Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Species | Indole | Methyl Red | Voges-Proskauer | Citrate |
| --- | --- | --- | --- | --- |
| Escherichia coli | Positive | Positive | Negative | Negative |
| Shigella spp. | Negative | Positive | Negative | Negative |
| Salmonella spp. | Negative | Positive | Negative | Positive |
| Klebsiella spp. | Negative | Negative | Positive | Positive |
| Proteus vulgaris | Positive | Positive | Negative | Negative |
| Proteus mirabilis | Negative | Positive | Negative | Positive |
Question:
Which species show a negative result with both voges-proskauer and indole?
Answer:
Shigella spp., Salmonella spp., Proteus mirabilis