Characterization of a serologically atypical Shigella flexneri Z isolated from diarrheal patients in Bangladesh and a proposed serological scheme for Shigella flexneri
Notice bibliographique
Résumé
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.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».