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Antimicrobial Agents and Chemotherapy Apr 2018Infection by spp. is a common cause of dysentery in Southeast Asia. Antimicrobials are thought to be beneficial for treatment; however, antimicrobial resistance in...
Infection by spp. is a common cause of dysentery in Southeast Asia. Antimicrobials are thought to be beneficial for treatment; however, antimicrobial resistance in spp. is becoming widespread. We aimed to assess the frequency and mechanisms associated with decreased susceptibility to azithromycin in Southeast Asian isolates and use these data to assess appropriate susceptibility breakpoints. isolates recovered in Vietnam and Laos were screened for susceptibility to azithromycin (15 μg) by disc diffusion and MIC. Phenotypic resistance was confirmed by PCR amplification of macrolide resistance loci. We compared the genetic relationships and plasmid contents of azithromycin-resistant isolates using whole-genome sequences. From 475 available spp. isolated in Vietnam and Laos between 1994 and 2012, 6/181 isolates (3.3%, MIC ≥ 16 g/liter) and 16/294 isolates (5.4%, MIC ≥ 32 g/liter) were phenotypically resistant to azithromycin. PCR amplification confirmed a resistance mechanism in 22/475 (4.6%) isolates ( in 19 isolates and in 3 isolates). The susceptibility data demonstrated the acceptability of the (MIC ≥ 16 g/liter, zone diameter ≤ 15 mm) and (MIC ≥ 32 g/liter, zone diameter ≤ 11 mm) breakpoints with a <3% discrepancy. Phylogenetic analysis demonstrated that decreased susceptibility has arisen sporadically in Vietnamese isolates on at least seven occasions between 2000 and 2009 but failed to become established. While the proposed susceptibility breakpoints may allow better recognition of resistant isolates, additional studies are required to assess the impact on the clinical outcome. The potential emergence of azithromycin resistance highlights the need for alternative options for management of infections in countries where is endemic.
Topics: Anti-Bacterial Agents; Asia, Southeastern; Azithromycin; Drug Resistance, Bacterial; Drug Resistance, Multiple, Bacterial; Dysentery, Bacillary; Microbial Sensitivity Tests; Phylogeny; Shigella; Shigella flexneri; Shigella sonnei
PubMed: 29378707
DOI: 10.1128/AAC.01748-17 -
FEMS Immunology and Medical Microbiology Nov 2012Shigella flexneri is an important human pathogen causing shigellosis. Strains of S. flexneri are serologically heterogeneous and, based on O-antigens, are currently...
Shigella flexneri is an important human pathogen causing shigellosis. Strains of S. flexneri are serologically heterogeneous and, based on O-antigens, are currently classified into 14 types. Structures of the O-antigens (O-polysaccharides) of S. flexneri have been under study since 1960s but some gaps still remained. In this work, using one- and two-dimensional (1) H- and (13) C-NMR spectroscopy, the O-polysaccharides of several S. flexneri types were reinvestigated, and their structures were either confirmed (types 2b, 3b, 3c, 5b, X) or amended in respect to the O-acetylation pattern (types 3a, Y, 6, 6a). As a result, the O-acetylation sites were defined in all O-polysaccharides that had not been studied in detail earlier, and the long story of S. flexneri type strain O-antigen structure elucidation is thus completed. New and published data on the S. flexneri O-antigen structures are summarized and discussed in view of serological and genetic relationships of the O-antigens within the Shigella group and between S. flexneri and Escherichia coli.
Topics: Acetylation; Carbohydrate Sequence; Magnetic Resonance Spectroscopy; O Antigens; Shigella flexneri
PubMed: 22724405
DOI: 10.1111/j.1574-695X.2012.01000.x -
Microbiology (Reading, England) Apr 2022Enterobacteriales have evolved a specialized outer membrane polysaccharide [Enterobacterial Common Antigen (ECA)] which allows them to persist in various environmental...
Enterobacteriales have evolved a specialized outer membrane polysaccharide [Enterobacterial Common Antigen (ECA)] which allows them to persist in various environmental niches. Biosynthesis of ECA initiates on the cytoplasmic leaflet of the inner membrane (IM) where glycosyltransferases assemble ECA repeat units (RUs). Complete RUs are then translocated across the IM and assembled into polymers by ECA-specific homologues of the Wzy-dependent pathway. Consisting of the membrane proteins Wzx, Wzy and Wzz, the Wzy-dependent pathway is the most common polysaccharide biosynthetic pathway in Gram-negative bacteria where it is most notably involved in LPS O antigen (Oag) biosynthesis. As such, the majority of research directed towards these proteins has been orientated towards Oag biosynthetic homologues with little directed towards ECA homologues. Belonging to the Shape, Elongation, Division and Sporulation (SEDS) protein family, Wzy proteins are polymerases, and are characterized as possessing little or no peptide homology among homologues as well as being polytopic membrane proteins with functionally relevant residues within periplasmic loops, as defined by C-terminal reporter fusion topology mapping. Here, we present the first the first major study into the ECA polymerase WzyE. Multiple sequence alignments and topology mapping showed that WzyE is unlike WzyB proteins involved with Oag biosynthesis WzyE displays high peptide conservation across Enterobacteriales structures and reporter mapping allowed us to identify possible functionally conserved residues with WzyE's periplasmic loops, which we showed were crucial for its function. This work provides novel insight into Wzy proteins and suggests that WzyE is an optimal model to investigate Wzy proteins and the Wzy-dependent pathway.
Topics: Antigens, Bacterial; Bacterial Proteins; Membrane Proteins; Nucleotidyltransferases; O Antigens; Shigella flexneri
PubMed: 35470793
DOI: 10.1099/mic.0.001183 -
BMC Genomics Jul 2006Shigella bacteria cause dysentery, which remains a significant threat to public health. Shigella flexneri is the most common species in both developing and developed... (Comparative Study)
Comparative Study
BACKGROUND
Shigella bacteria cause dysentery, which remains a significant threat to public health. Shigella flexneri is the most common species in both developing and developed countries. Five Shigella genomes have been sequenced, revealing dynamic and diverse features. To investigate the intra-species diversity of S. flexneri genomes further, we have sequenced the complete genome of S. flexneri 5b strain 8401 (abbreviated Sf8401) and compared it with S. flexneri 2a (Sf301).
RESULTS
The Sf8401 chromosome is 4.5-Mb in size, a little smaller than that of Sf301, mainly because the former lacks the SHI-1 pathogenicity island (PAI). Compared with Sf301, there are 6 inversions and one translocation in Sf8401, which are probably mediated by insertion sequences (IS). There are clear differences in the known PAIs between these two genomes. The bacteriophage SfV segment remaining in SHI-O of Sf8401 is clearly larger than the remnants of bacteriophage SfII in Sf301. SHI-1 is absent from Sf8401 but a specific related protein is found next to the pheV locus. SHI-2 is involved in one intra-replichore inversion near the origin of replication, which may change the expression of iut/iuc genes. Moreover, genes related to the glycine-betaine biosynthesis pathway are present only in Sf8401 among the known Shigella genomes.
CONCLUSION
Our data show that the two S. flexneri genomes are very similar, which suggests a high level of structural and functional conservation between the two serotypes. The differences reflect different selection pressures during evolution. The ancestor of S. flexneri probably acquired SHI-1 and SHI-2 before SHI-O was integrated and the serotypes diverged. SHI-1 was subsequently deleted from the S. flexneri 5b genome by recombination, but stabilized in the S. flexneri 2a genome. These events may have contributed to the differences in pathogenicity and epidemicity between the two serotypes of S. flexneri.
Topics: Chromosome Aberrations; Chromosome Inversion; Chromosome Mapping; Chromosomes, Bacterial; Evolution, Molecular; Genetic Variation; Genome, Bacterial; Genomic Islands; Sequence Deletion; Serotyping; Shigella flexneri; Virulence Factors
PubMed: 16822325
DOI: 10.1186/1471-2164-7-173 -
Infection and Immunity Apr 2016The SlyA transcriptional regulator has important roles in the virulence and pathogenesis of several members of the Enterobacteriaceae family, including Salmonella...
The SlyA transcriptional regulator has important roles in the virulence and pathogenesis of several members of the Enterobacteriaceae family, including Salmonella enterica serovar Typhimurium and Escherichia coli. Despite the identification of the slyA gene in Shigella flexneri nearly 2 decades ago, as well as the significant conservation of SlyA among enteric bacteria, the role of SlyA in Shigella remains unknown. The genes regulated by SlyA in closely related organisms often are absent from or mutated inS. flexneri, and consequently many described SlyA-dependent phenotypes are not present. By characterizing the expression of slyA and determining its ultimate effect in this highly virulent organism, we postulated that novel SlyA-regulated virulence phenotypes would be identified. In this study, we report the first analysis of SlyA in Shigella and show that (i) the slyA gene is transcribed and ultimately translated into protein, (ii) slyA promoter activity is maximal during stationary phase and is negatively autoregulated and positively regulated by the PhoP response regulator, (iii) the exogenous expression of slyA rescues transcription and virulence-associated deficiencies during virulence-repressed conditions, and (iv) the absence of slyA significantly decreases acid resistance, demonstrating a novel and important role in Shigella virulence. Cumulatively, our study illustrates unexpected parallels between the less conserved S. flexneri and S Typhimurium slyA promoters as well as a unique role for SlyA in Shigella virulence that has not been described previously in any closely related organism.
Topics: Bacterial Proteins; Base Sequence; DNA-Binding Proteins; Gene Expression Regulation, Bacterial; Homeostasis; Promoter Regions, Genetic; Shigella flexneri; Transcription Factors; Transcriptome; Up-Regulation; Virulence
PubMed: 26831468
DOI: 10.1128/IAI.00806-15 -
Infection and Immunity Aug 2006Shigella flexneri possesses at least two putative high-affinity manganese acquisition systems, SitABCD and MntH. Mutations in the genes encoding the components of both...
Shigella flexneri possesses at least two putative high-affinity manganese acquisition systems, SitABCD and MntH. Mutations in the genes encoding the components of both of these systems were constructed in S. flexneri. The sitA mntH mutant showed reduced growth, relative to the wild type, in Luria broth (L broth) containing the divalent metal chelator ethylene diamino-o-dihydroxyphenyl acetic acid, and the addition of either iron or manganese restored growth to the level of the wild-type strain. Although the sitA mntH mutant was not defective in surviving exposure to superoxide generators, it was defective in surviving exposure to hydrogen peroxide. The sitA mntH mutant formed wild-type plaques on Henle cell monolayers but had a reduced ability to survive in activated macrophage lines. Expression of the S. flexneri sit and mntH promoters was higher when Shigella was in Henle cells than when it was in L broth. Expression of both the sit and mntH promoters was repressed by either iron or manganese, and this repression was partially dependent upon Fur and MntR, respectively. The mntH promoter, but not the sit promoter, exhibited OxyR-dependent induction in the presence of hydrogen peroxide.
Topics: Bacterial Proteins; Cation Transport Proteins; Cell Line; Culture Media; Gene Expression Regulation, Bacterial; Humans; Intestines; Iron; Manganese; Mutation; Oligonucleotide Array Sequence Analysis; Oxidative Stress; Phenotype; Shigella flexneri; Virulence
PubMed: 16861654
DOI: 10.1128/IAI.00562-06 -
Applied and Environmental Microbiology Apr 2018Since the initial discovery of in an isolate from China, the gene has also been detected in and but is rarely reported in other Here, we report the isolation and...
Since the initial discovery of in an isolate from China, the gene has also been detected in and but is rarely reported in other Here, we report the isolation and identification of a strain harboring from stool samples in a pig farm in China from 2009. The MIC of colistin for the isolate is 4 μg/ml. Conjugation assays showed that the donor strain has functional and transferable colistin resistance. Sequencing revealed that was present on a putative composite transposon flanked by inverted repeats of IS There are four species of , and is the most frequently isolated species in low- and middle-income countries (LMICs). In this study, we report a functional, transferable, plasmid-mediated gene in We have shown that is located on a novel composite transposon which is flanked by inverted repeats of IS The host strain is multidrug resistant, and this multidrug resistance is also transferable. The finding of a functional gene in , a human-associated family member, is a cause for concern as infections due to are the main infections in most low- and middle-income countries.
Topics: Animals; Anti-Bacterial Agents; Bacterial Proteins; Colistin; Drug Resistance, Bacterial; Feces; Plasmids; Shigella flexneri; Sus scrofa
PubMed: 29500254
DOI: 10.1128/AEM.02655-17 -
Gut Microbes Nov 2016Shigella flexneri is a Gram-negative pathogen that invades the colonic epithelium and causes millions of cases of watery diarrhea or bacillary dysentery predominately in...
Shigella flexneri is a Gram-negative pathogen that invades the colonic epithelium and causes millions of cases of watery diarrhea or bacillary dysentery predominately in children under the age of 5 years in developing countries. The effector Shigella enterotoxin 2 (ShET2), or OspD3, is encoded by the sen or ospD3 gene on the virulence plasmid. Previous literature has suggested that ospD3 is in an operon downstream of the ospC1 gene, and expression of both genes is controlled by a promoter upstream of ospC1. Since the intergenic region is 328 bases in length and contains several putative promoter regions, we hypothesized the genes are independently expressed. Here we provide data that ospD3 and ospC1 are not co-transcribed and that OspC1 is not required for OspD3/ShET2 function. Most importantly, we identified strong promoter activity in the intergenic region and demonstrate that OspD3/ShET2 can be expressed and secreted independently of OspC1. This work increases our understanding of the synthesis of a unique virulence factor and provides further insights into Shigella pathogenesis.
Topics: Bacterial Proteins; Dysentery, Bacillary; Gene Expression Regulation, Bacterial; Humans; Plasmids; Promoter Regions, Genetic; Shigella flexneri; Virulence Factors
PubMed: 27657187
DOI: 10.1080/19490976.2016.1239682 -
PloS One 2018Atypical Shigella flexneri Z variant, that agglutinate with E1037 group factor specific monoclonal antisera against Shigella flexneri IV-I but not with other group or...
BACKGROUND
Atypical Shigella flexneri Z variant, that agglutinate with E1037 group factor specific monoclonal antisera against Shigella flexneri IV-I but not with other group or type specific antisera, has continuously being isolated in Bangladesh since 1997. Later this serotype has been reported in Indonesia, China and Argentina. Despite being a provisional serotype, continuous isolation of these strains in diverse geographical regions implicated a great necessity to study the overall characteristics of these strains. Therefore, we extensively characterized S. flexneri Z strains using various phenotypic and molecular tools.
METHOD
Of 3569 S. flexneri isolated between 1997 and 2015, 95 strains were identified as S. flexneri Z using a panel of polyvalent absorbed antisera and monoclonal antisera of S. flexneri (MASF). Of them, randomly selected 65 strains were molecular O-serotyped using multiplex PCR and characterized using different phenotypic and molecular techniques (i.e.biotyping, plasmid profile, virulence marker and PFGE) to determine relationship with other subserotypes of S. flexneri.
RESULTS
All these atypical S. flexneri Z strains were agglutinated with MASF B and IV-I antisera. Concordantly, these strains were positive to opt-gene, responsible for MASF IV-I sero-positive phenotype. However, molecular O-serotyping of all 65 strains could not differentiate between Z and Yb giving similar amplification products (wzx1-5 and opt). Contrarily, MASF based serotypic scheme distinguished among Z and Yb as well as Ya. All these S. flexneri Z showed typical biochemical reaction of S. flexneri, harboured a 140 MDa virulence plasmid and virulence markers namely ipaH, ial, sen, sigA and sepA genes. Along with the virulence plasmid, small plasmids (2.6, 1.8 and 1.6 MDa) were present as core plasmid. Moreover, a middle ranged plasmid and a 4.0 MDa sized plasmid were observed in 65% and 20% strains, respectively. Analysis of PFGE on XbaI-digested chromosomal DNA of Bangladeshi strains showed that S. flexneri Z had a close relatedness with Ya and Yb but completely different than the strains of Xa, Xb, 2a and 2b. This observation was found to be unequivocal while the overall result of biotyping, plasmid profile, and virulence factors was compared. Therefore, we conclude that these atypical serotype Z isolated in Bangladesh had a clonal relationship with Ya and Yb of Bangladesh and the opt gene played an important role in serotypic switching among them. Current serotyping scheme of S. flexneri strains fails to place many such atypical strains (1c, 1c+6, 1d, type 4, and 4c) including S. flexneri Z isolated from different parts of the world. Therefore, an updated serotyping scheme for identification of subserotypes of S. flexneri has been proposed to avoid multiple naming of the same subserotype having similar agglutination pattern.
Topics: Anti-Bacterial Agents; Bangladesh; DNA, Bacterial; Dysentery, Bacillary; Electrophoresis, Gel, Pulsed-Field; Humans; Microbial Sensitivity Tests; Multiplex Polymerase Chain Reaction; Phylogeny; Plasmids; Serogroup; Shigella flexneri; Virulence Factors
PubMed: 30142163
DOI: 10.1371/journal.pone.0202704 -
Journal of Bacteriology Jul 2014Shigella flexneri two-component regulatory systems (TCRS) are responsible for sensing changes in environmental conditions and regulating gene expression accordingly. We...
Shigella flexneri two-component regulatory systems (TCRS) are responsible for sensing changes in environmental conditions and regulating gene expression accordingly. We examined 12 TCRS that were previously uncharacterized for potential roles in S. flexneri growth within the eukaryotic intracellular environment. We demonstrate that the TCRS EvgSA, NtrBC, and RstBA systems are required for wild-type plaque formation in cultured epithelial cells. The phenotype of the NtrBC mutant depended in part on the Nac transcriptional regulator. Microarray analysis was performed to identify S. flexneri genes differentially regulated by the NtrBC system or Nac in the intracellular environment. This study contributes to our understanding of the transcriptional regulation necessary for Shigella to effectively adapt to the mammalian host cell.
Topics: Bacterial Proteins; Cell Line; Gene Expression Regulation, Bacterial; Humans; Intestines; Protein Array Analysis; RNA, Bacterial; Regulatory Elements, Transcriptional; Shigella flexneri
PubMed: 24794563
DOI: 10.1128/JB.01613-14