  An efficient method is reported for rapid identification of bacterial or
mycobacterial infection in a suspected clinical/biological sample. The method
is based on the fact that the ring methylene protons of cyclic fatty acids
(constituting the cell membrane of several species of bacteria and
mycobacteria) resonate specifically between -0.40 and 0.68 ppm region of the 1H
NMR spectrum. These cyclic fatty acids are rarely found in the eukaryotic cell
membranes. Therefore, the signals from cyclic ring moiety of these fatty acids
can be used as markers (a) for the identification of bacterial and
mycobacterial infections and (b) for differential diagnosis of bacterial and
fungal infections. However, these microbial fatty acids when present inside the
membrane are not easily detectable by NMR owing to their fast T2 relaxation.
Nonetheless, the problem can easily be circumvented if these fatty acids become
suspended in solution. This has been achieved by abolishing the membrane
integrity using broad spectrum antibiotics (including ampicillin). The
suspended fatty acids are then detected by NMR to probe the infection.
Therefore, the method has been given the name AADNMR i.e. Add Antibiotic to
Detect by NMR. The method has been tested here using both Gram positive and
Gram negative bacterial strains and finally the utility of method is
demonstrated for discriminating bacterial and fungal infections to aid timely
diagnosis of infectious peritonitis (a life threatening complication associated
with prolonged peritoneal dialysis).
