As if Sanlu does not have enough to worry about – A pathogenic bacterium has been found in milk powder that was also contaminated with melamine, according to a report in the Lanzhou Daily.  The report said that the Administration of Quality and Technology Supervision in Gansu Province issued an emergency notice on September 21, saying that Sanlu’s older and younger infant formulas contained enterobacter sakazakii as well as the toxic melamine.  Enterobacter sakazakii (E. sakazakii) is a gram-negative, non-spore-forming bacterium belonging to the Enterobacteriaceae family. It has previously been found in powdered infant formula around the world.  A 2007 World Health Organisation report, Microbiological Risk Assessment Series, No. 6, concluded "Intrinsic contamination of powdered formula with E. sakazakii can cause infection and illness in infants, including severe disease … and death."

Enterobacter sakazakii is an uncommon, but often fatal, invasive pathogen that causes bloodstream and central nervous system infections.  The gram-negative, non-spore-forming, rod-shaped bacterium is from the family Enterobacteriaceae – the same family that E. coli O157:H7 belongs to.

While E. sakazakii has caused disease in all age groups, it is likely that immunocompromised or medically debilitated infants are more susceptible to infections with E. sakazakii.  One contributing factor in infant cases could be that the stomach of newborns, especially of premature babies, is less acidic than that of adults.  Several outbreaks traced to contaminated infant formula have occurred in neonatal intensive care units worldwide.