Bengal Bay clone ST772-MRSA-V outbreak: conserved clone causes investigation challenges.

Area of Science:

• Microbiology
• Infectious Diseases
• Epidemiology

Background:

• The ST772-MRSA-V clone, known for multidrug resistance and Panton-Valentine leukocidin (PVL), is a global concern.
• This clone has caused hospital outbreaks in Norway, complicating investigations due to its conserved nature.

Purpose of the Study:

• To assess the effectiveness of spa typing, MLVF/MLVA, and PFGE in investigating outbreaks caused by a conserved MRSA clone.
• To determine the most suitable typing method for outbreak investigations of the ST772-MRSA-V clone.

Main Methods:

• Analysis of 25 MRSA isolates (2004-2014), including hospital outbreak and sporadic cases.
• Utilized spa typing, PCR for PVL genes, MLVF/MLVA, and PFGE for isolate characterization.

Main Results:

• All isolates were ST772-MRSA-V-t657, exhibiting resistance to erythromycin, gentamicin, and norfloxacin; 88% were PVL positive.
• PFGE showed limited discriminatory power (≥85% similarity).
• MLVF and MLVA differentiated isolates into five and six types, respectively, identifying two hospital outbreaks, but could not distinguish all epidemiologically unlinked cases over 10 years.

Conclusions:

• MLVF/MLVA provided better discrimination than PFGE for the ST772-MRSA-V clone but struggled with isolates spanning a decade.
• MLVA demonstrated higher discriminatory power and unambiguous profiles, making it more suitable.
• The low diversity within the Bengal Bay clone suggests that higher-resolution typing methods may be necessary for precise outbreak demarcation.