Virulence Potential of Rhizopus Species in an Embryonated Chicken Egg Model

Little is known about the pathogenicity and virulence properties of the Rhizopus species used in food fermentation. This study aimed to investigate the virulence potential of Rhizopus arrhizus and R. microsporus strains obtained from a wide selection of clinical and environmental sources in an embryonated chicken egg model.

In total, 26 strains (13 strains from each species) were inoculated in embryonated eggs with final concentration of 106 spore/ml/egg. The eggs were inoculated (0.1 ml) through chorio-allantoic membrane in day 10 and incubated at 37.6 °C and 60% humidity and monitored for 7 days. Ethics code: IR.MUMS.fm.REC.1396.457

The mortality rate for R. microsporus was slightly higher than that of R. arrhizus. The ability of R. arrhizus and R. microsporus to cause infection was strain-specific but source-independent in the embryonated chicken eggs. The presence of endosymbiont bacteria (Burkhulderia) in some strains of R. microspores did not show any effect on their virulence.

The occurrence of virulence in strains isolated from fermented food indicates the opportunistic nature of these fungi and possibility of a public health risk for consumers.