9444
We performed surface plasmon resonance ( SPR ) studies to determine their binding avidity to two cell wall models , each made with either a vancomycin - susceptible ( D ) - Ala - ( D ) - Ala or vancomycin - resistant ( D ) - Ala - ( D ) - Lac cell wall precursor .
 vancomycin, ( D ) - Ala - ( D ) - Ala, vancomycin, ( D ) - Ala - ( D ) - Lac
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 vancomycin, ( D ) - Ala - ( D ) - Ala, vancomycin, ( D ) - Ala - ( D ) - Lac