Evaluation of the Copan eSwab®, a liquid-based microbiology transport system, for the preservation of Neisseria gonorrhoeae at different temperatures

Lindy Gumede,Venessa Maseko,Duduzile Nhlapo,Frans Radebe,Tendesayi Kufa-Chakezha

doi:10.4102/sajid.v32i3.46

Abstract

Aims and objectives: To evaluate the survival duration of Neisseria gonorrhoeae from male urethral discharge specimens collected using the Copan eSwab® liquid-based microbiology transport system, at both ambient and refrigerator temperatures.Methods: Three urethral swabs (one Dacron, two Copan eSwabs®) were collected from each male patient presenting with purulent urethral discharge to a community-based primary healthcare centre in Johannesburg. The Dacron swab was directly inoculated onto New York city agar medium, and the Copan eSwabs® transported and held at room and refrigerator temperature, for daily sub-culture onto New York city agar over a total period of seven days (168 h). The utility of Copan eSwabs® for the transport and survival of N. gonorrhoeae at different temperatures was determined by comparison to culture obtained by ‘gold standard’ direct plate inoculation.Results: N. gonorrhoeae isolation rates from Copan eSwabs® at fridge temperature and ambient temperature were as follows: 87.9% vs 79.3% at 48 h; 67.2% vs 60.3% at 72 h; 60.3% vs 22.4% at 96 h; and, 53.4% vs 3.4% at 120 h, respectively. The viability of subculture decreased significantly from eSwabs® maintained at room temperature from 96 h onwards of specimen collection.Conclusion: To ensure the preservation and an acceptable isolation rate of N. gonorrhoeae from urethral discharge specimens, Copan eSwabs® should be transported and maintained at refrigerator temperatures, and must reach the processing laboratory by at least 120 h (5 days) after collection.

Highlights

The probability of success in the isolation of pathogenic Neisseria species from clinical specimens is related to three factors, namely: the amount of care taken in obtaining good specimens and inoculating them correctly; the provision of a culture medium capable of growing demanding strains of Neisseria from small inocula; and, the inclusion of selective agents in the medium which are capable of preventing overgrowth of commensal organisms, but do not inhibit the growth of the species required
The yield of N. gonorrhoeae from elution swab (eSwab)® held at room temperature versus refrigerator temperature was as follows: 79.3% vs 87.9% at 48 h; 60.3% vs 67.2% at 72 h; 22.4% vs 60.3% at 96 h; and, 3.4% vs 53.4% at 120 h, respectively (Table 1; Figure 1)
Thereafter, the N. gonorrhoeae culture yield from Copan eSwabs® stored in the refrigerator declined to 27.6% and 12.1% at 144 and 168 h

Summary

Introduction

The probability of success in the isolation of pathogenic Neisseria species from clinical specimens is related to three factors, namely: the amount of care taken in obtaining good specimens and inoculating them correctly; the provision of a culture medium capable of growing demanding strains of Neisseria from small inocula; and, the inclusion of selective agents in the medium which are capable of preventing overgrowth of commensal organisms, but do not inhibit the growth of the species required. Liquid-based microbiology is becoming increasingly utilised to enhance the efficiency of specimen processing and maximise recovery of micro-organisms.[2] Specimen collection devices transform samples into liquid to improve specimen release and elution, and allow for automation where needed. The advantages of this are that a homogeneous suspension is obtained, which provides multiple sample aliquots for standardisation of the diagnostic process and enhances the preservation micro-organisms.

Methods

Results

Discussion

Conclusion