Development of a Multilocus Sequence Typing System for Medically Relevant Bipolaris Species

Area of Science:

• Medical Mycology
• Molecular Epidemiology
• Infectious Diseases

Background:

• Multilocus sequence typing (MLST) is a standard for microbial genotyping, offering high resolution and standardization.
• An unusual cluster of Bipolaris surgical site infections (SSIs) in cardiothoracic surgery patients prompted the need for a refined typing method.
• Previous Bipolaris outbreaks, including a 2012 endophthalmitis outbreak linked to a contaminated product, highlighted the importance of accurate strain identification.

Purpose of the Study:

• To develop and validate a novel MLST system for Bipolaris species.
• To investigate the sources of Bipolaris SSIs in postoperative cardiothoracic surgery (POCS) patients.
• To confirm the source of a Bipolaris endophthalmitis outbreak.

Main Methods:

• Development of a novel multilocus sequence typing (MLST) scheme targeting conserved housekeeping genes in Bipolaris species.
• Application of the MLST system to clinical isolates from POCS patients (2008-2013) and isolates from a 2012 endophthalmitis outbreak.
• Phylogenetic analysis of MLST data to assess isolate relatedness and infer epidemiological links.

Main Results:

• The novel MLST system demonstrated high discriminatory power for key Bipolaris species, including B. spicifera, B. hawaiiensis, and B. australiensis.
• MLST analysis supported distinct environmental sources for the POCS surgical site infections.
• The data confirmed a single point source, a contaminated medication, for the 2012 endophthalmitis outbreak.

Conclusions:

• The developed MLST system is a valuable tool for high-resolution genotyping of Bipolaris species.
• The findings suggest that Bipolaris SSIs in POCS patients likely arise from diverse environmental exposures.
• The endophthalmitis outbreak was definitively linked to a contaminated pharmaceutical product, underscoring the importance of stringent product quality control.