Final answer:
Based on the provided references, the organism in question, S. pyogenes, is sensitive to bacitracin and there is no evidence suggesting resistance to SXT, hence statement 4 is true.
Step-by-step explanation:
To determine which of the statements is true about the organism in question, we must look into the properties of S. pyogenes and general principles regarding bacterial identification. Bacitracin susceptibility assists in the differentiation of bacterial species, particularly those belonging to the genus Streptococcus. As per the provided reference indicating that S. pyogenes is indeed susceptible to 0.04 units of bacitracin, we can affirm that statement 1, which asserts that the organism is sensitive to bacitracin, is true. When it comes to the resistance to trimethoprim-sulfamethoxazole, often abbreviated as SXT, the information suggests that ß-lactams remain effective against S. pyogenes, which hints at no significant resistance mentioned. Therefore, without direct evidence of SXT resistance in the provided data, statement 2 cannot be substantiated, and thus, we lack proof to confirm it as true.
To address statement 3 regarding the PYR test: this test is commonly used to identify organisms that are PYRase positive, typically associated with Group A Streptococci such as S. pyogenes. Since our references point to techniques confirming the identity of S. pyogenes but do not provide specific results on the PYR test, we cannot conclusively affirm the validity of statement 3 from the given information. Combining this analysis, the conclusion is that the fourth statement is correct, as it combines the validated sensitivity to bacitracin with the unconfirmed resistance to SXT, which is not indicated as a characteristic of the organism based on the given references.