Infection and contamination control products supplier Tristel saw profits fall in the six months to 31 December, despite higher revenues, as it stepped up expansion.Pre-tax profits fell by 34% from the same period the previous year to £0.433m, even as revenues jumped by 13.4% to £4.565m.Tristel increased spending in areas such as marketing and hopes this will lead to increased sales."We have invested heavily in our expansion programme in the first half and look forward to an acceleration in turnover growth in the second half in accordance with our internal plan and market expectations."Tristel saw strong international growth, with overseas sales jumping by nearly 150% to £386,000. Chief executive Paul Swinney said the company is targeting overseas sales to account for about 30% in two years' time, from about 10% currently.Sales in the UK slipped by 2.8% to £3.186m. This was largely due to a decline in revenues from the digestive endoscopy business, part of a longer term trend. Sales in products used to clean surfaces in hospitals were up though and Tristel expects this to continue. It said 27 out of 412 NHS acute hospitals use its products and this is rising steadily.