Sahyun Hong

Escherichia coli O104:H4 from 2011 European Outbreak and Strain from South Korea

To the Editor: Beginning in early May 2011, an outbreak caused by Shiga toxin–producing Escherichia coli O104:H4 was reported in Germany and other countries in Europe. In this outbreak, the number of hemolytic uremic syndrome (HUS) cases has been unusually high (1). As of June 9, 2011, a total of 722 cases of HUS, 19 deaths, and 2,745 cases of enterohemorrhagic E. coli (EHEC) infection were reported (2). A case of HUS caused by E. coli O104:H4 was first reported in South Korea in 2004 (3). Because infections caused by E. coli O104:H4 have been reported rarely, interest has arisen in the E. coli O104:H4 strain from South Korea. We characterized the E. coli O104:H4 strain isolated in South Korea (EC0417119) in 2004 and compared it with the E. coli O104:H4 strain associated with the current EHEC outbreak in Europe. The serotype EC0417119, isolated from a patient with HUS in 2004, was reconfirmed as E. coli O104:H4. The strain was positive for stx1 and stx2 by PCR (4) but negative for aggR by PCR (5). In the antimicrobial drug susceptibility test using VITEK 2 AST-N169 test kit (bioMerieux, Marcy L’Etoile, France), the strain was resistant to ampicillin, ampicillin/sulbactam, and trimethoprim/sulfamethoxazole but susceptible to ceftriaxone, cefotaxime, nalidixic acid, and tetracycline. We also performed pulsed-field gel electrophoresis (PFGE) for EC0417119, according to the PulseNet standard protocol (6), and compared its PFGE profile with that of the current outbreak strain E. coli O104:H4, which was obtained from the PulseNet Asia Pacific network. PFGE profiles resolved by either XbaI or BlnI did not match each other. The percentage similarity of XbaI- and BlnI-digested PFGE profiles of the 2 isolates was 75% and 66.7%, respectively, as shown in the Figure. Figure Clustering of A) XbaI- and B) BlnI-digested DNA fragments by pulsed-field gel electrophoresis (PFGE) for Escherichia coli O104:H4 2011 outbreak strain in Europe and isolate obtained in South Korea in 2004. Infections with the EHEC O104 strain were reported several times worldwide. In Europe, such occurrence was rare, and before the current outbreak, the EHEC O104:H4 strain was documented only once in South Korea. For this reason, it was logical to examine the possible relatedness of the EC0417119 strain and the strain causing the current outbreak. However, the EC0417119 strain has many different characteristics compared with the current outbreak strain: not possessing enteroaggregative E. coli determinant, not producing extended-spectrum β-lactamases, and not showing indistinguishable PFGE patterns. In conclusion, there is no evidence that the E. coli O104:H4 strain isolated in South Korea in 2004 is related to the strain that has a caused the massive and unprecedented EHEC outbreak in Europe.

Outbreak of Ciprofloxacin-Resistant Shigella sonnei Associated with Travel to Vietnam, Republic of Korea

We investigated an October 2014 outbreak of illness caused by Shigella sonnei in a daycare center in the Republic of Korea (South Korea). The outbreak strain was resistant to extended-spectrum cephalosporins and fluoroquinolones and was traced to a child who had traveled to Vietnam. Improved hygiene and infection control practices are needed for prevention of shigellosis.

Enteric Bacteria Isolated from Diarrheal Patients in Korea in 2014

Objectives The aim of this study was to characterize the pathogens responsible for causing diarrhea according to season, region of isolation, patient age, and sex as well as to provide useful data for the prevention of diarrheal disease. Methods Stool specimens from 14,886 patients with diarrhea were collected to identify pathogenic bacteria from January 2014 to December 2014 in Korea. A total of 3,526 pathogenic bacteria were isolated and analyzed according to season, region of isolation, and the age and sex of the patient. Results The breakdown of the isolated pathogenic bacteria were as follows: Salmonella spp. 476 (13.5%), pathogenic Escherichia coli 777 (22.0%), Vibrio parahaemolyticus 26 (0.74%), Shigella spp. 13 (0.37%), Campylobacter spp. 215 (6.10%), Clostridium perfringens 508 (14.4%), Staphylococcus aureus 1,144 (32.4%), Bacillus cereus 356 (10.1%), Listeria monocytogenes 1 (0.03%), and Yersinia enterocolitica 10 (0.3%). The isolation rate trend showed the highest ratio in the summer season from June to September for most of the pathogenic bacteria except the Gram-positive bacteria. The isolation rate of most of the pathogenic bacteria by patient age showed highest ratio in the 0–19 year age range. For isolation rate by region, 56.2% were isolated from cities and 43.8% were isolated from provinces. Conclusion Hygiene education should be addressed for diarrheal disease-susceptible groups, such as those younger than 10 years, aged 10–19 years, and older than 70 years, and monitoring for the pathogens is still required. In addition, an efficient laboratory surveillance system for infection control should be continued.

The Prevalence and Characteristics of Bacteria Causing Acute Diarrhea in Korea, 2012

Background: Through change in the climate and living environment, bacterial pathogens that cause diarrhea also change. This study sought to determine the characteristics of pathogens according to species, isolated region, and patient age/sex using National Surveillance Data for diarrhea, and to provide basic data for the prevention of diarrheal disease. Methods: From January to December 2012, stool specimens were collected from 21,180 diarrheal patients in Korea to identify the pathogenic bacteria involved. Pathogenic bacteria were analyzed according to isolated region and patient age/sex. Identification and analysis of the pathogens were conducted based on the Guidelines of the National Institute of Health Diagnostic Laboratory: Disease-specific protocol (2005). Results: Among the 21,180 stool specimens, pathogenic bacteria known to cause diarrhea were isolated from 2,444 stool specimens (11.5%). The isolation rate was highest in the summer (from June to September) for most pathogenic bacteria, except Escherichia coli, Staphylococcus aureus, and Clostridium perfringens. The isolation rate of pathogenic bacteria based on patient age was highest in children under the age of 10. Conclusion: Hygiene education should be addressed in diarrheal disease-susceptible groups, such as children under 10, people in their 50s, and those greater than 70 years old, and ongoing monitoring for pathogens is needed. In addition, an efficient information system and surveillance program should be continued for infection prevention. (Ann Clin Microbiol 2013;16: 174-181)

Complete nucleotide sequence of the IncI1 plasmid pSH4469 encoding CTX-M-15 extended-spectrum β-lactamase in a clinical isolate of Shigella sonnei from an outbreak in the Republic of Korea

An outbreak of extended-spectrum β-lactamase (ESBL)-producing Shigella sonnei infections occurred in a school for disabled children in Gyeongbuk Province, Republic of Korea, in 2008. Five students were affected. Pulsed-field gel electrophoresis (PFGE) analysis revealed that all of the ESBL-producing S. sonnei isolates belonged to the same clone, and nucleotide sequence analysis of ESBL genes revealed that they harboured bla(CTX-M-15). This is the first identification of bla(CTX-M-15) in Shigella spp. in South Korea. In this study, a plasmid carrying the bla(CTX-M-15) gene, designated pSH4469, recovered from a S. sonnei isolate responsible for the outbreak was characterised. Replicon typing and plasmid multilocus sequence typing (pMLST) analysis of plasmids in the outbreak strain identified that the bla(CTX-M-15) gene was located on an IncI1 incompatibility group plasmid of sequence type 16 (ST16). The complete nucleotide sequence of pSH4469 revealed that this plasmid is 91109bp and harbours 119 putative genes, including another antibiotic resistance gene (bla(TEM-1b)) that is often associated with the ISEcp1-bla(CTX-M-15)-orf477delta transposable unit. The plasmid consists of a large backbone with considerable homology to the pEK204 plasmid isolated from Escherichia coli in the UK, except for insertion of an IS66 element found in pEK204. These data demonstrate that IncI1 plasmids are used as a successful platform for efficient horizontal gene transfer, thereby resulting in the dissemination of CTX-M-type β-lactamases among Enterobacteriaceae.

Anti-Shiga toxin immunoglobulin G antibodies in healthy South Korean slaughterhouse workers

Abstract Background: Slaughterhouse workers are in direct contact with cattle nearly every day. The purpose of this study was to survey the presence and distribution of anti-Shiga toxin 1 (Stx1) immunoglobulin G (IgG) in slaughterhouse workers, enabling a study of the serologic response to this toxin while working in an area at high-risk of Stx-producing Escherichia coli (STEC) infection. Methods: One thousand seven hundred and twenty-nine serum samples from healthy slaughterhouse employees were collected and surveyed by indirect enzyme-linked immunosorbent assay (ELISA). Results: Among the 5 slaughterhouse positions, slaughterers had the highest distribution of anti-Stx1 IgG values by an ELISA. Based on the ELISA values, 25% (433/1729) of the workers had anti-Stx1 IgG. Slaughterers, residual products handlers, inspectors, livestock hygiene controllers, and grading testers had anti-Stx1 IgG-positive rates of 28%, 25%, 20%, 19%, and 17%, respectively. The ELISA values of anti-Stx1 IgG increased with increases in the number of years worked by slaughterers, but not by residual products handlers, inspectors, livestock hygiene controllers, or grading testers. Conclusions: From these results, slaughterhouse workers are healthy and asymptomatic; slaughterers in particular are at high-risk for STEC exposure.

Cholera Outbreak due to Raw Seafood Consumption in South Korea, 2016

Three cases of cholera occurred in South Korea during a period of three weeks in August 2016. All the cases were associated with the consumption of raw seafood in southern coastal area of South Korea. Epidemiologic investigations were performed to track the spread of cholera, including persons in contact with the cholera patients, seafood, and seawater from the fish tank and marine environments. A microbiological investigation demonstrated that cholera isolated from the three patients and a seawater sample at the Korea Strait showed identical serotype (O1 Ogawa), biotype (El tor), and toxin (ctx-positive). Pulsed-field gel electrophoresis analysis showed that the three clinical strains are identical (100%) and shared 97% identity with the seawater sample.

Genome Sequencing Analysis of Atypical Shigella flexneri Isolated in Korea

Objectives An atypical Shigella flexneri strain with a plural agglutination pattern [i.e., reacting not only with serum samples containing type antigen II but also with serum samples containing group antigens (3)4 and 7(8)] was selected for genome sequencing, with the aim of obtaining additional comparative information about such strains. Methods The genomic DNA of atypical S. flexneri strain NCCP 15744 was sequenced using an Ion Torrent PGM sequencing machine (Life Technologies, USA). The raw sequence data were preprocessed and reference-assembled in the CLC Assembly Cell software (version 4.0.6; CLC bio, USA). Results Ion Torrent sequencing produced 1,450,025 single reads with an average length of 144 bp, totaling ~209 Mbp. The NCCP 15744 genome is composed of one chromosome and four plasmids and contains a gtrX gene. Among the published genome sequences of S. flexneri strains, including 2457T, Sf301, and 2002017, strain NCCP 15744 showed high similarity with strain 2002017. The differences between NCCP 15744 and 2002017 are as follows: i) NCCP 15744 carries four plasmids whereas 2002017 carries five; ii) 19 genes (including CI, CII, and cro) were lost in the SHI-O genomic island of NCCP 15744 and six genes were gained as compared with strain 2002017. Conclusion Strain NCCP 15744 is genetically similar to 2002017, but these two strains have different multilocus sequence types and serotypes. The exact reason is unclear, but the 19 lost genes may be responsible for the atypical seroconversion of strain NCCP 15744.

Surveillance of Bacillus cereus Isolates in Korea from 2012 to 2014

OBJECTIVES To investigate the prevalence and toxin production characteristics of non-emetic and emetic Bacillus cereus strains isolated via the laboratory surveillance system in Korea. METHODS A total of 667 B. cereus strains were collected by the Korea National Research Institute of Health laboratory surveillance system from 2012 to 2014. The collected strains were analyzed by geographical region, season, patient age, and patient sex. Additionally, the prevalence rates of enterotoxin and emetic toxin genes were evaluated. RESULTS The isolation rate of B. cereus strains increased during the summer, but the isolation rate was evenly distributed among patient age groups. Emetic toxin was produced by 20.2% of the isolated strains. The prevalence rates of five enterotoxin genes (entFM, nheA, cytK2, hblC, and bceT) were 85.0, 78.6, 44.5, 36.6, and 29.7%, respectively, among non-emetic strains and 77.8, 59.3, 17.8, 11.9 and 12.6%, respectively, among emetic strains. Thus, the prevalence rates of all five enterotoxin genes were lower in emetic B. cereus. CONCLUSION The prevalence of enterotoxin genes differed between non-emetic and emetic B. cereus strains. Among emetic B. cereus strains, the prevalence rates of two enterotoxin genes (cytK2 and hblC) were lower than those among the non-emetic strains. In both the emetic and non-emetic strains isolated in Korea, nheA and entFM were the most prevalent enterotoxin genes.

Enhanced Type III Secretion System Expression of Atypical Shigella flexneri II:(3)4,7(8)

Objectives We aimed at evaluating the virulence of atypical Shigella flexneri II:(3)4,7(8) by DNA microarray and invasion assay. Methods We used a customized S. flexneri DNA microarray to analyze an atypical S. flexneri II:(3)4,7(8) gene expression profile and compared it with that of the S. flexneri 2b strain. Results Approximately one-quarter of the atypical S. flexneri II:(3)4,7(8) strain genes showed significantly altered expression profiles; 344 genes were more than two-fold upregulated, and 442 genes were more than 0.5-fold downregulated. The upregulated genes were divided into the category of 21 clusters of orthologous groups (COGs), and the “not in COGs” category included 170 genes. This category had virulence plasmid genes, including the ipa-mxi-spa genes required for invasion of colorectal epithelium (type III secretion system). Quantitative reverse-transcription polymerase chain reaction results also showed the same pattern in two more atypical S. flexneri II:(3)4,7(8) strains. Atypical S. flexneri II:(3)4,7(8) showed four times increased invasion activity in Caco-2 cells than that of typical strains. Conclusion Our results provide the intracellularly regulated genes that may be important for adaptation and growth strategies of this atypical S. flexneri.