Tryptone soya agar

To determine levels of microbial air contamination within the Podiatry clinic impact samplers (MicroBio 2, Fred Parrett Ltd, UK) were employed sampling 400 litres of air at a sample rate of 100 l min^-1. Air samples were taken before, during and after consultations. Bacterial samples were taken on Tryptone Soya Agar (TSA)(LabM Ltd, UK) and were incubated at 37°C for 24 hours; Sabouraud Dextrose agar with Chloramphenicol (SABC) was used for general fungal isolation with Dermasel agar (Oxoid LTD, UK) used to isolate dermatophytes. Fungal plates were incubated at 30°C for up to 6 weeks. In all cases colonies were sub-cultured for analysis.
In addition to air samples, sterile cellulose acetate filters (0.45 μm pore size, Whatman) were employed to determine the ability of the UV cabinet to prevent airborne contamination during routine podiatry consultations. Triplicate filters were placed in sterile Petri dishes located in both the UV cabinet and the standard instrument cabinet and exposed during routine podiatry consultations. After exposure the filters were placed on either TSA, SABC or Dermasel plates and incubated as specified for the air samples.

Tryptone soya agar (TSA) and tryptone soya broth (TSB) were purchased from Lab M Ltd. (Lancashire, UK) and prepared according to the manufacturer’s protocol. Both TSB and TSA media contain peptone (20 g/L) and glucose (2.5 g/L). All basal salts used in the preparation of BSM (low nitrogen content) were obtained from BDH Chemicals Ltd. (Dorset, UK) and prepared accordingly: 1 L of distilled water, 1 g/L K₂HPO₄, 1 g/L KH₂PO₄, 1 g/L KNO₃, 1 g/L (NH₄)₂SO₄, 0.1 g/L MgSO₄.7H₂O, 0.1 g/L NaCl, and 10 mL/L trace elements. The trace elements solution contained 2 mg/L CaCl₂, 2 mg/L CuSO₄.5H₂O, 2 mg/L MnSO₄.5H₂O, 2 mg/L ZnSO₄.5H₂O, 2 mg/L FeSO₄, and 2 mg/L (NH₄)₆Mo₇O₂₄.4H₂O. Ringer’s solution (Lab M, Lancashire, UK) was used as a saline solution for the analysis of viable cells during the cultivation process. To prepare this solution, a ¼-strength tablet was left to completely dissolve in 500 mL of deionised water with constant stirring. All media used in this study were sterilised by autoclaving (Priorclave Ltd., London, UK) for 15 min at 121 °C.

Bacillus subtilis natto (ATCC15245) obtained from the National Collection of Industrial and Marine Bacteria (NCIMB) were freeze-dried and kept at −20 °C. Before use, cultures were resuscitated and grown on Tryptone Soya Agar TSA (Lab M, Heywood, UK) overnight at 37 °C. Highly mucoid colonies were selected and grown aerobically in shake flasks containing 100 mL of TSB medium (Lab M, Heywood, UK) at 37 °C for 24 h.