A simple, rapid typing method for Streptococcus agalactiae based on ribosomal subunit proteins by MALDI-TOF MS

Area of Science:

• Microbiology
• Genetics
• Public Health

Background:

• Streptococcus agalactiae (Group B Streptococcus, GBS) is a common human colonizer and a significant cause of neonatal meningitis.
• Emerging evidence suggests atypical GBS genotypes from animal sources can cause invasive human diseases via foodborne zoonotic infections.

Purpose of the Study:

• To apply MALDI-TOF MS for classifying GBS strains based on ribosomal subunit protein profiles.
• To identify novel GBS genotypes and assess their zoonotic potential from food sources.

Main Methods:

• MALDI-TOF MS typing was used to analyze 249 GBS isolates from patients and food animals (fish, pig) in Hong Kong (2016-2018).
• Classification was based on molecular weight variations of 28 ribosomal subunit proteins (rsp) to define phylogenetic lineages.

Main Results:

• Over 84% of non-invasive GBS patient isolates were classified into 5 dominant rsp-profiles.
• Over 90% of fish GBS and 13% of pig GBS matched known profiles; two novel rsp-profiles were identified from food animals.
• One fish GBS strain could not be assigned to any cluster.

Conclusions:

• MALDI-TOF MS is a rapid, high-throughput method for GBS strain typing and novel genotype detection.
• This technique is adaptable for diagnostic laboratories for surveillance of emerging GBS genotypes with zoonotic potential.