Microbiologist — Division of Microbiology

Youngbeom Ahn, Ph.D.
(870) 543-7121
NCTRResearch@fda.hhs.gov  

Back to NCTR Principal Investigators page

 About  |  Publications 

Background

After earning a Ph.D. from Hanyang University, Korea, Dr. Youngbeom Ahn’s career continued as a postdoctoral fellow in the Research Center for Molecular Microbiology at Seoul National University, Korea. He further advanced his career as a postdoctoral fellow in the Environmental Biology Department at the University of Guelph, Canada from 1999 to 2001. From 2001 to 2008, Dr. Ahn was a postdoctoral fellow and then a research associate in the Biotechnology Center for Agriculture and the Environment at Rutgers University. Prior to joining NCTR, he  investigated the in situ enhancement of anaerobic dechlorination of polychlorinated dibenzo-p-dioxins and dibenzofurans in marine sediments. The project focused on the stimulation of dehalogenation by anaerobic bacteria using structural analogues to the polychlorinated dibenzo-p-dioxins. The information gained from these fundamental studies are pivotal to development of new bioremediation technologies for cleanup of contaminated coastal sediments, a major problem requiring innovative solutions. Another major area of research interest included the description of anaerobic dehalogenating bacteria in marine sponges, a possible natural source of these organisms, funded by the National Science Foundation.

Dr. Ahn joined the Division of Microbiology at NCTR as a staff fellow in 2009. Since 2009, his research interests have focused on projects of FDA regulatory science including antimicrobial residues in foods and the safety of pharmaceutical products as related to microbial contamination. In cooperation with FDA’s Center for Veterinary Medicine (CVM), Dr. Ahn developed a project to assess the impact of antimicrobial residues on the human gastrointestinal tract microbiota in 2012. He also initiated a collaboration with FDA’s Center for Drug Evaluation and Research (CDER) to develop a project which was funded by CDER to explore strategies for resuscitation and enrichment of Burkholderia cepacia complex strains in pharmaceutical products. Dr. Ahn’s research has provided information on methodological questions that have concerned national regulatory authorities in in vitro testing to determine if concentrations of veterinary antimicrobial agent residues entering the human colon remain microbiologically active. His research resulted in data of high significance that has assisted FDA and other national regulatory authorities in the International Cooperation on Harmonization of Technical Requirements for Registration of Veterinary Medical Products (VICH) Expert Working Group organized by CVM to evaluate the VICH GL36 guideline on the human safety of veterinary antimicrobial drugs. For his scientific contributions, the incumbent has been awarded the FDA/NCTR Outstanding Junior Investigator in 2013. He received the NCTR “Special Act Award” in 2017 for outstanding research and regulatory impact on providing data to FDA/CVM on the effect of short- and long-term exposure to residual levels of tetracycline in food on the intestinal microbiome.

Research Interests

The laboratory of Microbiome and Host Interactions within the division has been established to investigate the effects of food-contaminant residues on the gastrointestinal-tract microbiota. Dr. Ahn’s current studies are focused on the impact of antibiotics on the human gastrointestinal-tract microbiota. Most studies on drug binding to fecal contents in the literature have used therapeutic human doses, rather than levels below or slightly above the MRL allowed in edible tissues. In the research project, the pivotal methodological question raised by the International Cooperation on Harmonization of Technical Requirements for Registration of Veterinary Medicinal Products Guideline (VICH GL) #36 Step 3 was addressed. This question is ‘‘Do residues entering the human colon remain microbiologically active,’’ by comparing the fecal binding of selected antibiotics concentrations with various incubation conditions using physicochemical, analytical chemistry, microbiological, and molecular methods?”

Another study is a collaborative project with CDER “Exploring strategies for resuscitation and enrichment of Burkholderia cepacia complex strains in pharmaceutical products.” CDC has requested FDA to issue a rule or policy that establishes B. cepacia as an objectionable organism in pharmaceuticals, and United States Pharmacopeia (USP) has revisited the concept of including B. cepacia in its chapters. For USP to include this species as an organism of interest, they must have a test that can be done by nearly any microbiology laboratory, which means it would use conventional technology. However, existing USP methods use enrichment in Trypticase Soy Broth (TSB), which is inadequate for all strains. The objectives of Dr. Ahn’s research are to 1) develop a resuscitative step and enrichment technique for BCC recovery and 2) develop methodology to detect the Burkholderia cepacia and its 16 related genomovars. He also looks to evaluate the use of modern molecular technologies to identify the BCC.

Professional Societies/National and International Groups

American Society for Microbiology
Member
2012 — Present

Selected Publications

An In Vitro Study To Assess the Impact of Tetracycline on the Human Intestinal Microbiome.
Jung J., Ahn Y., Khare S., Gokulan K., Piñeiro S., and Cerniglia C.
Anaerobe. 2018, 49:85-94. doi: 10.1016/j.anaerobe.2017.12.011. Epub 2017 Dec 30.

Effects of Extended Storage of Chlorhexidine Gluconate and Benzalkonium Chloride Solutions on the Viability of Burkholderia Cenocepacia.
Ahn Y., Kim J., Lee Y., LiPuma J., Hussong D., Marasa B., and Cerniglia C.
J Microbiol Biotechnol. 2017, 27(12):2211-2220. doi: 10.4014/jmb.1706.06034.

Novel Reductive Dehalogenases from the Marine Sponge Associated Bacterium Desulfoluna Spongiiphila.
Liu J., Lopez N., Ahn Y., Goldberg T., Bromberg Y., Kerkhof L., and Häggblom M.
Environ Microbiol Rep. 2017, 9(5):537-549. doi: 10.1111/1758-2229.12556. Epub 2017 Jul 21.

Improved High-Quality Draft Genome Sequence and Annotation of Burkholderia Contaminans LMG 23361T.
Jung J., Ahn Y., Kweon O., LiPuma J., Hussong D., Marasa B., and Cerniglia C.
Genome Announc. 2017, 5(16). pii: e00245-17. doi: 10.1128/genomeA.00245-17.

Intrinsic Resistance of Burkholderia Cepacia Complex to Benzalkonium Chloride.
Ahn Y., Kim J., Kweon O., Kim S., Jones R., Woodling K., Gamboa da Costa G., LiPuma J., Hussong D., Marasa B., and Cerniglia CE.
MBio. 2016, 7(6). pii: e01716-16. doi: 10.1128/mBio.01716-16.

Survival and Susceptibility of Burkholderia Cepacia Complex in Chlorhexidine Gluconate and Benzalkonium Chloride.
Kim J., Ahn Y., LiPuma J., Hussong D., and Cerniglia C.
J Ind Microbiol Biotechnol. 2015, 42(6):905-13. 

Pleiotropic and Epistatic Behavior of a Ring-Hydroxylating Oxygenase System in the Polycyclic Aromatic Hydrocarbon Metabolic Network from Mycobacterium Vanbaalenii PYR-1.
Kweon O., Kim S., Kim D., Kim J., Kim H., Ahn Y., Sutherland J., and Cerniglia C.
J Bacteriol. 2014, 196(19):3503-15. doi: 10.1128/JB.01945-14. Epub 2014 Jul 28.

Evaluation of Liquid and Solid Culture Media for the Recovery and Enrichment of Burkholderia Cenocepacia from Distilled Water.
Ahn Y., Kim J., Ahn H., Lee Y., LiPuma J., Hussong D., and Cerniglia C.
J Ind Microbiol Biotechnol. 2014, 41(7):1109-18.

Influence of Sterilized Human Fecal Extract on the Sensitivity of Salmonella enterica ATCC 13076 and Listeria monocytogenes ATCC 15313 to Enrofloxacin.
Ahn Y., Stuckey R., Sung K., Rafii F., and Cerniglia C.
Antibiotics (Basel). 2013, 2(4):485-99. doi: 10.3390/antibiotics2040485.

In Vitro Analysis of the Impact of Enrofloxacin Residues on the Human Intestinal Microbiota Using H-NMR Spectroscopy.
Ahn Y., Jung J., Chung Y., Chae M., Jeon C., and Cerniglia C.
J Mol Microbiol Biotechnol. 2012, 22(5):317-25.

Effect of Sterilized Human Fecal Extract on the Sensitivity of Escherichia Coli ATCC 25922 to Enrofloxacin.
Ahn Y., Sung K., Rafii F., and Cerniglia C.
J Antibiot (Tokyo). 2012, 65(4):179-84.

In Vitro Enrofloxacin Binding in Human Fecal Slurries.
Ahn Y., Linder S., Veach B., Steve Yan S., Haydée Fernández A., Pineiro S., and Cerniglia C.
Regul Toxicol Pharmacol. 2012, 62(1):74-84.

Desulfoluna Spongiiphila sp. nov., a Dehalogenating Bacterium in the Desulfobacteraceae from the Marine Sponge Aplysina Aerophoba.
Ahn Y., Kerkhof L., and Häggblom M.
Int J Syst Evol Microbiol. 2009, 59(Pt 9):2133-9.

Degradation of Phenol via Phenylphosphate and Carboxylation to 4-Hydroxybenzoate by a Newly Isolated Strain of the Sulfate-Reducing Bacterium Desulfobacterium Anilini.
Ahn Y., Chae J., Zylstra G. and Häggblom M.
Appl Environ Microbiol. 2009, 75(13):4248-53.

Biostimulation and Bioaugmentation to Enhance Dechlorination of Polychlorinated Dibenzo-p-Dioxins in Contaminated Sediments.
Ahn Y., Liu F., Fennell D., and Häggblom M.
FEMS Microbiol Ecol. 2008, 66(2):271-81.

Comparison of Anaerobic Microbial Communities from Estuarine Sediments Amended with Halogenated Compounds to Enhance Dechlorination of 1,2,3,4-Tetrachlorodibenzo-p-Dioxin.
Ahn Y., Häggblom M., and Kerkhof L.
FEMS Microbiol Ecol. 2007, 61(2):362-71.

Co-Amendment with Halogenated Compounds Enhances Anaerobic Microbial Dechlorination of 1,2,3,4-Tetrachlorodibenzo-p-Dioxin and 1,2,3,4-Tetrachlorodibenzofuran in Estuarine Sediments.
Ahn Y., Häggblom M., and Fennell D.
Environ Toxicol Chem. 2005, 24(11):2775-84.

Detection and Characterization of a Dehalogenating Microorganism by Terminal Restriction Fragment Length Polymorphism Fingerprinting of 16S rRNA in a Sulfidogenic, 2-Bromophenol-Utilizing Enrichment.
Fennell D., Rhee S., Ahn Y., Häggblom M., and Kerkhof L.
Appl Environ Microbiol. 2004, 70(2):1169-75.

Reductive Dehalogenation of Brominated Phenolic Compounds by Microorganisms Associated with the Marine Sponge Aplysina Aerophoba.
Ahn Y., Rhee S., Fennell D., Kerkhof L., Hentschel U., and Häggblom M.
Appl Environ Microbiol. 2003, 69(7):4159-66.

Survival of a GFP-Labeled Polychlorinated Biphenyl Degrading Psychrotolerant Pseudomonas spp. in 4 and 22°C Soil Microcosms.
Ahn Y., Beaudette L., Lee H., and Trevors J.
Microb Ecol. 2001, 42(4):614-623.