Bioburden Assessment by Passive Methods on a Clinical Pathology Service in One Central Hospital from Lisbon: What Can it Tell Us Regarding Patients and Staff Exposure?

Abstract

The assessment and control of microbial contamination in health care facilities is presently a mandatory and vital part of strategies to prevent and control hospital-acquired infections. This study aims to assess the bioburden with two passive sampling methods (30 ventilations grids swabs and 16 electrostatic dust collectors (EDCs)) at Clinical Pathology Services. The fungal burden was characterized through molecular tools, antifungal resistance, and the mycotoxins and cytotoxicity profile. Total bacteria presented the highest prevalence in both matrixes, whereas Gram-bacteria presented the lowest. Swabs presented a higher prevalence (27.6%) for fungal burden. Chrysonilia sitophila presented the highest prevalence in swabs, whereas for EDCs, C. sitophila and Mucor sp. were the most prevalent. Concerning Aspergillus genera on swabs, section Flavi was the one with the highest prevalence (58.02%), whereas, for EDCs, section Versicolores was the only section observed (100%). Aspergillus section Fumigati was detected in 10 swabs and 7 EDC samples and Aspergillus section Versicolores was detected in one EDC sample. Fungal growth on azole-supplemented media was observed in eight EDC samples. No mycotoxins were detected in any of the samples. A low cytotoxic effect was observed in two sites upon incubation of collected samples with A549 and SK cells and in two other sites upon incubation of collected samples with SK cells only. A medium cytotoxic effect was observed with one EDC sample upon incubation with A549 cells. This study reinforces the need of determination of the azole resistance profile for fungal species and allowed a preliminary risk characterization regarding the cytotoxicity. An intervention including the use of a ultraviolet with wavelength between 200 nm and 280 nm (UVC)—emitting device and an increased maintenance and cleaning of the central heating, ventilation, and air conditioning (HVAC) systems should be ensured to promote the reduction of microbial contamination.

Assessment of Children’s Potential Exposure to Bioburden in Indoor Environments

“…To contribute to the assessment of children's exposure to particles and bioburden, EDC was exposed for an extended period to collect dust in two home locations and at schools [27] (Figure 1). Although with some downsides, that rely mainly on the fact that bioaerosols are highly dynamic, thus difficult to collect in a representative way [43], settled dust is considered to be a long-term integrated sample of particles that have been airborne.…”

“…As such this method is more reliable to sample bioaerosols [44]. Indeed, settled dust evidences a composite view of bioaerosols in the indoor environment that is being assessed [19,22,27]. Therefore, EDC permits consistent estimation of exposure, since a single EDC analysis is equal to the sum of several air-impaction measurements [45].…”

“…Therefore, EDC permits consistent estimation of exposure, since a single EDC analysis is equal to the sum of several air-impaction measurements [45]. Furthermore, EDC allows for an exclusive identification of some fungal species and higher fungal diversity, when compared to air samples obtained by impaction or even with other passive methods [27]. The coupling of this sampling method with particle measurement allowed a more complete analysis of children's exposure in their daily lives.…”

“…The target fungi were selected based on the classification as indicators of harmful fungal contamination [37]. EDC samples were subject to extraction and bioburden characterized by culture-based methods as previously described [16,19,22,26,27]. EDC were washed and 0.15 mL seeded onto 2% malt extract agar (MEA) with 0.05 g/L chloramphenicol media; dichloran glycerol (DG18) agar-based media; tryptic soy agar (TSA) with 0.2% nystatin for total bacteria assessment; violet red bile agar (VRBA) for Gram-negative bacteria.…”

“…The electrostatic dust collector (EDC) is a passive collection device easy-to-use that comprises an electrostatic polypropylene cloth [17]. The use of this device is gradually increasing since it is low-cost and effective for the collection of dust [16,18,19], and it has already been applied for the bioburden assessment in several indoor environments [16,[19][20][21][22][23][24][25][26][27].…”