bact/alert did not require a needle to be introduced into the bottle for sampling; this reduced the frequency of contamination and made it the first system to provide truly continuous monitoring of blood cultures. this non-invasive measurement method was adopted in 1992 by the bactec 9000 series, which used fluorescent indicators to detect ph changes. the difco esp, a direct predecessor of the contemporary versatrek system which detects gas production by measuring pressure changes, was also first approved in 1992. by 1996, an international study found that 55% of 466 laboratories surveyed were using the bactec or bact/alert systems, with other automated systems accounting for 10% of the total. notes chlorhexidine is not recommended for use in infants under two months old, and iodine-based antiseptics are contraindicated in low-birth-weight infants.