Multiplex Polymerase Chain Reaction for the Diagnosis of Sexually Transmitted Diseases

Fluoroquinolone-resistant Neisseria gonorrhoeae: the inevitable epidemic

The worldwide incidence of fluoroquinolone-resistant Neisseria gonorrhoeae has increased dramatically in the last few years. Single doses of fluoroquinolones can no longer be used to treat N gonorrhoeae infections acquired in the Far East, parts of the Middle East, the Pacific Islands, and parts of Western Europe and the United States. Although California and Hawaii account for most of the current United States cases, the increased incidence of FQR in some high-risk groups independent of geography heralds an imminent spread of drug-resistant strains throughout the rest of the population. The use of molecular tests has revolutionized the diagnostic field in STIs. The main limitation of their application in N gonorrhoeae testing has been the loss of culture specimens that allow antimicrobial sensitivity testing. New molecular methods have made it possible to detect antimicrobial resistance without the use of live organisms. These tests hold the promise of improving epidemiologic tracking of N gonorrhoeae drug resistance, leading to better patient management at the local level. The loss of fluoroquinolones limits available oral regimens to a single CDC-recommended antibiotic, cefixime. Oral, inexpensive, single-dose alternatives are needed to ensure continued therapeutic success.

Primer on medical genomics part II: Background principles and methods in molecular genetics

The nucleus of every human cell contains the full complement of the human genome, which consists of approximately 30,000 to 70,000 named and unnamed genes and many intergenic DNA sequences. The double-helical DNA molecule in a human cell, associated with special proteins, is highly compacted into 22 pairs of autosomal chromosomes and an additional pair of sex chromosomes. The entire cellular DNA consists of approximately 3 billion base pairs, of which only 1% is thought to encode a functional protein or a polypeptide. Genetic information is expressed and regulated through a complex system of DNA transcription, RNA processing, RNA translation, and posttranslational and cotranslational modification of proteins. Advances in molecular biology techniques have allowed accurate and rapid characterization of DNA sequences as well as identification and quantification of cellular RNA and protein. Global analytic methods and human genetic mapping are expected to accelerate the process of identification and localization of disease genes. In this second part of an educational series in medical genomics, selected principles and methods in molecular biology are recapped, with the intent to prepare the reader for forthcoming articles with a more direct focus on aspects of the subject matter.

Simultaneous detection of multiplex-amplified human immunodeficiency virus type 1 RNA, hepatitis C virus RNA, and hepatitis B virus DNA using a flow cytometer microsphere-based hybridization assay

The feasibility of performing a multiplex assay for the detection of human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) RNAs and hepatitis B virus (HBV) DNA is demonstrated. This assay is based (i) on the coamplification of a 142-bp fragment from the gag region of the HIV-1 genome and a 142-bp HIV-1 quantitation standard fragment, a 244-bp fragment from the 5' noncoding region of the HCV genome, and a 104-bp fragment from the pre-C and C gene regions of the HBV genome, using three sets of specific primers; (ii) on the capacity of these four biotinylated PCR products to hybridize to their specific oligonucleotide probe-coated microspheres; and (iii) on the ability of the flow cytometer to discriminate between distinct fluorescent-microsphere categories. Absence of cross-hybridization between the unrelated oligonucleotide probes and PCR products generated by the multiplex reverse transcription-PCR (RT-PCR) and the highly sensitive detection method allowed us to assess unambiguously the HIV-1 viral load and the infectious status of 35 serologically well-established clinical samples and 20 seronegative blood donor plasma samples tested. The results indicate that multiplex RT-PCR and flow cytometer microsphere-based hybridization assays, when combined, provide a rapid, sensitive, and specific method for the quantitation and detection of the major viral agents of infectious diseases in a single plasma sample.