Survey of Zoonotic Trematode Metacercariae in Fish from Water Systems of Geum-gang (River) in Republic of Korea.

The infection status of zoonotic trematode metacercariae (ZTM) was surveyed in freshwater fishes from the water systems of Geum-gang (River) in the Republic of Korea (Korea). A total of 1,161 freshwater fishes from 6 local sites of Geum-gang were examined with the artificial digestion method for 4 years (2012-2015). Clonorchis sinensis metacercariae were detected in 122 (37.2%) out of 328 fishes in the positive fish species from 4 surveyed areas, and their mean intensity was 43 per fish infected. Metagonimus spp. metacercariae were found in 432 (51.7%) out of 835 fishes in the positive fish species from all 6 surveyed areas, and their mean intensity was 30 per fish infected. Centrocestus armatus metacercariae were detected in 285 (75.0%) out of 380 fishes in the positive fish species from 6 surveyed areas, and their mean intensity was 2,100 per fish infected. Echinostoma spp. metacercariae were found in 56 (19.7%) out of 284 fishes in the positive fish species from 5 surveyed areas, and their mean intensity was 10 per fish infected. Clinostomum complanatum metacercariae were detected in 98 (57.3%) out of 171 fishes in the positive fish species from only 2 surveyed areas, and their mean intensity was 11 per fish infected. Conclusively, the endemicity of ZTM is not so high in fishes from water systems of Geum-gang in Korea although it is more or less different by fish species, surveyed areas and ZTM species.

Prevalence and Infection Intensity of Zoonotic Trematode Metacercariae in Fish from Soyang-cheon (Stream), in Wanju-gun, Jeollabuk-do, Korea.

We surveyed on the infection status of zoonotic trematode metacercariae (ZTM) in freshwater fishes from Soyang-cheon (a branch stream of Mangyeong-gang) in Wanju-gun, Jeollabuk-do, the Republic of Korea. A total of 927 fishes were individually examined with the artificial digestion method during 2013-2015 (462 fish in 15 spp.) and 2018-2019 (465 fish in 25 spp.). Clonorchis sinensis metacercariae were detected in 207 (31.4%) out of 659 fishes in 14 positive fish species (PFS), and their mean intensity was 114 per fish infected (PFI). Metagonimus spp. metacercariae were found in 302 (37.4%) out of 808 fishes in 21 PFS, and their mean intensity was 12 PFI. Centrocestus armatus metacercariae were detected in 222 (59.0%) out of 376 fishes in 12 PFS, and their mean intensity was 383 PFI. Echinostoma spp. metacercariae were found in 139 (22.1%) out of 628 fishes in 10 PFS, and their mean intensity was 7 PFI. Clinostomum complanatum metacercariae were detected in 14 (6.5%) out of 214 fishes in 4 PFS, and their mean intensity was 2.4 PFI. Metorchis orientalis metacercariae were detected in 36 (13.5%) out of 267 fishes in 5 PFS, and their mean intensity was 4.3 PFI. Conclusively, the prevalence and infection intensity of ZTM is generally not so high in fishes from Soyang-cheon. However, those of C. sinensis metacercariae are more or less higher in 2 fish species, Pungtungia herzi and Sarcocheilichthys variegatus wakiyae.

Infection Status with Metagonimus spp. Metacercariae in Fishes from Seomjin-gang and Tamjin-gang in Republic of Korea.

To grasp the infection status of Metagonimus spp. metacercariae (MsMc), the freshwater fishes were surveyed from Seomjin-gang (river) and Tamjin-gang in the Republic of Korea. Total 1,604 fishes from 7 local sites of Seomjin-gang and 1,649 fishes from 2 sites of Tamjin-gang were examined for 6 years (2012-2017) by the artificial digestion method. MsMc were detected in fishes from 7 sites, i.e., Osucheon in Imsil-gun (36.3% fish in 6 spp.), Seomjin-gang in Sunchanggun (49.8% in 18 spp.), Songdaecheon in Namwon-si (64.5% in 8 spp.), Seomjin-gang in Gokseong-gun (72.4% in 14 spp.) and in Gurye-gun (78.8% in 17 spp.), Hoengcheon (75.9% in 11 spp.) and Namsancheon (58.9% in 7 spp.) in Hadong-gun. Their average densities were 4.2, 86.8, 39.9, 43.1, 246.5, 173.6 and 67.5 per fish infected respectively. Prevalence with MsMc in rasborinid fish from Seomjin-gang was 89.2% and their intensity was 73.6 per fish infected. Endemicities of MsMc in rasborinid fish from Seomjin-gang were significantly higher in fishes from the lower reaches (prevalence: 98.7%; density: 137) rather than in fishes from the middle (93.5%; 38) and upper (72.4%; 13) reaches. MsMc were also detected in 56.1% and 66.4% fishes from 2 surveyed areas, i.e., the middle reaches in Jangheung-gun and the lower reaches in Gangjin-gun, of Tamjin-gang, and their densities were 147 and 121 per fish infected. In susceptible fishes from Tamjin-gang, the prevalence was 84.1% and density was 227 per fish infected. By the present study, it was confirmed that MsMc is highly prevalent in the fishes from Seomjin-gang and Tamjin-gang in Korea.

Infections with Centrocestus armatus Metacercariae in Fishes from Water Systems of Major Rivers in Republic of Korea.

The infection status of Centrocestus armatus metacercariae (CaMc) was broadly surveyed in freshwater fishes from major river systems in the Republic of Korea (Korea) during 2008-2017. A total of 14,977 fishes was caught and examined by the artificial digestion method. CaMc were detected in 3,818 (97.1%) (2,114 Z. platypus: 96.1% and 1,704 Z. temminckii: 98.4%) out of 3,932 Zacco spp. examined and their density was 1,867 (2,109 in Z. platypus and 1,567 in Z. temminckii) per fish infected. The prevalences with CaMc were high, 93.7-100%, in Zacco spp. from all surveyed areas. However, their densities were more or less different by the surveyed areas and fish species. They were most high in Nakdong-gang in Gyeongsangnam-do (4,201 in average), and followed by Geum-gang (2,343), Nakdong-gang in Gyeongsangbuk-do (1,623), Han-gang (1,564), Tamjin-gang and Yeongsan-gang (1,540), streams in the east coast (1,028), Seomjin-gang (488) and Mangyeong-gang (170). In another species of rasborinid fish, Opsariichthys uncirostris amurensis, CaMc were detected in 222 (74.8%) out of 297 ones examined and their density was 278 (1-4,480) per fish infected. CaMc were also detected in total 41 fish species except for the rasborinid fish, Z. platypus, Z. temminckii and O. uncirostris amurensis. Conclusively, it was confirmed that among the 3 species of rasborinid fish, Z. platypus and Z. temminckii are highly prevalent and O. uncirostris amurensis is moderately prevalent with CaMc. Additionally, we could know that variety of fish species act as the second intermediate hosts of C. armatus in Korea.

Prevalence of Clonorchis sinensis Metacercariae in Fish from Water Systems of Seomjin-gang (River).

The prevalence of Clonorchis sinensis metacercariae (CsMc) was examined in freshwater fish from the water systems of Seomjin-gang (River), the Republic of Korea. Total 1,604 fish from 7 local sites of Seomjin-gang were examined by artificial digestion methods. The metacercariae of C. sinensis were detected in 102 (39.8%) out of 256 fish (14 species) from the upper reaches of Seomjin-gang, i.e., Osucheon (22.3% in 6 fish species) in Imsil-gun, and Seomjin-gang (63.9% in 9 fish species) in Sunchang-gun, Jeollabuk-do. Their average density was 9.0 per infected fish. They were also found in 132 (48.0%) out of 275 fish (12 spp.) from the middle reaches of Seomjin-gang, i.e., Songdaecheon (58.9% in 4 fish species) in Namwon-si, Jeollabuk-do, and Seomjin-gang (45.2% in 10 fish species) in Gokseong-gun, Jeollanam-do. Their average density was 21.0 per infected fish. CsMc were detected in 77 (56.6%) out of 136 fish (11 species) from the lower reaches of Seomjin-gang, i.e., Seomjin-gang (73.3% in 11 fish species) in Gurye-gun, Jeollanam-do, and Namsancheon (8.6% in 1 fish species) in Hadong-gun, Gyeongsangnam-do. Their average density was 64.9 per infected fish. The metacercariae of Metorchis orientalis were also detected in 6 fish species from 4 sites of Seomjin-gang. Conclusively, it has been confirmed that CsMc are more or less prevalent in fish from some water systems of Seomjin-gang in Korea.

High Seroprevalence of Mycoplasma pneumoniae and Chlamydia pneumoniae among Scrub Typhus Patients in South Korea.

Scrub typhus is an acute febrile illness caused by the obligate intracellular organism Orientia tsutsugamushi, endemic to South Korea. The course of scrub typhus can range from a self-limiting disease to a fatal illness. Serological cross-reactivity has been reported with other intracellular organisms, including Rickettsia species, Chlamydophila species, and Mycoplasma pneumoniae. We conducted a retrospective study to assess the current seroprevalence of M. pneumoniae IgM and Chlamydia pneumoniae IgM in scrub typhus patients in South Korea. We enrolled 150 patients with suspected rickettsial disease over the course of 2 years. Of these patients, 60 were confirmed to have scrub typhus and had paired acute and convalescent serum. Among the 60 scrub typhus patients, 40 (66.7%) had M. pneumoniae IgM and 19 (31.7%) had C. pneumoniae IgM in acute- or convalescent phase sera. The seroconversion rates of M. pneumoniae IgG and IgM were 16.7% and 33.3%, respectively. The seroconversion rates of C. pneumoniae IgG and IgM were 8.3% and 11.7%, respectively. Compared with previous study results, this may indicate a relatively high seroprevalence of M. pneumoniae IgM and C. pneumoniae IgM in scrub typhus patients, indicating possible misdiagnosis of M. pneumoniae and C. pneumoniae infections in non-endemic scrub typhus areas.

A waterborne outbreak of multiple diarrhoeagenic Escherichia coli infections associated with drinking water at a school camp.

BACKGROUND: In June 2015, a local public health laboratory was notified that students had developed gastroenteritis symptoms after attending a camp. An outbreak investigation was conducted to determine the extent and cause of the outbreak. METHOD: A retrospective cohort study was conducted to determine the correlations between the illness and specific exposures at the school camp. All attendees were interviewed with a standard questionnaire that addressed clinical symptoms, food consumption, and environmental exposures. Clinical specimens were cultured using standard microbiological methods for bacterial and viral pathogens. The genetic relationships of all isolates were determined using pulsed-field gel electrophoresis (PFGE). RESULTS: A total 188 patients with symptoms of diarrhoea, abdominal pain, and nausea were identified. The completed questionnaires suggested that the consumption of drinking water was likely to be linked to this outbreak. Using microbiological methods, enterohaemorrhagic Escherichia coli, enteropathogenic E. coli, and enteroaggregative E. coli were isolated, and the isolates from both patient stool and environmental water samples displayed indistinguishable XbaI-PFGE patterns. The water system in the camp used groundwater drawn from a private underground reservoir for cooking and drinking. The environmental investigation revealed some problems with the water supply system, such as the use of inappropriate filters in the water purifier and a defect in the pipeline between the reservoir and the chlorination device. CONCLUSIONS: This outbreak points to the importance of drinking water quality management in group facilities where underground water is used and emphasizes the need for periodic sanitation and inspection to prevent possible waterborne outbreaks.

Low-density lipoprotein protects Vibrio vulnificus-induced lethality through blocking lipopolysaccharide action.

Lipoprotein plays a role in the host defense against bacterial infection, and its serum level has been demonstrated to be an important prognosis factor of survival. We have previously demonstrated that LDL directly inactivates the hemolytic activity of Vibrio vulnificus cytolysin (VVC) in vitro. The object of this study was therefore to examine whether the LDL-mediated inactivation of VVC leads to protection against lethal infection of V. vulnificus in vivo, using wild and VVC-deficient V. vulnificus strains. Unexpectedly, we found that LDL protects mouse lethality induced by VVC-deficient as well as wild V. vulnificus strain. We also demonstrated that LDL blocks V. vulnificus LPS-induced lethality in mice. These results suggest that LDL preferentially act on endotoxin rather than exotoxin in the protection against V. vulnificus-induced mice lethality.

Epidemiological relationships of Campylobacter jejuni strains isolated from humans and chickens in South Korea.

Thirty-nine human isolates of Campylobacter jejuni obtained from a national university hospital during 2007-2010 and 38 chicken isolates of C. jejuni were collected from poultry farms during 2009-2010 in South Korea were used in this study. Campylobacter genomic species and virulence-associated genes were identified by PCR. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed to compare their genetic relationships. All isolates were highly resistant to ciprofloxacin, nalidixic acid, and tetracycline. Of all isolates tested, over 94% contained seven virulence associated genes (flaA, cadF, racR, dnaJ, cdtA, cdtB, and cdtC). All isolates were classified into 39 types by PFGE clustering with 90% similarity. Some chicken isolates were incorporated into some PFGE types of human isolates. MLST analysis for the 39 human isolates and 38 chicken isolates resulted in 14 and 23 sequence types (STs), respectively, of which 10 STs were new. STs overlapped in both chicken and human isolates included ST-21, ST-48, ST-50, ST-51, and ST-354, of which ST-21 was the predominant ST in both human and chicken isolates. Through combined analysis of PFGE types and STs, three chicken isolates were clonally related to the three human isolates associated with food poisoning (VII-ST-48, XXII-ST-354, and XXVIII-ST-51). They were derived from geographically same or distinct districts. Remarkably, clonal spread of food poisoning pathogens between animals and humans was confirmed by population genetic analysis. Consequently, contamination of campylobacters with quinolone resistance and potential virulence genes in poultry production and consumption may increase the risk of infections in humans.

The first outbreak of giardiasis with drinking water in Korea.

OBJECTIVES: To identify the pathogen of the diarrhea outbreak in a village in Jeollabuk province in Korea in April 2010. METHODS: DNA extraction was performed from the 120 L of collected water, which was centrifuged at 10,000 x g for 30 min. PCR reactions were conducted in a total of 25 ul, which included PCR premix (GenDEPOT, Barker, TX, USA), 2 ul (∼100 ng) of extracted DNA, and 10 pmol of each primer. RESULTS: Nine people out of 25 had a symptom of abdominal pain accompanied by diarrhea after they used stored valley water in a water tank as a provisional water supply source without chlorine sterilization. Among them Giardia lamblia was detected in fecal samples of 7 people using the polymerase chain reaction method. Although G. lamblia was also detected from water provided by the provisional water supply system stored in the water tank and used as drinking water, it was not detected in the water tank itself. This water-borne outbreak is considered to have occurred when the provisional water supply tube was destroyed under a building construction and contaminated by G. lamblia, but its precise cause has not been clarified. CONCLUSION: This outbreak resulting from G. lamblia is very meaningful as the first outbreak of an infection by a water-borne parasite in Korea.

Emetic toxin producing Bacillus cereus Korean isolates contain genes encoding diarrheal-related enterotoxins.

Bacillus cereus can cause the diarrheal and emetic type of food poisoning but the symptoms of emetic food poisoning caused by B. cereus occasionally include emesis and diarrhea. The enterotoxin characteristics of emetic toxin (cereulide) producing B. cereus were needed to be determined. Therefore, forty B. cereus strains isolated from various sources in Korea were investigated for the presence of enterotoxin genes. All strains were confirmed to produce the emetic toxin using HPLC-MS methods. The rates of the nheABC, hblCDA, entFM and cytK genes amongst emetic toxin producing B. cereus strains were 82.5, 7.5, 50.0 and 27.5%, respectively. Pattern III harbored nheABC and entFM genes and pattern V processed entFM gene and were shown to be the major patterns, being present in 55.0% (21 of 40) of the emetic toxin producing B. cereus strains. Our findings revealed that 34 (85.0%) of 40 emetic toxin producing B. cereus strains isolated in Korea have the potential to cause diarrheal and emetic type of food poisoning, simultaneously. Thus, emetic toxin and enterotoxin genes should be constantly screened to provide insight into B. cereus food poisoning.