Genotypic diversity and serotype distribution of group B streptococcus isolated from women before and after delivery

Intrinsic Maturational Neonatal Immune Deficiencies and Susceptibility to Group B Streptococcus Infection

Although a normal member of the gastrointestinal and vaginal microbiota, group B Streptococcus (GBS) can also occasionally be the cause of highly invasive neonatal disease and is an emerging pathogen in both elderly and immunocompromised adults. Neonatal GBS infections are typically transmitted from mother to baby either in utero or during passage through the birth canal and can lead to pneumonia, sepsis, and meningitis within the first few months of life. Compared to the adult immune system, the neonatal immune system has a number of deficiencies, making neonates more susceptible to infection. Recognition of GBS by the host immune system triggers an inflammatory response to clear the pathogen. However, GBS has developed several mechanisms to evade the host immune response. A comprehensive understanding of this interplay between GBS and the host immune system will aid in the development of new preventative measures and therapeutics.

CRISPR: A Useful Genetic Feature to Follow Vaginal Carriage of Group B Streptococcus

Clustered regularly interspaced short palindromic repeats (CRISPR) and Cas (CRISPR-associated proteins) play a critical role in adaptive immunity against mobile genetic elements, especially phages, through their ability to acquire novel spacer sequences. Polarized spacer acquisition results in spacer polymorphism and temporal organization of CRISPR loci, making them attractive epidemiological markers. Group B Streptococcus (GBS), a genital commensal for 10 to 30% of healthy women and a major neonatal pathogen, possesses a ubiquitous and functional CRISPR1 locus. Our aim was to assess the CRISPR1 locus as an epidemiological marker to follow vaginal carriage of GBS in women. This study also allowed us to observe the evolution of the CRISPR1 locus in response to probable phage infection occurring in vivo. We followed carriage of GBS among 100 women over an 11-year period, with a median duration of approximately 2 years. The CRISPR1 locus was highly conserved over time. The isolates that show the same CRISPR1 genotype were collected from 83% of women. There was an agreement between CRISPR genotyping and other typing methods [MLVA (multilocus variable number of tandem repeat Analysis) and MLST (multilocus sequence typing)] for 94% of the cases. The CRISPR1 locus of the isolates from 18 women showed modifications, four of which acquired polarized spacer, highlighting the in vivo functionality of the system. The novel spacer of one isolate had sequence similarity with phage, suggesting that phage infection occurred during carriage. These findings improve our understanding of CRISPR-Cas evolution in GBS and provide a glimpse of host-phage dynamics in vivo.

Genotype Characterization of Group B Streptococcus Isolated From Infants With Invasive Diseases in South Korea

BACKGROUND

Group B streptococcus (GBS) is one of the leading causes of invasive infections in infants. This study aimed to investigate the genotypic diversity of GBS causing invasive infections in infants and to observe the prevalence of the highly virulent clone in South Korea.

METHODS

Invasive strains of GBS were collected prospectively from infants admitted at 4 hospitals during 1995-2015. Serotype and multilocus sequence typing were determined. All isolates underwent polymerase chain reaction amplification to detect the presence of the hypervirulent GBS adhesin (hvgA) gene. Antibiotic susceptibility testing was done by E-test, and erythromycin resistance genes were detected using polymerase chain reaction amplification.

RESULTS

Among 98 GBS isolates collected, 14 sequence types (STs) were found; ST1 (20.4%), ST17 (19.4%) and ST19 (18.4%) were the most prevalent. The dominant serotype capsule expressed by ST1 was serotype V, ST17 and ST19 were all serotype III and ST23 was serotype Ia. hvgA gene was detected in 19.4% (n = 19) of the isolates; all were ST17, serotype III. A significant temporal trend of serotype III isolates was observed; as ST17 increased (P = 0.001) in proportion, ST19 decreased (P = 0.009). Erythromycin resistance was found in 42.9% (42/98); dominant strains were ermB-positive ST1 serotype V (n = 18/20, 90%), ermB-positive ST17 serotype III (n = 10/19, 52.6%) and ermA-positive ST335 serotype III (n = 7/7, 100%).

CONCLUSIONS

The predominant STs causing invasive infections in South Korea were ST1, ST19 and ST17. Among serotype III isolates, an increase in proportion of the hypervirulent ST17 strains was observed. Erythromycin resistance was significantly associated with ST1.

Group B streptococcal colonization and transmission dynamics in pregnant women and their newborns in Nigeria: implications for prevention strategies

OBJECTIVES

Because few studies have been conducted on group B Streptococcus (GBS) in Nigeria, we sought to estimate GBS colonization and transmission frequencies for 500 women and their newborns and identify risk factors for both outcomes.

METHODS

GBS strains were characterized for antibiotic susceptibilities, capsule (cps) genotype, pilus island profile and multilocus sequence type (ST).

RESULTS

In all, 171 (34.2%) mothers and 95 (19.0%) of their newborns were colonized with GBS; the vertical transmission rate was 48.5%. One newborn developed early-onset disease, yielding an incidence of 2.0 cases per 1000 live births (95% CI 0.50-7.30). Rectal maternal colonization (OR 26.6; 95% CI 13.69-51.58) and prolonged rupture of membranes (OR 4.2; 95% CI 1.03-17.17) were associated with neonatal colonization, whereas prolonged membrane rupture (OR 3.4; 95% CI 1.04-11.39) and young maternal age (OR 2.0; 95% CI 1.22-3.39) were associated with maternal colonization. Women reporting four or more intrapartum vaginal examinations (OR 6.1; 95% CI 3.41-10.93) and douching (OR 3.7; 95% CI 2.26-6.11) were also more likely to be colonized. Twelve STs were identified among 35 mother-baby pairs with evidence of transmission; strains of cpsV ST-19 (n = 9; 25.7%) and cpsIII ST-182 (n = 7; 20.0%) predominated.

CONCLUSIONS

These data demonstrate high rates of colonization and transmission in a population that does not use antibiotics to prevent neonatal infections, a strategy that should be considered in the future.

Neonatal Group B Streptococcus Infections: Prevention Strategies, Clinical and Microbiologic Characteristics in 7 Years of Surveillance

BACKGROUND

The characteristics of group B streptococcus (GBS) neonatal disease in a period of 7 years are reported.

METHODS

The estimation of the neonatal GBS disease risk and prevention strategies adopted at delivery in absence of national guidelines was evaluated by the analysis of 3501 questionnaires. Notification of 194 neonatal GBS infections was recorded. In addition, 115 strains from neonatal early-onset disease (EOD) and late-onset disease, respectively, plus 320 strains from pregnant women were analyzed by molecular typing methods and for antibiotic resistance.

RESULTS

Preterm deliveries, precipitous labor and GBS negatively screened mothers were the prominent causes for an inadequate or lack of intrapartum antibiotic prophylaxis and EOD occurrence. The superimposable serotype distribution of GBS strains from EOD and from antenatal screening confirmed the vertical transmission from mother to neonate as the cause of disease. On the contrary, late-onset disease was almost exclusively caused by the internationally diffused clonal complex 17. Erythromycin resistance was detected in 17% of strains. Resistance to clindamycin was 15.3 %.

CONCLUSIONS

The administration of intrapartum antibiotic prophylaxis to negatively GBS screened women in presence of risk factors was a deviation from the recommendations issued by the Centers for Disease Control and Prevention, and it should deserve further consideration. Routine surveillance and molecular typing of circulating clones are essential for the effective management of the neonatal GBS disease.

Risk factors for group B streptococcal disease in neonates of mothers with negative antenatal testing

OBJECTIVE

The aim of this study was to identify risk factors for early-onset group B Streptococcus (EOGBS) disease in neonates of mothers with negative antenatal screening.

STUDY DESIGN

We performed a retrospective cohort study of neonates born to mothers with negative antenatal GBS screening between 2002 and 2012. Our primary outcome was EOGBS infection. We used multivariable logistic regression to assess factors associated with EOGBS.

RESULTS

EOGBS was confirmed in 492 of the 179 818 neonates that met the study inclusion criteria. Risk factors for EOGBS included black race (reference: white, odds ratio (OR) =1.81 (95% confidence interval: 1.43, 2.31)), maternal age <18 years (reference: >35 years, OR=2.63 (1.54, 4.51)) and maternal age 18 to 35 years (reference: >35 years, OR=1.94 (1.30, 2.88)).

CONCLUSION

Maternal age <18 years and black race were the strongest predictors of EOGBS. Further research investigating contributors to the discordance between screening results and neonatal outcomes in these populations is needed.

A Murine Model of Group B Streptococcus Vaginal Colonization

Streptococcus agalactiae (group B Streptococcus, GBS), is a Gram-positive, asymptomatic colonizer of the human gastrointestinal tract and vaginal tract of 10 - 30% of adults. In immune-compromised individuals, including neonates, pregnant women, and the elderly, GBS may switch to an invasive pathogen causing sepsis, arthritis, pneumonia, and meningitis. Because GBS is a leading bacterial pathogen of neonates, current prophylaxis is comprised of late gestation screening for GBS vaginal colonization and subsequent peripartum antibiotic treatment of GBS-positive mothers. Heavy GBS vaginal burden is a risk factor for both neonatal disease and colonization. Unfortunately, little is known about the host and bacterial factors that promote or permit GBS vaginal colonization. This protocol describes a technique for establishing persistent GBS vaginal colonization using a single β-estradiol pre-treatment and daily sampling to determine bacterial load. It further details methods to administer additional therapies or reagents of interest and to collect vaginal lavage fluid and reproductive tract tissues. This mouse model will further the understanding of the GBS-host interaction within the vaginal environment, which will lead to potential therapeutic targets to control maternal vaginal colonization during pregnancy and to prevent transmission to the vulnerable newborn. It will also be of interest to increase our understanding of general bacterial-host interactions in the female vaginal tract.

Differing mechanisms of surviving phagosomal stress among group B Streptococcus strains of varying genotypes

Group B Streptococcus (GBS), a leading cause of neonatal sepsis and meningitis, asymptomatically colonizes up to 30% of women and can persistently colonize even after antibiotic treatment. Previous studies have shown that GBS resides inside macrophages, but the mechanism by which it survives remains unknown. Here, we examined the ability of 4 GBS strains to survive inside macrophages and then focused on 2 strains belonging to sequence type (ST)-17 and ST-12, to examine persistence in the presence of antibiotics. A multiple stress medium was also developed using several stressors found in the phagosome to assess the ability of 30 GBS strains to withstand phagosomal stress. The ST-17 strain was more readily phagocytosed and survived intracellularly longer than the ST-12 strain, but the ST-12 strain was tolerant to ampicillin unlike the ST-17 strain. Exposure to sub-inhibitory concentrations of ampicillin and erythromycin increased the level of phagocytosis of the ST-17 strain, but had no effect on the ST-12 strain. In addition, blocking acidification of the phagosome decreased the survival of the ST-17 strain indicating a pH-dependent survival mechanism for the ST-17 strain. Congruent with the macrophage experiments, the ST-17 strain had a higher survival rate in the multiple stress medium than the ST-12 strain, and overall, serotype III isolates survived significantly better than other serotypes. These results indicate that diverse GBS strains may use differing mechanisms to persist and that serotype III strains are better able to survive specific stressors inside the phagosome relative to other serotypes.

Association between genotypic diversity and biofilm production in group B Streptococcus

BACKGROUND

Group B Streptococcus (GBS) is a leading cause of sepsis and meningitis and an important factor in premature and stillbirths. Biofilm production has been suggested to be important for GBS pathogenesis alongside many other elements, including phylogenetic lineage and virulence factors, such as pili and capsule type. A complete understanding of the confluence of these components, however, is lacking. To identify associations between biofilm phenotype, pilus profile and lineage, 293 strains from asymptomatic carriers, invasive disease cases, and bovine mastitis cases, were assessed for biofilm production using an in vitro assay.

RESULTS

Multilocus sequence type (ST) profile, pilus island profile, and isolate source were associated with biofilm production. Strains from invasive disease cases and/or belonging to the ST-17 and ST-19 lineages were significantly more likely to form weak biofilms, whereas strains producing strong biofilms were recovered more frequently from individuals with asymptomatic colonization.

CONCLUSIONS

These data suggest that biofilm production is a lineage-specific trait in GBS and may promote colonization of strains representing lineages other than STs 17 and 19. The findings herein also demonstrate that biofilms must be considered in the treatment of pregnant women, particularly for women with heavy GBS colonization.

Epidemiology of Invasive Group B Streptococcal Disease in Alberta, Canada, from 2003 to 2013

Group B streptococci (GBS) cause severe invasive disease in both neonates and adults. Understanding the epidemiology of GBS provides information that can include determining disease prevalence rates in defined populations and geographic regions, documenting the success of GBS screening programs, and understanding antimicrobial susceptibility patterns. In Alberta, only neonatal invasive GBS (iGBS) disease is notifiable to health authorities. We performed a surveillance study of iGBS in Alberta, Canada, from 2003 to 2013. Over the 11-year period, the disease incidence rate increased from a low of 3.92 cases/100,000 population to a high of 5.99 cases/100,000 population. The capsular polysaccharide serotypes (CPSs) found were CPS III (20.3%), CPS V (19.1%), CPS Ia (18.9%), CPS Ib (12.7%), CPS II (11.1%), CPS IV (6.3%), and nontypeable GBS (9.4%). Rates of early-onset disease (0 to 7 days) increased from 0.15 cases/1,000 live births (in 2003) to 0.34 cases/1,000 live births (in 2013). Rates of late-onset disease (>7 to 90 days) also rose, from 0.15 cases/1,000 live births (in 2003) to 0.39 cases/1,000 live births (in 2013). Alberta also experienced an increase in CPS IV isolates, from 2 cases (in 2003) to 24 cases (in 2013), of which the majority were hvgA negative (93.4%) [corrected]. The predominant sequence type (ST) in 2013 was ST459. Erythromycin resistance rose from 23.6% to 43.9% (in 2013). Clindamycin resistance also increased, from 12.2% to 32.5%. In summary, Alberta, Canada, has experienced an increase in GBS disease; the increase includes both neonatal and adult disease. CPS IV cases also notably increased during the surveillance period, as did resistance to erythromycin and clindamycin.

Estimating the burden of invasive Group B Streptococcal disease in young infants in southern mainland China: an observational study

OBJECTIVES

To estimate the incidence, case fatality ratio and serotypes associated with early-onset (EOD) and late-onset (LOD) invasive GBS disease in infants in southern mainland China.

METHODS

During the six-month study period, infants aged ≤ 90 days with culture-confirmed GBS disease born in the study hospitals or elsewhere, but presenting to a study hospital, were enrolled. GBS-positive cultures were genotyped, serotyped and sequence typed. The incidence rate was calculated for infants born in the study hospitals, and case fatality ratio and causative serotypes identified for all enrolled GBS cases.

RESULTS

Ten cases were enrolled: 2 EOD cases born in the study hospitals and 8 LOD cases born elsewhere. Incidence rate was 0.28 (95% confidence interval: 0.08-1.03, n = 2/7061 successfully followed-up consenting subjects); no cases resulted in fatality. In the 8 GBS isolates available for typing, 4 serotypes (Ia, Ib, III and V) and 5 multi-locus sequence types (1, 10, 12, 17 and 23) were identified.

CONCLUSIONS

This is the first study specifically investigating the incidence of GBS invasive disease in infants in southern mainland China. Incidence and case fatality were low but further research is needed in larger, more diverse cohorts to estimate disease burden for the broader Chinese population.

Serotypes, antibiotic susceptibilities, and multi-locus sequence type profiles of Streptococcus agalactiae isolates circulating in Beijing, China

BACKGROUND

To investigate the serotypes, antibiotic susceptibilities, and multi-locus sequence type (MLST) profiles of Streptococcus agalactiae (S. agalactiae) in Beijing to provide references for the prevention and treatment of S. agalactiae infections.

METHODS

All isolates were identified using the CAMP test and the latex-agglutination assay and serotyped using a Strep-B-Latex kit, after which they were assessed for antibiotic susceptibility, macrolide-resistance genes, and MLST profiles.

RESULTS

In total, 56 S. agalactiae isolates were identified in 863 pregnant women (6.5%). Serotypes Ia, Ib, II, III, and V were identified, among which types III (32.1%), Ia (17.9%), Ib (16.1%), and V (14.3%) were the predominant serotypes. All isolates were susceptible to penicillin and ceftriaxone. The nonsusceptiblity rates measured for erythromycin, clarithromycin, azithromycin, telithromycin, clindamycin, tetracycline, and levofloxacin were 85.7%, 92.9%, 98.2%, 30.4%, 73.2%, 91%, and 39.3%, respectively. We identified 14 sequence types (STs) for the 56 isolates, among which ST19 (30.4%) was predominant. The rate of fluoroquinolone resistance was higher in serotype III than in the other serotypes. Among the 44 erythromycin-resistant isolates, 32 (72.7%) carried ermB.

CONCLUSION

S. agalactiae isolates of the serotypes Ia, Ib, III, and V are common in Beijing. Among the S. agalactiae isolates, the macrolide and clindamycin resistance rates are extremely high. Most of the erythromycin-resistant isolates carry ermB.

Serotype-specific acquisition and loss of group B streptococcus recto-vaginal colonization in late pregnancy

Background

Maternal recto-vaginal colonization with Group B Streptococcus (GBS) and consequent vertical transmission to the newborn predisposes neonates to early-onset invasive GBS disease. This study aimed to determine the acquisition and loss of serotype-specific recto-vaginal GBS colonization from 20–37+ weeks of gestational age.

Methods

Vaginal and rectal swabs were collected from HIV-uninfected women at 20–25 weeks of gestation age and at 5–6 weekly intervals thereafter. Swabs were cultured for GBS and isolates were serotyped by latex agglutination. Serologically non-typable isolates and pilus islands were characterized by PCR.

Results

The prevalence of recto-vaginal GBS colonization was 33.0%, 32.7%, 28.7% and 28.4% at 20–25 weeks, 26–30 weeks, 31–35 weeks and 37+ weeks of gestational age, respectively. The most common identified serotypes were Ia (39.2%), III (32.8%) and V (12.4%). Of 507 participants who completed all four study visits, the cumulative overall recto-vaginal acquisition rate of new serotypes during the study was 27.9%, including 11.2%, 8.2% and 4.3% for serotypes Ia, III and V, respectively. Comparing the common colonizing serotypes, serotype III was more likely to be associated with persistent colonization throughout the study (29%) than Ia (18%; p = 0.045) or V (6%; p = 0.002). The median duration of recto-vaginal GBS colonization for serotype III was 6.35 weeks, which was longer than other serotypes. Pilus island proteins were detected in all GBS isolates and their subtype distribution was associated with specific serotypes.

Conclusion

South African pregnant women have a high prevalence of GBS recto-vaginal colonization from 20 weeks of gestational age onwards, including high GBS acquisition rates in the last pregnancy-trimesters. There are differences in specific-serotype colonization patterns during pregnancy.

[Maternal and perinatal infections to Streptococcus agalactiae]

Streptococcus agalactiae (Group B Streptococcus, GBS) is a Gram-positive encapsulated bacterium, found in the digestive and vaginal tracts of 20-30% healthy individuals. It is the leading cause of neonatal invasive infections (septicaemia and meningitis). Two GBS-associated syndromes have been recognized in neonates, the early-onset disease (EOD) and the late-onset disease (LOD), which occur in the first week of life (age 0-6 days) and after (age 7 days-3 months), respectively. Since the establishment of early antibiotic prophylaxis there has been a decrease in the incidence of EOD. However, LOD incidence remains stable. Epidemiological studies revealed a strong association between LOD and a single capsular serotype III ST-17 clone. This ST-17 clone, referred to as the "hypervirulent" clone, possesses specific virulence factors that could account for its increased virulence and neonatal tropism. Conjugate vaccines directed against several capsular serotypes are being developed to prevent invasive disease. However, hypervirulent strains having made a switch to a capsular serotype not covered by such vaccines are emerging, reinforcing the need to identify new candidate vaccines.

High prevalence of fluoroquinolone-resistant group B streptococci among clinical isolates in China and predominance of sequence type 19 with serotype III

A total of 146 group B streptococcus isolates from 8 cities across China belonged to four serotypes. Serotype Ia was more common in children. A high prevalence of resistance was observed for levofloxacin (37.7%), erythromycin (71.2%), clindamycin, (53.4%), and tetracycline (81.5%). The levofloxacin and clindamycin resistances among the 4 serotypes differed significantly. Eighty percent of fluoroquinolone-resistant isolates belonged to the sequence type 19 (ST19)/serotype III clone, with GyrA-ParC-ParE triple substitutions. This clone carried the erm(B), mef(E), and tet(M) genes.

Whole-genome shotgun sequencing of a colonizing multilocus sequence type 17 Streptococcus agalactiae strain

This report highlights the whole-genome shotgun draft sequence for a Streptococcus agalactiae strain representing multilocus sequence type (ST) 17, isolated from a colonized woman at 8 weeks postpartum. This sequence represents an important addition to the published genomes and will promote comparative genomic studies of S. agalactiae recovered from diverse sources.

The impact of pH and nutrient stress on the growth and survival of Streptococcus agalactiae

Streptococcus agalactiae is a major neonatal pathogen that is able to colonise various host environments and is associated with both gastrointestinal and vaginal maternal carriage. Maternal vaginal carriage represents the major source for transmission of S. agalactiae to the foetus/neonate and thus is a significant risk factor for neonatal disease. In order to understand factors influencing maternal carriage we have investigated growth and long term survival of S. agalactiae under conditions of low pH and nutrient stress in vitro. Surprisingly, given that vaginal pH is normally <4.5, S. agalactiae was found to survive poorly at low pH and failed to grow at pH 4.3. However, biofilm growth, although also reduced at low pH, was shown to enhance survival of S. agalactiae. Proteomic analysis identified 26 proteins that were more abundant under nutrient stress conditions (extended stationary phase), including a RelE family protein, a universal stress protein family member and four proteins that belong to the Gls24 (PF03780) stress protein family. Cumulatively, these data indicate that novel mechanisms are likely to operate that allow S. agalactiae survival at low pH and under nutrient stress during maternal vaginal colonisation and/or that the bacteria may access a more favourable microenvironment at the vaginal mucosa. As current in vitro models for S. agalactiae growth appear unsatisfactory, novel methods need to be developed to study streptococcal colonisation under physiologically-relevant conditions.

The application of multiplex PCR to detect seven different DNA targets in group B streptococci

Group B Streptococcus (GBS) causes severe infections in infants and in immunocompromised adults. GBS pathogenicity varies between and within serotypes, with considerable variation in genetic content between strains. For this reason, it is important to be able to carry out immediate and comprehensive diagnostics of these infections. Seven genes important for screening of GBS infection were detected: cfb gene encoding the CAMP factor presented in every GBS; the cps operon genes such as cps1aH, cps1a/2/3IJ, and cps5O specific for capsular polysaccharide types Ia, III, and V, respectively; macrolide resistance genes ermB and mefA/E; and the gbs2018 S10 region specific for ST17 hypervirulent clone. Standardization of multiplex PCR with the use of seven primer pairs was performed on 81 bacterial strains representing different GBS isolates (n = 75) and other Gram-positive cocci (n = 10). Multiplex PCR can be used as an effective screening method to detect different sequences important for the screening of GBS infection.

Genetic differences between invasive and noninvasive neonatal group B streptococcal isolates

BACKGROUND

Streptococcus agalactiae, also known as group B streptococcus (GBS), is the most common cause of neonatal sepsis and meningitis. To improve our understanding of the pathogenesis of neonatal GBS sepsis, better knowledge of clonal relatedness and diversity among invasive and noninvasive GBS isolates is critical.

METHODS

In a Germany-based study, invasive neonatal GBS isolates were compared with noninvasive isolates from neonates in whom sepsis was suspected, but whose blood cultures were sterile. The comparison was conducted by means of pulsed-field gel electrophoresis and surface protein gene profiling. In addition, multilocus sequence typing was performed on invasive and noninvasive isolates of the most frequent invasive serotype III.

RESULTS

Pulsed-field gel electrophoresis analysis of noninvasive GBS showed a remarkably more diverse fingerprinting pattern than that of invasive isolates. In contrast to invasive strains, noninvasive isolates did not show any clustering. Surface protein gene profiling also showed significantly different distribution patterns between the 2 panels of isolates. Multilocus sequence typing of invasive and noninvasive serotype III isolates revealed the same clonal complexes, but displayed different sequence types (ST); ST-17 was most common (68.6%) among invasive strains, whereas ST-389 (clonal complex-19) was predominant among noninvasive strains (47.8%).

CONCLUSIONS

Our results illustrate a large molecular diversity among neonatal noninvasive GBS strains. Invasive strains, however, represent only a small proportion of the noninvasive GBS population. These findings suggest a selection process that prefers more virulent strains during invasion.

Outbreak of late-onset group B Streptococcus in a neonatal intensive care unit

BACKGROUND

In September 2007, the Tennessee Department of Health was notified of a cluster of late-onset group B streptococcal (GBS) infections in a neonatal intensive care unit (NICU). Outbreaks of late-onset GBS are rare.

METHODS

A case was defined as culture-confirmed invasive GBS infection in a neonate aged > or =7 days, identified in hospital A during August 23 to September 6, 2007. We reviewed medical records; examined NICU microbiology reports; and performed serotyping, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) on invasive isolates. Maternal GBS screening, prophylaxis, and infection control policies were reviewed and staff practices observed.

RESULTS

Five cases of late-onset GBS were identified. None of the mothers of the infants received optimal GBS prophylaxis. Patient isolates were of 2 serotypes, 3 PFGE patterns, and 2 MLST patterns. Three isolates were indistinguishable on subtyping. These 3 cases were clustered in time. No common health care providers were identified. Infection control deviations in the NICU were observed.

CONCLUSION

We identified a multiclonal cluster of 5 late-onset GBS cases. Multiple factors likely contributed to the outbreak, including nosocomial transmission of GBS. Further efforts to prevent late-onset GBS disease are necessary.

Association of Group B Streptococcus colonization and bovine exposure: a prospective cross-sectional cohort study

BACKGROUND

While Group B Streptococcus (GBS) human colonization and infection has long been suspected as originating from cows, several investigators have suggested that ongoing interspecies GBS transmission is unlikely due to genotyping data demonstrating that human and bovine-derived GBS strains represent mostly distinct populations. The possibility of ongoing transmission between humans and their livestock has not been systematically examined.

METHODOLOGY/PRINCIPAL FINDINGS

To examine ongoing interspecies transmission, we conducted a prospective cross-sectional cohort study of 68 families and their livestock. Stool specimens were collected from 154 people and 115 livestock; GBS was detected in 19 (12.3%) humans and 2 (1.7%) animals (bovine and sheep). Application of multilocus sequence typing (MLST) identified 8 sequence types (STs or clones), with STs 1 and 23 predominating. There were 11 families in which two members submitted stools and at least one had GBS colonization. In 3 of these families, both members (consisting of couples) were colonized, yielding a co-colonization rate of 27% (95% CI: 7%-61%). Two of these couples had strains with identical MLST, capsule (cps) genotype, susceptibility, and RAPD profiles. One couple co-colonized with ST-1 (cps5) strains also had a bovine colonized with the identical strain type. On multivariate analysis of questionnaire data, cattle exposure was a predictor of GBS colonization, with each unit increase in days of cattle exposure increasing the odds of colonization by 20% (P = 0.02). These results support interspecies transmission with additional evidence for transmission provided by the epidemiological association with cattle exposure.

CONCLUSIONS/SIGNIFICANCE

Although GBS uncommonly colonizes livestock stools, increased frequency of cattle exposure was significantly associated with human colonization and one couple shared the same GBS strains as their bovine suggesting intraspecies transmission. These results set the framework for GBS as a possible zoonotic infection, which has significant public health implications.

Evidence for rare capsular switching in Streptococcus agalactiae

The polysaccharide capsule is a major antigenic factor in Streptococcus agalactiae (Lancefield group B streptococcus [GBS]). Previous observations suggest that exchange of capsular loci is likely to occur rather frequently in GBS, even though GBS is not known to be naturally transformable. We sought to identify and characterize putative capsular switching events, by means of a combination of phenotypic and genotypic methods, including pulsed-field gel electrophoretic profiling, multilocus sequence typing, and surface protein and pilus gene profiling. We show that capsular switching by horizontal gene transfer is not as frequent as previously suggested. Serotyping errors may be the main reason behind the overestimation of capsule switching, since phenotypic techniques are prone to errors of interpretation. The identified putative capsular transformants involved the acquisition of the entire capsular locus and were not restricted to the serotype-specific central genes, the previously suggested main mechanism underlying capsular switching. Our data, while questioning the frequency of capsular switching, provide clear evidence for in vivo capsular transformation in S. agalactiae, which may be of critical importance in planning future vaccination strategies against this pathogen.

A multiplex PCR assay for the direct identification of the capsular type (Ia to IX) of Streptococcus agalactiae

A multiplex PCR assay for the identification of serotypes Ia to IX of Streptococcus agalactiae was developed. By using a single PCR reaction containing a mix of 19 primers the assay identified each serotype by the analysis of the unique two or three bands pattern on agarose gel.

Selection, recombination, and virulence gene diversity among group B streptococcal genotypes

Transmission of group B Streptococcus (GBS) from mothers to neonates during childbirth is a leading cause of neonatal sepsis and meningitis. Although subtyping tools have identified specific GBS phylogenetic lineages that are important in neonatal disease, little is known about the genetic diversity of these lineages or the roles that recombination and selection play in the generation of emergent genotypes. Here, we examined genetic variation, selection, and recombination in seven multilocus sequence typing (MLST) loci from 94 invasive, colonizing, and bovine strains representing 38 GBS sequence types and performed DNA sequencing and PCR-based restriction fragment length polymorphism analysis of several putative virulence genes to identify gene content differences between genotypes. Despite the low level of diversity in the MLST loci, a neighbor net analysis revealed a variable range of genetic exchange among the seven clonal complexes (CCs) identified, suggesting that recombination is partly responsible for the diversity observed between genotypes. Recombination is also important for several virulence genes, as some gene alleles had evidence for lateral gene exchange across divergent genotypes. The CC-17 lineage, which is associated with neonatal disease, is relatively homogeneous and therefore appears to have diverged independently with an exclusive set of virulence characteristics. These data suggest that different GBS genetic backgrounds have distinct virulence gene profiles that may be important for disease pathogenesis. Such profiles could be used as markers for the rapid detection of strains with an increased propensity to cause neonatal disease and may be considered useful vaccine targets.

Multilocus sequence types associated with neonatal group B streptococcal sepsis and meningitis in Canada

Group B streptococci (GBS), a leading cause of neonatal sepsis and meningitis, are transferred to neonates from colonized mothers during childbirth. Prior studies using multilocus sequence typing (MLST) have found specific GBS clones (e.g., sequence type 17 [ST-17]) to be associated with neonatal disease in several geographic locations. Few population-based studies, however, have been conducted to determine the frequency of disease caused by specific GBS clones. MLST was used to assess the genetic diversity of 192 GBS strains from neonates and young children identified by population-based surveillance in Alberta, Canada, from 1993 to 2002. Comparisons were made to 232 GBS strains collected from colonized pregnant women, and all strains were characterized for one of nine capsule (cps) genotypes. A total of 47 STs were identified, and more than 80% of GBS strains were represented by 7 STs that have been shown to predominate in other populations. ST-17 and ST-19 were more prevalent in strains causing early onset disease (EOD) and late onset disease (LOD) than from pregnant women, whereas STs 1, 12, and 23 were more common in pregnant women. In addition, ST-17 strains and close relatives more frequently caused meningitis than sepsis and LOD versus EOD in this population of neonates. Further research is required to better understand why strains belonging to the ST-17 phylogenetic lineage are more likely to cause both LOD and meningitis and may provide clues into the pathogenesis of these conditions.