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Laboratory observations on Plesiomonas shigelloides strains isolated from children with diarrhea in Peru
1Division of Bacterial Diseases, Center for Disease Control, Atlanta, Georgia 30333.
Abstract:
Eleven strains of Plesiomonas shigelloides isolated from 10 Peruvian children with diarrhea were examined. All the strains were resistant to two or more antibiotics, most commonly ampicillin, gentamicin, erythromycin, kanamycin, and streptomycin. The strains were all negative in the Sereny and cell culture assays used to test for enteroinvasiveness. One strain showed cytotoxic activity on Vero cells. The strains showed no antigenic relationship with Shigella organisms. Both bioassays and enzyme-linked immunosorbent assays used for detection of Escherichia coli enterotoxins were negative. Nucleic acid probes for such toxins likewise gave negative results. The strains all possessed a large (approximately 200-megadalton) plasmid in addition to one or more other plasmids. Several different plasmid profiles were observed among these 11 P. shigelloides strains, indicating that the isolates were not acquired from a common source or from a single bacterial clone.
Insights
Eleven strains of Plesiomonas shigelloides from Peruvian children with diarrhea were antibiotic-resistant and lacked virulence factors. These bacteria, carrying large plasmids, were not linked to Shigella or common E. coli toxins.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Plesiomonas shigelloides is an emerging cause of diarrheal illness.
- Understanding the virulence factors and genetic diversity of P. shigelloides is crucial for diagnosing and treating infections.
Purpose of the Study:
- To characterize eleven strains of Plesiomonas shigelloides isolated from Peruvian children with diarrhea.
- To investigate their antibiotic resistance, invasiveness, cytotoxic activity, antigenic relationship with Shigella, and enterotoxin production.
Main Methods:
- Antibiotic susceptibility testing.
- Sereny assay and cell culture for enteroinvasiveness.
- Vero cell cytotoxicity assay.
- Antigenic analysis.
- Bioassays, ELISA, and nucleic acid probes for enterotoxins.
- Plasmid profiling.
Main Results:
- All eleven P. shigelloides strains exhibited resistance to at least two antibiotics, commonly ampicillin, gentamicin, erythromycin, kanamycin, and streptomycin.
- None of the strains were enteroinvasive in Sereny or cell culture assays.
- One strain demonstrated cytotoxic activity against Vero cells.
- No antigenic relationship with Shigella organisms was found.
- No evidence of Escherichia coli enterotoxins was detected by bioassays, ELISA, or nucleic acid probes.
- All strains harbored a large (approx. 200-megadalton) plasmid, and varied plasmid profiles suggested diverse origins.
Conclusions:
- The P. shigelloides strains studied were antibiotic-resistant and lacked common virulence factors associated with Shigella and E. coli enterotoxins.
- The presence of large plasmids and diverse plasmid profiles indicates genetic heterogeneity among these isolates.
- Further research is needed to elucidate the specific mechanisms of pathogenicity for P. shigelloides in diarrheal diseases.