Interactions of Staphylococcus aureus and polystyrene on 2D minilung infection model

Nanoplastics are ubiquitous plastic particles smaller than 1µm that have been detected in our bodies. Many studies are elucidating their impact on health but little is known in regards of infection. Our aim is to study the impact of 50nm polystyrene (PS) particles on Staphylococcus aureus infection in bidimensional arrays of airways and lung cells generated from human embryonic pluripotent stem cells. The minilungs were infected at day 81 of differentiation. The impact of PS was studied through two approaches: 1)PS direct impact: PS 100µg/mL was added to the cultures and incubated for 24-48-72h, supernatants were used for cytotoxicity evaluation. 2)PS impact on infection outcome: S. aureus was incubated in tryptic soy broth (TSB) or co-cultured in TSB with PS 100µg/mL for 2,5h. Next, cultures were infected at a multiplicity of infection of 1 and incubated for 1-2-4-24h. Supernatants were used for cytotoxicity evaluation, and cells were lysed. Intracellular content was plated for colony forming units (CFU) quantification. In both infection conditions, intracellular CFU/mL counts decreased three orders of magnitude between 1h and 2h; then, CFU counts remained constant up to 24h. However, intracellular CFU counts at all timepoints were higher by an order of magnitude in PS-S. aureus cultures compared to S. aureus cultures. In regards to cytotoxicity, values ranged between 30-50% at all timepoints in both infection conditions. However, PS exposed cultures showed an increase of cytotoxicity through time. The presence of PS seems to cause cytotoxicity and facilitates the invasion and infection of S. aureus. Thus, PS might alter the host’s cellular response against infection.