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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. [...]

Abstract Background Shigella flexneri is the major pathogen causing bacillary dysentery. Fifteen serotypes have been recognized up to now. The genesis of new S. flexneri serotypes is commonly mediated by serotype-converting bacteriophages. Untypeable or novel serotypes from natural infections had been reported worldwide but have not been generated in laboratory. Results A new S. flexneri serotype-serotype 1 d was generated when a S. flexneri serotype Y strain (native LPS) was sequentially infected with 2 serotype-converting bacteriophages, SfX first and then SfI. The new serotype 1 d strain agglutinated with both serotype X-specific anti-7;8 grouping serum and serotype 1a-specific anti- I typing serum, and differed from subserotypes 1a, 1b and 1c. Twenty four S. flexneri clinical isolates of serotype X were all converted to serotype 1 d by infection with phage SfI. PCR and sequencing revealed that SfI and SfX were integrated in tandem into the proA-yaiC region of the host chromosome. Conclusions These findings suggest a new S. flexneri serotype could be created in nature. Such a conversion may be constrained by susceptibility of a strain to infection by a given serotype-converting bacteriophage. This finding has significant implications in the emergence of new S. flexneri serotypes in nature.

Background: The gene for New Delhi metallo-β-lactamase 1 (NDM-1) has been reported to be transmitted via plasmids which are easily transferable and capable of wide distribution. We report the isolation of two NDM-1 producing strains and possible in vivo transfer of blaNDM-1 in a patient. Methods: Clinical samples were collected for bacterial culture and antibiotic susceptibility testing from a patient during a 34-day hospitalization. The presence of blaNDM-1 was detected by PCR and sequencing. Plasmids of interest were sequenced. Medical records were reviewed for evidence of association between the administration of antibiotics and the acquisition of the NDM-1 resistance. Results: A NDM-1 positive Raoultella planticola was isolated from blood on the ninth day of hospitalization without administration of any carbapenem antibiotics and a NDM-1 positive Escherichia coli was isolated from feces on the 29th day of hospitalization and eight days after imipenem administration. The blaNDM-1 was carried by a 280 kb plasmid pRpNDM1-1 in R. planticola and a 58 kb plasmid pEcNDM1-4 in E. coli. The two plasmids shared a 4812 bp NDM-1-ISCR1 element which was found to be excisable from the plasmid as a free form and transferrable in vitro to a NDM-1 negative plasmid from E. coli. Conclusion: blaNDM-1 was embedded in an ISCR1 complex class 1 integron as a novel 4812 bp NDM-1-ISCR1 element. The element was found to be able to self excise to become a free form, which may provide a new vehicle for NDM-1 dissemination. This mechanism could greatly accelerate the spread of NDM-1 mediated broad spectrum β-lactam resistance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: The gene for New Delhi metallo-β-lactamase 1 (NDM-1) has been reported to be transmitted via plasmids which are easily transferable and capable of wide distribution. We report the isolation of two NDM-1 producing strains and possible in vivo transfer of blaNDM-1 in a patient. Methods: Clinical samples were collected for bacterial culture and antibiotic susceptibility testing from a patient during a 34-day hospitalization. The presence of blaNDM-1 was detected by PCR and sequencing. Plasmids of interest were sequenced. Medical records were reviewed for evidence of association between the administration of antibiotics and the acquisition of the NDM-1 resistance. Results: A NDM-1 positive Raoultella planticola was isolated from blood on the ninth day of hospitalization without administration of any carbapenem antibiotics and a NDM-1 positive Escherichia coli was isolated from feces on the 29th day of hospitalization and eight days after imipenem administration. The blaNDM-1 was carried by a 280 kb plasmid pRpNDM1-1 in R. planticola and a 58 kb plasmid pEcNDM1-4 in E. coli. The two plasmids shared a 4812 bp NDM-1-ISCR1 element which was found to be excisable from the plasmid as a free form and transferrable in vitro to a NDM-1 negative plasmid from E. coli. Conclusion: blaNDM-1 was embedded in an ISCR1 complex class 1 integron as a novel 4812 bp NDM-1-ISCR1 element. The element was found to be able to self excise to become a free form, which may provide a new vehicle for NDM-1 dissemination. This mechanism could greatly accelerate the spread of NDM-1 mediated broad spectrum β-lactam resistance. [ABSTRACT FROM AUTHOR]

Shigella flexneri O-antigen is an important and highly variable cell component presented on the outer leaflet of the outer membrane. Most Shigella flexneri bacteria share an O-antigen backbone composed of →2)-α-L-Rhap(III)-(1→2)-α-L-Rhap(II)-(1→3)-α-L-Rhap(I)-(1→3)-β-D-GlcpNAc-(1→ repeats, which can be modified by adding various chemical groups to different sugars, giving rise to diverse O-antigen structures and, correspondingly, to various serotypes. The known modifications include glucosylation on various sugar residues, O-acetylation on Rha(I) or/and Rha(III), and phosphorylation with phosphoethanolamine on Rha(II) or/and Rha(III). Recently, a new O-antigen modification, namely, O-acetylation at position 6 of N-acetylglucosamine (GlcNAc), has been identified in S. flexneri serotypes 2a, 3a, Y, and Yv. In this study, the genetic basis of the 6-O-acetylation of GlcNAc in S. flexneri was elucidated. An O-acyltransferase gene designated oacD was found to be responsible for this modification. The oacD gene is carried on serotype-converting bacteriophage SfII, which is integrated into the host chromosome by lysogeny to form a prophage responsible for the evolvement of serotype 2 of S. flexneri. The OacD-mediated 6-O-acetylation also occurs in some other S. flexneri serotypes that carry a cryptic SfII prophage with a dysfunctional gtr locus for type II glucosylation. The 6-O-acetylation on GlcNAc confers to the host a novel O-antigen epitope, provisionally named O-factor 10. These findings enhance our understanding of the mechanisms of the O-antigen variation and enable further studies to understand the contribution of the O-acetylation to the antigenicity and pathogenicity of S. flexneri., (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)

Background: From April to July in 2009 and 2010, unexplained severe hemorrhagic fever-like illnesses occurred in farmers from the Huaiyangshan mountains range., Methods: Clinical specimens (blood, urine, feces, and throat swabs) from suspected patients were obtained and stored. Mosquitoes and ticks in affected regions were collected. Virus was isolated from 2 patients and characterized by whole genome sequencing. Virus detection in additional patients and arthropods was done by virus-specific reverse transcription (RT) PCR. Clinical and epidemiological data of RT-PCR confirmed patients were analyzed., Results: An unknown virus was isolated from blood of two patients and from Haemaphysalis ticks collected from dogs. Whole genome sequence analysis identified the virus as a novel member of the family Bunyaviridae, most closely related to the viruses of the genus Phlebovirus within which it forms a separate lineage. Subsequently, infection was confirmed by RT-PCR in 33 of 58 suspected patients. The illness in these patients was characterized by fever, severe malaise, nausea, vomiting, and diarrhea. Prominent laboratory findings included low white cell- and platelet counts, coagulation disturbances, and elevation of liver enzymes. Hemorrhagic complications were observed in 3 cases, 5 (15%) patients died., Conclusions: A novel tick-borne Bunyavirus causing life-threatening hemorrhagic fever in humans has emerged in the Huaiyangshan mountain areas of China. Further studies are needed to determine the epidemiology, geographic distribution and vertebrate animal ecology of this virus.

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.

We constructed a food-grade secretion expression vector and used it for reporter protein expression in live delivery vehicle L lactis MBP71. The p32 fragment, which containing the stronger p32 promoter, was amplified by polymerase chain reaction (PCR) with the plasmid pMG36e as template. After being purified, the p32 fragment was ligated with SPusp45 fragment amplified from genomic DNA of L lactis MG1363. The fusion fragment p32-SPusp45 was inserted into the food-grade vector pSH91 to construct a secretion expression vector, pSQ. The coding sequence of NucA (nucA) was also amplified from Staphylococcus aureus chromosome and inserted into pSQ under the control of p32 promoter to construct a recombinant plasmid pSQ-nucA. Nuclease plate activity assay and zymograme assay demonstrate that NucA was secretion expressed from L lactis harboring the recombinant plasmid pSQ- nucA, and the quantity of NucA secreted into supernamant was about ten times more than which in cell lysate. Results also indicate that expression efficiency of L lactis/pSQ-nucA was higher than that of L lactis/pSQZ-nucA, constructed by us earlier.

The single cell gelelctrophoresis assay is a rapid, simple and sensitive technique for measuring DNA damage and repair at the single cell level. It is introduced into environmental hygiene and plays an important role in many aspects such as detecting and evaluating the genotoxity of environmental toxic substances. In this paper, the underlying principles of this assay in detecting DNA damage and repair, and its application in environmental hygiene are reviewed.