Tentative Colistin Epidemiological Cut-Off Value for Salmonella spp.

Yvonne Agersø, Mia Torpdahl, Camilla Zachariasen, Anne Mette Seyfarth, Anette M. Hammerum, Eva Møller Nielsen

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Abstract

The objective of this research was to determine minimal inhibitory concentration (MIC) population distributions for colistin for Salmonella on subtype level. Furthermore, we wanted to determine if differences in MIC for colistin could be explained by mutations in pmrA or pmrB encoding proteins involved in processes that influence the binding of colistin to the cell membrane. During 2008–2011, 6,583 Salmonella enterica subsp. enterica isolates of human origin and 1931 isolates of animal/meat origin were collected. The isolates were serotyped, and susceptibility was tested towards colistin (range 1–16 mg/L). Moreover, 37 isolates were tested for mutations in pmrA and pmrB by polymerase chain reaction (PCR) and DNA sequencing. MIC distribution for colistin at serotype level showed that Salmonella Dublin (n=198) followed by Salmonella Enteritidis (n=1247) were less susceptible than “other” Salmonella serotypes originating from humans (n=5,274) and Salmonella Typhimurium of animal/meat origin (n=1794). MIC was ≤1 mg/L for 98.9% of “other” Salmonella serotypes originating from humans, 99.4% of Salmonella Typhimurium, 61.3% of Salmonella Enteritidis, and 12.1% of Salmonella Dublin isolates. Interestingly, Salmonella Dublin and Salmonella Enteritidis belong to the same O-group (O:1, 9,12), suggesting that surface lipopolysaccharides (LPS) of the cell (O-antigen) play a role in colistin susceptibility. The epidemiological cut-off value of >2 mg/L for colistin suggested by European Committee on Antimicrobial Susceptibility Testing (EUCAST) is placed inside the distribution for both Salmonella Dublin and Salmonella Enteritidis. All tested Salmonella Dublin isolates, regardless of MIC colistin value, had identical pmrA and pmrB sequences. Missense mutations were found only in pmrA in one Salmonella Reading and in pmrB in one Salmonella Concord isolate, both with MIC of ≤1 for colistin. In conclusion, our study indicates that missense mutations are not necessarily involved in increased MICs for colistin. Increased MICs for colistin seemed to be linked to specific serotypes (Salmonella Dublin and Salmonella Enteritidis). We recommend that Salmonella with MIC of >2 mg/L for colistin be evaluated on the serovar level.
Original languageEnglish
JournalFoodborne Pathogens and Disease
Volume9
Issue number4
Pages (from-to)367-369
ISSN1535-3141
DOIs
Publication statusPublished - 2012

Cite this

Agersø, Y., Torpdahl, M., Zachariasen, C., Seyfarth, A. M., Hammerum, A. M., & Nielsen, E. M. (2012). Tentative Colistin Epidemiological Cut-Off Value for Salmonella spp. Foodborne Pathogens and Disease, 9(4), 367-369. https://doi.org/10.1089/fpd.2011.1015
Agersø, Yvonne ; Torpdahl, Mia ; Zachariasen, Camilla ; Seyfarth, Anne Mette ; Hammerum, Anette M. ; Nielsen, Eva Møller. / Tentative Colistin Epidemiological Cut-Off Value for Salmonella spp. In: Foodborne Pathogens and Disease. 2012 ; Vol. 9, No. 4. pp. 367-369.
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title = "Tentative Colistin Epidemiological Cut-Off Value for Salmonella spp.",
abstract = "The objective of this research was to determine minimal inhibitory concentration (MIC) population distributions for colistin for Salmonella on subtype level. Furthermore, we wanted to determine if differences in MIC for colistin could be explained by mutations in pmrA or pmrB encoding proteins involved in processes that influence the binding of colistin to the cell membrane. During 2008–2011, 6,583 Salmonella enterica subsp. enterica isolates of human origin and 1931 isolates of animal/meat origin were collected. The isolates were serotyped, and susceptibility was tested towards colistin (range 1–16 mg/L). Moreover, 37 isolates were tested for mutations in pmrA and pmrB by polymerase chain reaction (PCR) and DNA sequencing. MIC distribution for colistin at serotype level showed that Salmonella Dublin (n=198) followed by Salmonella Enteritidis (n=1247) were less susceptible than “other” Salmonella serotypes originating from humans (n=5,274) and Salmonella Typhimurium of animal/meat origin (n=1794). MIC was ≤1 mg/L for 98.9{\%} of “other” Salmonella serotypes originating from humans, 99.4{\%} of Salmonella Typhimurium, 61.3{\%} of Salmonella Enteritidis, and 12.1{\%} of Salmonella Dublin isolates. Interestingly, Salmonella Dublin and Salmonella Enteritidis belong to the same O-group (O:1, 9,12), suggesting that surface lipopolysaccharides (LPS) of the cell (O-antigen) play a role in colistin susceptibility. The epidemiological cut-off value of >2 mg/L for colistin suggested by European Committee on Antimicrobial Susceptibility Testing (EUCAST) is placed inside the distribution for both Salmonella Dublin and Salmonella Enteritidis. All tested Salmonella Dublin isolates, regardless of MIC colistin value, had identical pmrA and pmrB sequences. Missense mutations were found only in pmrA in one Salmonella Reading and in pmrB in one Salmonella Concord isolate, both with MIC of ≤1 for colistin. In conclusion, our study indicates that missense mutations are not necessarily involved in increased MICs for colistin. Increased MICs for colistin seemed to be linked to specific serotypes (Salmonella Dublin and Salmonella Enteritidis). We recommend that Salmonella with MIC of >2 mg/L for colistin be evaluated on the serovar level.",
author = "Yvonne Agers{\o} and Mia Torpdahl and Camilla Zachariasen and Seyfarth, {Anne Mette} and Hammerum, {Anette M.} and Nielsen, {Eva M{\o}ller}",
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Agersø, Y, Torpdahl, M, Zachariasen, C, Seyfarth, AM, Hammerum, AM & Nielsen, EM 2012, 'Tentative Colistin Epidemiological Cut-Off Value for Salmonella spp.', Foodborne Pathogens and Disease, vol. 9, no. 4, pp. 367-369. https://doi.org/10.1089/fpd.2011.1015

Tentative Colistin Epidemiological Cut-Off Value for Salmonella spp. / Agersø, Yvonne; Torpdahl, Mia; Zachariasen, Camilla; Seyfarth, Anne Mette; Hammerum, Anette M.; Nielsen, Eva Møller.

In: Foodborne Pathogens and Disease, Vol. 9, No. 4, 2012, p. 367-369.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Tentative Colistin Epidemiological Cut-Off Value for Salmonella spp.

AU - Agersø, Yvonne

AU - Torpdahl, Mia

AU - Zachariasen, Camilla

AU - Seyfarth, Anne Mette

AU - Hammerum, Anette M.

AU - Nielsen, Eva Møller

PY - 2012

Y1 - 2012

N2 - The objective of this research was to determine minimal inhibitory concentration (MIC) population distributions for colistin for Salmonella on subtype level. Furthermore, we wanted to determine if differences in MIC for colistin could be explained by mutations in pmrA or pmrB encoding proteins involved in processes that influence the binding of colistin to the cell membrane. During 2008–2011, 6,583 Salmonella enterica subsp. enterica isolates of human origin and 1931 isolates of animal/meat origin were collected. The isolates were serotyped, and susceptibility was tested towards colistin (range 1–16 mg/L). Moreover, 37 isolates were tested for mutations in pmrA and pmrB by polymerase chain reaction (PCR) and DNA sequencing. MIC distribution for colistin at serotype level showed that Salmonella Dublin (n=198) followed by Salmonella Enteritidis (n=1247) were less susceptible than “other” Salmonella serotypes originating from humans (n=5,274) and Salmonella Typhimurium of animal/meat origin (n=1794). MIC was ≤1 mg/L for 98.9% of “other” Salmonella serotypes originating from humans, 99.4% of Salmonella Typhimurium, 61.3% of Salmonella Enteritidis, and 12.1% of Salmonella Dublin isolates. Interestingly, Salmonella Dublin and Salmonella Enteritidis belong to the same O-group (O:1, 9,12), suggesting that surface lipopolysaccharides (LPS) of the cell (O-antigen) play a role in colistin susceptibility. The epidemiological cut-off value of >2 mg/L for colistin suggested by European Committee on Antimicrobial Susceptibility Testing (EUCAST) is placed inside the distribution for both Salmonella Dublin and Salmonella Enteritidis. All tested Salmonella Dublin isolates, regardless of MIC colistin value, had identical pmrA and pmrB sequences. Missense mutations were found only in pmrA in one Salmonella Reading and in pmrB in one Salmonella Concord isolate, both with MIC of ≤1 for colistin. In conclusion, our study indicates that missense mutations are not necessarily involved in increased MICs for colistin. Increased MICs for colistin seemed to be linked to specific serotypes (Salmonella Dublin and Salmonella Enteritidis). We recommend that Salmonella with MIC of >2 mg/L for colistin be evaluated on the serovar level.

AB - The objective of this research was to determine minimal inhibitory concentration (MIC) population distributions for colistin for Salmonella on subtype level. Furthermore, we wanted to determine if differences in MIC for colistin could be explained by mutations in pmrA or pmrB encoding proteins involved in processes that influence the binding of colistin to the cell membrane. During 2008–2011, 6,583 Salmonella enterica subsp. enterica isolates of human origin and 1931 isolates of animal/meat origin were collected. The isolates were serotyped, and susceptibility was tested towards colistin (range 1–16 mg/L). Moreover, 37 isolates were tested for mutations in pmrA and pmrB by polymerase chain reaction (PCR) and DNA sequencing. MIC distribution for colistin at serotype level showed that Salmonella Dublin (n=198) followed by Salmonella Enteritidis (n=1247) were less susceptible than “other” Salmonella serotypes originating from humans (n=5,274) and Salmonella Typhimurium of animal/meat origin (n=1794). MIC was ≤1 mg/L for 98.9% of “other” Salmonella serotypes originating from humans, 99.4% of Salmonella Typhimurium, 61.3% of Salmonella Enteritidis, and 12.1% of Salmonella Dublin isolates. Interestingly, Salmonella Dublin and Salmonella Enteritidis belong to the same O-group (O:1, 9,12), suggesting that surface lipopolysaccharides (LPS) of the cell (O-antigen) play a role in colistin susceptibility. The epidemiological cut-off value of >2 mg/L for colistin suggested by European Committee on Antimicrobial Susceptibility Testing (EUCAST) is placed inside the distribution for both Salmonella Dublin and Salmonella Enteritidis. All tested Salmonella Dublin isolates, regardless of MIC colistin value, had identical pmrA and pmrB sequences. Missense mutations were found only in pmrA in one Salmonella Reading and in pmrB in one Salmonella Concord isolate, both with MIC of ≤1 for colistin. In conclusion, our study indicates that missense mutations are not necessarily involved in increased MICs for colistin. Increased MICs for colistin seemed to be linked to specific serotypes (Salmonella Dublin and Salmonella Enteritidis). We recommend that Salmonella with MIC of >2 mg/L for colistin be evaluated on the serovar level.

U2 - 10.1089/fpd.2011.1015

DO - 10.1089/fpd.2011.1015

M3 - Journal article

VL - 9

SP - 367

EP - 369

JO - Foodborne Pathogens and Disease

JF - Foodborne Pathogens and Disease

SN - 1535-3141

IS - 4

ER -