A preliminary evaluation of a new GeneXpert (Gx) molecular point-of-care test for the detection of Trichomonas vaginalis.

OBJECTIVES: Global concerns regarding the prevalence, asymptomatic nature and burden of disease associated with Trichomonas vaginalis (TV) continue. The lack of a portable molecular point-of-care assay to detect this infectious disease has meant that many remote or low-resource settings still need to rely on delayed results from central laboratories and/or syndromic management as treatment strategies. We evaluated the new GeneXpert (Gx) TV nucleic acid amplification test (NAAT) compared with an in-house laboratory NAAT to determine whether it would be suitable for use at the point of care. METHODS: In a state-based laboratory and using their in-house NAAT, we selected the first 60 urine samples that were positive and the first 60 that were negative (n=120) in the study period for Gx TV testing in order to reduce collection delays and avoid the freezing of samples. RESULTS: Positive percentage agreement between the Gx TV and NAAT was 95.0% (95% CI 86.1% to 99.0%), negative percentage agreement was 100.0% (95% CI 93.5% to 100.0%) and overall percentage agreement was 97.4% (95% CI 92.5% to 99.5%). Three discordant results were detected with each being close to the cycle threshold of detection using the in-house NAAT assay. CONCLUSIONS: Findings suggest the Gx TV assay is easy to use and has suitable overall agreement for sexually transmissible infection (STI) testing at the point of care. It may be used in combination with the Gx CT/NG assay to test for all three STIs simultaneously using this portable and modular-based NAAT platform.

A reliable and easy to transport quality control method for chlamydia and gonorrhoea molecular point of care testing.

Quality control (QC) is an essential component of point-of-care testing programs. In the context of a randomised-controlled trial (TTANGO) using GeneXpert (Xpert) Chlamydia trachomatis and Neisseria gonorrhoeae (CT/NG) point-of-care testing in remote areas of Australia, we aimed to develop and utilise a stable positive control material. Bacterial cultures of CT and NG were resuspended together to provide cycle threshold (Ct) values of approximately 25 cycles for both CT and NG when tested on the Xpert CT/NG assay. These positive control suspensions were dried in aliquots, heat inactivated, and then provided to 12 participating health services as research-only QC samples in kit form. At each service, a QC sample was resuspended and tested each month on the Xpert. QC results, including Xpert Ct values, were analysed from each site over 30 months and we calculated costs per QC sample. Overall, at 12 health services there were 89 QC samples tested (average of 8 tests per site per year). Mean Ct values for the 89 controls samples were 25.25 cycles (SD = 1.15) for CT, 24.04 cycles (SD = 1.400) for one NG target and 23.35 cycles (SD = 1.55) for the other NG target. No significant differences in Ct value for CT or NG controls were observed over a trial period of 30 months. Positive QC samples for research use in a trial of a molecular point-of-care assay were inexpensive to produce and stable when stored at 2-8°C. For routine use, additional requirements such as meeting National Association of Testing Authority (NATA) regulations and Therapeutic Goods Administration (TGA) approval will need to be achieved.

An outbreak of Cryptosporidium hominis infection at an Illinois recreational waterpark.

Cryptosporidium has become increasingly recognized as a pathogen responsible for outbreaks of diarrhoeal illness in both immunocompetent and immunocompromised persons. In August 2001, an Illinois hospital reported a cryptosporidiosis cluster potentially linked to a local waterpark. There were 358 case-patients identified. We conducted community-based and waterpark-based case-control studies to examine potential sources of the outbreak. We collected stool specimens from ill persons and pool water samples for microscopy and molecular analysis. Laboratory-confirmed case-patients (n=77) were more likely to have attended the waterpark [odds ratio (OR) 16.0, 95% confidence interval (CI) 3.8-66.8], had pool water in the mouth (OR 6.0, 95% CI 1.3-26.8), and swallowed pool water (OR 4.5, 95% CI 1.5-13.3) than age-matched controls. Cryptosporidium was found in stool specimens and pool water samples. The chlorine resistance of oocysts, frequent swimming exposures, high bather densities, heavy usage by diaper-aged children, and increased recognition and reporting of outbreaks are likely to have contributed to the increasing trend in number of swimming pool-associated outbreaks of cryptosporidiosis. Recommendations for disease prevention include alteration of pool design to separate toddler pool filtration systems from other pools. Implementation of education programmes could reduce the risk of faecal contamination and disease transmission.