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Recognition of Streptococcus pseudoporcinus Colonization in Women as a Consequence of Using Matrix-Assisted Laser

Nuntra Suwantarat1, Maureen Grundy2, Mayer Rubin3

  • 1Division of Medical Microbiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA Chulabhorn International College of Medicine, Thammasat University, Pathumthani, Thailand nsuwantarat@gmail.com.

Journal of Clinical Microbiology
|October 16, 2015
PubMed

Insights

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) identified Streptococcus pseudoporcinus in 1% of group B Streptococcus screening cultures. These isolates cross-reacted with common GBS antigen tests, potentially impacting GBS identification accuracy.

Area of Science:

  • Clinical microbiology
  • Bacterial identification
  • Mass spectrometry

Background:

  • Group B Streptococcus (GBS) is a significant pathogen, particularly in pregnant women.
  • Accurate identification of GBS is crucial for timely treatment and prevention of neonatal disease.
  • Advancements in bacterial identification methods may reveal previously unrecognized species.

Purpose of the Study:

  • To report the prevalence of Streptococcus pseudoporcinus identified by MALDI-TOF MS in GBS screening cultures.
  • To assess the cross-reactivity of S. pseudoporcinus isolates with commercial GBS antigen agglutination kits.

Main Methods:

  • Utilized matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for bacterial identification over a 14-month period.
  • Analyzed 3,276 GBS screening cultures from female genital sources.
  • Tested identified S. pseudoporcinus isolates using three different GBS antigen agglutination kits: PathoDx, Prolex, and Streptex.

Main Results:

  • Identified 32 (1%) Streptococcus pseudoporcinus isolates from 3,276 GBS screening cultures.
  • The majority of S. pseudoporcinus isolates (25) were from pregnant women.
  • Significant cross-reactivity was observed between S. pseudoporcinus and GBS antigen kits: PathoDx (93%), Prolex (38%), and Streptex (53%).

Conclusions:

  • The implementation of MALDI-TOF MS may increase the detection of Streptococcus pseudoporcinus in clinical laboratories.
  • S. pseudoporcinus can be misidentified as GBS due to cross-reactivity with common antigen agglutination tests.
  • Clinical microbiology laboratories should be aware of potential misidentification issues with new bacterial identification approaches.

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