Variabilidade genética de amostras de Salmonella Typhi isoladas de surto e de casos esporádicos ocorridos em Belém, Brasil / Genetic variability of Salmonella Typhi samples isolated from outbreaks and sporadic cases of typhoid fever in Belém, Brazil

INTRODUÇÃO: Salmonella Typhi é o agente da febre tifóide (doença caracterizada por febre, cefaléia, mialgia, artralgia, diarréia ou constipação), cujo quadro pode se complicar e levar o paciente a óbito. No Brasil, a febre tifóide é endêmica nas regiões Norte e Nordeste, com surtos ocorridos nos meses de intenso calor. OBJETIVO: Analisar e comparar a variabilidade genética de S. Typhi isoladas de surto e casos esporádicos de febre tifóide ocorridos em determinado período na cidade de Belém (PA). MATERIAL E MÉTODOS: Foram analisadas 20 amostras de S. Typhi: 10 isoladas de um surto ocorrido no bairro do Guamá, Belém, entre os meses de dezembro/2005 e março/2006, e 10 de casos esporádicos ocorridos em diferentes localidades da mesma cidade e no mesmo período do surto. A caracterização genética foi realizada pela análise do perfil de macrorrestrição obtido pela enzima XbaI e definido por eletroforese em gel de campo pulsado (PFGE). RESULTADOS: A análise de XbaI-PFGE das amostras estudadas demonstrou uma similaridade genética de 83 por cento a 100 por cento. CONCLUSÃO: Este estudo pôde demonstrar a relação clonal das amostras S. Typhi causadoras de surto e de casos esporádicos de febre tifóide ocorridos na cidade de Belém no período de dezembro/2005 a março/2006.

BACKGROUND: Salmonella Typhi is the causative agent of typhoid fever, illness characterized by fever, migraine, myalgia, arthralgia, diarrhea or constipation, which may have complications and cause death. In Brazil, the typhoid fever is endemic in the Northern and Northeastern regions, with outbreaks occurring in scorching months. OBJECTIVE: To analyse and compare the genetic variability of S. Typhi strains isolated from outbreaks and sporadic cases of typhoid fever occurred in the city of Belém (PA) between December 2005 and March 2006. MATERIAL AND METHODS: Twenty samples of S. Typhi were analyzed: 10 of them were isolated from an outbreak occurred in Guamá neighborhood in Belém, between December 2005 and March 2006, and the other 10 were isolated from sporadic cases in different neighborhoods of the same city in the same outbreak period. The genetic characterization was performed by macrorestriction analysis of genomic DNA with XbaI enzyme defined by pulsed-field gel electrophoresis (PFGE). RESULTS: The Xbal-PFGE analysis of the studied samples revealed a genetic similarity of 83 percent to 100 percent. CONCLUSION: This study demonstrated the clonal relation between the S. Typhi samples from the outbreak and from the sporadic cases of typhoid fever occurred in the city of Belém between December 2005 and March 2006.

Study of genetic diversity of Salmonella typhi using pulsed-field gel electrophoresis.

DNA genomes of Salmonella typhi (S. typhi), which were isolated from sporadic typhoid fever cases who were hospitalized in Persahabatan Hospital, Jakarta, during the 1st semester of 1998, were examined for their genetic diversities. Pulsed-field gel electrophoresis (PFGE) of genomic DNA digested with Xbal was performed for 25 isolates. Electrophoresis patterns of most isolates varied and 18 PFGE types were identified. Cluster analysis showed that all isolates originated from two main groups; and at ≥ 84% level of similarity, 7 clusters were found. Thus, the results showed that genetic diversity of S. typhi was considerably high, and that S. typhi isolated from sporadic typhoid fever cases were derived from multiple clones.