Genetic Characteristics and Relatedness of Imported Vibrio cholerae O1 Biotype El Tor in Korea / 대한임상미생물학회지

BACKGROUND: Cholera is a representative water-borne disease that is caused by V. cholera ctx (+). V. cholera El Tor was previously the primary pathogen, but after the seventh pandemic outbreak, it was replaced by a V. cholera El Tor variant with a classical phenotype and genotype. In this study, we investigated the genotypic and phenotypic characteristics of imported V. cholerae El Tor in Korea. METHODS: Forty-nine V. cholerae O1 El Tor strains isolated from 2004 to 2011 were used in this study. Polymerase chain reaction amplification of the ctxB and rstR genes was used for biotype determination. An antimicrobial susceptibility test was performed for phenotypic analysis, and pulse field gel electrophoresis (PFGE) was used for analysis of genetic relatedness. RESULTS: Classical ctxB genes were found in all of the isolates, while classical, El Tor, and combined rstR genes were found. Twenty strains showed antimicrobial resistance against streptomycin, sulfamethoxazole/trimethoprim, nalidixic acid, and ciprofloxacin. Based on PFGE, all isolates were grouped as cluster B. The country of origin and resistance pattern were highly related, although the time of influx and serogroup were not. CONCLUSION: Isolates of V. cholera El Tor imported since 2004 were hybrids of V. cholera El Tor, which has the classical ctxB gene and is considered to be a CTX prophage. The SXT element plays an important role in antimicrobial resistance. PFGE patterns, which can be used for analysis of imported V. cholera, revealed the relatedness of the resistant isolates.

Detection of the Causative Agents of Traveler's Diarrhea Using a Real-Time PCR Screening Method / 대한임상미생물학회지

BACKGROUND: The incidence of infectious diarrheal disease in Korea has decreased over the past decade, but traveler's diarrhea (TD) is increasing in frequency. We therefore investigated the distribution of the causative agents of TD. METHODS: A total of 132 rectal swab specimens were acquired from TD patients who entered the country via Gimhae International Airport. The specimens were screened for 12 bacterial pathogens by real-time PCR, and target pathogens were isolated from the PCR positive specimens using conventional microbiological isolation methods. RESULTS: A total of 93 specimens (70.5%) showed positive PCR screening results, and of these specimens, nine species and 50 isolates (37.9%), including Vibrio parahaemolyticus (18 isolates) and ETEC (17 isolates), were isolated. No specimens were PCR positive for Listeria monocytogenes or Campylobacter jejuni, and no pathogenic Bacillus cereus were isolated. CONCLUSION: Even though viruses and EAEC were not included as target pathogens, the high isolation rate of these pathogens in this study provides indirect evidence that most cases of pathogen-negative TD are caused by undetected bacterial agents. Furthermore, our study results confirm the effectiveness of real-time PCR-based screening methods. This study is the first report in Korea to demonstrate that ETEC and V. parahaemolyticus are the major causative pathogens of TD, and this knowledge can be used to help treat and prevent TD.

Rapid Detection of Extended Spectrum beta-Lactamase (ESBL) for Enterobacteriaceae by use of a Multiplex PCR-based Method / 감염과화학요법

A multiplex PCR method has been developed to classify extended spectrum beta-lactamase (ESBL) and plasmid-mediated AmpC beta-lactamase (PABL). This method consists of the use of two four-multiplex PCRs for the detection of TEM, OXA, SHV, CTX-M, CMY, and DHA type beta-lactamases. We have compared findings from the use of conventional detection methods with that of this newly developed typing method. In testing for 73 ESBL-producing and PABL-producing isolates, 100% of the isolates were correctly identified as previously characterized types and, 44 types of beta-lactamases were additionally identified from 33 isolates. This assay not only reduces the time for classification but also increases the accuracy for detection.

Rapid Detection of Extended Spectrum beta-Lactamase (ESBL) for Enterobacteriaceae by use of a Multiplex PCR-based Method / 감염과화학요법

A multiplex PCR method has been developed to classify extended spectrum beta-lactamase (ESBL) and plasmid-mediated AmpC beta-lactamase (PABL). This method consists of the use of two four-multiplex PCRs for the detection of TEM, OXA, SHV, CTX-M, CMY, and DHA type beta-lactamases. We have compared findings from the use of conventional detection methods with that of this newly developed typing method. In testing for 73 ESBL-producing and PABL-producing isolates, 100% of the isolates were correctly identified as previously characterized types and, 44 types of beta-lactamases were additionally identified from 33 isolates. This assay not only reduces the time for classification but also increases the accuracy for detection.

The First Outbreak of Shigellosis Caused by Shigella dysenteriae Type 8 in Korea / 대한임상미생물학회지

BACKGROUND: In May 2004, an outbreak of a diarrheal disease occurred among tourists returning from Mt. Geumgang in North Korea; Shigella dysenteriaetype 8 was isolated from 12 of the 36 patients who were suffering from diarrhea. We investigated the genetic relatedness of the isolates. METHODS: The isolates were identified by VITEK system an serotyped by a slide agglutination test. Antimicrobial susceptibility was determined by the disk diffusion method and genetic relatedness was examined by pulsed-field gel electrophoresis (PFGE). RESULTS: All 12 isolates were identified as Shigella spp., and agglutinated by S. dysenteriae type 8 antisera. All of these isolates showed the same antibiotic susceptibility pattern, and were resistant to streptomycin, tetracycline and trimethoprim/sulfamethoxazole. PFGE patterns were classified into 2 types, sdx1 and sdx2, and the relatedness between these two types was 80.5%. Eleven isolates belonged to sdx1. CONCLUSION: The antibiotic susceptibility pattern and genetic relatedness of the isolates strongly suggest that they were from the same origin. Because this is the first report of S. dysenteriae type 8 isolation in Korea, and all of these cases were related to foreign travel, the surveillance system and the ability of the clinical laboratory should be strengthened to prevent the entry and spread of rare and hitherto not reported infectious agents into Korea.