Little is known about the pathogenesis of E. sakazakii although there appears to be differences in virulence among the various strains and there may be several different biotypes of the organism that causes human illness.
The pathogen has been implicated in outbreaks of severe meningitis or necrotising enterocolitis in premature babies. A mortality rate of 40 - 80 per cent has been reported in these outbreaks and surviving patients may incur side effects such as retarded neural development.
Infant formulae are pasteurised during manufacturing and E. sakazakii does not survive such heat treatment. Nevertheless, E. sakazakii has been isolated from such infant formulae and it is thought that the pathogen originates from the factory environment, possibly from heat sensitive micro-nutrients added after pasteurisation or from bottle preparation.
The Dutch team first investigated the natural habitat of E. sakazakii but no reservoir was found in surface water, soil, mud, rotting wood, grain, bird dung, rodents, domestic environments, cattle, or untreated cow's milk. The bacterium was however found in cheese, minced beef, sausage meat, and vegetables so the team then investigated the extent of the spread of the bacteria by testing nine factories and 16 households using a 'refined isolation and detection method'.
Samples were obtained by scraping or sweeping surfaces in the production line environment or by sampling vacuum cleaner bags.
According to the findings environmental samples from eight of nine food factories and from five of 16 households contained E sakazakii
'The widespread nature of this micro-organism needs to be taken into account when designing preventive control measures,' warned the authors of the paper, (Volume 363, Number 9402, 3 January 2004) M Chantal Kandhai and colleagues at Wageningen university in The Netherlands who also worked with the Nestle Research centre in Switzerland on the project.