New Gram-negative enteropathogens: fact or fancy?

Bacterial gastroenteritis is a leading cause of morbidity and mortality worldwide. Epidemiologic investigations indicate that in > 30% of cases where diarrhea appears to be of an infectious etiology, no agent can be recovered. This suggests that there is still a number of new bacterial and viral enteropathogens yet to be discovered or proven to be causes of gastroenteritis. This review summarizes the present information in the medical literature for a number of Gram-negative bacteria belonging to five separate families implicated as causes of infectious gastroenteritis. This review covers criteria used in assessing enteropathogenicity and makes a case for the recognition of several new groups as bona fide enteropathogens, including Providencia alcalifaciens and Bacteroides fragilis, while suggesting there is little tangible evidence at present to support the role of other groups, such as Hafnia alvei, as causative agents of intestinal disease syndromes.