Prevalence of pathogenic role of Morganella-proteus providencia-group of bacteria in human faeces.

Speculation in literature that organisms of the Morganella-Proteus-Providencia (MPP) group can cause diarrhoea led to the present studies which investigated their occurrence and pathogenic role in human faeces. Faecal specimens were collected from a total of 307 subjects, 80 of which were from diarrhoea cases and 277 from healthy controls. Ninety-two species of the MPP (24/80 diarrhoea and 68/277 control) were isolated from 30% of all subjects. None of the species of the MPP group was significantly associated with diarrhoea as their isolation rate in the controls matched that of the diarrhoea cases (30% of each group). Additional evidence of apparent non-involvement as de facto causative agents of diarrhoea was in their inability to demonstrate the LT or ST enterotoxin production. Tests for invasiveness by Sereny test was also negative. There was a concurrent isolation of other proven diarrhoeal pathogens, such as Salmonella spp and enteropathogenic Escherichia coli (EPEC), with the MPP spp in all the cases in the diarrhoeal group. MPP spp was never isolated as the sole pathogen in any diarrhoeal case. We therefore found no strong evidence from our study to associate the species of the MPP group with diarrhoeal production.