Could β-hemolytic, group B Enterococcus faecalis be mistaken for Streptococcus agalactiae?

Area of Science:

• Clinical microbiology and infectious diseases.
• Bacterial identification and characterization.
• Antenatal screening and obstetric care.

Background:

• Streptococcus agalactiae (Group B Streptococcus [GBS]) screening is crucial during antenatal care.
• Accurate identification of bacteria is essential to prevent misdiagnosis and inappropriate treatment.
• Enterococcus faecalis is a common bacterium, but unusual agglutination patterns can cause diagnostic challenges.

Purpose of the Study:

• To report the first observation of an Enterococcus faecalis isolate exhibiting multi-Lancefield antisera agglutination.
• To highlight the potential for this isolate to be misidentified as GBS.
• To underscore the implications for antenatal screening and intrapartum antibiotic prophylaxis.

Main Methods:

• Isolation and identification of bacteria from a rectovaginal swab during antenatal screening.
• Serological testing using Lancefield group antisera (A, B, C, D, F, and G).
• Phenotypic characterization including beta-hemolysis.

Main Results:

• A β-hemolytic Enterococcus faecalis isolate was identified.
• This isolate agglutinated with multiple Lancefield antisera, including Group B.
• This represents the first reported instance of such a multi-reactive E. faecalis strain.

Conclusions:

• The multi-Lancefield agglutinating Enterococcus faecalis strain poses a significant risk of false-positive GBS identification.
• Misidentification can lead to unnecessary intrapartum antibiotic administration, contributing to antibiotic resistance.
• Enhanced diagnostic vigilance is required for bacterial isolates from antenatal screening, especially those with atypical serological profiles.