27570
The MACOM for the 551st is ( TRADOC ) and they fall directly under the 15th Regimental Signal Brigade .
 551st, 15th Regimental Signal Brigade
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 551st, 15th Regimental Signal Brigade