An alternative microthread for the study of airborne survival of bacteria outdoors

Abstract

B.A. HANDLEY AND J.M. ROE 1994. The microthread technique has frequently been used to study the survival outdoors of bacteria attached to the escape line of small spiders. Use of spiders was found to be frustrating and time‐consuming. An artificial fibre of ethylene vinyl acetate was produced easily and efficiently with a modified commercial hot glue gun. Although the resulting fibres were not as fine as spider web, no significant difference in survival of suspended bacteria was demonstrated between the two fibres either when enclosed or exposed outdoors.

Some factors affecting the airborne survival of bacteria outdoors

“…Cox (Chemical and Biological Defence Establishment, Porton Down, UK). Bacteria were maintained and cultured as described by Handley and Webster (1993) and Handley and Roe (1994) except for experiments in Oban where cultures were grown on a shaker at room temperature. This was marginally less than 20°C.…”

“…Fine microthreads of ethylene vinyl acetate were generated using a modified hot glue gun (Handley and Roe 1994) and wound onto metal frames which were subsequently inserted into a metal tube or 'sow' . Aerosols of either E. coli or 24 h cultures of Ps.…”

“…JEuorescens in spent 10% TSB were initially generated and sprayed directly from a disposable plastic nebulizer (Medix Ltd, Lutterworth, Leicester, UK) onto the microthreads. Subsequently, aerosols of either 24 or 48 h cultures of the three strains in spent TYB were diluted with ambient air, as described by Handley and Roe (1994), until microscopic examination revealed deposition of predominantly single cells. For all studies except for those using bacteria suspended as clusters, recently pasteurized spores of B. subtilis subsp.…”

“…coli or pseudomonad, respectively) transferred to an enclosed sow, from which frames could be sampled without exposure to outside air (Handley and Roe 1994). After transport of both sows to the exposure site, the frames from the original sow were exposed outdoors under to protect from exposure to direct daylight (Handley and Roe 1994). On 10 occasions at Langford additional frames were exposed to direct daylight on top of the roundabout.…”

“…On 10 occasions at Langford additional frames were exposed to direct daylight on top of the roundabout. Samples were removed at timed intervals from both sow and roundabout and were placed in sampling tubes containing 4 ml of 0.1% peptone in 0.85% saline (Corry 1979) and mixed vigorously to suspend both fibre and cells (Handley and Roe 1994). Samples were diluted further in peptone saline as required and viable counts performed on 10% TSB with 2% agar (Agar No.…”