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Surveillance cultures for detection of rectal and lower respiratory tract carriage of colistin-resistant Gram-negative bacilli in intensive care unit patients: comparison of direct plating and pre-enrichment step.
J Med Microbiol. 2019 Sep; 68(9):1269-1278.JM

Abstract

Purpose.

Increasing consumption of colistin as treatment for infections with multidrug-resistant (MDR) Gram-negative bacilli (GNB) has been accompanied by increasingly frequent reports of colistin-resistant (ColR) MDR GNB. Higher selective pressure creates a favourable environment that can facilitate the spread of ColR isolates. Monitoring of asymptomatic ColR GNB carriage can give us a better understanding of this emerging healthcare problem, particularly in wards with higher polymyxin selective pressure and prevalence of carbapenem-resistant GNB. Our aim was to assess the ColR GNB colonization rate in intensive care unit (ICU) patients and evaluate the performance of two surveillance protocols using a selective medium.Methodology. A prospective study included 739 surveillance samples (rectal swabs and tracheal aspirates) from 330 patients that were screened for ColR GNB carriage using SuperPolymyxin medium. Two approaches were used: direct sample plating and overnight pre-enrichment of samples followed by plating. Colistin resistance was confirmed with broth microdilution. ColR isolates were molecularly screened for plasmid-mediated mcr genes.

Results.

A total of 44/739 samples (45 ColR GNB isolates) were positive for ColR GNB, which included 31/330 (9.4 %) colonized patients; mcr genes were not detected. The direct plating method only identified 17/45 (37.8 %) isolates correctly, whereas the pre-enrichment protocol identified all 45 ColR GNB.

Conclusion.

The colonization rate among our ICU patients was 9.4 %. Based on our findings, the pre-enrichment step is necessary for the determination of ColR GNB carriage - even though the time to result takes an additional day, fewer than half of ColR GNB carriers were detected using the direct plating protocol.

Authors+Show Affiliations

Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.Department of Infectious Diseases, University Medical Centre Ljubljana, Ljubljana, Slovenia.Department of Infectious Diseases, University Medical Centre Ljubljana, Ljubljana, Slovenia.Department of Infectious Diseases, University Medical Centre Ljubljana, Ljubljana, Slovenia. Infection Control Unit, University Medical Centre Ljubljana, Ljubljana, Slovenia.Institute of Oncology, Ljubljana, Slovenia.Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31237536

Citation

Germ, Julija, et al. "Surveillance Cultures for Detection of Rectal and Lower Respiratory Tract Carriage of Colistin-resistant Gram-negative Bacilli in Intensive Care Unit Patients: Comparison of Direct Plating and Pre-enrichment Step." Journal of Medical Microbiology, vol. 68, no. 9, 2019, pp. 1269-1278.
Germ J, Cerar Kišek T, Kokošar Ulčar B, et al. Surveillance cultures for detection of rectal and lower respiratory tract carriage of colistin-resistant Gram-negative bacilli in intensive care unit patients: comparison of direct plating and pre-enrichment step. J Med Microbiol. 2019;68(9):1269-1278.
Germ, J., Cerar Kišek, T., Kokošar Ulčar, B., Lejko Zupanc, T., Mrvič, T., Kerin Povšič, M., Seme, K., & Pirs, M. (2019). Surveillance cultures for detection of rectal and lower respiratory tract carriage of colistin-resistant Gram-negative bacilli in intensive care unit patients: comparison of direct plating and pre-enrichment step. Journal of Medical Microbiology, 68(9), 1269-1278. https://doi.org/10.1099/jmm.0.001029
Germ J, et al. Surveillance Cultures for Detection of Rectal and Lower Respiratory Tract Carriage of Colistin-resistant Gram-negative Bacilli in Intensive Care Unit Patients: Comparison of Direct Plating and Pre-enrichment Step. J Med Microbiol. 2019;68(9):1269-1278. PubMed PMID: 31237536.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Surveillance cultures for detection of rectal and lower respiratory tract carriage of colistin-resistant Gram-negative bacilli in intensive care unit patients: comparison of direct plating and pre-enrichment step. AU - Germ,Julija, AU - Cerar Kišek,Tjaša, AU - Kokošar Ulčar,Barbara, AU - Lejko Zupanc,Tatjana, AU - Mrvič,Tatjana, AU - Kerin Povšič,Milena, AU - Seme,Katja, AU - Pirs,Mateja, Y1 - 2019/06/25/ PY - 2019/6/27/pubmed PY - 2019/9/19/medline PY - 2019/6/26/entrez KW - colistin-resistant Gram-negative bacilli KW - intensive care units KW - screening KW - surveillance cultures SP - 1269 EP - 1278 JF - Journal of medical microbiology JO - J. Med. Microbiol. VL - 68 IS - 9 N2 - Purpose. Increasing consumption of colistin as treatment for infections with multidrug-resistant (MDR) Gram-negative bacilli (GNB) has been accompanied by increasingly frequent reports of colistin-resistant (ColR) MDR GNB. Higher selective pressure creates a favourable environment that can facilitate the spread of ColR isolates. Monitoring of asymptomatic ColR GNB carriage can give us a better understanding of this emerging healthcare problem, particularly in wards with higher polymyxin selective pressure and prevalence of carbapenem-resistant GNB. Our aim was to assess the ColR GNB colonization rate in intensive care unit (ICU) patients and evaluate the performance of two surveillance protocols using a selective medium.Methodology. A prospective study included 739 surveillance samples (rectal swabs and tracheal aspirates) from 330 patients that were screened for ColR GNB carriage using SuperPolymyxin medium. Two approaches were used: direct sample plating and overnight pre-enrichment of samples followed by plating. Colistin resistance was confirmed with broth microdilution. ColR isolates were molecularly screened for plasmid-mediated mcr genes.Results. A total of 44/739 samples (45 ColR GNB isolates) were positive for ColR GNB, which included 31/330 (9.4 %) colonized patients; mcr genes were not detected. The direct plating method only identified 17/45 (37.8 %) isolates correctly, whereas the pre-enrichment protocol identified all 45 ColR GNB.Conclusion. The colonization rate among our ICU patients was 9.4 %. Based on our findings, the pre-enrichment step is necessary for the determination of ColR GNB carriage - even though the time to result takes an additional day, fewer than half of ColR GNB carriers were detected using the direct plating protocol. SN - 1473-5644 UR - https://www.unboundmedicine.com/medline/citation/31237536/Surveillance_cultures_for_detection_of_rectal_and_lower_respiratory_tract_carriage_of_colistin_resistant_Gram_negative_bacilli_in_intensive_care_unit_patients:_comparison_of_direct_plating_and_pre_enrichment_step_ L2 - http://jmm.microbiologyresearch.org/pubmed/content/journal/jmm/10.1099/jmm.0.001029 DB - PRIME DP - Unbound Medicine ER -