Specialist staffing business SThree reported a drop in third quarter profits but the figures also showed its expansion into new sector disciplines has been paying off.Third quarter profits were down 2% year-on-year but they were up 5% compared with the second quarter and there was a particularly strong performance from the energy, pharma and biotech sectors.The contract side of the business had a strong quarter with profits up 7% year-on-year but permanent profits were down 11%.Chief Executive Gary Elden said: "Our trading momentum was positive in the period, with a sequential improvement in our performance over the second quarter, led by contract and our newer sector disciplines."After starting out in the information and communications technology sector SThree expanded into new sectors and markets. It now has 58 offices in 20 countries and provides staff to a wide range of industries.Gideon Adler, analyst at Investec Securities, said: "Looking under the bonnet, the strategic imperative to invest behind contract and diversify income streams into new sectors and geographies seems to be playing out."Shares in SThree were down 2% at 347p. TB