Implantação da técnica de PCR para estreptococos do grupo B (EGB) e detecção de alguns fatores de virulência

Abstract

Streptococcus agalactiae or group B Streptococcus (GBS) is a leading cause of invasive neonatal infection and bovine mastitis. Serotyping of GBS is important as regard epidemiological trends and vaccine development. Serotyping of GBS by latex agglutination has been the predominant typing method, but more recently genotyping has been introduced as an alternative method. For this reason, we decided to implement the PCR technique in our laboratory to typing from human and bovine strains. In addition, we analyzed two important virulence factors (laminin and pilus type 2a) and the sequence types ST-1 and ST-17 as genomic biomarkers in all GBS strains. Genotyping gave a result in all 31 GBS strains (15 human and 16 animal) using PCR method. In human strains, the serotype III (46.67%) was the most predominant, followed by serotypes Ia (20%), V (20%) and II (13.33%). However, all GBS bovine strain were genotyped as II (100%). Molecular typing by PFGE showed that GBS bovine strains were associated with two clones (A and B). The lmb virulence gene was detected in 60% human isolates and 93.75% of bovine strains, while pilus 2a was detected in 6,45% isolates. Moreover, both human and bovine strains tested produced biofilm in a model pilus 2a-independent. All strains tested presented the sequence type ST-1, but only the GBS strain 90356-líquor/III was positive for ST-17, showing that this invasive strain belongs to hypervirulent ST-17 clone. In conclusion, the PCR method facilitates the detection of DNA polymorphism in cps genes and was successfully implemented in our laboratory.