Table 3. Mutations detected in the ampC promoter region of CTX-M β-lactam–resistant Escherichia coli*.

Isolate	CEF MIC, mg/L	CTX-M	Phylogenetic group	Mutation at position†
				−42	−32	−28	−18	−1	+22	+26	+27	+32	+58	+70	+81
E. coli K12 (U00096)	–	–	–	C	T	G	G	C	C	T	A	G	C	C	G
CEC1	16	Yes	D						T	G	T	A		T
CEC3	32	No	D						T	G	T	A		T
CEC4	32	No	D				A	T					T
CEC6	32	Yes	D						T	G	T	A		T
CEC8	32	Yes	D						T	G	T	A		T
CEC9	32	Yes	D						T	G	T	A		T
CEC10	32	Yes	D						T	G	T	A		T
CEC13	32	Yes	D						T	G	T	A		T
CEC14	16	Yes	D											T
CEC15	16	Yes	D											T
CEC19	32	No	D						T	G	T	A		T
CEC21	16	Yes	D			A							T		A
CEC22	16	Yes	D											T
CEC31	16	Yes	D			A							T		A
CEC57	32	No	D		A				T	G	T	A		T
CEC88	32	No	B2			A									A
CEC89	32	Yes	D						T	G	T	A		T
CEC92	>128	Yes	D	T			A	T					T
CEC93	>128	No	D						T	G	T	A		T

*CEF, cefoxitin; CEC, Cambodian E. coli.
†According to numbering of Jaurin and Grundström (30).