Development and application of loop-mediated isothermal amplification methods targeting the seM gene for detection of Streptococcus equi subsp. equi.

The research article reports on the development and testing of a new diagnostic tool – a loop-mediated isothermal amplification (LAMP) method – to detect Streptococcus equi, a bacteria causing a highly contagious horse disease called strangles, with the help of a target gene called seM.

Method Development

• The researchers created a new testing technique using loop-mediated isothermal amplification (LAMP) aimed at identifying the seM gene of the strangles-causing bacteria, Streptococcus equi subsp. equi.
• Named seM-LAMP, this tool was able to accurately detect the target genetic sequence in a controlled 63-degree Celsius environment within an hour.
• However, the sensitivity of this method was noted to be slightly lower than with seM semi-nested PCR, a different detection strategy.

Specificity and Clinical Usefulness

• To determine the specificity of seM-LAMP, the researchers tested 100 strains of S. equi and 189 strains of non-S. equi bacteria.
• The results indicated that the seM-LAMP test was highly specific as it only amplified the DNA belonging to S. equi within an hour of incubation and did not react to non-S. equi strains.
• These findings align with those obtained via the seM semi-nested PCR method.
• The researchers then examined the clinical usefulness by testing seM-LAMP on 590 nasal swab samples from an active strangles outbreak.
• Both seM-LAMP and seM semi-nested PCR tests showed identical results, with 79 swabs testing positive for S. equi and 511 swabs testing negative; these results perfectly matched the findings from traditional culture examinations.

Conclusion

• This study suggests that the newly developed seM-LAMP diagnostic tool is viable for routine use in detecting infections caused by Streptococcus equi subsp. equi.
• The method has shown marked specificity and practicality by aligning perfectly with the results of traditional culture tests and seM semi-nested PCR tests.