Stool culture less effective for cholera diagnosis compared to PCR

USA: A recent study has shown the poor performance of stool culture compared to polymerase chain reaction (PCR) testing for cholera diagnosis during declining cholera cases. Stool culture is historically considered the "gold standard" for cholera diagnosis. 

The findings, published in Open Forum Infectious Diseases, underscore the importance of utilizing alternative methods to identify this gastrointestinal illness's new surges.

Cholera, a severe diarrheal disease, often occurs in regions with weak or broken-down infrastructure, where laboratory capabilities may be limited. Dr Louise C. Ivers, the Harvard Global Health Institute director, emphasized the significance of robust laboratory-based surveillance to detect ongoing transmission, identify outbreaks early, and facilitate prompt public health responses.

● To evaluate whether cholera had been eliminated or was still circulating at lower rates in Haiti, the researchers enrolled 60 participants with acute watery diarrhoea meeting the clinical definition of cholera.

● The study participants, aged seven months to 80 years of age, were enrolled between September 2018 and March 2019.

● Stool culture demonstrated reduced reliability in identifying cholera cases, with a sensitivity of 33.3% and specificity of 97.4% compared to PCR, considered the gold standard.

● The addition of PCR testing allowed for a more comprehensive assessment of cholera cases that may have been missed during the period of low incidence in Haiti.

Although the study's results are based on a small sample size and do not drastically alter our understanding of cholera, they highlight the potential benefits of incorporating novel techniques into cholera surveillance. Molecular tools like PCR can enhance the ability to accurately identify and differentiate cholera from other pathogens causing diarrheal diseases.

Dr. Ivers emphasized the importance of understanding when and how to utilize molecular tools for cholera research, screening, and surveillance. These tools can play a vital role in improving our understanding of the disease's transmission patterns and facilitating timely interventions.

Cholera, which plagued Haiti for almost a decade after a devastating earthquake in 2010, was declared eradicated in the country in early 2022. However, a recent resurgence of the disease since last fall has raised concerns. Between October and December alone, over 13,600 suspected cholera cases and 283 deaths were reported in Haiti.

While the study highlights the limitations of stool culture during periods of low cholera transmission, further research and larger-scale studies are needed to validate the findings. Implementing traditional and molecular diagnostic methods could enhance cholera surveillance and response strategies, particularly in resource-limited settings.

Efforts to control cholera outbreaks and prevent the spread of this waterborne disease require ongoing vigilance, improved laboratory infrastructure, and innovative approaches for timely detection and response to emerging cases.

Reference:

Guillaume Y, et al. Open Forum Infect Dis 2023;doi:10.1093/ofid/ofad301.