Dong Jin

Hemorrhagic Fever Caused by a Novel Bunyavirus in China: Pathogenesis and Correlates of Fatal Outcome

BACKGROUND  Hemorrhagic fever-like illness caused by a novel Bunyavirus, Huaiyangshan virus (HYSV, also known as Severe Fever with Thrombocytopenia virus [SFTSV] and Fever, Thrombocytopenia and Leukopenia Syndrome [FTLS]), has recently been described in China. METHODS  Patients with laboratory-confirmed HYSV infection who were admitted to Union Hospital or Zhongnan Hospital between April 2010 and October 2010 were included in this study. Clinical and routine laboratory data were collected and blood, throat swab, urine, or feces were obtained when possible. Viral RNA was quantified by real-time reverse-transcriptase polymerase chain reaction. Blood levels of a range of cytokines, chemokines, and acute phase proteins were assayed. RESULTS  A total of 49 patients with hemorrhagic fever caused by HYSV were included; 8 (16.3%) patients died. A fatal outcome was associated with high viral RNA load in blood at admission, as well as higher serum liver transaminase levels, more pronounced coagulation disturbances (activated partial thromboplastin time, thrombin time), and higher levels of acute phase proteins (phospholipase A, fibrinogen, hepcidin), cytokines (interleukin [IL]-6, IL-10, interferon-γ), and chemokines (IL-8, monocyte chemotactic protein 1, macrophage inflammatory protein 1b). The levels of these host parameters correlated with viral RNA levels. Blood viral RNA levels gradually declined over 3-4 weeks after illness onset, accompanied by resolution of symptoms and laboratory abnormalities. Viral RNA was also detectable in throat, urine, and fecal specimens of a substantial proportion of patients, including all fatal cases assayed. CONCLUSIONS. Viral replication and host immune responses play an important role in determining the severity and clinical outcome in patients with infection by HYSV.

Streptococcus suis sequence type 7 outbreak, Sichuan, China.

An outbreak of Streptococcus suis serotype 2 emerged in the summer of 2005 in Sichuan Province, and sporadic infections occurred in 4 additional provinces of China. In total, 99 S. suis strains were isolated and analyzed in this study: 88 isolates from human patients and 11 from diseased pigs. We defined 98 of 99 isolates as pulse type I by using pulsed-field gel electrophoresis analysis of SmaI-digested chromosomal DNA. Furthermore, multilocus sequence typing classified 97 of 98 members of the pulse type I in the same sequence type (ST), ST-7. Isolates of ST-7 were more toxic to peripheral blood mononuclear cells than ST-1 strains. S. suis ST-7, the causative agent, was a single-locus variant of ST-1 with increased virulence. These findings strongly suggest that ST-7 is an emerging, highly virulent S. suis clone that caused the largest S. suis outbreak ever described.

Emergence of a New Multidrug-Resistant Serotype X Variant in an Epidemic Clone of Shigella flexneri

ABSTRACT Shigella spp. are the causative agent of shigellosis with S higella flexneri serotype 2a being the most prevalent in developing countries. Epidemiological surveillance in China found that a new serotype of S. flexneri appeared in 2001 and replaced serotype 2a in 2003 as the most prevalent serotype in Henan Province. The new serotype also became the dominant serotype in 7 of the 10 other provinces under surveillance in China by 2007. The serotype was identified as a variant of serotype X. It differs from serotype X by agglutination to the monovalent anti-IV type antiserum and the group antigen-specific monoclonal antibody MASF IV-I. Genome sequencing of a serotype X variant isolate, 2002017, showed that it acquired a Shigella serotype conversion island, also as an SfX bacteriophage, containing gtr genes for type X-specific glucosylation. Multilocus sequence typing of 15 genes from 37 serotype X variant isolates and 69 isolates of eight other serotypes, 1a, 2a, 2b, 3a, 4a, 5b, X, and Y, found that all belong to a new sequence type (ST), ST91. Pulsed-field gel electrophoresis revealed 154 pulse types with 655 S. flexneri isolates analyzed and identified 57 serotype switching events. The data suggest that S. flexneri epidemics in China have been caused by a single epidemic clone, ST91, with frequent serotype switching to evade infection-induced immunity to serotypes to which the population was exposed previously. The clone has also acquired resistance to multiple antibiotics. These findings underscore the challenges to the current vaccine development and control strategies for shigellosis.

Spread of Streptococcus suis Sequence Type 7, China

Streptococcus suis sequence type (ST) 7 has been spreading throughout China. To determine events associated with its emergence, we tested 114 isolates. In all 106 ST7 strains responsible for human outbreaks and sporadic infections, the tetracycline-resistance gene, tetM, was detected on the conjugative transposon Tn916. Horizontal transmission of tetM is suspected.

O:8 serotype Yersinia enterocolitica strains in China.

Serotypes O:3, O:8 and O:9 Yersinia enterocolitica strains carrying virulence determinants are common pathogens causing human infections. In many years of surveillance in China for Y. enterocolitica, no pathogenic O:8 strains have been found where the isolated O:8 serotypes lacked the major virulence genes and in contrast to O:3 and O:9 strains, none of the O:8 isolates were from humans. These O:8 isolates lack ail, ystA, yadA and virF genes but possess the ystB gene and all belong to Biotype 1A. These O:8 strains did not kill mice and could protect immunized mice against challenge with a pathogenic O:8 strain. Compared to the Chinese pathogenic O:3 and O:9 strains which have similar pulsed-field gel electrophoresis patterns, the 39 Chinese O:8 animal and food isolates were different from the pathogenic O:8 reference strains. This suggests the O:8 strains lacking virulence determinants may not disseminate rapidly in humans and are maintained in animal reservoirs; and therefore exhibit higher variance and divergence from the virulent type.

Genetic diversity and molecular typing of Listeria monocytogenes in China

BackgroundListeria monocytogenes can cause invasive diseases in humans and farm animals and is frequently isolated from dairy products and poultry. Listeriosis is uncommon in China but L. monocytogenes has been isolated from foods and food processing environments in China. However little is known of genetic diversity of Chinese L. monocytogenes isolates and their relationships with global isolates.ResultsTwo hundred and twelve isolates of L. monocytogenes from food sources from 12 provinces/cities in China were analysed by serotyping, Pulsed Field Gel Electrophoresis (PFGE) and Multi-locus Sequence Typing (MLST). The predominant serotypes are 1/2a, 1/2b and 1/2c accounting for 90.1% of the isolates. PFGE divided the isolates into 61 pulse types (PTs). Twenty nine PTs were represented by more than one isolates with PT GX6A16.0004 containing the most number of isolates. MLST differentiated the isolates into 36 STs, among which 15 were novel. The 3 most common STs were ST9 (29.1%), ST8 (10.7%) and ST87 (9.2%), accounting for 49.0% of the isolates.ConclusionsSTs prevalent in other parts of the world are also prevalent in China including 7 STs (ST1-ST3, ST5, ST6, ST8, ST9) which caused maternal fetal infections or outbreaks, suggesting that these STs potentially can also cause severe human infections or outbreaks in China. Surveillance of these STs will provide important information for prevention of listeriosis. This study also enhances our understanding of genetic diversity of L. monocytogenes in China.

Pathogenic Strains of Yersinia enterocolitica Isolated from Domestic Dogs (Canis familiaris) Belonging to Farmers Are of the Same Subtype as Pathogenic Y. enterocolitica Strains Isolated from Humans and May Be a Source of Human Infection in Jiangsu Province, China

ABSTRACT We isolated 326 Yersinia enterocolitica strains from 5,919 specimens from patients with diarrhea at outpatient clinics, livestock, poultry, wild animals, insect vectors, food, and the environment in the cities of Nantong and Xuzhou in Jiangsu Province, China, from 2004 to 2008. The results showed that the 12 pathogenic strains were of the O:3 serotype. Six strains were isolated from domestic dogs (Canis familiaris) belonging to farmers and were found to be the primary carriers of pathogenic Y. enterocolitica strains, especially in Xuzhou. Pulsed-field gel electrophoresis analysis of the pathogenic strains from dogs belonging to farmers showed that they shared the same patterns as strains from diarrhea patients isolated in 1994. This indicates that the strains from domestic dogs have a close correlation with the strains causing human infections.

A Novel Plasmid-Encoded Serotype Conversion Mechanism through Addition of Phosphoethanolamine to the O-Antigen of Shigella flexneri

Shigella flexneri is the major pathogen causing bacillary dysentery in developing countries. S. flexneri is divided into at least 16 serotypes based on the combination of antigenic determinants present in the O-antigen. All the serotypes (except for serotype 6) share a basic O-unit containing one N-acetyl-d-glucosamine and three l-rhamnose residues, whereas differences between the serotypes are conferred by phage-encoded glucosylation and/or O-acetylation. Serotype Xv is a newly emerged and the most prevalent serotype in China, which can agglutinate with both MASF IV-1 and 7,8 monoclonal antibodies. The factor responsible for the presence of MASF IV-1 (E1037) epitope has not yet been identified. In this study, we analyzed the LPS structure of serotype Xv strains and found that the MASF IV-1 positive phenotype depends on an O-antigen modification with a phosphoethanolamine (PEtN) group attached at position 3 of one of the rhamnose residues. A plasmid carried gene, lpt-O (LPS phosphoethanolamine transferase for O–antigen), mediates the addition of PEtN for serotype Xv and other MASF IV-1 positive strains. These findings reveal a novel serotype conversion mechanism in S. flexneri and show the necessity of further extension of the serotype classification scheme recognizing the MASF IV-1 positive strains as distinctive subtypes.

Characterization of Shiga toxin-producing Escherichia coli isolated from healthy pigs in China

BackgroundShiga toxin-producing Escherichia coli (STEC) is recognized as an important human diarrheal pathogen. Swine plays an important role as a carrier of this pathogen. In this study we determined the prevalence and characteristics of STEC from healthy swine collected between May 2011 and August 2012 from 3 cities/provinces in China.ResultsA total of 1003 samples, including 326 fecal, 351 small intestinal contents and 326 colon contents samples, was analyzed. Two hundred and fifty five samples were stx-positive by PCR and 93 STEC isolates were recovered from 62 stx-positive samples. Twelve O serogroups and 19 O:H serotypes including 6 serotypes (O100:H20/[H20], O143:H38/[H38], O87:H10, O172:H30/[H30], O159:H16, O9:H30/[H30]) rarely found in swine and ruminants were identified. All 93 STEC isolates harbored stx2 only, all of which were stx2e subtype including 1 isolate being a new variant of stx2e. 53.76%, 15.05% and 2.15% STEC isolates carried astA, hlyA and ehxA respectively. Four STEC isolates harbored the high-pathogenicity island. Of the 15 adherence-associated genes tested, 13 (eae, efa1, iha, lpfAO113, lpfAO157/OI-154, lpfAO157/OI-141, toxB, saa, F4, F5, F6, F17 or F41) were all absent while 2 (paa and F18) were present in 7 and 4 STEC isolates respectively. The majority of the isolates were resistant to tetracycline (79.57%), nalidixic acid (78.49%), trimethoprim-sulfamethoxazole (73.12%) and kanamycin (55.91%). The STEC isolates were divided into 63 pulsed-field gel electrophoresis patterns and 21 sequence types (STs). Isolates of the same STs generally showed the same or similar drug resistance patterns. A higher proportion of STEC isolates from Chongqing showed multidrug resistance with one ST (ST3628) resistant to 14 antimicrobials.ConclusionsOur results indicate that swine is a significant reservoir of STEC strains in China. Based on comparison by serotypes and sequence types with human strains and presence of virulence genes, the swine STEC may have a low potential to cause human disease.

Identification and Characterization of a Novel Shigella flexneri Serotype Yv in China

Shigella flexneri is the major cause of bacterial shigellosis in developing countries. S. flexneri is divided into at least 19 serotypes, the majority of which are modifications of the same basic O-antigen by glucosylation and/or O-acetylation of its sugar residues by phage encoded serotype-converting genes. Recently, a plasmid encoded phosphoethanolamine (PEtN) modification of the O-antigen has been reported, which is responsible for the presence of the MASF IV-1 determinant and results in conversion of traditional serotypes X, 4a and Y to novel serotypes Xv, 4av and Yv, respectively. In this study, we characterized 19 serotype Yv strains isolated in China. A variant of the O-antigen phosphoethanolamine transferase gene opt (formerly called lpt-O) carried by a pSFxv_2-like plasmid was found in serotype Yv strains, which specifies the phosphorylation pattern on the O-antigen of this serotype. For the majority of the O-antigen units, the PEtN modification occurs on RhaIII, while for a minority, modifications occur on both RhaII and RhaIII. Serotype-specific gene detection and PFGE analysis suggested that these serotype Yv isolates were originated from serotypes Y, Xv and 2a by acquisition of an opt-carrying plasmid and/or inactivation of serotype-specific gene gtrII or gtrX. These data, combined with those of serotypes Xv and 4av reported earlier, demonstrate that the plasmid-encoded PEtN modification is an important serotype conversion mechanism in S. flexneri, in addition to glucosylation and O-acetylation.