Bacterial cell wall synthessis; lipopolysaccharides and phospholipids in the outer cell membrane of gram-negative bacteria

At the same multiples of the MIC, colistin methanesulfonate had less bactericidal activity than colistin. The two components, colistins A and B (1), that make up colistin and colistin methanesulfonate are uneven combinations of salts that may have distinct in vitro activities[1].

---

The in vitro pharmacodynamic properties of colistin and colistin methanesulfonate were investigated by studying the MICs, time-kill kinetics, and postantibiotic effect (PAE) against mucoid and nonmucoid strains of Pseudomonas aeruginosa isolated from patients with cystic fibrosis. Twenty-three clinical strains, including multiresistant strains, and one type strain were selected for MIC determination. Eleven strains were resistant; MICs for these strains were >128 mg/liter. For the susceptible strains, MICs of colistin ranged from 1 to 4 mg/liter, while the MICs of colistin methanesulfonate were significantly higher and ranged from 4 to 16 mg/liter. The time-kill kinetics were investigated with three strains at drug concentrations ranging from 0.5 to 64 times the MIC. Colistin showed extremely rapid killing, resulting in complete elimination at the highest concentrations within 5 min, while colistin methanesulfonate killed more slowly, requiring a concentration of 16 times the MIC to achieve complete killing within 24 h. Colistin exhibited a significant PAE of 2 to 3 h at 16 times the MIC against the three strains after 15 min of exposure. For colistin methanesulfonate, PAEs were shorter at the concentrations tested. Colistin methanesulfonate had lower overall bactericidal and postantibiotic activities than colistin, even when adjusted for differences in MICs. Our data suggest that doses of colistin methanesulfonate higher than the recommended 2 to 3 mg/kg of body weight every 12 h may be required for the effective treatment of P. aeruginosa infections in cystic fibrosis patients[1].

MIC determination.[1]
MICs were determined by both broth macrodilution and microdilution in cation-adjusted Mueller-Hinton broth ccording to NCCLS standards. Strains were considered resistant to colistin and colistin methanesulfonate if the MICs were ≥32 mg/liter.

---

Time-kill kinetics.[1]
The time-kill kinetics of four strains, ATCC 27853 and three clinical isolates, two of which were mucoid, were examined. The clinical isolates were selected in order to have a range of MICs within the susceptible category. The MICs of colistin and colistin methanesulfonate, respectively, for the four strains were as follows: ATCC 27853, 4 and 16 mg/liter; 18982, 4 and 8 mg/liter; 19056, 1 and 8 mg/liter; and 20223, 4 and 16 mg/liter. Colistin and colistin methanesulfonate were added to a logarithmic-phase broth culture of approximately 106 CFU/ml to yield concentrations of 0, 0.5, 1, 2, 4, 8, 16, 32, and 64 times the MIC for the strain under study. Subcultures for viable counts were performed on nutrient agar at 0, 5, 10, 15, 20, 25, 30, 45, and 60 min and 2, 3, 4, and 24 h after antibiotic addition. Viable counts were determined after 24 h of incubation of subcultures at 37°C.

---

PAE.[1]
The in vitro PAE was determined by the standard in vitro method for two of the three clinical strains noted above and the ATCC strain with both agents. For each experiment, P. aeruginosa (≈106 CFU/ml) in logarithmic phase growth was exposed for 15 min (for colistin) or 1 h (for colistin methanesulfonate) in Mueller-Hinton broth to the antibiotics at concentrations of 0.5, 1, 2, 4, 8, and 16 times the MIC. Fifteen minutes of exposure was used for colistin due to its very rapid bactericidal effect, to ensure that there were adequate numbers of bacteria for sampling at the end of the exposure interval. Antibiotic was removed by twice centrifuging at 3,000 × g for 10 min, decanting the supernatant, and resuspending in prewarmed broth. Viable counts were performed at 0, 1, 2, 3, 4, 5, 6, and 24 h on nutrient agar. A growth control was performed in the same fashion but without exposure to antibiotic. The colonies were counted after 24 h of incubation at 37°C. PAE was determined by comparing regrowth of treated and growth control cultures, using the standard formula of the time for the control culture to increase 10-fold subtracted from the time for the treated culture to do the same.

[1]. In Vitro Pharmacodynamic Properties of Colistin and Colistin Methanesulfonate against Pseudomonas aeruginosa Isolates from Patients with Cystic Fibrosis. Antimicrob Agents Chemother. 2001 Mar; 45(3): 781–785.

Colistin A sodium methanesulfonate is colistin A in which each of the primary amino groups is converted into the corresponding aminomethanesulfonic acid sodium salt, commonly by treatment with formaldehyde followed by sodium bisulfite. It is an organic sodium salt, a polymyxin and a peptide antibiotic. It contains a colistimethate A(5-). It is functionally related to a colistin A.

---

The in vitro pharmacodynamic properties of colistin and colistin methanesulfonate were investigated by studying the MICs, time-kill kinetics, and postantibiotic effect (PAE) against mucoid and nonmucoid strains of Pseudomonas aeruginosa isolated from patients with cystic fibrosis. Twenty-three clinical strains, including multiresistant strains, and one type strain were selected for MIC determination. Eleven strains were resistant; MICs for these strains were >128 mg/liter. For the susceptible strains, MICs of colistin ranged from 1 to 4 mg/liter, while the MICs of colistin methanesulfonate were significantly higher and ranged from 4 to 16 mg/liter. The time-kill kinetics were investigated with three strains at drug concentrations ranging from 0.5 to 64 times the MIC. Colistin showed extremely rapid killing, resulting in complete elimination at the highest concentrations within 5 min, while colistin methanesulfonate killed more slowly, requiring a concentration of 16 times the MIC to achieve complete killing within 24 h. Colistin exhibited a significant PAE of 2 to 3 h at 16 times the MIC against the three strains after 15 min of exposure. For colistin methanesulfonate, PAEs were shorter at the concentrations tested. Colistin methanesulfonate had lower overall bactericidal and postantibiotic activities than colistin, even when adjusted for differences in MICs. Our data suggest that doses of colistin methanesulfonate higher than the recommended 2 to 3 mg/kg of body weight every 12 h may be required for the effective treatment of P. aeruginosa infections in cystic fibrosis patients.[1]

C58H115N16NA5O28S5

1759.89796376228

1758.615

C, 39.81; H, 6.05; N, 12.81; Na, 6.57; O, 25.60; S, 9.16

8068-28-8

46224595

White to off-white solid powder

18

33

39

112

3430

13

CC[C@H](CCCCC([O-])=N[C@H](C(N[C@H](C(N[C@H](C([O-])=N[C@H]1CCNC([C@@H](NC([C@@H](N=C([O-])[C@@H](NC([C@@H](NC([C@H](N=C([O-])[C@@H](N=C1[O-])CCNCS(=O)(O)=O)CC(C)C)=O)CC(C)C)=O)CCNCS(=O)(O)=O)CCNCS(=O)(O)=O)=O)[C@H](O)C)=O)CCNCS(=O)(O)=O)=O)[C@H](O)C)=O)CCNCS(=O)(O)=O)C.[Na+].[Na+].[Na+].[Na+].[Na+]

IQWHCHZFYPIVRV-VLLYEMIKSA-I

InChI=1S/C58H110N16O28S5.5Na/c1-9-35(6)12-10-11-13-46(77)65-38(14-20-59-28-103(88,89)90)53(82)74-48(37(8)76)58(87)70-41(17-23-62-31-106(97,98)99)50(79)68-43-19-25-64-57(86)47(36(7)75)73-54(83)42(18-24-63-32-107(100,101)102)67-49(78)39(15-21-60-29-104(91,92)93)69-55(84)44(26-33(2)3)72-56(85)45(27-34(4)5)71-52(81)40(66-51(43)80)16-22-61-30-105(94,95)96;;;;;/h33-45,47-48,59-63,75-76H,9-32H2,1-8H3,(H,64,86)(H,65,77)(H,66,80)(H,67,78)(H,68,79)(H,69,84)(H,70,87)(H,71,81)(H,72,85)(H,73,83)(H,74,82)(H,88,89,90)(H,91,92,93)(H,94,95,96)(H,97,98,99)(H,100,101,102);;;;;/q;5*+1/p-5/t35-,36-,37-,38+,39+,40+,41+,42+,43+,44+,45-,47+,48+;;;;;/m1...../s1

pentasodium;[2-[(2S,5R,8S,11S,14S,17S,22S)-17-[(1R)-1-hydroxyethyl]-22-[[(2S)-2-[[(2S,3R)-3-hydroxy-2-[[(2S)-2-[[(6R)-6-methyloctanoyl]amino]-4-(sulfonatomethylamino)butanoyl]amino]butanoyl]amino]-4-(sulfonatomethylamino)butanoyl]amino]-5,8-bis(2-methylpropyl)-3,6,9,12,15,18,23-heptaoxo-11,14-bis[2-(sulfonatomethylamino)ethyl]-1,4,7,10,13,16,19-heptazacyclotricos-2-yl]ethylamino]methanesulfonate

CHEBI:59663; colistin A sulfomethate sodium; Colistin X; DSSTox_CID_25822;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : 100 mg/mL

Solubility in Formulation 1: 100 mg/mL (Infinity mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

---

 (Please use freshly prepared in vivo formulations for optimal results.)