From the linked article:

"Results: Normal microflora (Lactobacillus species) was not present in 42.86% of bidet toilet users, compared to 8.77% of non-users. Fecal bacteria were detected in 50 of the 268 cases (18.66%), 46 cases in users (92%) and only 4 cases in non-users (8%). Contamination by other pathogens was 4 to 6 times higher in users than in non-users. Conclusion: Habitual use of bidet toilets aggravates vaginal microflora, either by depriving normal microflora or facilitating opportunistic infection of fecal bacteria and other microorganisms"

Mmmm feces.... The nozzle surface and spray water of 192 bidet toilets were sampled for contamination. Of the 192 toilets sampled, the nozzle surface of 167 (87%) and the spray water of 181 (94%) were found to be contaminated by one or more of the following organisms: Enterobacteriaceae, Enterococcus spp., Staphylococcus spp., non-glucose-fermenting rods, other Gram-negative bacteria, other Gram-positive bacteria, and Candida spp.