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Persistent colonization of carbon dioxide incubators with Candida parapsilosis
G Schär1, M Grehn, A von Graevenitz
1Department of Medical Microbiology, University of Zurich, Switzerland.
Abstract:
Recurrent contamination of bacteriological specimens with Candida parapsilosis led to epidemiological investigations which indicated persistent colonization of carbon dioxide incubators as the most likely source. Changes in the technical arrangements and institution of a meticulous cleansing protocol eliminated contamination of specimens but not colonization of the incubators. Tests for tolerance of 17% NaCl and survival at 50 degrees C, and SDS-PAGE analysis of crude cell extracts allowed discrimination between epidemic and non-epidemic isolates, while enzyme profile analysis and susceptibility studies failed as typing methods.
Insights
Recurrent Candida parapsilosis contamination in lab specimens was traced to incubators. Specific lab tests differentiated strains, but cleaning protocols only reduced contamination, not incubator colonization.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Environmental Hygiene in Healthcare
Background:
- Recurrent contamination of bacteriological specimens with Candida parapsilosis posed a significant challenge.
- Epidemiological investigations were initiated to identify the source of persistent contamination.
Purpose of the Study:
- To identify the source of recurrent Candida parapsilosis contamination in bacteriological specimens.
- To evaluate methods for discriminating between epidemic and non-epidemic isolates.
- To assess the effectiveness of technical and cleansing protocols in eliminating contamination and colonization.
Main Methods:
- Epidemiological investigation to pinpoint the contamination source.
- Implementation of revised technical arrangements and a meticulous cleansing protocol.
- Laboratory testing including 17% NaCl tolerance, 50°C survival, SDS-PAGE of cell extracts, enzyme profiling, and susceptibility studies for isolate discrimination.
Main Results:
- Persistent colonization of carbon dioxide incubators was identified as the most likely source of contamination.
- Changes in technical arrangements and cleansing protocols eliminated specimen contamination but not incubator colonization.
- SDS-PAGE, 17% NaCl tolerance, and 50°C survival tests effectively discriminated between epidemic and non-epidemic Candida parapsilosis isolates.
- Enzyme profile analysis and susceptibility studies were ineffective as typing methods.
Conclusions:
- Carbon dioxide incubators can serve as a persistent reservoir for Candida parapsilosis, necessitating specific control measures.
- While specimen contamination can be eliminated through rigorous protocols, eradicating incubator colonization requires further investigation.
- Specific genotypic and phenotypic tests (SDS-PAGE, salt/heat tolerance) are valuable for differentiating clinical isolates of Candida parapsilosis.