Table 1.

Physicochemical properties of biocides and their MICs for M. smegmatis SMR5 and isogenic porin mutants

Antimicrobial substance	Molecular mass (g/mol)	Partition coefficient (log Pow)a,f	MIC for M. smegmatis (μg/ml)b				Resistance factorc
			Wild type	ML02	ML10	ML16
Ampicillin	349	0.43	125	250	2,000	2,000	16
OIT (Kathon 893)	213	3.89	0.94	1.88	15	15	16
MCI/MId (Kathon 886)	150/115	0.72/0.48	0.18	0.35	0.7	0.7	4
MBO (Grotan OX)	186	0.45	0.01	0.02	0.02	0.02	2
HHT (Grotan BK)	219	−2.16	0.01	0.02	0.02	0.02	2
PHMBe	400–8,000	ND	5	5	10	10	2
Octenidine dihydrochloride	624	11.16	1	2	2	2	2
Gigasept Instru AF	Formulation	ND	6.25	12.5	50	50	8

^aPartition coefficients were calculated using ALOGPS 2.1 (available from the Virtual Computational Chemistry Laboratory at http://www.vcclab.org).

^bMICs were determined by MABA (see Materials and Methods) and represent biocide concentrations that reduced viability of the cells by ≥90%.

^cThe resistance factor R is the quotient of the MIC of the triple porin knockout strain M. smegmatis ML16 and the MIC of the M. smegmatis wild type.

^dKathon 886 contains a mixture of the active ingredients methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) in a ratio of 3:1.

^ePHMB is a mixture of hexamethylene biguanide hydrochloride polymers (n = 2 to 40) with an average chain length of 12 units. The partition coefficient cannot be calculated due to the polycationic nature of the molecules.

^fND, the partition coefficient cannot be determined for mixtures of compounds.