Prevalence, serotypes and virulence genes of Streptococcus agalactiae isolated from pregnant women with 35–37 weeks of gestation

Abstract

Background In pregnant women Streptococcus agalactiae (GBS) can be transmitted to newborn causing severe infections. It is classified into 10 serotypes (Ia, Ib, II-IX). The severity of neonatal disease is determined by the capsular serotype and virulence factors such as the polysaccharide capsule, encoded by the cps gene, protein C, which includes the Cα surface proteins (bca gene), Rib (rib gene) and Cβ (bac gene); the proteins Lmb (lmb gene), FbsB (fbsB gene), FbsA (fbsA gene), the cyl operon encoding a β-hemolysin (hylB gene), the CAMP factor (cfb gene) and the C5a peptidase (scpB gene). The aim of this work was to determine the degree of GBS colonization in pregnant women, the serotypes distribution and to investigate virulence-associated genes. Methods We worked with 3480 samples of vagino-rectal swabs of women with 35–37 weeks of gestation. The identification of the strains was carried out using conventional biochemical tests and group confirmatory serology using a commercial latex particle agglutination kit. Two hundred GBS strains were selected. Their serotype was determined by agglutination tests. The monoplex PCR technique was used to investigate nine virulence-associated genes (cps, bca, rib, bac, lmb, fbsB, fbsA, hylB and scpB). Results The maternal colonization was 9.09%. The serotypes found were: Ia (33.50%), III (19.00%), Ib (15.50%), II (14.00%), V (7.00%) and IX (5.50%). 5.50% of strains were found to be non-serotypeable (NT). The nine virulence genes investigated were detected simultaneously in 36.50% of the strains. The genes that were most frequently detected were scpB (100.00%), fbsA (100.00%), fbsB (100.00%), cylB (95.00%), lmb (94.00%) and bca (87.50%). We found associations between serotype and genes bac (p = 0.003), cylB (p = 0.02), rib (p = 0.01) and lmb (p < 0.001). Conclusions The frequency of vaginal-rectal colonization, serotypes distribution and associated virulence genes, varies widely among geographical areas. Therefore, epidemiological surveillance is necessary to provide data to guide decision-making and planning of prevention and control strategies.

Prevalence, Resistance Profile and Virulence Genes of Streptococcus agalactiae Colonizing Near-term Pregnant Women Attending Ain Shams University Hospital

“…Some studies suggest that the presence of the scpB gene in GBS human isolates is required, and only strains carrying the scpB gene are infectious to humans 69 . This result agrees with Sadaka et al 18 , Dmitriev et al 69 , Dutra et al 70 and Bobadilla 71 who also detected the presence of scpB gene in all isolates. However, other studies by Hannoun et al 10 , Mudzana et al 65 and Lysakowska et al 11 detected scpB in 94.7%, 90.1% and 92.5% of human isolates respectively.…”

The Role of Streptococcus spp. in Bovine Mastitis

“…Serotype III of GBS has been shown to be capable of producing a protein called Rib coded by the rib gene. Rib is suspected to be one of the reasons for S. agalactiae host-immune evasion thanks to a structure that confers domain atrophy (a phenomenon where protein domains lose a significant number of core structural elements) [ 61 ]. One final important virulence factor in terms of immune evasion is a superantigen named S. dysgalactiae -derived mitogen.…”

Molecular characterization of prevalence, serotypes, virulence factors, and antibiotic resistance of Streptococcus agalactiae in a maternity hospital, Iran

“…The vagino-rectal swab was seeded in 1-2 mL of Todd-Hewitt broth supplemented with colistin (10 μg mL − 1 ) and nalidixic acid (15 μg mL − 1 ). The sown stock was grown 18-24 h in an incubator under microaerophilic conditions (5% CO 2 ) at 35 °C [10]. After incubation, it was transferred to a 5% sheep blood agar plate with a seeding technique for isolation.…”

“…The group B antigen, common to all strains, and the specific capsular polysaccharide antigen that allows its classification into 10 serotypes (Ia, Ib, II-IX), with different geographic distribution [3]. The severity of the neonatal disease is determined by the capsular serotype and virulence factors such as the polysaccharide capsule, encoded by the cps gene, protein C, which includes the α-subunit of C protein (bca gene), and β-subunits of the C protein (bac), resistance to protease immunity protein (rib); the laminin binding protein Lmb (lmb gene), secreted fibrinogen-binding protein FbsA (fbsA gene), fibrinogen-binding protein FbsB (fbsB gene), the cyl operon encoding a β-hemolysin hyaluronidase (hylB gene), the CAMP factor (cfb gene) that promote pathogen entry into host cells and facilitate its intracellular survival and spread, and the C5a peptidase (scpB gene) [10,11]. Penicillin is recommended as the first choice to prevent GBS infection in newborns, for intrapartum prophylaxis in pregnant women.…”