SXT (sulfamethoxazole-trimethoprim) susceptibility testing differentiates group A and B streptococci from other hemolytic streptococci. Group A and B streptococci are SXT resistant, whereas other hemolytic streptococci are susceptible to SXT.

2024年5月8日 · The SXT (sulfamethoxazole-trimethoprim) susceptibility test tells the difference between group A and B streptococci and other hemolytic streptococci.

2022年8月10日 · SXT disc susceptibility test in conjunction with bacitracin is used for the presumptive identification of beta hemolytic streptococci on blood agar (presumptively identifying beta-hemolytic streptococci as either group A, B or not group A and B).

SXT is representative of a family of conjugative-transposon-like mobile genetic elements that encode multiple antibiotic resistance genes. In recent years, SXT-related conjugative, self-transmissible integrating elements have become widespread in Asian Vibrio cholerae. We have determined the 100-kb DNA sequence of SXT.

A bacitracin (0.04 units, BBL)-SXT (trimethoprim, 1.25 mg, plus sulfamethoxazole, 23.75 mg, BBL) susceptibility test was 94% accurate in presumptively identifying streptococci as either group A, B or not group A and B.

This selective medium allowed much better recovery of group A and B streptococci and suppressed the growth of the normal flora, including "viridans" streptococci. In an initial study of 700 throat cultures, SXT-BA recovered 42% more group A and 49% more group B …

2022年8月10日 · Many laboratories use this test as the sole test for diagnosing GAS infections due to the difficulty in performing sero-grouping and high cost of antisera. The test is used for presumptive identification and differentiation of beta-hemolytic group A streptococci (Streptococcus pyogenes – susceptible) from other beta-hemolytic streptococci.

Thus, the sensitivity of GBS detection by BA, SXT, and Lim is 51%, 49%, and 99%, respectively. These data suggest that the use of Lim broth increases the recovery rate of GBS by 48% after 48 h while the use of the SXT plate reduced the recovery rate by 2% as compared with the conventional BA plate.

SXT excises from the chromosome to form a circular but nonreplicative extrachromosomal molecule that is required for its transfer. Here we found that a significant fraction of freshly isolated SXT exconjugants contained tandem SXT arrays. There was heterogeneity in the size of the SXT arrays detected in single exconjugant colonies.

The resistance to SXT is used for the primary recovery of groups A and B streptococci from specimens with mixed culture. Their resistance allows them to selectively grow out from contaminating bacteria that are inhibited by this antibiotic.