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Laboratory investigation of hospital outbreak caused by two different multiresistant Acinetobacter calcoaceticus
J Vila1, M Almela, M T Jimenez de Anta
1Servei de Microbiologia i Parasitologia, Hospital Clinic i Provincial de Barcelona, Spain.
Abstract:
During a 7-month period, from December 1986 to June 1987, multiresistant strains of Acinetobacter calcoaceticus subsp. anitratus were isolated from 25 patients in a respiratory intensive care unit. The biochemical characteristics defined two groups of strains, group 1 (14 strains) and group 2 (11 strains). Both groups had the same biochemical characteristics, but group 2 strains could assimilate adipate and phenyl acetate. Moreover, of 16 antibiotics tested only netilmicin and imipenem had some inhibitory activity for group 1 strains; group 2 strains were susceptible to mezlocillin, piperacillin, and ticarcillin. Plasmid profiles of the groups were also different. The results of a laboratory investigation (biochemical characteristics, antibiotic susceptibility, and plasmid isolation) identified two different A. calcoaceticus subsp. anitratus strains as the causes of the outbreak.
Insights
Two distinct strains of Acinetobacter calcoaceticus subsp. anitratus caused a multi-resistant outbreak in a respiratory intensive care unit. Laboratory analysis revealed differences in assimilation, antibiotic susceptibility, and plasmid profiles between the two strains.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Clinical Bacteriology
Background:
- Multiresistant Acinetobacter calcoaceticus subsp. anitratus outbreaks pose significant challenges in healthcare settings.
- Respiratory intensive care units are particularly vulnerable to the spread of nosocomial infections.
Purpose of the Study:
- To investigate the etiological agents responsible for a multiresistant Acinetobacter calcoaceticus subsp. anitratus outbreak.
- To differentiate between co-circulating strains of Acinetobacter calcoaceticus subsp. anitratus using laboratory methods.
Main Methods:
- Biochemical characterization of isolated Acinetobacter calcoaceticus subsp. anitratus strains.
- Antibiotic susceptibility testing against a panel of 16 antibiotics.
- Plasmid profiling to assess genetic relatedness and diversity.
Main Results:
- Two distinct groups of Acinetobacter calcoaceticus subsp. anitratus strains were identified based on biochemical profiles.
- Group 2 strains exhibited unique assimilation capabilities (adipate, phenyl acetate) compared to Group 1.
- Significant differences in antibiotic susceptibility were observed; Group 1 was susceptible to netilmicin and imipenem, while Group 2 responded to beta-lactam antibiotics (mezlocillin, piperacillin, ticarcillin).
- Distinct plasmid profiles further supported the identification of two separate strains.
Conclusions:
- The outbreak was caused by two genetically distinct strains of Acinetobacter calcoaceticus subsp. anitratus.
- Differentiating these strains is crucial for effective infection control and treatment strategies in intensive care units.