Related Experiment Videos
Sequential acquisition of R-plasmids in vivo by Salmonella typhimurium
Abstract:
Salmonella typhimurium, resistant only to trimethoprim and sulphamethoxazole, was isolated from the faeces and blood of a chronic alcoholic patient in acute renal failure. The isolates harboured an 18 Md non-conjugative plasmid. He was dialysed peritoneally and treated with ampicillin; four days later there was no clinical improvement and his peritoneal dialysis fluid (PDF) had become infected. Salm. typhimurium was isolated from faeces and PDF. Both isolates were additionally resistant to ampicillin and contained two plasmids (55 Md and 18 Md). Therapy was changed to chloramphenicol and gentamicin was added to the PDF. Two weeks later Salm. typhimurium was again isolated from PDF and faeces. The PDF isolate was unchanged but 4% of the colonies isolated from this faecal specimen were resistant to chloramphenicol and had acquired an additional 62 Md plasmid. From all PDF and faecal specimens two different strains of Escherichia coli and one strain of Klebsiella pneumoniae were isolated which contained plasmids indistinguishable, on the basis of molecular weight and transferable resistance markers, from those acquired by Salm. typhimurium. The transferability of these plasmids in vitro to E. coli K12 and to the patient's initial Salm. typhimurium was studied and the results discussed.
Insights
Antibiotic resistance in Salmonella typhimurium evolved rapidly in a patient with acute renal failure, acquiring new plasmids and resistance markers. This highlights the dynamic nature of antimicrobial resistance in clinical settings.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Salmonella typhimurium is a significant human pathogen.
- Antimicrobial resistance is a growing global health concern.
- Patients with compromised renal function may be at increased risk for complex infections.
Observation:
- A chronic alcoholic patient in acute renal failure developed Salmonella typhimurium infection.
- Initial Salmonella typhimurium isolate was resistant to trimethoprim and sulphamethoxazole, carrying an 18 Md plasmid.
- Following ampicillin treatment, the infection persisted, with isolates acquiring ampicillin resistance and a 55 Md plasmid.
- Further treatment led to chloramphenicol resistance and acquisition of a 62 Md plasmid in a subset of isolates.
- Other Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae) isolated from the patient shared similar plasmid profiles.
Findings:
- Salmonella typhimurium demonstrated rapid acquisition of multiple antibiotic resistance plasmids during treatment.
- The patient's peritoneal dialysis fluid became a reservoir for resistant bacterial strains.
- Evidence suggests potential plasmid transfer between different bacterial species within the patient.
Implications:
- This case underscores the rapid evolution and dissemination of antimicrobial resistance in vivo.
- It highlights the importance of careful antibiotic selection and monitoring in immunocompromised patients.
- Understanding plasmid dynamics is crucial for managing multidrug-resistant infections.