Automated screening of blood cultures with the Malthus microbiological growth analyser.

A total of 3347 blood cultures from patients in all hospital wards were examined on a Malthus microbiological growth analyser and by a conventional system. There was no significant difference in the total numbers of positive cultures of clinical importance between the two systems (p greater than 0.05). Staphylococcus aureus, however, was isolated more often by the conventional method (p less than 0.05). Failure of the automatic detection routine limited the potential of the Malthus system for earlier detection of positive cultures. Daily visual examination of Malthus curves and subculture of bottles not promptly attached to the apparatus were necessary to avoid missing some positive cultures. False positive rates were 13% for the Malthus system and 2% for the conventional system. The contamination rate was considerably lower in the Malthus system (p less than 0.001). Further development would be necessary for the apparatus to be acceptable for routine screening of blood cultures.