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J Appl Microbiol. 2019 Jun 20. doi: 10.1111/jam.14359. [Epub ahead of print]

The impact of sample storage on molecular-based detection of Mycoplasma genitalium.

Author information

1
Centre for Women's Infectious Diseases, The Royal Women's Hospital, Park Parkville, Vic, Australia.
2
Molecular Microbiology Research Group, Murdoch Children's Research Institute, Parkville, Vic, Australia.
3
Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Vic, Australia.
4
Department of Obstetrics and Gynaecology, University of Melbourne, Melbourne, Vic, Australia.
5
Centre for Epidemiology and Biostatistics, School of Population and Global Health, University of Melbourne, Vic, Australia.
6
Melbourne Sexual Health Centre, Alfred Health, Carlton, Vic, Australia.
7
Central Clinical School, Monash University, Melbourne, Vic, Australia.
8
The Royal Children's Hospital, Parkville, Vic, Australia.

Abstract

AIMS:

Mycoplasma genitalium causes a common, sexually transmitted bacterial infection. This study assessed the detection of M. genitalium in stored urine samples to understand the impact of sample storage on M. genitalium detection.

METHODS:

Aliquots of M. genitalium-positive urine (n = 20 patients) were stored at either room temperature (22°C) or 4°C, without a preservative. At weekly intervals, samples were tested using the commercial test ResistancePlus MG® (SpeeDx® , Australia). We report the analysis at 1 week, an acceptable collection-to-test turnaround time, with further analysis over 5 weeks to illustrate degradation trends.

RESULTS:

After storing at 4°C, the proportion of specimens that remained positive for M. genitalium was 100% after 1 week and 95% after 4 weeks. Storage at 22°C led to more rapid decline in detection in the first 4 weeks, with 95% detected after 1 week and 85% at 2 weeks onwards. At 5 weeks, samples stored at both temperatures had an 85% M. genitalium detection rate, with increase in crossing points (Cq) of 0·72 (95% confidence interval (CI) 0·01-1·43; P-trend = 0·027) at 4°C, and 1·75 ((95% CI 0·79-2·71), P-trend <0·001) at 22°C.

CONCLUSIONS:

Urine samples stored without preservative, and unfrozen, retained high M. genitalium detection levels over the short term (up to 5 weeks). To minimize degradation, storing at 4°C is recommended.

SIGNIFICANCE AND IMPACT OF THE STUDY:

There is little known about the stability of clinical samples for M. genitalium detection. This study found that a high proportion (85-100%) of samples are still suitable for M. genitalium detection after storage for up to 5 weeks.

KEYWORDS:

PCR; degradation; detection; diagnosis; molecular genetic

PMID:
31220405
DOI:
10.1111/jam.14359

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