[Serotype and phage type distribution of human Salmonella strains isolated in Spain, 1997-2001].
BACKGROUND
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.
Echeita
María Aurora
MA
Sección de Enterobacterias, Servicio de Bacteriología, Centro Nacional de Microbiología, Majadahonda, Madrid, Spain. aecheita@isciii.es
Aladueña
Ana María
AM
Díez
Rosa
R
Arroyo
Margarita
M
Cerdán
Francisca
F
Gutiérrez
Rafaela
R
de la Fuente
Manuela
M
González-Sanz
Rubén
R
Herrera-León
Silvia
S
Usera
Miguel Angel
MA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology; D001434:Bacteriophage Typing; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012475:Salmonella / Q000145:classification* / Q000276:immunology / Q000302:isolation & purification / Q000821:virology; D012480:Salmonella Infections / Q000453:epidemiology / Q000382:microbiology*; D012483:Salmonella Phages / Q000302:isolation & purification; D012703:Serotyping; D013030:Spain / Q000453:epidemiology; D013045:Species Specificity
D000907:Antibodies, Bacterial