Advanced Techniques in Diagnostic Microbiology

22
Review of Molecular Techniques
for Sexually Transmitted
Diseases Diagnosis
ANGUS C.T. LO ANDKAI MAN KAM
Introduction
Sexually transmitted diseases (STDs) constitute the most common infectious diseases
around the world and bear significant consequences for both the individual
and public health of the community. More than 20 STDs have now been identified,
and they affect more than 13 million men and women in the United States
each year (CDC, 2002). Data from the Centers for Disease Control and Prevention
(CDC) show that more than 7 million cases of Chlamydia trachomatis infection
and more than 350,000 cases of Neisseria gonorrhoeae infection were reported in
2000 (CDC, 2001). In the past decade, the rapid development of molecular techniques
has gradually shifted the paradigm of laboratory diagnosis from traditional
biological to molecular amplification and detection of major causative agents of
sexually transmitted infections.
A milestone in biotechnology that heralded the beginning of molecular diagnostics
was the development of the polymerase chain reaction (PCR) by Mullis
and colleagues (Saiki et al., 1988). Since then, numerous molecular detection techniques
have been designed to detect specific nucleic acids without relying on the
ability to culture or directly observe intact organisms. As a result, stringency in
transport of clinical samples, in terms of preserving organism viability, has become
less strict. With automation, a faster turn-around time of molecular tests became
an advantage that significantly enhances this paradigm shift. Silent pathogens such
as human papillomavirus (HPV) that cannot be cultivated in vitro can now be detected
and typed by using molecular detection techniques that can also determine
oncogenic potential and prognostic outcome of different infections. These powerful
molecular techniques have a significant impact on strategies and public health
programs designed for the control and prevention of STDs worldwide.
An estimated 50% of STDs occur asymptomatically, and this forms a major
reservoir of infectious source that persists in the community. More sensitive detection
techniques are often required for detecting asymptomatic individuals with low
microbial load (Yoshida et al., 2002). Currently available molecular techniques using
nucleic acid amplification can now offer high sensitivity in screening for these
infections and disrupt the transmission chains within the community. This would,
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