Tible S. epidermidis ATCC12228 (MIC 0.0625 mg/l and MBC 2 mg/l

Tible S. epidermidis ATCC12228 (MIC 0.0625 mg/l and MBC 2 mg/l in our assay). Five of the eight clinical S. epidermidis isolates with tolerance towards triclosan also had identical fabI amino acid sequence to ATCC 12228 and none of these isolates had mutations in the putative promoter region of fabI. The three remaining UKI 1 tolerant S. epidermidis isolates had between one and three non synonymous mutations causing changes in the predicted amino acid sequence: Isolate BD-18 had a substitution of a phenylalanine for a valine, at position 204 (F204V), isolate BD-38 had a A198GTriclosan tolerant isolates are not clonalMLST results (supplementary material, Table S1) revealed that the triclosan tolerant isolates were not due to the expansion of a clone. Out of 15 current isolates (seven triclosan susceptible andTable 1. Susceptibility to triclosan among S. epidermidis isolates from 1965?6 (old) and from 2010?1 (current) as determined by their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC).Number Old Current 34MIC50 0.0625 0.MIC90 0.0625 0.MIC range #0.0156?.125 #0.0156?MBC50 1MBC90 2MBC range #0.0625? #0.0625?MIC/MBC50 = Minimum Inhibitory/Bactericidal Concentration required to inhibit the growth/kill of 50 of isolates. MIC/MBC90 = Minimum Inhibitory/Bactericidal Concentration required to inhibit the growth/kill of 90 of isolates. doi:10.1371/journal.pone.0062197.tTriclosan Resistance in Staphylococcus epidermidisFigure 1. Triclosan MIC and MBC distributions for S. epidermidis isolates from 1965-66 and from 2010-11. A: Triclosan MIC (Mininmum inhibitory concentration) distributions. B: Triclosan MBC (Mininmum bactericidal concentration) distributions. Black bars = S. epidermidis blood isolates from 2010-11. White bars = S. epidermidis blood isolates from 1965-66. The lowest dilutions represent a MIC of#0.0156 mg/l and a MBC of#0.0652 mg/l. Eight isolates in the current group have a MIC 0.25 mg/l and the same eight isolates are the ones with a MBC = 8 mg/l. doi:10.1371/journal.pone.0062197.gsubstitution. Mutations at those two positions have previously been described in fabI of S. aureus with triclosan tolerance [24?7]. BD24 had three amino acid substitutions a H60Q, a H61Y and a S78A as well as several nucleotide changes in the putative promoter region. None of these substitutions have been described previously and interestingly H61Y and S78A were also found in two old, triclosan susceptible, S. epidermidis isolates (65?2, 65?2) while the other two old isolates from which we obtained a fabI sequence were 1516647 identical to the ATCC 12228 fabI. Three of the triclosan-adapted isolates, one old and two current, developed an identical mutation that predicted a substitution in amino acid residue 95 from alanine to valine (A95V). This change was not found in any of the current triclosan tolerant S. epidermidis isolates, but it has also been identified as the most frequent mutation in in vitro selected S. aureus mutants with triclosan tolerance [26,27]. The two triclosan tolerant isolates (that were not possible to adapt further to triclosan in measure of MIC/MBC) did also not develop further mutations in fabI following the adaptation experiments with the BD-12 descendent, BD-12a*, MedChemExpress CP21 keeping the fabI sequence identical to ATCC12228, and BD-24a* just keeping the mutations from its parent BD-24 (Table 4). The mRNA expression of fabI of the six parent and six descendant isolates from the adaptation experiment was measured Ta.Tible S. epidermidis ATCC12228 (MIC 0.0625 mg/l and MBC 2 mg/l in our assay). Five of the eight clinical S. epidermidis isolates with tolerance towards triclosan also had identical fabI amino acid sequence to ATCC 12228 and none of these isolates had mutations in the putative promoter region of fabI. The three remaining tolerant S. epidermidis isolates had between one and three non synonymous mutations causing changes in the predicted amino acid sequence: Isolate BD-18 had a substitution of a phenylalanine for a valine, at position 204 (F204V), isolate BD-38 had a A198GTriclosan tolerant isolates are not clonalMLST results (supplementary material, Table S1) revealed that the triclosan tolerant isolates were not due to the expansion of a clone. Out of 15 current isolates (seven triclosan susceptible andTable 1. Susceptibility to triclosan among S. epidermidis isolates from 1965?6 (old) and from 2010?1 (current) as determined by their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC).Number Old Current 34MIC50 0.0625 0.MIC90 0.0625 0.MIC range #0.0156?.125 #0.0156?MBC50 1MBC90 2MBC range #0.0625? #0.0625?MIC/MBC50 = Minimum Inhibitory/Bactericidal Concentration required to inhibit the growth/kill of 50 of isolates. MIC/MBC90 = Minimum Inhibitory/Bactericidal Concentration required to inhibit the growth/kill of 90 of isolates. doi:10.1371/journal.pone.0062197.tTriclosan Resistance in Staphylococcus epidermidisFigure 1. Triclosan MIC and MBC distributions for S. epidermidis isolates from 1965-66 and from 2010-11. A: Triclosan MIC (Mininmum inhibitory concentration) distributions. B: Triclosan MBC (Mininmum bactericidal concentration) distributions. Black bars = S. epidermidis blood isolates from 2010-11. White bars = S. epidermidis blood isolates from 1965-66. The lowest dilutions represent a MIC of#0.0156 mg/l and a MBC of#0.0652 mg/l. Eight isolates in the current group have a MIC 0.25 mg/l and the same eight isolates are the ones with a MBC = 8 mg/l. doi:10.1371/journal.pone.0062197.gsubstitution. Mutations at those two positions have previously been described in fabI of S. aureus with triclosan tolerance [24?7]. BD24 had three amino acid substitutions a H60Q, a H61Y and a S78A as well as several nucleotide changes in the putative promoter region. None of these substitutions have been described previously and interestingly H61Y and S78A were also found in two old, triclosan susceptible, S. epidermidis isolates (65?2, 65?2) while the other two old isolates from which we obtained a fabI sequence were 1516647 identical to the ATCC 12228 fabI. Three of the triclosan-adapted isolates, one old and two current, developed an identical mutation that predicted a substitution in amino acid residue 95 from alanine to valine (A95V). This change was not found in any of the current triclosan tolerant S. epidermidis isolates, but it has also been identified as the most frequent mutation in in vitro selected S. aureus mutants with triclosan tolerance [26,27]. The two triclosan tolerant isolates (that were not possible to adapt further to triclosan in measure of MIC/MBC) did also not develop further mutations in fabI following the adaptation experiments with the BD-12 descendent, BD-12a*, keeping the fabI sequence identical to ATCC12228, and BD-24a* just keeping the mutations from its parent BD-24 (Table 4). The mRNA expression of fabI of the six parent and six descendant isolates from the adaptation experiment was measured Ta.