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Sublethal Concentrations of Antibiotics Cause Shift to Anaerobic Metabolism in Listeria monocytogenes and Induce Phenotypes Linked to Antibiotic Tolerance.

Knudsen GM, Fromberg A, Ng Y, Gram L - Front Microbiol (2016)

Bottom Line: A mutant in the bifunctional acetaldehyde-CoA/alcohol dehydrogenase encoded by lmo1634 did not have altered antibiotic tolerance.However, a mutant in lmo1179 (eutE) encoding an aldehyde oxidoreductase where rerouting caused increased ethanol production was tolerant to three of four antibiotics tested.Thus, sublethal concentrations of antibiotics caused metabolic and physiological changes indicating that the organism is preparing to withstand lethal antibiotic concentrations.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, Technical University of Denmark Kongens Lyngby, Denmark.

ABSTRACT
The human pathogenic bacterium Listeria monocytogenes is exposed to antibiotics both during clinical treatment and in its saprophytic lifestyle. As one of the keys to successful treatment is continued antibiotic sensitivity, the purpose of this study was to determine if exposure to sublethal antibiotic concentrations would affect the bacterial physiology and induce antibiotic tolerance. Transcriptomic analyses demonstrated that each of the four antibiotics tested caused an antibiotic-specific gene expression pattern related to mode-of-action of the particular antibiotic. All four antibiotics caused the same changes in expression of several metabolic genes indicating a shift from aerobic to anaerobic metabolism and higher ethanol production. A mutant in the bifunctional acetaldehyde-CoA/alcohol dehydrogenase encoded by lmo1634 did not have altered antibiotic tolerance. However, a mutant in lmo1179 (eutE) encoding an aldehyde oxidoreductase where rerouting caused increased ethanol production was tolerant to three of four antibiotics tested. This shift in metabolism could be a survival strategy in response to antibiotics to avoid generation of ROS production from respiration by oxidation of NADH through ethanol production. The monocin locus encoding a cryptic prophage was induced by co-trimoxazole and repressed by ampicillin and gentamicin, and this correlated with an observed antibiotic-dependent biofilm formation. A monocin mutant (ΔlmaDCBA) had increased biofilm formation when exposed to increasing concentration of co-trimoxazole similar to the wild type, but was more tolerant to killing by co-trimoxazole and ampicillin. Thus, sublethal concentrations of antibiotics caused metabolic and physiological changes indicating that the organism is preparing to withstand lethal antibiotic concentrations.

No MeSH data available.


Related in: MedlinePlus

Listeria monocytogenes EGD genes differentially expressed when exposed to ampicillin, tetracycline, gentamicin, or co-trimoxazole. (A) Functional categories of differentially expressed genes in response to the four antibiotics. Genes that passed the statistical filtering (p < 0.05, q < 0.05 and a twofold cut-off) are shown as percentage of genes in each functional category up-regulated (blue) or down-regulated (red), respectively, when comparing antibiotic-exposed L. monocytogenes EGD with MilliQ control. The list of genes included in each functional category was based on cluster of orthologous groups (COGs) of L. monocytogenes EGD-e genes (http://www.ncbi.nlm.nih.gov/sutils/coxik.cgi?gi=204%25253e). Asterisk indicate that the functional category was overrepresented in a hypergeometric distribution test (p = 0.01). (B) Venn diagram with up-regulated genes showing antibiotic-specific and common genes significantly differentially expressed genes. (C) Venn diagram with down-regulated genes showing antibiotic-specific and common genes significantly differentially expressed genes. Ampicillin (AMP), tetracycline (TET), gentamicin (GEN), and co-trimoxazole (SXT).
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Figure 1: Listeria monocytogenes EGD genes differentially expressed when exposed to ampicillin, tetracycline, gentamicin, or co-trimoxazole. (A) Functional categories of differentially expressed genes in response to the four antibiotics. Genes that passed the statistical filtering (p < 0.05, q < 0.05 and a twofold cut-off) are shown as percentage of genes in each functional category up-regulated (blue) or down-regulated (red), respectively, when comparing antibiotic-exposed L. monocytogenes EGD with MilliQ control. The list of genes included in each functional category was based on cluster of orthologous groups (COGs) of L. monocytogenes EGD-e genes (http://www.ncbi.nlm.nih.gov/sutils/coxik.cgi?gi=204%25253e). Asterisk indicate that the functional category was overrepresented in a hypergeometric distribution test (p = 0.01). (B) Venn diagram with up-regulated genes showing antibiotic-specific and common genes significantly differentially expressed genes. (C) Venn diagram with down-regulated genes showing antibiotic-specific and common genes significantly differentially expressed genes. Ampicillin (AMP), tetracycline (TET), gentamicin (GEN), and co-trimoxazole (SXT).

Mentions: Each of the four antibiotics caused between 106 and 119 genes or sRNA to be differentially expressed as compared to a non-treated control when using a statistical filter of p < 0.05, q < 0.05 and a threshold of twofold (Supplementary Tables S2 and S3) corresponding to 3.6–4.0% of all genes and sRNA. A hypergeometric distribution test of the functional category analysis showed that only five groups were overrepresented (Figure 1A). The ‘cell cycle control, cell division, and chromosome partitioning’ category was overrepresented among genes upregulated by ‘ampicillin and tetracycline. Secondary metabolites biosynthesis, transport and catabolism’ and ‘general function prediction only’ were overrepresented among genes repressed by co-trimoxazole and ‘not in COG’ was overrepresented in genes upregulated by co-trimoxazole.


Sublethal Concentrations of Antibiotics Cause Shift to Anaerobic Metabolism in Listeria monocytogenes and Induce Phenotypes Linked to Antibiotic Tolerance.

Knudsen GM, Fromberg A, Ng Y, Gram L - Front Microbiol (2016)

Listeria monocytogenes EGD genes differentially expressed when exposed to ampicillin, tetracycline, gentamicin, or co-trimoxazole. (A) Functional categories of differentially expressed genes in response to the four antibiotics. Genes that passed the statistical filtering (p < 0.05, q < 0.05 and a twofold cut-off) are shown as percentage of genes in each functional category up-regulated (blue) or down-regulated (red), respectively, when comparing antibiotic-exposed L. monocytogenes EGD with MilliQ control. The list of genes included in each functional category was based on cluster of orthologous groups (COGs) of L. monocytogenes EGD-e genes (http://www.ncbi.nlm.nih.gov/sutils/coxik.cgi?gi=204%25253e). Asterisk indicate that the functional category was overrepresented in a hypergeometric distribution test (p = 0.01). (B) Venn diagram with up-regulated genes showing antibiotic-specific and common genes significantly differentially expressed genes. (C) Venn diagram with down-regulated genes showing antibiotic-specific and common genes significantly differentially expressed genes. Ampicillin (AMP), tetracycline (TET), gentamicin (GEN), and co-trimoxazole (SXT).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940397&req=5

Figure 1: Listeria monocytogenes EGD genes differentially expressed when exposed to ampicillin, tetracycline, gentamicin, or co-trimoxazole. (A) Functional categories of differentially expressed genes in response to the four antibiotics. Genes that passed the statistical filtering (p < 0.05, q < 0.05 and a twofold cut-off) are shown as percentage of genes in each functional category up-regulated (blue) or down-regulated (red), respectively, when comparing antibiotic-exposed L. monocytogenes EGD with MilliQ control. The list of genes included in each functional category was based on cluster of orthologous groups (COGs) of L. monocytogenes EGD-e genes (http://www.ncbi.nlm.nih.gov/sutils/coxik.cgi?gi=204%25253e). Asterisk indicate that the functional category was overrepresented in a hypergeometric distribution test (p = 0.01). (B) Venn diagram with up-regulated genes showing antibiotic-specific and common genes significantly differentially expressed genes. (C) Venn diagram with down-regulated genes showing antibiotic-specific and common genes significantly differentially expressed genes. Ampicillin (AMP), tetracycline (TET), gentamicin (GEN), and co-trimoxazole (SXT).
Mentions: Each of the four antibiotics caused between 106 and 119 genes or sRNA to be differentially expressed as compared to a non-treated control when using a statistical filter of p < 0.05, q < 0.05 and a threshold of twofold (Supplementary Tables S2 and S3) corresponding to 3.6–4.0% of all genes and sRNA. A hypergeometric distribution test of the functional category analysis showed that only five groups were overrepresented (Figure 1A). The ‘cell cycle control, cell division, and chromosome partitioning’ category was overrepresented among genes upregulated by ‘ampicillin and tetracycline. Secondary metabolites biosynthesis, transport and catabolism’ and ‘general function prediction only’ were overrepresented among genes repressed by co-trimoxazole and ‘not in COG’ was overrepresented in genes upregulated by co-trimoxazole.

Bottom Line: A mutant in the bifunctional acetaldehyde-CoA/alcohol dehydrogenase encoded by lmo1634 did not have altered antibiotic tolerance.However, a mutant in lmo1179 (eutE) encoding an aldehyde oxidoreductase where rerouting caused increased ethanol production was tolerant to three of four antibiotics tested.Thus, sublethal concentrations of antibiotics caused metabolic and physiological changes indicating that the organism is preparing to withstand lethal antibiotic concentrations.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, Technical University of Denmark Kongens Lyngby, Denmark.

ABSTRACT
The human pathogenic bacterium Listeria monocytogenes is exposed to antibiotics both during clinical treatment and in its saprophytic lifestyle. As one of the keys to successful treatment is continued antibiotic sensitivity, the purpose of this study was to determine if exposure to sublethal antibiotic concentrations would affect the bacterial physiology and induce antibiotic tolerance. Transcriptomic analyses demonstrated that each of the four antibiotics tested caused an antibiotic-specific gene expression pattern related to mode-of-action of the particular antibiotic. All four antibiotics caused the same changes in expression of several metabolic genes indicating a shift from aerobic to anaerobic metabolism and higher ethanol production. A mutant in the bifunctional acetaldehyde-CoA/alcohol dehydrogenase encoded by lmo1634 did not have altered antibiotic tolerance. However, a mutant in lmo1179 (eutE) encoding an aldehyde oxidoreductase where rerouting caused increased ethanol production was tolerant to three of four antibiotics tested. This shift in metabolism could be a survival strategy in response to antibiotics to avoid generation of ROS production from respiration by oxidation of NADH through ethanol production. The monocin locus encoding a cryptic prophage was induced by co-trimoxazole and repressed by ampicillin and gentamicin, and this correlated with an observed antibiotic-dependent biofilm formation. A monocin mutant (ΔlmaDCBA) had increased biofilm formation when exposed to increasing concentration of co-trimoxazole similar to the wild type, but was more tolerant to killing by co-trimoxazole and ampicillin. Thus, sublethal concentrations of antibiotics caused metabolic and physiological changes indicating that the organism is preparing to withstand lethal antibiotic concentrations.

No MeSH data available.


Related in: MedlinePlus