Methicillin-susceptible ST398 Staphylococcus aureus responsible for bloodstream infections: an emerging human-adapted...

Area of Science:

• Infectious Diseases
• Microbiology
• Epidemiology

Background:

• Methicillin-susceptible ST398 Staphylococcus aureus (MSSA ST398) is an emerging pathogen.
• The incidence of ST398 bloodstream infections (BSI) in French healthcare institutions has not been well-characterized.
• Understanding the transmission dynamics and adaptation of ST398 is crucial for infection control.

Purpose of the Study:

• To investigate the incidence and characteristics of ST398 Staphylococcus aureus BSI over a four-year period.
• To compare ST398 BSI isolates with known pig-borne clones.
• To explore potential transmission routes and factors contributing to the emergence of ST398 BSI.

Main Methods:

• Conducted an annual 3-month survey of BSIs across 31 healthcare institutions in France.
• Collected and characterized 18 ST398 Staphylococcus aureus BSI isolates.
• Utilized spa-typing, MLVA, and phage analysis to compare BSI isolates with pig-borne strains.

Main Results:

• Reported 18 ST398 Staphylococcus aureus BSI cases, with a seven-fold increase in incidence from 2007 to 2010.
• ST398 BSI isolates were predominantly methicillin-susceptible and lacked typical pig-borne spa-types.
• BSI isolates harbored the Sau3int phage, suggesting horizontal gene transfer, and were associated with digestive portals of entry.

Conclusions:

• The emergence of ST398 BSI is likely driven by horizontal transfer of phages, such as Sau3int, in diverse MSSA ST398 isolates.
• Phage acquisition may enhance the colonization ability of ST398, contributing to its increasing prevalence in hospitals.
• The association with digestive portals and lack of livestock exposure suggests potential foodborne transmission, warranting active surveillance.