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At least 19 recordsLinked to original sources
PubMed1998

Escherichia coli clone Sonnei (Shigella sonnei) had a chromosomal O-antigen gene cluster prior to gaining its current plasmid-borne O-antigen genes.

O antigen is part of the lipopolysaccharide present in the outer membrane of gram-negative bacteria. The surface-exposed O antigen is subject to selection by the host immune system, which may account for the maintenance of many different O-antigen forms. Characteristically, all genes specific to O-antigen synthesis are clustered in a region close to the his and gnd genes on the chromosome of Escherichia coli and related species. Shigella sonnei, essentially a clone of E. coli (E. coli clone Sonnei), is an important human pathogen and is unusual in that its O-antigen gene cluster is located on a plasmid. Our results suggest that it once had a normal chromosomal O-antigen gene cluster which has been largely deleted. We suggest that the O antigen encoded by the plasmid-borne genes offered a selective advantage in adapting to a new environment and that the chromosomal O-antigen genes were eventually inactivated. We also identified, by PCR and sequencing, a potential ancestor of E. coli Sonnei among the 166 known E. coli serotype strains.

Bacterial Proteins↗
PubMed1991

Restriction fragment length polymorphisms in rRNA operons for subtyping Shigella sonnei.

Shigella sonnei is the most frequent cause of shigellosis in the United States. Epidemiologic studies of this organism have been hampered by the lack of adequate typing procedures. Ribosomal DNA analysis (ribotyping), a method which analyzes restriction fragment length polymorphisms in the chromosomal genes that encode rRNA, has recently been shown to be useful for microbial species identification and subtyping. To determine whether ribotyping could be used to distinguish between S. sonnei isolates, we conducted Southern hybridization studies on isolates from 16 different geographic locations and from four recent outbreaks. S. sonnei genomic DNA fragments generated following digestion with SalI hybridized with Escherichia coli 16S and 23S rRNAs to produce six distinct patterns; strains with patterns 1, 2, and 3 were each further subdivided into two additional patterns by using PvuII, SmaI, and SstI, respectively. Epidemiologically related strains had identical patterns. Ribotyping appears to be a useful tool for epidemiologic studies of shigellosis caused by S. sonnei.

Bacterial Typing Techniques↗
PubMed2005

Identification of the plasmid and the structural gene of colicin type 7 of Shigella sonnei.

Shigella sonnei colicin 7 (Scol7) is a unique bacteriocin acting only on certain dysentery-causing bacteria, like enteroinvasive Escherichia coli, S. sonnei or S. boydii. We identified a 4.2 Md plasmid (pScol7) conferring Scol7 production to the transformants. The entire plasmid was sequenced (Gene Bank Accession number AJ318075) and the structure gene of Scol7 production (sc7a) was identified. Analyzing the sequence of the plasmid revealed extensive homology to other colicin plasmids, particularly to pColE1 but only in areas not related to the bacteriocin activity gene. The similarity of the putative promoter for sc7a to the respective sequences of other colicins suggested that the production of Scol7 is under SOS regulation. Indeed, its production could be increased eightfold by mitomycin C treatment. The molecular mass of the translated polypeptide as deduced from the nucleotide sequence of sc7a (i.e. 11.2 kDa) is in good agreement with previous estimations for its subunit, but molecular filtration experiments suggest a multimeric structure of at least 50 kDa. While current data are not sufficient to predict the mode of action of Scol7, the presence of a DTLSN pentapeptide motive suggests that it could be imported to sensitive cells via the TonB transport system.

Amino Acid Sequence↗
PubMed1962

Role of suspending and recovery media in the survival of frozen Shigella sonnei.

Shigella sonnei was frozen at -20 C in saline, nutrient broth, and milk, and plated, after thawing, upon synthetic medium, nutrient agar, and blood heart infusion agar. There was a difference in the numbers of cells recovered when the frozen and thawed cells were grown on different media. The synthetic medium was unable to recover cells injured by freezing or did so only poorly compared to the complex media. The addition of meat extract, peptone, or Casamino acids to the synthetic medium improved its ability to recover injured cells as measured by bacterial colony counts. This is suggestive of metabolic injury caused by the freezing processes since the cells which survived freezing required an enriched medium for growth. In this paper the term metabolic injury is used to express a change in the nutritional requirements of the organisms which resulted in an increase in growth factor requirements. Freezing the cells in saline resulted in greater injury compared to cells frozen in nutrient broth or milk; this suggested that these suspending agents possessed some protective quality. The metabolic injury increased with an increase in the length of time the cells were held in the frozen state.

Animals↗
PubMed1971

Colicin typing as an epidemiological tool in the investigation of outbreaks of Shigella sonnei.

Shigella sonnei has become the most frequently reported cause of shigellosis in the United States. Since Shigella subgroup D has no other serotypes, colicin production has been used as a basis for differentiating and identifying epidemiologically related strains. The results of colicin typing 115 cultures of S. sonnei from eight outbreaks of shigellosis occurring in widely separated regions of the United States support the usefulness of this technique. In each outbreak, the cultures were either of the same colicin type or were uniformly untypable. Unrelated cases yielded a variety of types. Definitions of the relative frequencies and geographic distributions of the various strains of S. sonnei in the United States await an accumulation of experience with the method.

Adult↗
PubMed1993

rRNA gene restriction patterns and biotypes of Shigella sonnei.

Shigella sonnei is a major agent of diarrhoeal disease in developed as well as in developing countries. Several phenotypic methods to define strain differences have been applied to this species of Shigella including, more recently, analysis of extrachromosomal and chromosomal DNA. In this study, 432 endemic and epidemic strains isolated between 1975 and 1991 in Italy, France and Switzerland were submitted to rRNA gene restriction pattern analysis, after digestion of whole-cell DNA by Hinc II, and to concomitant biotyping. Thirteen ribotypes, H1 to H13, and five biotypes, a, d, e, f, g, were detected. Ninety-five percent of the sporadic strains were assigned to ribotypes H1 to H4, which could be subtyped, except for H4, in different biotypes. Strains from each of seven different outbreaks had indistinguishable ribotype-biotype patterns. In contrast, 65 strains, isolated in Sicily in 1980 over an extended period of apparently epidemic increase of isolations and which had previously been considered to be a single bacterial clone on the basis of resistance pattern and phage type, were found to belong to two different and scarcely related ribotypes. Ribotyping and biochemical subtyping appear to be a useful epidemiological tool in studies on the circulation and distribution of strains of S. sonnei.

Bacterial Typing Techniques↗
PubMed1997

Characterization and quantitative analysis of serum IgG class and subclass response to Shigella sonnei and Shigella flexneri 2a lipopolysaccharide following natural Shigella infection.

The IgG subclass response to Shigella sonnei and Shigella flexneri 2a lipopolysaccharide (LPS) was examined in subjects naturally exposed to these organisms. Affinity-purified LPS antibodies obtained using a column of Shigella LPS bound to epoxy-activated Sepharose 6B were used as standards to calibrate the serum antibody response to natural Shigella infection. The geometric mean concentrations of specific IgG in sera from those not exposed to Shigella organisms were 7.9 microg/mL against S. sonnei LPS and 18.6 microg/mL against S. flexneri 2a LPS. After natural exposure to S. sonnei or S. flexneri 2a, the concentrations rose to 30.3 and 127.9 microg/mL, respectively. IgG2 was the major component in the anti-S. flexneri subclass response, while the anti-S. sonnei response was dominated by IgG1. High levels of IgG1 antibodies before exposure to organisms from either Shigella serogroup correlated with a lower risk of developing symptomatic infection.

Adolescent↗
PubMed1999

Safety and immunogenicity of Shigella sonnei and Shigella flexneri 2a O-specific polysaccharide conjugates in children.

O-specific polysaccharide conjugates of shigellae were safe and immunogenic in young adults, and a Shigella sonnei conjugate conferred protection [1-3]. Shigellosis is primarily a disease of children; therefore, the safety and immunogenicity of S. sonnei and Shigella flexneri 2a conjugates were studied in 4- to 7-year-old children. Local and systemic reactions were minimal. The first injection of both conjugates elicited significant rises in geometric mean levels of serum IgG only to the homologous lipopolysaccharide (LPS) (S. sonnei, 0.32-8.25 ELISA units [EU]; S. flexneri 2a, 1.15-20.5 EU; P<.0001). Revaccination at 6 weeks induced a booster response to S. flexneri 2a LPS (20.5-30.5 EU, P=.003). Six months later, the geometric mean levels of IgG anti-LPS for both groups were higher than the prevaccination levels (P<.0001). Similar, but lesser, rises were observed for IgM and IgA anti-LPS. The investigational Shigella conjugates were safe and immunogenic in children and merit evaluation of their efficacy.

Antibodies, Bacterial↗
PubMed1985

'O'-antigens are essential virulence factors of Shigella sonnei and Shigella dysenteriae 1.

A novel transposon mutagenesis system has been developed for Shigella. We have used it to isolate specific mutants of Shigella sonnei and Shigella dysenteriae 1 that fail to produce lipopolysaccharide 'O' side chains. The virulence of the mutants was evaluated in the Sereny test and in a HeLa cell invasion assay. All HO'-minus mutants failed to provoke a positive Sereny reaction but retained the ability to invade HeLa cells. This demonstrates that 'O' side chains are virulence factors of S. sonnei and S. dysenteriae 1. 'O'-minus mutants of S. sonnei which still contained the Form I plasmid were capable of invading HeLa cells whilst plasmid-minus mutants were not, demonstrating that this plasmid encodes properties other than 'O'-antigen production that are involved in virulence.

Antigens, Bacterial↗
PubMed2006

Molecular characteristics of class 1 and class 2 integrons and their relationships to antibiotic resistance in clinical isolates of Shigella sonnei and Shigella flexneri.

OBJECTIVES: To analyse the gene cassettes and determine the roles of class 1 and class 2 integrons in antibiotic-resistant strains of Shigella sonnei (n=31) and Shigella flexneri (n=33). METHODS: Various molecular techniques, including PCR and Southern-blotting analysis, were used to analyse various markers of class 1 and class 2 integrons in these 64 S. sonnei and S. flexneri isolates collected in Hangzhou, China. The gene cassette arrays in integrons were identified by DNA sequencing and/or restriction fragment length polymorphism. Two genomic DNA fragments, one containing intI1 from a S. flexneri isolate that contains intI1 but lacks 3'-conserved region and another containing intI2 from a S. sonnei isolate, were cloned into pUC19 vectors and sequenced. The links between integron gene cassette arrays and antibiotic resistance were analysed. RESULTS: Class 2 integrons were present in 80.6% (25/31) of the S. sonnei isolates and 87.9% (29/33) of the S. flexneri isolates. All of these integron 2-positive isolates contained constant gene cassette arrays of dfrA1+sat1+aadA1 which confer resistance to trimethoprim and streptomycin. It was demonstrated that the class 2 integron was located in the Tn7 region inside the attTn7 locus downstream of glmS in Shigella. Class 1 integrons were found in 9.4% (6/64) of Shigella spp. isolates. An atypical class 1 integron without a 3'-conserved segment on the Shigella chromosome, termed Shigella atypical class 1 integron (SAI), was present in 84.9% (28/33) of S. flexneri isolates. The SAI contained two gene cassettes, bla(OXA30) and aadA1; however, the SAI conferred resistance to ampicillin, but not to streptomycin, in Escherichia coli host. The bla(OXA30) and aadA1 cassettes of the SAI seemed to be always coordinately excised or integrated. CONCLUSIONS: Multiple and complex mechanisms involving mobile genetic elements in class 1 and class 2 integrons and antibiotic resistance have been developed in the evolution of Shigella strains.

Ampicillin Resistance↗
PubMed2003

Antimicrobial effect of spices and herbs on Shigella sonnei and Shigella flexneri.

Of 17 spices and herbs tested at 1% (wt/vol) in Mueller-Hinton (MH) agar, only cloves, thyme, oregano, allspice, basil, rosemary, and marjoram showed antimicrobial effects on Shigella. The MICs of thyme, oregano, basil, and rosemary (as determined by the agar dilution method) ranged from 0.5 to 1% (wt/vol) depending on the Shigella strain used. With the use of various combinations of temperatures (12, 22, and 37 degrees C), pHs (5.0, 5.5, and 6.0), and NaCl concentrations (1, 2, 3, and 4%, wt/vol) and the inclusion or exclusion of thyme or basil at 1% (wt/vol) in an MH agar model system, it was established that basil or thyme can contribute to combination processing as a growth-inhibitory factor for Shigella spp. In the presence of basil and thyme, Shigella flexneri did not develop CFU during the 7-day incubation period for, respectively, 14 and 16 of the 18 tested combinations, while growth was noted in the corresponding temperature-pH-NaCl concentration combinations without basil or thyme. A growth-inhibitory effect on Shigella sonnei was also noted. The results of an orientation study involving the addition of basil and thyme to spaghetti sauce prior to autoclaving and S. sonnei inoculation indicated that basil and thyme contributed to the reduction of S. sonnei after 16 days at 12 degrees C but not at 4 degrees C.

Colony Count, Microbial↗
PubMed2002

Acid tolerance of Shigella sonnei and Shigella flexneri.

AIMS: Determination of the behaviour of Shigella sonnei and Sh. flexneri under acid conditions. METHODS AND RESULTS: The growth and survival of Shigella spp. (9 isolates) in acidified Brain Heart Infusion (BHI) (pH 5.0-3.25 with pH intervals of 0.25) was determined after 6, 24 and 30 h incubation at 37 degrees C. Subsequently, survival of shigellae was studied in apple juice and tomato juice stored at 7 degrees C and 22 degrees C for up to 14 days and in strawberries and a fresh fruit salad, kept at 4 degrees C for 4 and 48 h. CONCLUSIONS: The minimum pH for growth in acidified BHI for Sh. flexneri and Sh. sonnei was, respectively, pH 4.75 and pH 4.50. Survival in fruit juices and fresh fruits depended upon their pH, the type of strain and the incubation temperature. Shigella spp. Survived for up to 14 days in tomato juice and apple juice stored at 7 degrees C. The shortest survival time (2-8 d) was observed in apple juice at 22 degrees C. Sh. sonnei but not Sh. flexneri was recovered after 48 h from strawberries and fruit salad kept at 4 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: Acid foods, especially if kept at refrigeration temperatures, support survival of Shigella spp. and may cause Shigella food poisoning.

Beverages↗
PubMed1999

Quantitative analysis of IgG class and subclass and IgA serum response to Shigella sonnei and Shigella flexneri 2a polysaccharides following vaccination with Shigella conjugate vaccines.

It has been recently reported that a conjugate vaccine composed of the O-specific polysaccharide of S. sonnei bound to Pseudomonas aeruginosa recombinant exoprotein A (rEPA) conferred 74% protection against S. sonnei shigellosis. In the present study affinity purified Shigella antibodies were used as standards to quantify and characterize the serum antibody response to vaccination with Shigella sonnei or Shigella flexneri 2a polysaccharide conjugated to rEPA. The geometric mean concentrations of antibodies at the pre-vaccination stage were 3.8 microg/ml for IgG anti-S. sonnei LPS and 11.26 microg/ml for IgG anti-S. flexneri 2a LPS. Vaccination with S. sonnei-rEPA and S. flexneri 2a-rEPA induced the production of specific IgG antibodies to levels of 115.8 microg/ml and 126.5 microg/ml, respectively. The levels of specific antibodies above the pre-vaccination values persisted for at least 2 years. The IgG response to S. flexneri 2a-rEPA conjugate was almost entirely represented by the IgG2 subclass. The concentration of IgG1 anti-S. sonnei LPS was significantly higher than that of IgG2 14 days after vaccination with the homologous conjugate, but decreased to similar levels to those of IgG2 6, 12 and 24 months after immunization. Since the only difference between the S. sonnei and S. flexneri 2a conjugates lies in the different polysaccharides of the two Shigella serogroups (the protein rEPA, is identical in both cases), it follows that the different pattern of IgG subclass response is a result of the different structures of the two O-polysaccharides of S. sonnei and S. flexneri 2a.

Adolescent↗
PubMed2005

Molecular evolution of the lysine decarboxylase-defective phenotype in Shigella sonnei.

Shigella, the etiological agent of the bacillary dysentery, belongs to the extremely diverse species of Escherichia coli. In the evolutionary route of Shigella from commensal E. coli ancestors towards a pathogenic lifestyle, the critical events have been the acquisition of the pINV plasmid, through horizontal transfer and the inactivation of pre-existing genes. These so-called pathoadaptive mutations affect the expression of genes negatively interfering with the newly acquired functions necessary for the colonization of the host niche. Cadaverine, a small polyamine resulting from decarboxylation of lysine, has been shown to hamper the full expression of Shigella invasiveness mainly by altering the inflammatory response. Recent analysis of the evolution of the Shigella and enteroinvasive E. coli (EIEC) cad region indicates that silencing of the cad locus has been attained with several strategies. The increasing relevance of S. sonnei in both, developing and industrial countries, prompted us to analyze the molecular origin of the LDC- phenotype in these strains. The results obtained on several S. sonnei strains reveal that despite the difference in geographic origin and antibiotic resistance patterns, all the strains have undergone the same modifications. Multiple IS insertions into the cadBA operon have interrupted gene continuity without inducing deletions or inversions of the cadA and cadB genes which are remained entirely conserved. Moreover, by functional analysis we show that all the strains carry a defective cadC gene, thus strengthening the hypothesis that inactivation of the regulatory cadC gene might have been the first step towards a complete lack of the cad locus.

Bacterial Proteins↗
PubMed1987

Genetic and physical characterization of trimethoprim resistance plasmids from Shigella sonnei and Shigella flexneri.

Analysis of six Shigella flexneri and four S. sonnei isolates with trimethoprim (Tp) resistance from clinical cases in Ontario has shown that, in all isolates, the Tp resistance is mediated by gene(s) on conjugative, multiple antibiotic-resistance plasmids. The physical and genetic characterization of these plasmids revealed that there are three different Tp resistance plasmids. One group, composed of all six S. flexneri plasmids, consists of plasmids which are about 70 megadaltons (MDa) and inhibit the fertility of an Escherichia coli Hfr strain (Fi+). A representative member of this group, pPT4, demonstrates a weak incompatibility reaction with IncFl plasmid R455-2. Another group, three of the four S. sonnei plasmids, contains plasmids which are about 43 MDa, Fi-, and mediate propagation of phage PRD1. The third group, the remaining S. sonnei plasmid, is 53 MDa, fi+, mediates propagation of phages fd and MS2, and is incompatible with IncFII plasmid R100. These plasmids also have been differentiated by restriction endonuclease fragment profiles. Analysis of pPT4 has revealed that the Tp resistance of this plasmid is transposable. The transposon, Tn536, is different from previously described Tp resistance transposons; it is 16 MDa, and in addition to Tp, it encodes resistance to mercuric chloride ions, spectinomycin, streptomycin, and sulfonamides.

Colicins↗