The authors found a reduction in contaminated cultures from 1.1% to 0.6% (OR 0.57, p 0.009) with sterile gloves.
It's worth pointing out that cultures drawn through lines were excluded, as were cultures obtained in the Emergency Department (an area of high contamination rates in some hospitals), pediatrics wards and surgical wards. In addition, povidone-iodine was used as the skin disinfectant.
When I was a resident, all blood cultures were drawn by housestaff and I proudly recall that I never had a contaminated blood culture (and I did wear sterile gloves). But we had a vested interest in avoiding contaminants, as it would mean drawing more cultures and potentially extending the patient's hospital stay, all of which meant more work for us.