Group B Streptococcal Colonization in African Countries: Prevalence, Capsular Serotypes, and Molecular Sequence Types

Molecular typing and antimicrobial resistance of group B Streptococcus clinical isolates in Saudi Arabia

OBJECTIVES

Group B Streptococcus (GBS) has emerged as an important cause of severe infections in adults. However, limited data are available regarding the epidemiology of GBS in Saudi Arabia.

METHODS

Isolates were collected over a period of eight months from colonized (n = 104) and infected adults (n = 95). Serotypes and virulence determinants were detected by polymerase chain reactions (PCRs). Genetic relatedness was assessed using Multiple Locus Variable Number Tandem Repeat Analysis (MLVA). Antimicrobial susceptibilities were determined by disk diffusion.

RESULTS

Serotypes III and V (25% each) were the most prevalent, followed by serotypes II (16.18%), Ia (13.24%), VI (9.31%), and Ib (8.82%), while five isolates remained non-typeable (2.45%). Hypervirulent serotype III/CC17 clone (n = 21) accounted for 41.18% of the serotype III isolates. Most isolates (53.92%) harboured pilus island (PI) 1 and 2a types, while PI-2b was predominantly detected in the hypervirulent clone. Isolates were variably resistant to tetracycline (76.47%), erythromycin (36.76%), clindamycin (25.49%), and levofloxacin (6.37%), but remained susceptible to penicillin. Macrolide resistant isolates exhibited constitutive (55.42%) and inducible macrolide-lincosamide-streptogramin B resistance phenotypes (33.74%), while a few had L (9.64%) or M (1.2%) phenotypes. MLVA patterns of dominant serotypes III and V revealed 40 different types divided into 12 clusters and 28 singletons. Interestingly, macrolide resistance was significantly associated with two major MLVA types.

CONCLUSIONS

GBS isolates belonged predominantly to serotypes III and V, but there were no clear associations between serotypes and patient groups. The studied isolates exhibited high levels of resistance to erythromycin and clindamycin that need further surveillance.

Molecular Epidemiology of Group B Streptococcus Isolates from Pregnant Women with Premature Rupture of Membranes in Fuzhou, China

Objective

This study investigated the molecular epidemiology of Group B Streptococcus (GBS) in pregnant women with premature rupture of membranes (PROM) in Fuzhou region of China as a source of clinical reference.

Methods

GBS isolates were obtained from pregnant women with PROM. All isolates were genotyped, serotyped, and tested for drug-resistance and virulence genes using PCR and DNA sequencing. Antibiotic susceptibility testing was performed using the Vitek^® 2 automated system.

Results

Among the 140 GBS isolates, seventeen sequence types (STs) were identified, of which ST19 (20.0%) was the most prevalent, followed by ST862, ST10, and ST12. Three clonal complexes (CC19, CC10 and CC1) were identified. The predominant serotype was III (45.7%), followed by V (23.6%), Ib (18.6%), Ia (7.1%), and II (3.6%). The prevalence of multidrug resistance was 72.8% (102/140). All isolates were susceptible to penicillin G, ampicillin, quinupristin, linezolid, vancomycin, and tigecycline. The majority of isolates were resistant to erythromycin (70.0%), clindamycin (72.1%), and tetracycline (81.4%), and 28.6% of isolates were resistant to levofloxacin and moxifloxacin. Of the 98 erythromycin-resistant strains, mreA, ermB, mefA, mefE, ermA, and ermTR were detected in 100%, 70.4%, 49.0%, 22.4%, 13.3%, and 9.2%, respectively. No linB was detected among 101 clindamycin-resistant strains. Of the 114 tetracycline-resistant strains, tetM, tetK, tetL and tetO were detected in 52.6%, 61.4%, 7.9%, and 23.7%, respectively. Regarding virulence genes, all strains carried rib and hylB, followed by scpB (98.6%), and bca (80.7%), whereas only one strain carried bac.

Conclusion

ST19/III and ST862/III were the most prevalent GBS subtypes. Penicillin G remains a first-line antibiotic for intrapartum antibiotic prophylaxis and treatment of GBS infections. The prevalence of resistance to clindamycin, erythromycin, and tetracycline is high among GBS isolates in the Fuzhou region. ST862 and ST651 are emerging animal origin STs in human infections, and may become potential zoonotic threats.

Sublingual immunisation with GBS serotype III capsular polysaccharide-tetanus toxoid conjugate vaccine induces systemic and mucosal antibody responses which are opsonophagocytic and inhibit GBS colonisation of vaginal epithelial cells

No vaccines are currently licensed against Group B streptococcus (GBS), an important cause of morbidity and mortality in babies and adults. Using a mouse model, and in vitro opsonophagocytosis and colonisation assays, we evaluated the potential of a sublingually-administered polysaccharide-conjugate vaccine against GBS serotype III. Sublingual immunisation of mice with 10 µg of GBS conjugate vaccine once a week for 5 weeks induced a substantial systemic IgG anti-polysaccharide response which was similar to the level induced by subcutaneous immunsation. In addition, sublingual immunisation also induced mucosal (IgA) antibody responses in the mouth, intestines and vagina. Immune sera and intestinal washes were functionally active at mediating killing of the homologous GBS serotype III in an opsonophagocytosis assay. In addition, intestinal and vaginal washes inhibited the colonisation of mouse vaginal epithelial cells by the vaccine homologous strain. These results suggest that, in addition to the induction of high levels of IgG antibodies that could be transduced from the immunised mother to the foetus to protect the newborn against GBS infection, sublingual immunisation can elicit a substantial mucosal antibody response which might play an important role in the prevention of GBS colonisation in immunised women, thereby eliminating the risk of GBS transmission from the mother to the baby during pregnancy or at birth.

Characterisation of Staphylococci species from neonatal blood cultures in low- and middle-income countries

Background

In low- and middle-income countries (LMIC) Staphylococcus aureus is regarded as one of the leading bacterial causes of neonatal sepsis, however there is limited knowledge on the species diversity and antimicrobial resistance caused by Gram-positive bacteria (GPB).

Methods

We characterised GPB isolates from neonatal blood cultures from LMICs in Africa (Ethiopia, Nigeria, Rwanda, and South Africa) and South-Asia (Bangladesh and Pakistan) between 2015–2017. We determined minimum inhibitory concentrations and performed whole genome sequencing (WGS) on Staphylococci isolates recovered and clinical data collected related to the onset of sepsis and the outcome of the neonate up to 60 days of age.

Results

From the isolates recovered from blood cultures, Staphylococci species were most frequently identified. Out of 100 S. aureus isolates sequenced, 18 different sequence types (ST) were found which unveiled two small epidemiological clusters caused by methicillin resistant S. aureus (MRSA) in Pakistan (ST8) and South Africa (ST5), both with high mortality (n = 6/17). One-third of S. aureus was MRSA, with methicillin resistance also detected in Staphylococcus epidermidis, Staphylococcus haemolyticus and Mammaliicoccus sciuri. Through additional WGS analysis we report a cluster of M. sciuri in Pakistan identified between July-November 2017.

Conclusions

In total we identified 14 different GPB bacterial species, however Staphylococci was dominant. These findings highlight the need of a prospective genomic epidemiology study to comprehensively assess the true burden of GPB neonatal sepsis focusing specifically on mechanisms of resistance and virulence across species and in relation to neonatal outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07541-w.