Determinants of Group B streptococcal virulence potential amongst vaginal clinical isolates from pregnant women

Abstract

Streptococcus agalactiae, also known as Group B Streptococcus (GBS), is a Gram-positive bacterium isolated from the vaginal tract of approximately 25% of women. GBS colonization of the female reproductive tract is of particular concern during pregnancy as the bacteria can invade gestational tissues or be transmitted to the newborn during passage through the birth canal. Infection of the neonate can result in life-threatening pneumonia, sepsis and meningitis. Thus, surveillance of GBS strains and corresponding virulence potential during colonization is warranted. Here we describe a panel of GBS isolates from the vaginal tracts of a cohort of pregnant women in Michigan, USA. We determined that capsular serotypes III and V were the most abundant across the strain panel, with only one isolate belonging to serotype IV. Further, 12.8% of strains belonged to the hyper-virulent serotype III, sequence type 17 (ST-17) and 15.4% expressed the serine rich repeat glycoprotein-encoding gene srr2. Functional assessment of the colonizing isolates revealed that almost all strains exhibited some level of β-hemolytic activity and that ST-17 strains, which express Srr2, exhibited increased bacterial adherence to vaginal epithelium. Finally, analysis of strain antibiotic susceptibility revealed the presence of antibiotic resistance to penicillin (15.4%), clindamycin (30.8%), erythromycin (43.6%), vancomycin (30.8%), and tetracycline (94.9%), which has significant implications for treatment options. Collectively, these data provide important information on vaginal GBS carriage isolate virulence potential and highlight the value of continued surveillance.

Identification of Zinc-Dependent Mechanisms Used by Group B Streptococcus To Overcome Calprotectin-Mediated Stress

“…S1A to C in the supplemental material). Additionally, we determined how a panel of 27 vaginal isolates collected from the vaginal tracts of pregnant women ( 49 ) survived in the presence of calprotectin. All strains were grown with or without 120 μg/ml calprotectin, and data are displayed as percent inhibition in treated versus untreated controls for isolates belonging to five different capsular serotypes.…”

“… Streptococcus agalactiae (GBS) isolates A909 (serotype Ia), CJB111 (serotype V), COH1 (serotype III), a cohort of 25 vaginal colonization isolates (serotypes Ia, Ib, II, III, and V) ( 49 ), and mutant strains (A909 Δ adcA , A909 Δ adcAII , A909 Δ lmb , A909 Δ adcA Δ adcAII Δ lmb , and CJB111 Δ adcA Δ adcAII Δ lmb ) were cultured in Todd-Hewitt broth (THB) at 37°C. Mutant strains were constructed as previously described ( 40 , 41 ).…”

Group B Streptococcus serotypes associated with different clinical syndromes: Asymptomatic carriage in pregnant women, intrauterine fetal death, and early onset disease in the newborn

“…The high resistance rates described by us prohibits empirical use of these antibiotics for women with penicillin allergy. The increasing reports regarding penicillin resistance [ 12 , 13 ] warrant also routine susceptibility test for penicillin.…”

“…Recent data reports increasing rates of macrolide resistance [ 10 , 11 ]. Also, several recent studies demonstrated a worrying increase in GBS isolates with resistance to penicillin [ 12 , 13 ]. In Israel, screening does not include antibiotic susceptibility and there is no data regarding GBS resistance rates.…”

Streptococcus agalactiae in pregnant women: serotype and antimicrobial susceptibility patterns over five years in Eastern Sicily (Italy)

“…The importance to identify GBS serotypes lies in their different abilities to cause disease. According to this potential, neonatal invasive disease and meningitis are prevalently due to virulent serotype III, whereas serotypes Ia, Ib, II, III, and V are recognized as the most common isolated strains associated with GBS disease [ 7 , 19 ]. Epidemiological studies, aimed to establish the predominant serotype/s in a specific country, could constitute a first step for the development of prevention strategies such as vaccines, which is being intensively worked on for several years [ 20 ].…”