Blind comparison of traditional serotyping with three multiplex PCRs for the identification of Salmonella serotypes.

Salmonella serotypes are defined on the basis of somatic (O) antigens which define the serogroup and flagellar (H) factor antigens, both of which are present in the cell wall of Salmonella. Most Salmonella organisms alternatively express phase-1 or phase-2 flagellar antigens encoded by fliC and fljB genes, respectively. Our group previously published two multiplex PCRs for distinguishing the most common first- and second-phase antigens. In this paper we describe a third multiplex PCR to identify the most common serogroups (O:B; O:C1; O:C2; O:D and O:E). The combination of these three PCRs enabled us to completely serotype organisms belonging to the Salmonella species. This multiplex PCR includes 10 primers. A total of 67 Salmonella strains belonging to 32 different serotypes were tested. Each strain generated one serogroup-specific fragment ranging between 162 and 615bp. Twenty-eight strains belonging to 21 serotypes, with a serogroup different from those tested in this work, did not generate any fragments. To compare molecular serotyping with traditional serotyping, 500 strains, received according to the order of arrival in the laboratory, were serotyped using both methods. The three multiplex PCRs were able to serotype 84.6% of the tested strains. This method was found to be very helpful in our laboratory as an alternative method for typing strains causing outbreaks, and it can be used to supplement conventional serotyping, since it is also applicable to motionless and rough strains.

Molecular characterization of a new serovar of Salmonella bongori 13,22:z39:- isolated from a lizard.

Three Salmonella strains isolated from a lizard (Gallotia simoni) in the "Isla del Hierro" (Canary Islands, Spain) were serotyped as Salmonella bongori serotype 13,22:z39:-, which has not been described in the Kauffmann-White scheme of Salmonella serovars. In order to shed light on the assignment of those strains to the S. bongori species, several genes were amplified and/or sequenced. The iroB gene has been reported to be present only in S. enterica, while the invA gene has been described as being a helpful tool in distinguishing Salmonella from other bacterial species. Both genes were amplified and, as expected, only invA could be amplified. The fliC gene, encoding the phase 1 flagellin fljB gene, encoding phase 2 flagellin, and the gapA gene, which is believed to present polymorphic alleles among different subspecies, were amplified and sequenced. The sequence obtained from fliC(z39) matched with the sequences fliC(z39) obtained from other serovars. The sequence obtained from gapA clustered into the S. bongori group when it was compared to others previously described. We conclude that these three isolates are members of the S. bongori species representing a new serovar that will be described in the next supplement to the Kauffmann-White scheme.

[Serotype and phage type distribution of human Salmonella strains isolated in Spain, 1997-2001]. / Distribución de los serotipos y fagotipos de Salmonella de origen humano aislados en España en 1997-2001.

INTRODUCTION: Salmonellosis is one of the most frequent causes of gastroenteritis in Spain. Serotyping is the gold standard epidemiological marker for subdividing Salmonella spp. strains. A small number of serotypes are very frequently isolated, reducing the discriminatory power of serotyping. Thus, to increase our knowledge of Salmonella spp. epidemiology, additional epidemiological markers, such as phage typing, should be used for this purpose. METHODS: Salmonella spp. strains of human origin sent to the Laboratorio Nacional de Referencia de Salmonella y Shigella (LNRSSE, Spanish Reference Laboratory for Salmonella and Shigella) between 1997 and 2001 were serotyped using conventional agglutination methods, and Enteritidis, Typhimurium, Hadar, Virchow and Typhi serotypes were additionally phage typed according to internationally-developed schemes. RESULTS: A total of 30,856 Salmonella spp. strains, isolated in the majority of Spanish Autonomous Communities, were analyzed. Enteritidis (51%) and Typhimurium (24%) were the most frequently isolated serotypes. The following were the most frequent serotype/phage type combinations: Enteritidis/PT1 (18%), Enteritidis/PT4 (15%), Enteritidis/PT6a (5%), Typhimurium/DT104 (5%) and Enteritidis/PT6 (3%). The serotype Enteritidis/PT1 showed the greatest increase over the period studied, from 11.61% in 1997 to 24.74% in 2001. CONCLUSIONS: A hierarchical typing approach for Salmonella spp., using serotyping coupled with phage typing allowed a higher level of discrimination among Salmonella serotypes. Application of this approach in epidemiological studies could be highly useful for early characterization of related strains.

Distribución de los serotipos y fagotipos de Salmonella de origen humano aislados en España en 1997-2001 / Serotype and phage type distribution of human Salmonella strains isolated in Spain, 1997-2001

INTRODUCCIÓN. La salmonelosis continúa siendo una de las causas principales de gastroenteritis en España, siendo la serotipificación el marcador epidemiológico universalmente utilizado para la caracterización de los aislamientos de Salmonella spp. Algunos serotipos se identifican muy frecuentemente, reduciendo el poder de discriminación de esta técnica. Por ello, para el estudio epidemiológico de las salmonelosis producidas por estos serotipos es necesario utilizar marcadores complementarios como la fagotipificación. MÉTODOS. Se serotipificaron, por aglutinación directa, las cepas de Salmonella spp. de origen humano recibidas en el Laboratorio Nacional de Referencia de Salmonella y Shigella (LNRSSE) entre los años 1997 y 2001 y se fagotipificaron, según esquemas internacionales, las cepas de los serotipos Enteritidis, Typhimurium, Hadar,Virchow y Typhi. RESULTADOS. Se analizaron 30.856 cepas de Salmonella spp. procedentes de la mayoría de las Comunidades Autónomas. Los serotipos Enteritidis (51%) y Typhimurium (24%) fueron los mayoritarios. Las combinaciones serotipo/fagotipo más frecuentes fueron: Enteritidis/FT1 (18%), Enteritidis/FT4 (15%),Enteritidis/FT6a (5%), Typhimurium/FT104 (5%)y Enteritidis/FT6 (3%). Las cepas del serotipo Enteritidis/FT1 tuvieron el mayor aumento en este período de tiempo, pasando del 11,61% en 1997al 24,74% en 2001. CONCLUSIONES. La utilización jerárquica de la serotipificación y posteriormente de la fagotipificación en cepas de Salmonella spp. de los serotipos más frecuentes aumentó enormemente el poder de discriminación de la serotipificación. Su aplicación en estudios epidemiológicoses de gran utilidad en la caracterización temprana de cepas relacionadas (AU)

INTRODUCTION. Salmonellosis is one of the most frequent causes of gastroenteritis in Spain. Serotyping is the gold standard epidemiological marker for subdividing Salmonella spp. strains. A small number of serotypes are very frequently isolated, reducing the discriminatory power of serotyping. Thus, to increase our knowledge of Salmonella spp. epidemiology, additional epidemiological markers, such as phage typing, should be used for this purpose. METHODS. Salmonella spp. strains of human origin sent to the Laboratorio Nacional de Referencia de Salmonellay Shigella (LNRSSE, Spanish Reference Laboratory for Salmonella and Shigella) between 1997 and 2001 were serotyped using conventional agglutination methods, and Enteritidis, Typhimurium, Hadar, Virchow and Typhiserotypes were additionally phage typed according to internationally-developed schemes. RESULTS. A total of 30,856 Salmonella spp. strains, isolatedin the majority of Spanish Autonomous Communities,were analyzed. Enteritidis (51%) and Typhimurium (24%)were the most frequently isolated serotypes. The following were the most frequent serotype/phage type combinations: Enteritidis/PT1 (18%), Enteritidis/PT4 (15%),Enteritidis/PT6a (5%), Typhimurium/DT104 (5%) and Enteritidis/PT6 (3%). The serotype Enteritidis/PT1 showed the greatest increase over the period studied, from 11.61%in 1997 to 24.74% in 2001. CONCLUSIONS. A hierarchical typing approach for Salmonellaspp., using serotyping coupled with phage typing allowed a higher level of discrimination among Salmonella serotypes. Application of this approach in epidemiological studies could be highly useful for early characterization of related strains (AU)

Caracterización de un nuevo serotipo de Salmonella enterica subespecie enterica: serotipo Bata / Characterization of a new serotype of Salmonella enterica subsp. enterica: serotype Bata

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