RESUMO
Salmonella 4,[5],12:i:- is a variant of Salmonella Typhimurium, which lacks the expression of phase-2 flagellar antigen, generally associated with the deletion of the fljB gene. Additional mechanisms involving the fljAB operon ( fljA, fljB, and hin genes) lead to the lack of expression of phase-2 flagellar antigens also in Salmonella strains harboring the fljB gene. For 20 S. 4,[5],12:i:- strains, defined as "inconsistent" Salmonella Typhimurium variants since they had phenotypically behaved as monophasic, even though the fljB gene was conserved, the fljAB operon was characterized in order to explain the ineffective expression of the phase-2 flagellar antigen. The monophasic phenotype for a first group of strains (9) was likely due to the absence of the hin gene, leading to the inhibited switch between the expression of phase-1 and phase-2 flagellar genes. For a second group of strains (5), the monophasic phenotype could be attributed to nonconservative point mutations identified in fljA and hin genes, which could hamper the proper expression of invertase gene and the fljA, acting as repressor of the phase-1 flagellar gene. Finally, for a last group of inconsistent strains (6), a plausible reason for their monophasic phenotype was not found, since the genes involved in the expression of phase-2 flagellar antigen were fully conserved. Moreover, the collection of inconsistent Salmonella Typhimurium isolates investigated were characterized by distinct molecular profiles, as demonstrated by multiple-locus variable-number tandem repeat analysis, and phenotype variability, as demonstrated by phage-typing. This study highlights the usefulness of investigating the entire fljAB operon when a definitive identification of the monophasic or biphasic status of Salmonella Typhimurium strains is needed (for instance, in the context of epidemiological investigations aimed to identify the relatedness among strains).
Assuntos
Proteínas de Bactérias/metabolismo , Flagelina/metabolismo , Variação Genética , Modelos Biológicos , Óperon , Proteínas Repressoras/metabolismo , Salmonella typhimurium/isolamento & purificação , Animais , Proteínas de Bactérias/genética , Tipagem de Bacteriófagos , Fezes/microbiologia , Flagelina/genética , Perfilação da Expressão Gênica , Regulação Bacteriana da Expressão Gênica , Humanos , Itália , Carne/microbiologia , Tipagem Molecular , Tipagem de Sequências Multilocus , Mutação , Proteínas Repressoras/genética , Reprodutibilidade dos Testes , Intoxicação Alimentar por Salmonella/microbiologia , Salmonella typhimurium/classificação , Salmonella typhimurium/genética , Salmonella typhimurium/metabolismo , Especificidade da EspécieRESUMO
Salmonella enterica subspecies enterica serotype 4,[5],12:i:- is an emerging serovar considered as a monophasic variant of Salmonella enterica serotype Typhimurium. The antigenic and genetic similarity between Salmonella 4,[5],12:i:- and Salmonella Typhimurium suggests that they may behave in a similar way and represent a comparable threat to public health. As serotyping alone does not necessarily provide for identification of Salmonella 4,[5],12:i:- and its differentiation from Salmonella Typhimurium, a method that combines traditional serotyping and a multiplex polymerase chain reaction has been tested on 208 strains serotyped as Salmonella 4,[5],12:i:-, Salmonella Typhimurium, and similar serovars of serogroup B sharing the same phase-1 antigen "i." For 191 strains, the combined method fully confirmed the results provided by traditional serotyping, whereas for 17 strains of Salmonella 4,[5],12:i:- and Salmonella Typhimurium some inconsistencies emerged between the two methods. The combined method resulted in a more accurate and faster identification of these two relevant serovars.
Assuntos
Técnicas de Tipagem Bacteriana , Salmonella enterica/classificação , Salmonella enterica/genética , Salmonella typhimurium/classificação , Salmonella typhimurium/genética , Antígenos de Bactérias/análise , Doenças Transmissíveis Emergentes/diagnóstico , Doenças Transmissíveis Emergentes/epidemiologia , Doenças Transmissíveis Emergentes/microbiologia , DNA Bacteriano/genética , DNA Intergênico/genética , Diagnóstico Diferencial , Europa (Continente)/epidemiologia , Humanos , Tipagem Molecular , Reação em Cadeia da Polimerase , Reprodutibilidade dos Testes , Infecções por Salmonella/diagnóstico , Infecções por Salmonella/epidemiologia , Infecções por Salmonella/microbiologia , Salmonella enterica/imunologia , Salmonella enterica/isolamento & purificação , Salmonella typhimurium/imunologia , Salmonella typhimurium/isolamento & purificação , Deleção de Sequência , SorotipagemRESUMO
Salmonella strains isolated from poultry and poultry products over the period 2005-2006 have been investigated in order to ascertain the presence of extended spectrum cephalosporins (ESC) resistance. Twelve (ESC)-resistant isolates (n=1 S. Enteritidis, n=1 S. Braenderup and n=10 S. Livingstone) were characterized as SHV-12-positive. The multi-drug resistant S. Livingstone SHV-12-producing isolates, untypeable by pulsed-field gel electrophoresis (PFGE), showed a clonal relationship by random amplified polymorphic DNA (RAPD) analysis. The SHV-12 beta-lactamase is reported for the first time in Salmonella enterica strains isolated from poultry in Italy. The results suggest poultry as a source of Salmonella carrying extended spectrum beta-lactamases (ESBLs) genes and highlights the need of monitoring animal productions to prevent spreading of (ESC)-resistant strains.
