cd11) were a single epidemic strain. Strain Cd5 could be related to the epidemic strain; the origin of strain Cd12 remains uncertain.
Insights
An intensive care unit identified eight strains of extended-spectrum cephalosporin-resistant Citrobacter diversus. Six strains were a single epidemic strain producing SHV-4 beta-lactamase, suggesting potential hospital transmission.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Extended-spectrum cephalosporins and monobactams are crucial antibiotics.
- Citrobacter diversus (Citrobacter koseri) can cause infections, particularly in intensive care settings.
- Antibiotic resistance in Gram-negative bacteria is a growing global health concern.
Purpose of the Study:
- To investigate the genetic relatedness and resistance mechanisms of multidrug-resistant Citrobacter diversus strains isolated from an intensive care unit.
- To identify the source and spread of extended-spectrum cephalosporin and monobactam resistance in Citrobacter diversus.
Main Methods:
- Antibiotic resistance pattern analysis.
- Beta-lactamase content analysis, including enzyme isoelectric focusing (pI) and plasmid DNA hybridization.
- Molecular typing methods: plasmid profiling, EcoRI ribotyping, and arbitrarily primed (AP)-PCR.
Main Results:
- Eight strains of Citrobacter diversus resistant to extended-spectrum cephalosporins and monobactams were isolated over six months.
- All strains possessed a conjugative plasmid mediating SHV-4 type extended-spectrum beta-lactamase.
- Six of the eight strains (Cd6-Cd11) were indistinguishable by all molecular markers, indicating a single epidemic strain.
Conclusions:
- The findings suggest a single epidemic strain of SHV-4-producing Citrobacter diversus circulated within the intensive care unit.
- Strain Cd5 may be related to the epidemic strain, while the origin of strain Cd12 is uncertain.
- The study highlights the importance of molecular surveillance for controlling the spread of multidrug-resistant organisms in healthcare settings.