The microbiological swab sampler--a quantitative experimental investigation.

The aim of the investigation was to give an in vitro experimental account of the commonly used cotton swab as a sampler for quantitative determination of bacteria in operation wounds. The transfer of staphylococci with the swab from an inoculated to a non-inoculated agar culture plate was used as a model, and three different ways of swab handling were tested. A direct transfer of 19 per cent staphlococci from the inoculated to the non-inoculated plate was found. When the swab was rinsed in a small volume of saline and the rinsing fluid was plated, 39 per cent were transfered. When the swab was kept in a Stuart transport medium, as is the usual procedure in clinical practice, only 4 per cent were transfered. Quantitative wound swab cultures depend on a thorough sampling of the wound and an efficient recovery of bacteria from the swab. It is concluded that the use of a Stuart transport medium would appear to hamper quantitative determination, and a rinsing procedure should be preferred.