A compound represented by formula (1),
a tautomer thereof, or a salt of the compound or tautomer, which is useful as a bactericide/disinfectant. In the formula, R
1
represents a hydrogen atom, an optionally substituted alkyl group or the like, R
2
represents a hydrogen atom or an optionally substituted alkyl group, or alternatively R
1
and R
2
may combine together with an adjacent nitrogen atom to form an optionally substituted nitrogen-containing heterocyclic group; R
4
represents a hydrogen atom or an optionally substituted alkyl group; R
3
represents an optionally substituted alkyl group; and R
5
and R
6
each represents a hydrogen atom or a methyl group, excluding a compound wherein both R
2
and R
4
represent a hydrogen atom and a compound wherein both R
1
and R
4
represent a hydrogen atom are excluded.