Drug Resistant Bacterial Strains Impact Infectious Disease Diagnostic Segment

The expanding population of drug resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA) and multidrug resistant Mycobacterium tuberculosis (TB) will vindicate the use of nucleic acid-based tests (NAT).

The two traditional methods, culture-based assays and immunoassays, are becoming increasingly inadequate for infectious disease testing. Emergence of drug-resistant bacterial strains means that immunoassays have no analytical potential. Culture-based assays for bacterial susceptibility/sensitivity, although inexpensive, are slow and often difficult.

Laboratories are still largely equipped with immunoassay instrumentation, but not all have access to a thermal cycler or the expertise to perform a molecular MRSA test. According to a report by life science market research company Kalorama Information, (New York, NY, USA) replacement of current assays with molecular-based tests will be slow because of the recession. Therefore, both culture-based assays and immunoassays will remain in use for infectious disease tests that do not require rapid turn-around or are otherwise difficult to perform. The cost of nuclear acid-based NAT assays, which are not usually analyzed outside the hospital laboratory, is high at around $25-$35, while selective media cost about $5 a plate.

"Relevancy is established through significantly improved efficacy and not marginal improvement,” said Bruce Carlson, publisher of Kalorama Information. "NAT testing can be put to many uses, but what will get it into more labs is its role in determining the genetic differences that make a bacterial strain […..] drug resistant, with results in 2-4 hours.”

NAT testing will allow physicians to rapidly select combination therapeutics for infections caused by resistant organisms. In viral applications, for example in human immunodeficiency virus (HIV) infection, NAT testing successfully detected drug resistance that developed in response to therapy.

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