The Salmonella Typhi IgM and IgG test is used to detect antibodies produced by the immune system in response to Salmonella Typhi, the bacterium responsible for causing typhoid fever. Here are some key points about this test: 
It helps diagnose and confirm cases of typhoid fever. 
IgM antibodies indicate an active or recent infection, while IgG antibodies suggest a past infection or previous vaccination. 
The test becomes positive within 2–3 days of infection and separately identifies IgM and IgG antibodies.