Streptococcus throat by PCR

Streptococcus A, C or G bacteria cause frequent pharyngitis and sore throats, especially in children. These bacterial infections are effectively treated with antibiotics. However, viruses are much more often the cause of sore throats than bacteria, but in the case of viral infections, no treatment is necessary and the infection disappears on its own within a few days. In order to avoid the development of resistance in bacteria, it is important to use antibiotics only in proven bacterial infections.

A rapid screening test for a strep antigen (Strepto-Direct) used as a first-line test can detect the presence of strepto A on a throat swab within minutes. A positive result indicates the presence of Group A Streptococcus and an antibiotic can be prescribed immediately. However, a negative result does not eliminate the possibility of a bacterial infection and all Strepto-Direct negative specimens must be confirmed in the laboratory. The traditional technique for confirmation is a 48-hour bacterial culture. An initial observation is made after 24 hours to identify rapidly positive cultures. 24-hour negative cultures are re-examined after 48 hours to obtain a final negative or positive result. In many cases, the antibiotic prescription is therefore delayed by 24 or even 48 hours. Group C and G streptococci are also detected.

Molecular identification of the bacteria by nucleic acid amplification (PCR) significantly shortens these delays. Now, all Strepto-Direct negative throat swabs are confirmed by analysis of the microbial DNA after amplification. The PCR technique detects more positive cases than Strepto-Direct and even bacterial culture. Depending on the time of arrival of the specimen at the laboratory, results are often available on the same day of collection or the next day at the latest, thus accelerating the proper management of the infection.