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Year : 2003  |  Volume : 21  |  Issue : 2  |  Page : 68-

Molecular biology techniques, making their way into clinical microbiology laboratories

S Sharma 
 Jhaveri Microbiology Centre, LV Prasad Eye Institute, Hyderabad - 500 034, India

Correspondence Address:
S Sharma
Jhaveri Microbiology Centre, LV Prasad Eye Institute, Hyderabad - 500 034

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Sharma S. Molecular biology techniques, making their way into clinical microbiology laboratories.Indian J Med Microbiol 2003;21:68-68

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Sharma S. Molecular biology techniques, making their way into clinical microbiology laboratories. Indian J Med Microbiol [serial online] 2003 [cited 2020 Jun 3 ];21:68-68
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Obvious from the recent publications in the Indian Journal of Medical Microbiology (IJMM) is the fact that the days of molecular microbiology are here to stay in the Indian clinical microbiology laboratories. A large number of microbiologists are resorting to diagnostic methods based on hybridizing or amplifying nucleic acids. Although sequencing the DNA of pathogenic organisms to establish diagnosis is still out of reach for many, it is heartening to know of some of the research oriented corporate sector laboratories that have already initiated this technique into the realm of clinical microbiology. This does not mean that initiating these new techniques in clinical laboratories is without hurdles. Several challenges need to be met before these techniques are widely used by larger number of laboratories.

With the introduction of the Roche Amplicor Monitor for HIV viral load, molecular testing has become a routine assay in some laboratories. Amplification assays in kit forms have also become available for hepatitis C virus and probably close to follow will be assays for cytomegalovirus, herpes simplex virus and hepatitis B virus. Apart from the commercial kits, several laboratories are using in-house developed probes or polymerase chain reaction (PCR) techniques. Nevertheless, at the present time, most of the information provided in journal articles and at meeting presentations are more about analytical performance rather than clinical application. There is a serious need to evaluate sensitivity and specificity of these tests from a clinical point of view, especially in terms of application of the test results in making therapeutic decisions by the clinicians.

The onus is on the clinical microbiologists turning into molecular microbiologists, to provide clinically relevant data based on nucleic acid techniques. Users of these techniques need to be aware of inhibitors in clinical specimens that can interfere with the tests and the possibility of contamination.[1] More studies addressing the issue of reliability of nucleic acid techniques need to be done and published in the interest of learning from shared experience. There is a pressing need for standardization of methods, reference sequences, primer selections and most of all the interpretation. While the potential of these tests is phenomenal, we need to realise that molecular technology is not going to answer all questions about cause of infections. A judicious use of conventional and molecular techniques is likely to provide the best answers. Awareness regarding background signal contamination, i.e., endogenous microbial molecular background of the human body, is critical. While we know what to expect as normal flora in standard conventional techniques of culture we are yet to learn the same with molecular methods. Sequence diversity is obviously much greater than cultivar diversity. Interpretation of molecular tests on clinical samples would require understanding of endogenous microbial molecular flora.

Patrick Murray, Director of Clinical Microbiology at the University of Maryland Medical System in Baltimore, has compared the initial problems and scepticism about utility of PCR and related techniques to that of induction of enzyme-linked immunosorbent assays into clinical laboratories several decades ago. Many laboratories had problems justifying immunoassays initially, however, we are well aware of the wide and comfortable usage of these assays presently by even smallest of the laboratories. Murray says that the presently used nucleic acid-based molecular diagnostics are now a first-generation technology with major problems which are sure to improve with time and are here to stay.


1S Sharma, D Das, R Anand, TP Das, C Kannabiran. Reliability of nested PCR in the diagnosis of bacterial endophthalmitis. Am J Ophthalmol 2002;133(1):142-144.