Plasmid-specified sucrose fermentation in Salmonella arizonae

Area of Science:

• Microbiology
• Bacteriology
• Genetics

Background:

• Salmonella arizonae (Ar 23:24-25) is a bacterium that can be found in reptiles.
• Certain bacterial strains exhibit unique metabolic or resistance characteristics due to plasmid-borne genes.

Purpose of the Study:

• To characterize unusual Salmonella arizonae isolates from a captive reptile.
• To investigate the genetic basis for atypical biochemical reactions, specifically sucrose fermentation and o-nitrophenyl-beta-D-galactosidase production.

Main Methods:

• Isolation and culture of Salmonella arizonae from reptile faeces over a 7-month period.
• Biochemical testing to assess o-nitrophenyl-beta-D-galactosidase activity and sucrose fermentation.
• Plasmid profiling to determine molecular mass and associated traits.

Main Results:

• Thirty Salmonella arizonae (Ar 23:24-25) cultures were isolated.
• All isolates were negative for o-nitrophenyl-beta-D-galactosidase and positive for sucrose fermentation.
• A 72-megadalton plasmid conferring tetracycline resistance and a 5-megadalton plasmid enabling sucrose fermentation were identified.

Conclusions:

• The identified 5-megadalton sucrose plasmid is distinct from previously reported sucrose plasmids due to its small size.
• These findings highlight the genetic diversity within Salmonella arizonae and the role of plasmids in bacterial adaptation.