specifies value of has specified value K antigen E. coli K antigen specification K(1|2a|2ac|3|4|5|6|7|8|9|10|11|12|13|14|15|16|18a|18ab|19|20|22|23|24|26|27|28|29|30|31|34|37|39|40|41|42|43|44|45|46|47|49|50|51|52|53|54|56|96|55|74|82|84|85ab|85ac|87|92|93|95|97|98|100|101|102|103|X104|X105|X106) string value specification