Lots of good info here: https://www.cdc.gov/meningitis/bacterial.html
Most common causative organisms are Streptococcus pneumoniae, Neisseria meningitides, and Haemophilus influenzae.
Key symptoms are fever, headache, and stiff neck. Most common diagnostic test is checking cerebrospinal fluid for presence of the bacteria. Bacterial meningitis can be fatal or cause serious long term damage, so rapid diagnosis and treatment is critical.