Comparative Analysis of Methods of Environmental Surface Sampling for Assessment of Viral and Bacterial Contamination

Introduction: One of the key elements of the infectious disease surveillance system is microbiological monitoring of contamination of environmental objects and healthcare personnel hands. In the context of the COVID-19 pandemic, virology testing of swabs from hospital objects and personal protective equipment of workers of infectious disease hospitals for patients with COVID-19 has acquired special importance. According to the current regulatory documents, however, greater priority in microbiological monitoring is given to determination and identification of bacterial pathogens, thus necessitating the development and implementation of an advanced technique of a simultaneous assessment of viral and bacterial contamination.

Objective: To compare different environmental surface sampling techniques used to assess viral and bacterial contamination. Materials and methods: Samples for environmental swab testing were collected in accordance with the “Scheme for sampling environmental swabs for simultaneous assessment of viral and bacterial contamination” patented by the authors (Industrial Design Patent No. 132971 of September 5, 2022). We applied bacteriological, molecular genetic, and statistical methods in the study.

Results: Overall, 343 wipe samples were tested, of which 68 were atypical (two 38-swab portions, 11.1 % each, contained SARS-CoV-2 RNA and opportunistic microorganisms). Among the opportunistic microorganisms, 42 bacterial strains were identified, including 16 strains of Enterococcus faecalis (38.1 %), 9 strains of Klebsiella pneumoniae (21.4 %), 7 strains of Escherichia coli (16.7 %), 3 strains of Enterococcus faecium (7.1 %), 3 strains of Staphylococcus aureus (7.1 %), 2 strains of Pseudomonas aeruginosa (4.9 %), and 2 strains of Pantoea agglomerans (4.9 %). Eleven variants of viral and bacterial associations were identified. The comparison of environmental swabbing performed by the technique under study with that performed by the standard method, based on test results, indicated a significant 11.1 and 12.3-fold difference in the proportion of non-standard findings for SARS-CoV-2 and opportunistic microorganisms, respectively.

Conclusions: The study results prove that our technique of environmental swabbing meets all modern requirements and facilitates an objective assessment of the level of viral and bacterial contamination of the study objects. This approach can be used for laboratory testing within state and industrial control at institutions of various specialties (healthcare, food industry, childcare facilities, etc.).

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