Salmonella typhimurium resistant to silver nitrate, chloramphenicol, and ampicillin

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• A specific strain of Salmonella typhimurium was identified in three patients within a burn unit.
• Epidemiological data suggested person-to-person transmission of the organism.
• The patients experienced both colonization and invasive infections.

Purpose of the Study:

• To investigate the characteristics of a unique Salmonella typhimurium strain found in a burn unit.
• To determine the antibiotic and metal ion susceptibility of the identified strain.
• To assess the transferability of resistance patterns and the implications for burn wound management.

Main Methods:

• Epidemiological investigation of patient cases.
• In vitro antibiotic and metal ion susceptibility testing.
• In vitro mating experiments to assess resistance transfer between bacterial strains.

Main Results:

• The isolated Salmonella typhimurium strain exhibited resistance to silver nitrate, mercuric chloride, ampicillin, chloramphenicol, tetracycline, streptomycin, and sulphonamides.
• This resistance pattern was transferable to sensitive strains of Escherichia coli and Salmonella typhimurium via in vitro mating.
• Other Salmonella strains from non-burn patients and geographically distinct S. typhimurium strains did not share this complete resistance profile.

Conclusions:

• The emergence of this multidrug-resistant Salmonella typhimurium in burn units presents a serious clinical challenge.
• Topical treatments like silver nitrate may inadvertently select for resistant strains, exacerbating the threat.
• The resistance to ampicillin and chloramphenicol, crucial systemic antibiotics, combined with topical resistance, highlights a critical public health concern in burn care settings.