Development of a PCR test to differentiate between Staphylococcus aureus and Staphylococcus intermedius

Area of Science:

• Microbiology
• Food Safety
• Molecular Diagnostics

Background:

• Distinguishing Staphylococcus intermedius from Staphylococcus aureus in food is challenging due to shared phenotypic traits, hindering accurate food poisoning outbreak investigations.
• Current diagnostic methods, including phenotypic analysis and some PCR assays, lack the specificity to reliably differentiate these two important Staphylococcus species.

Purpose of the Study:

• To develop a rapid, accurate, and discriminative multiplex PCR method for specific identification of Staphylococcus aureus and Staphylococcus intermedius.
• To address the diagnostic gap in food safety by enabling reliable differentiation between these two coagulase-positive staphylococci.

Main Methods:

• Developed a multiplex PCR assay targeting species-specific sequences within the nuc gene (thermonuclease) of S. aureus and S. intermedius.
• Incorporated an internal positive control targeting a conserved region of the 16S ribosomal RNA gene (rDNA) for assay validation.
• Validated the assay using 116 Staphylococcus strains, including S. aureus (44) and S. intermedius (57), alongside other related species.

Main Results:

• The developed multiplex PCR method achieved 100% accuracy in discriminating between S. aureus and S. intermedius.
• The assay showed no cross-reactivity with other tested Staphylococcus species, including S. epidermidis, S. chromogenes, and S. hyicus.
• The method demonstrated high specificity and sensitivity for identifying these two species from various sources.

Conclusions:

• The novel multiplex PCR assay provides a reliable tool for the specific detection and differentiation of S. aureus and S. intermedius.
• This method significantly improves the ability to identify the causative agents of foodborne illnesses, enhancing food safety surveillance and outbreak investigations.