Molecular Diagnosis of Infectious Diseases Dr Masood Ziaee

Molecular Diagnosis of Infectious Diseases Dr. Masood Ziaee Professor of Infectious Diseases

PCR (Polymerase Chain Reaction)

Why use a molecular test to diagnose an infectious disease? n Need an accurate and timely diagnosis n Important for initiating the proper treatment n Important for preventing the spread of a contagious disease

What are the advantages of using a molecular test? n n High sensitivity n Can theoretically detect the presence of a single organism High specificity n Can detect specific genotypes n Can determine drug resistance n Can predict virulence

What are the advantages of using a molecular test? n n Speed n Quicker than traditional culturing for certain organisms Simplicity n Some assays are now automated

Leading uses for nucleic –acid based tests n Non culturable agents n n Human papilloma virus Hepatitis B virus Fastidious, slow-growing agents n Mycobacterium tuberculosis n Legionella pneumophilia Highly infectious agents that are dangerous to culture n Francisella tularensis n Brucella species

n n Agents present in low numbers n HIV in antibody negative patients n CMV in transplanted organs Organisms present in small volume specimens n Intra-ocular fluid n Forensic samples

n Antiviral drug susceptibility testing n May be important in helping to decide anti-viral therapy to use in HIV infections

OTHER USES OF MOLECULAR DIAGNOSTICS n Viral load monitoring n Viral genotyping n Bacterial resistance detection n Bacterial genotyping

What are the disadvantages of using a molecular test? n Expensive n Contamination n Will miss new organisms