Human Norovirus Genogroups Detected from Acute Gastroenteritis Patients in Seoul from May 2013 to April 2015

Norovirus is an important cause of acute nonbacterial gastroenteritis in communities worldwide. It was evaluated the prevalence of norovirus infections in patients with acute gastroenteritis occurring in Seoul from May 2013 to April 2015, with regular surveillance. 7.3% (252/3,485) of the fecal specimens were determined to be positive for noroviruses by reverse transcription-polymerase chain reaction (RT-PCR). Norovirus genogroup distribution was 19.1% (48/252) genogroup GI, 71.4% (180/252) genogroup GII, and 9.5% (24/252) genogroup G1+GII respectively. It was most norovirus detection rates from November 2013 to March 2015. And it was rotavirus 0.2% (7/3,485), astrovirus 0.03% (1/3,485), sapovirus 0.03% (1/3,485) and, it was non-detective on adenovirus. Norovirus genotypes identified were nine kinds of genogroup GI (GI-1, GI-2, GI-3, GI-4, GI-6, GI-7, GI-8, GI-12, GI-14) and eight kinds of genogroup GII (GII-2, GII-3, GII-4, GII-5, GII-6, GII-7, GII-14, GII-16, GII-17). The genetic characteristics of norovirus and the epidemiological patterns of a viral pathogen from acute gastroenteritis patients may give potentially effective data for epidemiological studies in Seoul, Korea.

Molecular Characteristics of Noroviruses Genogroup I and Genogroup II Detected in Patients With Acute Gastroenteritis

Noroviruses are the leading cause of epidemic gastroenteritis, including foodborne outbreak, in Korea. The prevalence of human noroviruses was studied in diarrheal stool samples of patients with acute gastroenteritis by conventional duplex reverse transcription (RT)-PCR. Diarrheal stool samples were collected from 1,685 patients from the local hospitals in Seoul. The prevalence of the noroviruses was 22.8% (222/972 patients) in 2012 and 11.2% (80/713 patients) in 2013, with a total of 17.9% (302/1,685 patients). Genotyping was performed on 302 norovirus-positive stool samples to reveal 5.6% prevalence of genogroup I (GI) (17/302) and 94.4% prevalence of genogroup II (GII) (285/302). The patients with norovirus-associated acute gastroenteritis mostly showed prevalence of GII norovirus, especially GII.4 (64.6%; 195/302).

Epidemiological Relationship of Enterotoxigenic Escherichia coli and Enteroaggregative E. coli Isolated from Patients with Diarrhea in Seoul

Of total 1,438 specimens of patients with diarrhea in Seoul, 2011, 217 samples (15%) were found pathogenic Escherichia coli that included 192 strains (89%) of enterotoxigenic E. coli (ETEC) and enteroaggregative E. coli (EAEC). The highest isolation rate for ETEC and EAEC was found in August and September. Sixty two pathogenic E. coli strains (34 ETEC and 28 EAEC strains) were selected from 175 strains (94 ETEC and 81 EAEC strains) isolated in August and September. Of 94 strains characterized for ETEC phenotype, 76 (81%) expressed heat-stable toxin (ST) only. Antimicrobial susceptibility test was carried out by using sixteen types of antibiotics. A high level of antimicrobial resistance to tetracycline (57%), ampicillin and ticarcillin (54%) was observed among EAEC isolates while the highest resistance rate of ETEC was found for nalidixic acid (47%), followed by tetracycline (32%). As to the antimicrobial susceptibility test, EAEC showed the complicated multi-drug resistant patterns in which the resistance was higher than ETEC. Pulsed-field gel electrophoresis (PFGE) was carried out to examine the genetic relatedness among ETEC and EAEC isolates. Except for 11 strains, 51 strains were divided by eight pulsotypes. In PFGE analysis, isolates from foodborne disease outbreaks in August and September 2011 showed close relation.