I'm slightly confused - your profile says you are a Professor of Medical Microbiology, so I would assume you know the answers to some of your questions???
In regards to 3. and 4. all the info you have given us is that it's a blood infection - you don't even tell us what culture methods you have tried that are not working. No info on patient symptoms... any bloodwork results... which tests you have done already... any pictures of slides from the blood sample