Epidemiologic analysis of sporadic Salmonella typhi isolates and those from outbreaks by pulsed-field gel electrophoresis

Abstract

Pulsed-field gel electrophoresis (PFGE) was used to compare and analyze 158 isolates of Salmonella typhi from five well-defined outbreaks of typhoid fever in Malaysia and also isolates involved in sporadic cases of typhoid fever occurring during the same period. Digestion of chromosomal DNAs from these S. typhi isolates with the restriction endonucleases XbaI (5'-TCTAGA-3'), SpeI (5'-ACTAGT-3'), and AvrII (5'-CCTAGG-3') and then PFGE produced restriction endonuclease analysis (REA) patterns consisting of 11 to 24 DNA fragments ranging in size from 20 to 630 kbp. Analysis of the REA patterns generated by PFGE after digestion with XbaI and Spel indicated that the S. typhi isolates obtained from sporadic cases of infection were much more heterogeneous (at least 13 different REA patterns were detected; Dice coefficient, between 0.73 and 1.0) than those obtained during outbreaks of typhoid fever. The clonal nature and the close genetic identities of isolates from outbreaks in Alor Setar, Penang, Kota Kinabalu, Johor Bahru, and Kota Bahru were suggested by the fact that only a limited number of REA patterns, which mostly differed by only a single band, were detected (one to four patterns; Dice coefficient, between 0.82 and 1.0), although a different pattern was associated with each of these outbreaks. Comparison of REA patterns with ribotyping for 18 S. typhi isolates involved in sporadic cases of infection showed a good correlation, in that 72% of the isolates were in the same group. There was no clear correlation of phage types with a specific REA pattern. We conclude that PFGE of S. typhi chromosomal DNA digested with infrequently cutting restriction endonucleases is a useful method for comparing and differentiating S. typhi isolates for epidemiological purposes.

Epidemiologic Study of Shigella sonnei from Sequential Outbreaks and Sporadic Cases Using Different Typing Techniques

“…This analysis also indicates that rather heterogeneous isolates existed among the sporadic isolates of S. sonnei, and that a few of these were similar to outbreak-related isolates. These findings were essentially similar to the report of Thong et al, in which considerable heterogeneity existed among the isolates of S. typhi in Malaysia, and that most of the periodic outbreaks of typhoid fever were caused by a single clone or very closely related clones (18). In addition, the shared characteristics of related or closely related S. sonnei from outbreak-related and sporadic isolates of travelers in Asia suggests that distinctive clones of S. sonnei existing in Asia at the time might have had some relationship with the outbreaks during this period, probably because of the extensive movement of people or food (7,20).…”

Avian Colibacillosis and Salmonellosis: A Closer Look at Epidemiology, Pathogenesis, Diagnosis, Control and Public Health Concerns

“…Reference Inadequate level of hygiene [87,88] Salmonella contamination of the previous flock [89,90] with a persistence inside the house [91] Contaminated day-old chicks and feed [89,[92][93][94] The farm structure (>3 houses on the farm) [89] Wet and cold season [89] Litter-beetle infestation of the house [91] In more recent years, the use of DNA-related techniques such as plasmid analysis [95,96], ribotyping [97][98][99][100], and PFGE [101,102] have proved to be useful in discriminating isolates of Salmonella species. Lapuz et al [103] investigated the prevalence of Salmonella in four layer farms in eastern Japan between 2004 and 2006 to determine the role of roof rats (Rattus rattus) in the epizootology of Salmonella enterica subsp.…”

Molecular characterization of antibiotic resistance in clinical Salmonella typhi isolated in Ghana

“…Typhoid fever remains a serious health threat to developing countries. Globally, it is estimated there are over 20 million cases annually, resulting in greater than 700 000 deaths [1]. The incidence of this disease in the industrialized world is rare primarily due to proper sanitary facilities.…”