Younghee Oh

Antimicrobial Resistance Patterns and Corresponding Multilocus Sequence Types of the Campylobacter jejuni Isolates from Human Diarrheal Samples

A total of 121 Campylobacter isolates from 4,788 humans with gastroenteritis were identified and characterized by biochemical detection methods, polymerase chain reaction, and multilocus sequence typing (MLST). These samples were obtained during a 3-year period, from January 2007 to December 2009, using the National Notifiable Diseases Surveillance System at the Research Institute of Public Health and Environment in Seoul Metropolitan, Korea. Antimicrobial susceptibilities of the bacterium were also determined with the agar dilution method. All 121 isolates were identified as Campylobacter jejuni, with all (100%) of them having two virulence genes (ceuE and cadF) and a toxin gene (cdtB). Twenty-three different sequence types (STs), including 9 new STs, were determined by MLST. The most prevalent ST and clonal complex (CC) observed in this study were ST-45 (28.9%) and ST-45 CC (53.7%), respectively. Percentages of antimicrobial-resistant isolates were 1.9% for ampicillin, 0.8% for chloramphenicol, 24% for ciprofloxacin, 46.3% for enrofloxacin, 0.8% for erythromycin, 6.6% for gentamicin, and 46.3% for tetracycline. This study demonstrated that the majority of the Campylobacter isolates obtained from human samples in Korea were C. jejuni with ST-45 CC, which has been detected mainly in broilers worldwide, and all strains with new STs were uniformly resistant to enrofloxacin and tetracycline. This study indicates that broilers may be a breeding ground for bacteria as well as an important potential source of human campylobacteriosis.

Characterization of norovirus infections in Seoul, Korea.

The present study has determined the detection rate of norovirus (NoV) with acute gastroenteritis (AGE) in hospitalized children and describes the molecular epidemiology of NoV circulating in Seoul, Korea. Six hundred and eighty‐three (9.8%) of samples were positive for NoV. Of these, the NoV GII genogroup was the most commonly found, with a prevalence of 96.2% (683 of 710). Only 27 samples were positive for the NoV GI genogroup. Ten kinds of GI genotype (GI/1, GI/2, GI/3, GI/4, GI/5, GI/6, GI/7, GI/9, GI/12, and GI/13) and eight kinds of GII genotype (GII/2, GII/3, GII/4, GII/8, GII/14, GII/15, GII/16, and GII/17) were identified in children with AGE during the years 2008–2011.

Antimicrobial Resistance Patterns and Characterization of Integrons of Shigella sonnei Isolates in Seoul, 1999-2008

A total of 66 Shigella sonnei isolates from 1999 to 2008 in Seoul was analyzed for their antimicrobial resistance, carriage of integron, and the patterns of Pulsed-field gel electrophoresis (PFGE). A high level of antimicrobial resistance to streptomycin (100%), trimethoprim/sulfamethoxazole (95%), tetracycline (94%), nalidixic acid (65%), and ampicillin (41%) was observed among S. sonnei isolates. Fourteen profiles of antimicrobial resistance were identified with the most common resistance profile being nalidixic acid, streptomycin, tetracycline, and trimethoprim/sulfamethoxazole (35%). PCR and DNA sequencing analysis revealed the presence of class 2 integron in all isolates, and class 1 and 2 integrons in 7 isolates. The class 2 integron carried two types of gene cassettes. One cassette array was dfrI, sat2, and aadA1 (91%), and the other was dfr1 and sat1 (8%). dfrA12 and aadA2 gene cassette was found in one isolate containing class 1 integron. PFGE was carried out to examine the genetic relatedness among isolates. All isolates except for one showed similar PFGE patterns (similarity of 80.1%). These results suggest that the S. sonnei isolated during 1999–2008 in Seoul have similar lineages that have not undergone evolutionary changes with time.

Characterization of Staphylococcus aureus faecal isolates associated with food-borne disease in Korea.

To characterize Staphylococcus aureus faecal isolates from people suspected to be infected with food poisoning by using antimicrobial susceptibility testing and molecular techniques.

First Report and Molecular Characterization of a Campylobacter jejuni Isolate with Extensive Drug Resistance from a Travel-Associated Human Case

Campylobacter is a common causative agent of bacterial diarrhea worldwide ([1][1]). Uncomplicated illnesses caused by Campylobacter spp. are characterized by symptoms such as fever, abdominal cramping, and diarrhea; they are usually self-limiting and do not require antimicrobial treatment. However,

Determination and identification of titanium dioxide nanoparticles in confectionery foods, marketed in South Korea, using inductively coupled plasma optical emission spectrometry and transmission electron microscopy

ABSTRACT Food-grade titanium dioxide (TiO2) is a common and widespread food additive in many processed foods, personal care products, and other industrial categories as it boosts the brightness and whiteness of colours. Although it is generally recognised as safe for humans, there is a growing interest in the health risks associated with its oral intake. This study quantified and identified TiO2 nanoparticles present in confectionery foods, which are children’s favourite foods, with inductively coupled plasma optical emission spectrometry (ICP-OES) and transmission electron microscopy (TEM). A reliable digestion method using hot sulphuric acid and a digestion catalyst (K2SO4:CuSO4 = 9:1) was suggested for titanium analysis. Validations of the experimental method were quite acceptable in terms of linearity, recoveries, detection limits, and quantification limits. Of all the 88 analysed foods, TiO2 was detected in 19 products, all except three declared TiO2 in their labelling. The mean TiO2 content of candies, chewing gums, and chocolates were 0.36 mg g−1, 0.04 mg g−1, and 0.81 mg g−1, respectively. Whitish particles isolated from the confectionery foods were confirmed as TiO2 nanoparticles via TEM and energy dispersive X-ray spectroscopy (EDX), in which nanosized particles (<100 nm) were identified. Graphical Abstract

Bacterial Contamination Reduction of Minimally Processed Agricultural Products using Antibacterial Foods and Molecular Biological Analysis

The purposes of this study are to confirm ways to reduce bacteria of minimally processed agricul- tural products, using antibacterial foods that are easily available in home and to improve bacterial hygienic condition of them. We chose garlic-allicin, ginger-gingerol, green tea-catechin, cinnamon-cinnamic aldehyde, wasabi-allyl isothiocyanate as antibacterial foods and their unique antibiotic materials. We confirmed the better washing effect when these antibiotic extracts were used, compared to washing effect by only distilled water. Their antibiosis was proved by statistical processing. PFGE (Pulsed Field Gel Electrophoresis) of Bacillus cereus shows continuous con- tamination probability of minimally processed vegetables by same product suppliers and the necessity of systematic measures against bacterial contamination.