Digital detection and the use of Artificial Intelligence to detect Group A Streptococcus using a chromogenic agar



Streptococcus pyogenes (Group A streptococci – GAS) is the major bacterial cause of pharyngitis occurring in people of all ages but seen most commonly among children 5 through 15 years of age. The use of antibiotics is recommended to treat GAS pharyngitis in children to shorten the duration of symptoms, reduce the likelihood of transmission to family members, classmates, and other close contacts, and prevent the development of complications, including acute rheumatic fever, peritonsillar abscess, and mastoiditis.

Materials and Methods

We studied the ability of a specialized Group A Strep chromogenic agar (Colorex Strep A agar – Chromagar) together with Copan’s Phenomatrix artificial intelligence (AI) software (WASPLab chromogenic detection module) to detect GAS on this media. Results were compared to manual detection of the organism on standardized SXT-blood agar and visual reading. Potential GAS organisms from both types of media were confirmed as GAS by MALDI identification. Cultures were considered positive for GAS if MALDI confirmed GAS from either the chromogenic agar plates or the SXT-blood agar plates. A pyrrolidonyl arylamidase (PYR) test was performed to confirm positive cultures for GAS from the SXT-blood agar plates.


A total of 252 specimens were tested from patients presenting to our medical centers, emergency rooms and clinics, as well as 25 samples spiked with S. pyogenes, which resulted in a total of 42 positive GAS cultures. The SXT -blood agar detected 40/42 (95.2% sensitivity, 100% specificity) of the positive cultures, while the Group A Strep chromogenic agar/PhenoMatrix AI algorithm software detected 42/42 (100% sensitivity, 97.45% specificity) of the positive cultures.


This study demonstrates that the utilization of Group A Strep chromogenic agar together with Copan’s Phenomatrix artificial intelligence software was superior to the use of standard cultures on SXT-blood agar combined with manual reading. When undetected infections are left untreated the symptoms of Group A streptococcal pharyngitis are usually self-limited, however, patients, regardless of age, who have a positive test for GAS should receive antibiotics to prevent complications. The use of chromogenic agar together with AI software will more accurately detect these infections and allow for more appropriate patient therapy.