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Updated: Sep 26, 2026
An Allelotyping PCR for Identifying Salmonella enterica serovars Enteritidis, Hadar, Heidelberg, and Typhimurium
Published on: July 22, 2011
Phenotypic and molecular characterization of Salmonella Enteritidis strains isolated in São Paulo, Brazil
Sueli A Fernandes1, Angela C R Ghilardi, Ana T Tavechio
1Seção de Bacteriologia, Instituto Adolfo Lutz, São Paulo, SP, Brasil. fernandessueli@hotmail.com
Abstract:
In São Paulo State, Brazil, the epidemic increase in isolation of Salmonella Enteritidis has been observed since 1994. A total of 105 S. Enteritidis strains (72 from human and 33 from non-human sources) isolated during the period 1975-1995, previously characterized by phage typing, was analyzed by antimicrobial susceptibility, plasmid profile, and ribotyping. Over 70% of the strains were susceptible to all antimicrobial agents tested, however, multiple resistance to antimicrobials was observed among the studied strains, mainly those from hospitalized patients. Phage type 8 (PT-8) was predominant among the strains isolated during the period of 1975-1992, but in the following years, PT-4 was the most frequent phage type identified. Seven different plasmid profiles were detected and 96% of the isolates harbored a plasmid of approximately 36 MDa. Ribotyping discriminated fourteen ribotypes (R1 to R14) among the strains examined. By analysis of dendrogram the strains were included in three groups with similarity level of 60%. The obtained results indicate that, a single ribotype (R11), determined for PT-4 strains isolated from 1993, characterizes the epidemic clone of S. Enteritidis in our region.
Insights
Salmonella Enteritidis is increasing in São Paulo. A specific clone, characterized by ribotype R11 and phage type 4, emerged around 1993, driving the epidemic in the region.
Area of Science:
- Microbiology
- Epidemiology
- Infectious Diseases
Background:
- An epidemic increase in Salmonella Enteritidis (S. Enteritidis) isolation has been noted in São Paulo State, Brazil, since 1994.
- Previous characterization of 105 S. Enteritidis strains (1975-1995) included phage typing.
Purpose of the Study:
- To analyze antimicrobial susceptibility, plasmid profiles, and ribotypes of S. Enteritidis strains.
- To identify the molecular characteristics of the epidemic clone of S. Enteritidis in São Paulo State.
Main Methods:
- Antimicrobial susceptibility testing.
- Plasmid profiling.
- Ribotyping and dendrogram analysis.
Main Results:
- Over 70% of strains were susceptible to all tested antimicrobials, but multiple resistance was observed, particularly in strains from hospitalized patients.
- Phage type 8 (PT-8) predominated from 1975-1992, with a shift to PT-4 from 1993 onwards.
- Seven plasmid profiles were detected; 96% of isolates had a ~36 MDa plasmid. Fourteen ribotypes were identified, with strains grouping into three similarity clusters.
- A single ribotype (R11), associated with PT-4 strains isolated from 1993, characterized the epidemic clone.
Conclusions:
- The epidemic spread of S. Enteritidis in São Paulo State is linked to a specific epidemic clone.
- This clone is characterized by phage type 4 and ribotype R11, emerging around 1993.
