Vaccines for other neonatal infections: Are group B streptococcal infections vaccine-preventable?

Streptococcus agalactiae in childbearing age immigrant women in Comunitat Valenciana (Spain)

Streptococcus agalactiae (GBS) remains the leading cause of meningitis and neonatal sepsis in the world, and causes disease in pregnant and puerperal women. This is a retrospective study of GBS infections on women of childbearing age living in Comunitat Valenciana, Spain (years 2009-2014) and GBS colonization rate on pregnant women attending Hospital La Fe (years 2013-2015) according to their origin. An aggregated total of 6,641,960 women exposed during the study period had an average GBS isolation rate of 5.19‰ (5.14-5.25‰), geographical group rates being: Western Europe (2.2‰), North America (2.1‰), Australia (3.7‰), Spain (4.6‰), Latin America II (4.5‰), Eastern Europe (5.3‰), Asia (6.7‰), Latin America I (7.7‰), Middle East (7.9‰), Indian Subcontinent (17.2‰), North Africa (17.8‰), Sub-Saharan Africa (22.7‰). The 4532 pregnant women studied had an average GBS colonization rate of 12.47% (11.51-13.43) and geographical group rates varied similar to geographical isolation rates. Low GDP and high temperatures of the birth country were associated with higher colonization rates. Thus, differences in GBS colonization depend on the country of origin; Africa and the Indian subcontinent presented the highest, while Western Europe and North America had the lowest. This variability portrays a geographical pattern influenced by temperature and GDP.

Molecular characteristics and antimicrobial resistance in invasive and noninvasive Group B Streptococcus between 2008 and 2015 in China

Group B streptococcus (GBS) is an increasing pathogen threat to newborns and adults with immunodepressive diseases. Here, a total of 193 GBS, including 51 invasive and 142 noninvasive isolates, were collected from the patients with infections in 7 tertiary hospitals from 5 cities in China during the year 2008 to 2015. The strains of GBS were characterized by classical and molecular techniques for capsular polysaccharide serotyping, genes for pilus island (PI) and α-like protein (alp), and antibiotic resistance profiling. Of 193 isolates, the predominant serotypes were III (45.6%) and Ia (18.7%). All strains carried at least 1 PI gene. The combination of PI-2b and PI-1 was present in 46.1% isolates, followed by PI-2a alone (80, 41.5%) and PI-2b alone (23, 11.9%). The most prevalent alp gene was rib (87, 45.1%), followed by α-C (47, 24.4%), ε (33, 17.1%), alp2/3 (7, 3.6%) and alp4 (2, 1.0%), respectively. The clonal relationships between strains were investigated using multilocus sequence typing. The strains were distinguished into 26 individual sequence typing, and further clustered into 6 clonal complexes. A significant association was noted between the distributions of alp genes, serotyping and PI profiles, such as serotype III-rib-PI+PI-2a, Ib-α-C, and Ia-ε-PI-2a. No penicillin-resistant strains were detected, and 74.1%, 64.2%, and 68.9% were resistant to erythromycin, clindamycin, and tetracycline, respectively. The infective GBS isolates in China demonstrated epidemical features.

Group B streptococcal disease and genotypes in Australian infants

AIMS

Estimate the incidence, risk factors and clinical features of group B streptococcal (GBS) disease in Australian infants and compare bacterial genotypes between infant disease and maternal carriage.

METHODS

The Australian Paediatric Surveillance Unit conducted a study of invasive GBS disease in infants aged 0-90 days between July 2005 and June 2008. Clinical data were obtained by questionnaire. GBS isolates from affected infants and antenatal carriers were referred for genotyping.

RESULTS

One hundred fifty confirmed cases were reported: 88 early-onset (EOD; 0-6 days) and 62 late-onset disease (LOD). Based on review of selected laboratory records, they represented ∼1/3 of all cases. Estimated national EOD and LOD rates were 0.38 and 0.19/1000 live births, respectively. Admission to intensive care was common (44%), and 7% of infants died. One or more obstetric indications for intrapartum antibiotic prophylaxis (IAP) were identified in 51% of mothers; 53% of mothers were screened for GBS carriage, and screening was positive in 45%; only 25% of women with clinical or microbiological risk factors were given IAP (no significant differences between EOD and LOD groups). Distribution of GBS genotypes differed significantly between invasive and vaginal isolates: virulent serosubtype III-2/sequence type 17 was strongly associated with LOD but uncommon among EOD and vaginal isolates.

CONCLUSIONS

Estimated GBS disease rates remain relatively low despite poor predictive values of clinical and microbiological criteria for, and compliance with, IAP. Clinical and microbiological epidemiology of LOD differs significantly from that of EOD. Further reduction in infant morbidity and mortality from GBS disease will require new strategies.

Distribution of pilus islands and alpha-like protein genes of group B Streptococcus colonized in pregnant women in Beijing, China

Group B Streptococcus (GBS) is one of the major pathogens of severe newborn sepsis and meningitis. Understanding its regional molecular epidemiology is helpful for regulating efficient prevention practice. A total of 160 GBS strains were collected from colonized pregnant women in six hospital settings in Beijing, China. Polymerase chain reaction (PCR) assays were used to identify the pilus island (PI), alp genes profiling of the alpha-like protein family, and capsular polysaccharide (cps) serotyping. The clonal relationships between strains were investigated using multilocus sequence typing (MLST). All isolates carried at least one pilus island. The most frequently detected pilus island was PI-2a alone (70 isolates, 43.8 %). The most prevalent alp gene was rib (60 isolates, 37.5 %). Moreover, a strong association was noted between alp genes, serotyping, and pilus island profiles. The GBS isolates under study hinted similar molecular epidemical characteristics in Beijing to those reported worldwide, but having their regional distributional features.

Molecular characterization of Streptococcus agalactiae isolated from bovine mastitis in Eastern China

One hundred and two Streptococcus agalactiae (group B streptococcus [GBS]) isolates were collected from dairy cattle with subclinical mastitis in Eastern China during 2011. Clonal groups were established by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE), respectively. Capsular polysaccharides (CPS), pilus and alpha-like-protein (Alp) family genes were also characterized by molecular techniques. MLST analysis revealed that these isolates were limited to three clonal groups and were clustered in six different lineages, i.e. ST (sequence type) 103, ST568, ST67, ST301, ST313 and ST570, of which ST568 and ST570 were new genotypes. PFGE analysis revealed this isolates were clustered in 27 PFGE types, of which, types 7, 8, 14, 15, 16, 18, 23 and 25 were the eight major types, comprising close to 70% (71/102) of all the isolates. The most prevalent sequence types were ST103 (58% isolates) and ST568 (31% isolates), comprising capsular genotype Ia isolates without any of the detected Alp genes, suggesting the appearance of novel genomic backgrounds of prevalent strains of bovine S. agalactiae. All the strains possessed the pilus island 2b (PI-2b) gene and the prevalent capsular genotypes were types Ia (89% isolates) and II (11% isolates), the conserved pilus type providing suitable data for the development of vaccines against mastitis caused by S. agalactiae.

Immunization of newborns with bacterial conjugate vaccines

Bacterial conjugate vaccines are based on the principle of coupling immunogenic bacterial capsular polysaccharides to a carrier protein to facilitate the induction of memory T-cell responses. Following the success of Haemophilus influenzae type b conjugate vaccines in the 1980s, conjugate vaccines for Streptococcus pneumoniae and Neisseria meningitidis infections were developed and proven to be effective in protecting children against invasive disease. In this review, the use of conjugate vaccines in human newborns is discussed. Neonatal Haemophilus influenzae type b and pneumococcal conjugate vaccination schedules have been trialed and proven to be safe, with the majority of studies demonstrating no evidence for the induction of immune tolerance. Whether their neonatal administration also results in an earlier induction of clinical protection in the first 2-3 critical months of life is still to be demonstrated.

Phenotypes, genotypes, serotypes and molecular epidemiology of erythromycin-resistant Streptococcus agalactiae in Italy

The purpose of this investigation was to analyse Streptococcus agalactiae (group B Streptococcus, GBS) isolates collected in Italy from vaginal and urine samples in respect to their clonality, distribution of virulence factors and antimicrobial resistance determinants. Three hundred and eighty-eight GBS were recovered from clinical samples. They were analysed for antibiotic resistance profiling. Erythromycin-resistant strains were further characterised by multilocus sequence typing (MLST), serotyping and the detection of alp genes of the alpha-like protein (Alp) family. GBS isolates represented 40 different sequence types (STs), grouped in five clonal complexes (CCs) and belonged to seven serotypes. Most serotype V strains (81%) possessed alp2-3; serotype Ia carried mainly epsilon, while the serotype III mainly rib. All isolates were susceptible to penicillin, whereas resistance to erythromycin was detected in 15% of isolates. Most erythromycin-resistant GBS strains were of serotype V (56.8%) and belonged to the CC-1 group (50%). Macrolide resistance phenotypes were the cMLS(B) (46.5%) and the M phenotypes (46.5%) due to the presence of ermB and mefA/E genes, respectively. These results provide data which establish a baseline for monitoring erythromycin resistance in this region and also provide an insight into the correlation among clonal types, serotypes, surface protein and resistance genes. The increased prevalence of strains that displayed the M phenotype strengthens the importance of the epidemiological surveillance of macrolide resistance in GBS, which may also represent an important reservoir of resistance genes for other species.

Population structure, virulence factors and resistance determinants of invasive, non-invasive and colonizing Streptococcus agalactiae in Poland

OBJECTIVES

To analyse Streptococcus agalactiae (group B Streptococcus; GBS) isolates collected in Poland from various human infections and carriage in respect of their clonality, distribution of virulence factors and antimicrobial resistance determinants, including the detection of transposons involved in the dissemination of antimicrobial resistance.

METHODS

One hundred and fourteen GBS isolates were analysed by multilocus sequence typing (MLST), serotyping and detection of alp genes of the alpha-like-protein (Alp) family. Determinants of resistance to macrolides and tetracycline, and associated transposons, were detected by PCR and analysed by sequencing.

RESULTS

GBS isolates represented 30 different sequence types (STs), grouped in four clonal complexes (CCs), and belonged to seven serotypes. Serotype III was predominant (36.0%), followed by Ia, V, Ib, II, IV and VI. The most common alp genes were rib (26.3%) and alp1/alp5 (23.7%). The bac gene encoding the beta-compound of the surface C-protein was present in 17.5% of isolates. Erythromycin resistance (18.4% of isolates) was found in all CCs, but was associated with serotype V and ST1. The most prevalent determinant of resistance was erm(B), usually located on the Tn3872-like transposon. Several changes were observed in the regulatory region of erm(B), some of them resulting in elevated ketolide MICs. Resistance to tetracycline was ubiquitous (91.2%) and its most common determinant was tet(M), occurring in several variants that were typically carried on Tn916-family transposons.

CONCLUSIONS

Analysis of bacterial serotypes, alp genes and antimicrobial resistance determinants in the background of MLST-based population structure strengthened evidence of the importance of horizontal gene transfer in GBS evolution.

Perinatal infection with Group B streptococci

Group B streptococcus (GBS) is a major cause of severe bacterial infection in newborns. Early neonatal GBS infection can be prevented by identifying high-risk pregnancies and administering intrapartum antibiotics. In the USA, a screening strategy has been introduced resulting in a reduction in early-onset GBS infection, but no decrease in late-onset neonatal GBS disease has been noted. In many European countries, a risk-based strategy is recommended. Vaccination may, in the future, be an alternative in preventing GBS infection in newborns.

Group B Streptococcus carriers among HIV-1 infected pregnant women: Prevalence and risk factors

OBJECTIVE

The objective was to determine the frequency and risk factors of anogenital colonization by Streptococcus agalactiae (GBS) in pregnant women infected with human immunodeficiency virus type 1 (HIV-1).

STUDY DESIGN

A prospective study was conducted on 207 pregnant women divided into two groups: HIV group (n=101) and a control group consisting of HIV-uninfected pregnant women (n=106) to assess regional colonization by GBS. Anal and vaginal swabs were collected and cultured in Todd-Hewitt broth, followed by a confirmatory test. For a control group with an anticipated proportion based on literature research of 10-30% and alpha=0.05, a sample size of 100 would have a power of 80% to detect a difference of 15% or greater with a study group. The mothers were studied in terms of frequency of anogenital colonization by GBS, maternal epidemiological data, and TCD4 lymphocyte counts. The results were analyzed using the chi(2)-test, Fisher's exact test and the Student's t-test, with the level of significance set at p<0.05.

RESULTS

Twenty (19.8%) HIV-1-infected pregnant women were found to be colonized by GBS at between 35 and 37 weeks' gestation. In the control group, the prevalence of GBS was 14.1%.

CONCLUSION

No significant increase in GBS colonization was observed in HIV-1-infected pregnant women. Maternal colonization of GBS in HIV-infected pregnant women was not found to be associated with their immunological status. Sexual contact does not seem to be the principal way of transmitting GBS.