Administrative Office
St. Joseph's Hospital Site, L301-10
50 Charlton Avenue East
HAMILTON, Ontario, CANADA L8N 4A6
PHONE: (905) 521-6141
FAX: (905) 521-6142
http://www.fhs.mcmaster.ca/hrlmp/
Issue No. 72
QUARTERLY NEWSLETTER
December 2003
Update on Chlamydia Trachomatis and
Neisseria Gonorrhoeae Testing
The detection and treatment of genitourinary tract infections caused by Neisseria gonorrhoeae and
Chlamydia trachomatis are of great importance as these agents are major causes of morbidity for
sexually active individuals (1). Treating based on clinical syndromes is of limited utility as up to 70% of
women and 50% of men will have asymptomatic disease (2). Despite having asymptomatic disease,
these individuals are still at risk for the sequelae of infection such as pelvic inflammatory disease,
epididymitis, infertility and ectopic preganancy and can transmit infection.
Significant advances have been made in the detection of Neisseria gonorrhoeae and Chlamydia
trachomatis over the last several years. The development of nucleic acid amplification testing (NAAT)
has been largely responsible for this. Isolation of Chlamydia trachomatis, an obligate intracellular
bacteria, has largely been replaced by nucleic acid amplification methods for testing most clinical
specimens. The sensitivity of culture for Chlamydia is often reduced by delayed delivery of specimens to
laboratories, reducing their viability (3). There are several methods for NAATs: PCR and ligase chain
reaction (LCR) were the first tests widely implemented. With the transition to LCR the sensitivity of
chlamydia detection improved significantly. Recently several other NAATs have been developed. The
Hamilton Regional Laboratory Medicine Program has recently changed over to the BDProbeTec amplified
DNA assay. This system uses a strand displacement amplification method coupled with a fluorescent
energy transfer measurement to detect the amplified product. The system also has the capacity to detect
Chlamydia and Neisseria simultaneously.
The BDProbeTec test performance has been evaluated in a number of studies and shown to have high
sensitivity and specificity for a number of specimen types. For female patients, cervical swabs are the
specimen of choice with a sensitivity of 92-93% and a specificity of 98-100% (3,4). Vaginal swabs appear
to have similar sensitivity and specificity compared with cervical swabs for the detection of Chlamydia
trachomatis but this specimen type is not currently FDA approved (4,5). An advantage of vaginal swabs
is that they may be self-collected and are preferred by patients (8). They are a reasonable alternative to
cervical swabs in those patients who have undergone a total hysterectomy or are unable to undergo a
pelvic examination. A cervical swab is, however, the specimen of choice whenever possible (4). Urine
specimens from females are reported to have sensitivities of 81%-94% and specificities of 98% in studies
evaluating large numbers of specimens (3,6). Currently we do not recommend the routine testing of
female urine specimens. For male specimens, urethral swabs and urines have been tested using NAATs.
Both appear to have similar sensitivities of >92% and specificity of >93% (3). Both are superior to culture,
which has a sensitivity in the range of 50-80%. Urine specimens are generally the specimen preferred by
male patients.
Traditionally culture has been the main diagnostic test for Neisseria gonorrhoeae (GC). Culture has the
advantage of providing the ability to do susceptibility testing on an isolate.. Unfortunately culture has poor
sensitivity. For females, culture of cervical specimens has the highest sensitivity of 70-93% (3,4). The
BDProbeTec NAAT is able to detect Neisseria gonorrhoeae from cervical specimens with a sensitivity
>90% (3,4). The specificities for this test are >99%. Self-collected vaginal swabs have also been tested
by NAAT for the detection of GC and sensitivity has been equivalent (4) or better (5) than that obtained
with cervical swabs.
Urine testing for GC using BDProbeTec was found to be less sensitive than cervical swabs with
sensitivities of 72-84% in two large studies (3,5). Higher sensitivities have been reported for male urines
for the detection of GC. The detection of GC by BDProbeTec NAAT from male urethral swab specimens
has a similar sensitivity compared with urine cultures (98.5% and 97.9% respectively) (3).
The Hamilton Regional Laboratory Medicine Program will provide the following testing of specimens for
which Chlamydia and N. gonorrhoeae have been requested.
1.
For female patients, all cervical specimens requesting Chlamydia and N.gonorrhoeae will be
tested using the BDProbetec NAAT. .A single cervical swab should be collected using the provided
“Culturette Direct Swabs” and sent in the container to the laboratory. No transport media is required.
Please specify clearly whether testing is required for either Chlamydia trachomatis or Neisseria
gonorrhoeae
alone
or
both.
Note: Vaginal swabs may be collected from patients who have had total hysterectomies and will be
processed as a cervical specimen.
2.
For male patients, Chlamydia and N. gonorrhoeae testing will be done from urine only. Collect 15 20 ml (maximum 60 ml) in a sterile container and properly close the container. Male urethral swabs
are no longer available. Male urethral specimens collected using the female swabs are not
appropriate and will be rejected.
3.
Other requests for Chlamydia (throat, rectal swab, eye swab) should be collected and sent to the
laboratory using the Multi-Microbe Media (M4RT) standard transport media for Chlamydia and
viruses. The specimen should be transported to the laboratory as quickly as possible where it will be
set up for Chlamydia culture. NAAT are currently not approved for these specimen types.
4.
Other specimens requesting N. gonorrhoeae (throat, rectum, skin lesions, eye swabs, fluid
aspirates) may be cultured if specifically requested. Routine culture swabs with charcoal transport
media should be used for these specimens. NAAT is not approved for these specimen types.
1)
De Schryver A, Meheus A. Epidemiology of sexually transmitted diseases: the global picture. 1990; W.H.O.
68:639-54.
2)
Jones C.A, Knaup R.C., Hayes M, Stoner B.P. Urine screening for gonococcal and chlamydia infections at
community-based organizations in a high morbidity area. 2000; Sex. Trans. Dis. 27:146-51.
3)
Van Der Pol B, Ferrero D.V, Buck-Barrington L, Hook E, Lenderman C, Quinn T, Gaydos C.A,
Lovchik J,
Schachter J, Moncada J, Hall G, Tuohy M.J, Jones R.B. Multicenter evaluation of
the BDProbeTec ET system for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in
urine specimens, female endocervical swabs, and male urethral swabs. 2001. J. Clin. Micro.
39(3):1008-1016.
4)
Cosentino L.A, Landers D.V, Hillier S.L. Detection of Chlamydia trachomatis and Neisseria gonorrhoeae by
strand displacement amplification and relevance of the amplification control for use with vaginal swab
specimens. 2003. J. Clin. Micro. 41(8); 3592-3596.
5)
Shafer M-A, Moncada J, Boyer C.B, Betsinger K, Flinn S.D, Schachter J. Comparing first-void urine
specimens, self-collected vaginals swabs, and endoscervical swabs to detect Chlamydia trachomatis and
Neisseria gonnorhoeae by a nucleic acid amplification test. 2003. J. Clin. Micro: 41(9); 4395-4399.
6)
Verkooyen R.P, Noordhoek G.T, Klapper P.E, Schirm J, Cleator G.M, Ieven M, Hoddevik G. Reliability of
nucleic acid amplification methods for detection of Chlamydia trachomatis in urine: results of the first
international collaborative quality control study among 96 laboratories. 2003. J. Clin. Micro. 41(7): 3013-3016.
7)
Akduman D, Ehret J.M, Messina K, Ragsdale S, Judson, F.N. Evaluation of a strand displacement
amplification assay (BD ProbeTec-SDA) for detection of Neisseria gonorrhea in urine specimens. 2002; J.
Clin. Micro. 40(1):281-283.
8)
Schachter, J., McCormack, W.M., Chernesky, M.A, Martin, D.H., Van Der Pol, B., Rice, P.A., Hook III, E.W.,
Stamm, W.E., Quinn, T.C., Chow, J.M. 2002. Vaginal Swabs are Appropriate Specimens for the Diagnosis of
Genital tract Infection with Chlamydia trachomatis. Submitted to JAMA for publication.
Cheryl Main, Dr. Jim Mahony, Santina Castriciano, Dr. Fiona Smaill
Discipline of Microbiology