Evaluation of Sigma Transwab® in Liquid Amies
Transport Medium for Neisseria gonorrhoeae Culture.
E. Graveling1, H. Venkatesh2, N. Banerjee3
Department of Microbiology and Infection Control,
North Laboratory, Victoria Hospital, Hayfield Road, Kirkcaldy, KY2 5AG. [email protected]
On receipt in the laboratory the Sigma Transwab® were inoculated on to individual LCAT plates and stroked out for single colonies. The direct culture
plates and the Sigma Transwab® cultured plates were then incubated in parallel
Direct inoculation of LCAT (Lincomycin, Colistin sulphate, Amphotericin B,
at 35 +/-2 ºC in an atmosphere of 5% CO2 for up to 48 hours.
The use of Sigma Transwab® in liquid Amies transport medium obtained in
Trimethoprim) agar plates has been considered technically superior for
parallel with the current LCAT culture plates has provided data which
recovery of Neisseria gonorrhoeae in clinical specimens. However, there are
Culture plates were examined at 24 & 48 hours and bacteria presumptively
demonstrates an increase in recovery of the target thereby contributing to
numerous disadvantages that make this procedure increasingly less
identified on the basis of colony morphology, oxidase (positive), Gram stain
a service improvement.
attractive in a busy, cost-driven, clinical environment. Direct inoculation
(Gram negative diplococci), and confirmed by biochemical reactions using API®
requires parameters which the laboratories are unable to strictly control
Growth of Neisseria gonorrhoeae was achieved in a total of 14 samples
NH Biomerieux (Product Code:10 400) (Acceptable profile 1000 & 1001) and
such as : agar plates have to be purchased, transported to, refrigerated, and
obtained from the Sigma Transwab® plates, while only 12 positive cultures
Reference laboratory confirmation by Scottish Bacterial Sexually Transmitted
kept in-date at Sexual Health Clinics. Due to the large geographical area
were isolated from the direct culture plates, a 14% increase in recovery
Infections Reference Laboratory, NRIE, Edinburgh.
served by NHS Fife, culture plates inoculated in the Sexual Health Clinics
capability. Growth was achieved from the Sigma Transwab® plates at 24
are often delayed in transit to the laboratory which in turn has an impact on
hours, in 6 cases, whereas all of the direct culture plates were incubated
the recovery of Neisseria gonorrhoeae. The introduction of Sigma
for a further 24 hours. The results indicate not only a more rapid
Transwab® (manufactured and distributed by Medical Wire) was evaluated
identification, but also a more accurate method of diagnosis. This is
as a method of improving specimen quality in these circumstances.
demonstrated in the 2 cases where Neisseria gonorrhoea was only
detected when using Sigma Transwab®. The current method of direct
inoculation would have produced false negative results in these cases.
To determine whether the use of foam-tipped swabs in liquid Amies transport
Delays in incubation of direct culture plates along with use of media below
medium would result in comparable recovery of Neisseria gonorrhoeae with
optimum conditions undoubtedly contribute to the failures of the current
direct near patient inoculation of specimens to LCAT culture plates.
system. Management of Sigma Transwab® stock is easier than culture
plates as they can be stored at room temperature and have a shelf life of 2 years.
Based on published recovery rate data, literature reviews and user
The Sigma Transwab® inoculated plates were stroked out for single
preference, the Sigma Transwab® was selected for the evaluation.
colonies which in some cases made the performance of further identification possible at 24 instead of 48 hours. This is particularly evident
• MW177S Mini tip swab, orange capped, for urethral sampling.
in rectal and throat swab cultures where mixed cultures are common.
• MW176S Standard tipped swab, purple capped, for cervical, rectal, throat
and eye sampling.
• LCAT (Lincomycin, Colistin sulphate, Amphotericin B, Trimethoprim)–
The use of Sigma Transwab® in liquid Amies transport medium provides a
Thermofisher product no: PB0226A).
superior recovery method for Neisseria gonorrhoeae from clinical material
which is not only a quality improvement but also a service improvement for
the patient, allowing for a more efficient management of the process.
The outcome of this study was a change in procedure at all Sexual health
The Sigma Transwabs® were obtained in parallel with the direct culture on
clinics. NHS Fife adopted the use of Sigma Transwab® in liquid Amies
LCAT plates in three Sexual health clinics over a 7 month period. Patients
transport medium to obtain the relevant anatomical samples for
were informed that the trial swabs would be obtained. If the patient declined
transportation to the Microbiology laboratory for culture and identification
the request this was noted in the clinical notes, "patient declined trial
of Neisseria gonorrhoeae.
Direct culture/ Trial swab POS: Neisseria gonorrhoeae isolated
Procedure for direct culture to LCAT agar plates
Direct culture/ Trial swab NEG: Neisseria gonorrhoeae NOT isolated
Acknowledgements and References
▪ 10µl disposable loops for urethral sampling were used to prepare a smear
Thank you to the Sexual Health clinic staff, NHS Fife. Microbiology and Infection control
slide and inoculate a single LCAT culture plate.
Of a possible 200 samples, 177 trial swabs were obtained from the 3
staff, North Laboratory & K. Graveling for assistance and advise.
▪ Urine sample was obtained for NAAT (Nucleic Acid Amplification Test -
selected trial sites. Confirmed Neisseria gonorrhoeae was isolated
Roche) for Chlamydia trachomatis and Neisseria gonorrhoeae PCR testing.
1. Olsen, C et al (1999). Comparison of direct inoculation and Copan transport system for
from 14 samples.
▪ For all other anatomical sites (cervical, throat, rectal and eye) the NAAT
isolation of Neisseria gonorrhoeae from endocervical specimens. J.Clin. Micro. 37:3583-3585.
sample was collected, followed by inoculation of a single LCAT culture plate
2. Thompson, D et al (1999). Comparison of commercial Amies transport systems with
using a dry cotton swab for each site.
inhouse Amies medium for recovery of Neisseria gonorrhoeae. J.Clin.Micro: 37:3020-3021.
3. Chernesky, M et al (2006). Use of flocked swabs and a universal transport medium to
Procedure for Sigma Transwab® sample collection
enhance molecular detection of Chlamydia trachomatis and Neisseria gonorrhoeae. J.Clin.Micro: 44:1084-1086.
4. Public Health England, UK Standards for Microbiology Investigation, B28 Investigation of
▪ Male urethral sampling - the Sigma Transwab® was obtained before the
Trial swab not obtained
genital tract and associated specimens. B28i4.3 (Dec 2012)
urine sample for NAAT. The swab was rolled over visible discharge or
Trial swabs taken
5. Public Health England, UK Standards for Microbiology Investigation, ID6 –Identification
inserted into but not beyond the terminal 2 cm of the urethra.
of Neisseria species, ID6i2.1 (Sept 2007)
▪ For all other sites the Sigma Transwab® was obtained after all other
6. Medical Wire – wwwTranstube and Sigma Transwab® with liquid modified Amies
samples for NAAT and direct culture plate inoculation had taken place.
medium –MW176S & MW177S.
1. Biomedical Scientist Microbiology
2. Consultant Microbiology 3. Consultant
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