Invasive neonatal GBS infections from an area-based surveillance study in Italy

Emergence of High-Level Gentamicin Resistance in Streptococcus agalactiae Hypervirulent Serotype IV ST1010 (CC452) Strains by Acquisition of a Novel Integrative and Conjugative Element

Streptococcus agalactiae (group B streptococci, GBS) is responsible for severe infections in both neonates and adults. Currently, empiric antimicrobial therapy for sepsis and meningitis is the combined use of penicillin and gentamicin due to the enhanced bactericidal activity. However, high-level gentamicin resistance (HLGR) abrogates the synergism. The rate of HLGR was investigated within a dataset of 433 GBS strains collected from cases of invasive disease in both adults and neonates as well as from pregnant carriers. GBS isolates (n = 20, 4.6%) presented with HLGR (gentamicin MIC breakpoint >1024 mg/L) that was differently diffused between strains from adults or neonates (5.2% vs. 2.8%). Notably, 70% of HLGR GBS strains (14 isolates) were serotype IV. Serotype IV HLGR-GBS isolates were susceptible to all antibiotics tested, exhibited the alpha-C/HvgA/PI-2b virulence string, and belonged to sequence type 1010 (clonal complex (CC) 452). The mobile element that harbored the HLGR aac(6')-aph(2)″ gene is a novel integrative and conjugative element (ICE) about 45 kb long, derived from GBS 515 ICE tRNALys. The clonal expansion of this HLGR hypervirulent serotype IV GBS CC452 sublineage may pose a threat to the management of infections caused by this strain type.

Novel antimicrobial peptides identified in legume plant, Medicago truncatula

One of the major issues in healthcare today is antibiotic resistance. Antimicrobial peptides (AMPs), a subclass of host defense peptides, have been suggested as a viable solution for the multidrug resistance problem. Legume plants express more than 700 nodule-specific cysteine-rich (NCR) peptides. Three NCR peptides (NCR094, NCR888, and NCR992) were predicted to have antimicrobial activity using in silico AMP prediction programs. This study focused on investigating the roles of the NCRs in antimicrobial activity and antibiofilm activity, followed by in vitro toxicity profiling. Different variants were synthesized, i.e., mutated and truncated derivatives. The effect on the growth of Klebsiella pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA) was monitored post-treatment, and survived cells were counted using an in vitro and ex vivo killing assay. The antibiofilm assay was conducted using subinhibitory concentrations of the NCRs and monitoring K. pneumoniae biomass, followed by crystal violet staining. The cytotoxicity profile was evaluated using erythrocyte hemolysis and leukemia (K562) cell line toxicity assays. Out of the NCRs, NCR094 and NCR992 displayed mainly in vitro and ex vivo bactericidal activity on K. pneumoniae. NCR094 wild type (WT) and NCR992 eradicated K. pneumoniae at different potency; NCR094 and NCR992 killed K. pneumoniae completely at 25 and 50 µM, respectively. However, both peptides in the wild type showed negligible bactericidal effect on MRSA in vitro and ex vivo. NCR094 and its derivatives relatively retained the antimicrobial activity on K. pneumoniae in vitro and ex vivo. NCR992 WT lost its antimicrobial activity on K. pneumoniae ex vivo, yet the different truncated and mutated variants retained some of the antimicrobial role ex vivo. All the different variants of NCR094 had no effect on MRSA in vitro and ex vivo. Similarly, NCR992's variants had a negligible bactericidal role on MRSA in vitro, yet the truncated variants had a significantly high bactericidal effect on MRSA ex vivo. NCR094.3 (cystine replacement variant) and NCR992.1 displayed significant antibiofilm activity more than 90%. NCR992.3 and NCR992.2 displayed more than 50% of antibiofilm activity. All the NCR094 forms had no toxicity, except NCR094.1 (49.38%, SD ± 3.46) and all NCR992 forms (63%-93%), which were above the cutoff (20%). Only NCR992.2 showed low toxicity on K562 (24.8%, SD ± 3.40), yet above the 20% cutoff. This study provided preliminary antimicrobial and safety data for the potential use of these peptides for therapeutical applications.IMPORTANCEThe discovery of new antibiotics is urgently needed, given the global expansion of antibiotic-resistant bacteria and the rising mortality rate. One of the initial lines of defense against microbial infections is antimicrobial peptides (AMPs). Plants can express hundreds of such AMPs as defensins and defensin-like peptides. The nodule-specific cysteine-rich (NCR) peptides are a class of defensin-like peptides that have evolved in rhizobial-legume symbioses. This study screened the antimicrobial activity of a subset of NCR sequences using online computational AMP prediction algorithms. Two novel NCRs, NCR094 and NCR992, with different variants were identified to exhibit antimicrobial activity with various potency on two problematic pathogens, K. pneumoniae and MRSA, using in vitro and ex vivo killing assays. Yet, one variant, NCR094.3, had no toxicity toward human cells and displayed antibiofilm activity, which make it a promising lead for antimicrobial drug development.

Evolving antibiotic resistance in Group B Streptococci causing invasive infant disease: 1970-2021

BACKGROUND

We sought to define the frequency of antibiotic resistance over time in a collection of invasive GBS isolates derived from infant early-onset disease (EOD), late-onset disease (LOD), and late-late onset disease (LLOD).

METHODS

A multicenter retrospective review of infants born from 1970 to 2021 with GBS isolated from blood, cerebrospinal fluid, synovial fluid, cellulitis, or bone. All isolates were serotyped and antimicrobial susceptibility testing performed using disk diffusion.

RESULTS

The most common serotypes in our 2017 isolates were III (n = 1112, 55.1%), Ia (n = 445, 22%), Ib (n = 182, 9%) and II (n = 146, 7.2%). A total of 945 (46.8%) isolates were from infants with EOD, 976 (48.3%) from LOD, and 96 (4.75%) from LLOD. All isolates were penicillin-susceptible. Compared to strains isolated <2000, strains isolated ≥2000 showed significantly greater frequency of erythromycin (4.0% to 32.3%, P < 0.0001) and clindamycin (1.5% to 17.5%, P < 0.0001) resistance. Year of isolation (≥2000) and serotype V were significantly associated with erythromycin and/or clindamycin resistance.

CONCLUSIONS

We document a rapid and significant increase in clindamycin and erythromycin resistance. As clindamycin may be considered in severely penicillin-allergic women needing GBS intrapartum prophylaxis, obstetricians, pediatricians, and neonatologist should be aware of this disturbing trend.

IMPACT

Group B streptococcal strains isolated from infants with invasive infection have become more resistant to second-line antibiotics over time. In this epidemiologic study of 2017 group B streptococci isolated from 1970 to 2021, penicillin susceptibility remained uniform; however, resistance to erythromycin and clindamycin increased significantly over time across all capsular serotypes. Clindamycin resistance exceeded 20% by 2010 in most serotypes. While penicillin remains the treatment of choice for group B streptococcal infant disease, pediatricians and neonatologists should be aware of the high prevalence of resistance to clindamycin, a recommended alternative drug used for intrapartum-antibiotic prophylaxis in penicillin-allergic women.

Group B Streptococcal Neonatal Meningitis

Neonatal bacterial meningitis is a devastating disease, associated with high mortality and neurological disability, in both developed and developing countries. Streptococcus agalactiae, commonly referred to as group B Streptococcus (GBS), remains the most common bacterial cause of meningitis among infants younger than 90 days. Maternal colonization with GBS in the gastrointestinal and/or genitourinary tracts is the primary risk factor for neonatal invasive disease. Despite prophylactic intrapartum antibiotic administration to colonized women and improved neonatal intensive care, the incidence and morbidity associated with GBS meningitis have not declined since the 1970s. Among meningitis survivors, a significant number suffer from complex neurological or neuropsychiatric sequelae, implying that the pathophysiology and pathogenic mechanisms leading to brain injury and devastating outcomes are not yet fully understood. It is imperative to develop new therapeutic and neuroprotective approaches aiming at protecting the developing brain. In this review, we provide updated clinical information regarding the understanding of neonatal GBS meningitis, including epidemiology, diagnosis, management, and human evidence of the disease's underlying mechanisms. Finally, we explore the experimental models used to study GBS meningitis and discuss their clinical and physiologic relevance to the complexities of human disease.

Maternal Carriage in Late-Onset Group B Streptococcus Disease, Italy

At the time of late-onset disease, mothers often have positive breast milk culture or group B Streptococcus bacteriuria, suggesting heavy maternal colonization.

We retrospectively investigated mother-to-infant transmission of group B Streptococcus (GBS) in 98 cases of late-onset disease reported during 2007–2018 by a network in Italy. Mothers with full assessment of vaginal/rectal carriage tested at prenatal screening and at time of late onset (ATLO) were included. Thirty-three mothers (33.7%) were never GBS colonized; 65 (66.3%) were vaginal/rectal colonized, of which 36 (36.7%) were persistently colonized. Mothers with vaginal/rectal colonization ATLO had high rates of GBS bacteriuria (33.9%) and positive breast milk culture (27.5%). GBS strains from mother–infant pairs were serotype III and possessed the surface protein antigen Rib. All but 1 strain belonged to clonal complex 17. GBS strains from 4 mother–infant pairs were indistinguishable through pulsed-field gel electrophoresis. At least two thirds of late-onset cases are transmitted from mothers, who often have vaginal/rectal carriage, positive breast milk culture, or GBS bacteriuria, which suggests heavy maternal colonization.

Systematic Review and Meta-Analyses of Incidence for Group B Streptococcus Disease in Infants and Antimicrobial Resistance, China

We performed a systematic review and meta-analysis of the incidence, case-fatality rate (CFR), isolate antimicrobial resistance patterns, and serotype and sequence type distributions for invasive group B Streptococcus (GBS) disease in infants <1–89 days of age in China. We searched the PubMed/Medline, Embase, Wanfang, and China National Knowledge Infrastructure databases for research published during January 1, 2000–March 16, 2018, and identified 64 studies. Quality of included studies was assessed by using Cochrane tools. Incidence and CFR were estimated by using random-effects meta-analyses. Overall incidence was 0.55 (95% CI 0.35–0.74) cases/1,000 live births, and the CFR was 5% (95% CI 3%–6%). Incidence of GBS in young infants in China was higher than the estimated global incidence (0.49 cases/1,000 live births) and higher than previous estimates for Asia (0.3 cases/1,000 live births). Our findings suggest that implementation of additional GBS prevention efforts in China, including maternal vaccination, could be beneficial.

Molecular characteristics of group B Streptococcus isolates from infants in southern mainland China

BACKGROUND

Invasive group B Streptococcus (GBS) disease in Chinese infants has gradually gained attention in recent years, but the molecular epidemiology of the pathogen is still not well known.

METHODS

This multicenter study retrospectively investigated distribution of capsular serotypes, sequence types (STs), and hypervirulent GBS adhesin gene (hvgA) in clinical GBS isolates that caused invasive disease in infants aged < 3 months of age in southern mainland China between January 2013 and June 2016. Genes for antibiotic resistance to tetracycline, erythromycin, and clindamycin were also examined.

RESULTS

From a total of 93 GBS isolates taken from 34 early-onset disease (EOD, 0-6 days after birth) and 59 late-onset disease (LOD, 7-89 days after birth) cases, four serotypes were identified: serotypes III (79.6%), Ib (12.9%), Ia (4.3%), and V (3.2%). Serotype III accounted for 73.5% of EOD and 83.1% of LOD and was responsible for 75.5% of cases involving meningitis. Fifteen STs were found, with the majority being ST17 (61.3%), ST12 (7.5%), ST19 (7.5%), and others (23.7%). 96.8% of STs belonged to only five clonal complexes (CCs): CC17 (64.5%), CC10 (12.9%), CC19 (9.7%), CC23 (6.5%), and CC1 (3.2%). The hvgA gene was detected in 66.7% of GBS isolates and 95% of CC17 isolates, all of which were serotype III except one serotype Ib/CC17 isolate. A large proportion of GBS isolates were found to be resistant to tetracycline (93.5%), clindamycin (65.5%), and erythromycin (60.2%). Genes of tetO (74.7%) and tetM (46.0%) were found in tetracycline resistant isolates, linB (24.6%) in clindamycin resistant isolates, and ermB (87.5%) and mefA (3.6%) in erythromycin resistant isolates.

CONCLUSION

Our results reveal higher prevalence of serotype III, ST17, CC17, hvgA expressing, and antibiotic resistant GBS isolates than previously reported in southern mainland China. This study provides guidance for appropriate measures of prevention and control to be taken in the future.

Two Overlapping Clusters of Group B Streptococcus Late-onset Disease in a Neonatal Intensive Care Unit

OBJECTIVES

Current predominant routes of group B Streptococcus (GBS) transmission in preterm neonates admitted to neonatal intensive care unit (NICU) are poorly defined. We report 2 overlapping clusters of GBS late-onset disease (LOD) from June to September 2015 in an Italian NICU.

METHODS

During the outbreak, possible sources of transmission (equipment, feeding bottles and breast pumps) were swabbed. Specimens from throat and rectum were collected on a weekly basis from all neonates admitted to NICU. Colonized or infected neonates had cohorting. Bacterial isolates were characterized by serologic and molecular typing methods.

RESULTS

GBS was isolated in 2 full-term and 7 preterm neonates. Strains belonged to serotype III, with 3 different sequence types (ST17, ST182 and ST19). Full-term neonates were colonized with GBS strains unrelated to the clusters (ST182 and ST19). Two distinct ST17 strains caused 2 clusters in preterm neonates: a first cluster with 1 case of LOD and a second, larger cluster with 6 LOD in 5 neonates (one of them had recurrence). ST17 strains were isolated from vaginorectal and milk samples of 2 mothers. Two preterm neonates had no evidence of colonization for weeks, until they presented with LOD.

CONCLUSIONS

Molecular analyses identified the presence of multiclonal GBS strains and 2 clusters of 7 cases of GBS-LOD. The dynamics of transmission of GBS within the NICU were complex. Breast milk was suspected to be one of the possible sources. In a research setting, the screening of GBS carrier mothers who deliver very preterm could contribute to the tracking of GBS transmission.

Molecular epidemiology of invasive and non-invasive group B Streptococcus circulating in Serbia

Streptococcus agalactiae (group B Streptococcus, GBS) remains the leading cause of invasive diseases in neonates and an important cause of infections in the elderly. The aim of this study was to access the prevalence of GBS genito-rectal colonisation of pregnant women and to evaluate the genetic characteristics of invasive and non-invasive GBS isolates recovered throughout Serbia. A total of 432 GBS isolates were tested for antimicrobial susceptibility, capsular polysaccharide (CPS) types and the presence of the hvgA gene. One hundred one randomly selected isolates were further characterized by clustered regularly interspaced short palindromic repeats (CRISPRs) analysis and/or multilocus sequence typing (MLST). The prevalence of GBS colonization in pregnant women was 15%. Overall, six capsular types (Ia, Ib, II to V) were identified, the most common being III (32.2%) and V (25.2%). The hiper-virulent clone type III/ST17 was present in 43.1% and 6.3% (p < 0.05) of paediatric and adults isolates, respectively. Comparative sequence analysis of the CRISPR1 spacers content indicated that a few clones comprised the vast majority of the tested GBS isolates. Thus, it was estimated that dominant clones recovered from infants were CPS III/ST17 in late-onset infections (19/23; 82.6%), and Ia/ST23 in early-onset disease (44.4%). Conversely, genotype CPS V/ST1 was the most prevalent in adults (4/9; 25.4%). All isolates were susceptible to penicillin. Macrolide resistance (23.1%) was strongly associated with the ermB gene and constitutive resistance to clindamycin (63.9%). The majority of strains was resistant to tetracycline (86.6%), mostly mediated by the tetM gene (87.7%). GBS isolates of CPS V/ST1 and CPS III/ST23 were significantly associated with macrolide and tetracycline resistance, respectively. In conclusion, hyper-virulent CPS III/ST17 and V/ST1 were recognized as dominant GBS clones in this study.

Microbiological and clinical characteristics of Group B Streptococcus isolates causing materno-neonatal infections: high prevalence of CC17/PI-1 and PI-2b sublineage in neonatal infections

PURPOSE

Group B Streptococcus (GBS) is one of the major pathogens in severe materno-neonatal infections. We aimed to describe the clinical and molecular characteristics of GBS isolates causing infections in 45 maternal and 50 neonatal subjects, collected from eight healthcare centres in mainland China over the period 2010- 2017.

METHODOLOGY

The phenotypic and genotypic features of the GBS isolates, including capsular polysaccharide (cps) serotypes, pilus island (PI) genes and antibiotic resistance profiles and genes, were characterized by both conventional and molecular methods. The clonal relationship between these strains was investigated using multilocus sequence typing (MLST).

RESULTS

Of the 95 isolates, the predominant serotypes were III (51, 53.7 %), V (13, 13.7 %) and Ib (13, 13.7 %). All GBS strains carried at least one pilus island, with 32.6 % carrying PI-2b and 67.4 % PI-2a, singly or in combination. The most frequently-detected pilus island pattern was the combination of PI-1 and PI-2a, accounting for 56.8 % (54 isolates), followed by PI-1 combined with PI-2b (28, 29.5 %), PI-2a (10, 10.5 %) and PI-2b (3, 3.2 %). The strains were classified into 17 individual sequence types, and further clustered into six clonal complexes (CCs). A high prevalence of CC17/PI-1 and PI-2b (17, 34.0 %) was detected in 50 GBS isolates causing neonatal infections. No strain was resistant to penicillin, ampicillin, ceftriaxone or vancomycin, whereas 78.9, 76.8 and 81.5 % were resistant to erythromycin, clindamycin and tetracycline, respectively.

CONCLUSION

Our study highlights the high genotypic diversity of GBS strains causing materno-neonatal infections, and the CC17/PI-1 and PI-2b sublineages should be noted in neonatal infections.

Group B streptococcus late-onset disease,contaminated breast milk and mothers persistently GBS negative: report of 3cases

Background

Human milk is fundamental for its nutritional properties and to protect newborns, but it is not sterile and can sometime transmit bacteria. Few anecdotal cases suggest that breast milk could be a possible source of group B Streptococcus (GBS) late onset disease, although the pathogenesis is not entirely understood.

Case presentation

We report 3 cases of GBS late onset disease in full-term newborns. Fresh breast milk cultures yielded GBS, but mothers of neonates had no signs of mastitis and remained persistently GBS negative at rectovaginal site.

Conclusions

Breast milk containing group B Streptococcus can be a risk factor for late onset disease. The persistent negative maternal GBS status supports the assumption that newborns, colonised in the throat, could be the initial source of GBS, while the mammary gland could act as a GBS replication site. It is unclear whether a low bacterial load may represent only contamination rather than true milk infection.

Infant Group B Streptococcal Disease Incidence and Serotypes Worldwide: Systematic Review and Meta-analyses

Background

Group B Streptococcus (GBS) remains a leading cause of neonatal sepsis in high-income contexts, despite declines due to intrapartum antibiotic prophylaxis (IAP). Recent evidence suggests higher incidence in Africa, where IAP is rare. We investigated the global incidence of infant invasive GBS disease and the associated serotypes, updating previous estimates.

Methods

We conducted systematic literature reviews (PubMed/Medline, Embase, Latin American and Caribbean Health Sciences Literature [LILACS], World Health Organization Library Information System [WHOLIS], and Scopus) and sought unpublished data regarding invasive GBS disease in infants aged 0–89 days. We conducted random-effects meta-analyses of incidence, case fatality risk (CFR), and serotype prevalence.

Results

We identified 135 studies with data on incidence (n = 90), CFR (n = 64), or serotype (n = 45). The pooled incidence of invasive GBS disease in infants was 0.49 per 1000 live births (95% confidence interval [CI], .43–.56), and was highest in Africa (1.12) and lowest in Asia (0.30). Early-onset disease incidence was 0.41 (95% CI, .36–.47); late-onset disease incidence was 0.26 (95% CI, .21–.30). CFR was 8.4% (95% CI, 6.6%–10.2%). Serotype III (61.5%) dominated, with 97% of cases caused by serotypes Ia, Ib, II, III, and V.

Conclusions

The incidence of infant GBS disease remains high in some regions, particularly Africa. We likely underestimated incidence in some contexts, due to limitations in case ascertainment and specimen collection and processing. Burden in Asia requires further investigation.

Neonatal colonization of group B Streptococcus in China: Prevalence, antimicrobial resistance, serotypes, and molecular characterization

BACKGROUND

Group B Streptococcus (GBS) remains a leading cause of neonatal mortality and morbidity. This study aimed to determine the prevalence, antimicrobial susceptibility, serotypes, and molecular characterization of GBS colonized in neonates.

METHODS

A cross-sectional study was conducted using a multistage sampling method. Swabs for GBS identification were taken from infants' ear, oral cavity, and umbilicus immediately after birth. All GBS isolates were tested for antimicrobial susceptibility, resistance genes, serotyping, multilocus sequence typing, and virulence genes.

RESULTS

Of the 1,814 neonates, 1.3% tested positive for GBS, with 66.7% tested as multidrug resistant. All GBS isolates were susceptible to penicillin, but rates of resistance to tetracycline and erythromycin were high (70.8%), with the predominant resistance genes being tetM and ermB. The predominant serotype was III, followed by Ia and Ib, and the most common genotypes were sequence type (ST) 19, ST10, and ST485. Notably, we found that ST19 and ST17 isolates were associated with serotype III, resistant to tetracycline, erythromycin, and clindamycin, and carrying ermB, tetM, and rib; ST10 and ST12 isolates were associated with serotype Ib, resistant to erythromycin and clindamycin, and carrying ermB and alphaC; and ST485 isolates were associated with serotype Ia and carrying mefA/E, tetM, and epsilon.

CONCLUSIONS

These findings indicate a high prevalence of multidrug-resistant GBS and specific phenotype-genotype combinations for GBS clones.

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.

Disease burden and antimicrobial resistance of invasive group B streptococcus among infants in China: a protocol for a national prospective observational study

Background

Group B Streptococcus (GBS) is a cause of neonatal sepsis, pneumonia, and meningitis that can lead to neurological sequelae in infants less than 3 months of age. The GBS disease burden is not known in China, therefore it cannot receive major attention. The main objectives of this study are the evaluation of the incidence of neonatal GBS infection, GBS case-fatality ratio, its serotypes and genotypes, bacterial resistance, clinical treatment and outcomes in China.

Methods

We are conducting a nation-wide, population-based, multi-center, prospective, observational cohort study in China from May 2016 to December 2017. Eighteen large urban tertiary care hospitals from 16 provinces were selected that cover the eastern, southern, western, northern and central regions of China. Meanwhile, we retrospectively collected data and GBS strains from January 2015 to April 2016 from selected hospitals. The incidence rate per 1000 live births will be defined as the total number of confirmed GBS cases born in the selected hospitals divided by the number of live births in the hospitals during the study period. All GBS cases detected in selected hospitals will be used to calculate the case-fatality ratio and for the typing analysis. GBS isolates will be serotyped using the Strep-B-Latex® rapid latex agglutination test for serotyping of Group B streptococci. Multi-locus sequence typing (MLST) will be performed by sequencing the internal fragments of seven house-keeping genes. Antimicrobial susceptibility will be tested per interpretive standards established by the Clinical and Laboratory Standards Institute. The presence of the common resistance genes ermA, ermB, mefA, tetI, tetO and tetM will be tested by PCR.

Discussion

We are conducting the first national study to estimate the invasive GBS disease burden and antimicrobial resistance of GBS among infants in China. Study findings will provide important evidence for improving clinical practice to ensure timely diagnosis of GBS disease and decisions for preventive measures. Surveillance of antimicrobial resistance will promote the rational use of antimicrobials.

Trial registration

The study was retrospectively registered at http://clinicaltrials.gov on June 13, 2016. It was granted a registration number of “NCT02812576”.

Neonatal Group B Streptococcal Disease in Otherwise Healthy Infants: Failure of Specific Neonatal Immune Responses

Only a small proportion of newborn infants exposed to a pathogenic microorganism develop overt infection. Susceptibility to infection in preterm infants and infants with known comorbidities has a likely multifactorial origin and can be often attributed to the concurrence of iatrogenic factors, environmental determinants, underlying pathogenic processes, and probably genetic predisposition. Conversely, infection occurring in otherwise healthy full-term newborn infants is unexplained in most cases. Microbial virulence factors and the unique characteristics of the neonatal immune system only partially account for the interindividual variability in the neonatal immune responses to pathogens. We here suggest that neonatal infection occurring in otherwise healthy infants is caused by a failure of the specific protective immunity to the microorganism. To explain infection in term and preterm infants, we propose an extension of the previously proposed model of the genetic architecture of infectious diseases in humans. We then focus on group B streptococcus (GBS) disease, the best characterized neonatal infection, and outline the potential molecular mechanisms underlying the selective failure of the immune responses against GBS. In light of the recent discoveries of pathogen-specific primary immunodeficiencies and of the role of anticytokine autoantibodies in increasing susceptibility to specific infections, we hypothesize that GBS disease occurring in otherwise healthy infants could reflect an immunodeficiency caused either by rare genetic defects in the infant or by transmitted maternal neutralizing antibodies. These hypotheses are consistent with available epidemiological data, with clinical and epidemiological observations, and with the state of the art of neonatal physiology and disease. Studies should now be designed to comprehensively search for genetic or immunological factors involved in susceptibility to severe neonatal infections.

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.

Identification, antimicrobial resistance and molecular characterization of the human emerging pathogen Streptococcus gallolyticus subsp. pasteurianus

This study aimed to retrospectively identify 22Streptococcus bovis clinical strains based on the new taxonomy, as well as to investigate their antibiotic-resistance and clonality. Strains were identified by Phoenix100 system, 16S rRNA sequencing, and two MALDI-TOF MS platforms (Bruker Biotyper, Vitek MS). Antibiotic resistance was determined both phenotypically and genotypically, and clonality was assessed by PFGE. Most of strains (63.6%) were isolated from urine, and diabetes was the most common underlying disease (31.8%). Phoenix100 system revealed all strains belonged to biotype II, and 16S rRNA sequencing identified all strains as S. gallolyticus subsp pasteurianus (SGSP). Although both MALDI-TOF MS systems correctly identified isolates to the species level, only Bruker Biotyper accurately identified to the subspecies level. Erythromycin-resistant strains (31.8%) were also clindamycin-resistant and positive for erm(B). Strains resistant to tetracycline (68.2%) were also resistant to erythromycin. PFGE showed high genetic variability identifying 17 different pulsotypes, most of which single.

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.

Group B streptococcal infections in the newborn infant and the potential value of maternal vaccination

Group B Streptococcus (GBS) is a leading cause of neonatal bacterial infections in developed countries. Early-onset disease (EOD) occurs at day 0-6 and late-onset disease occurs at day 7-89. Currently, the prevention of EOD relies upon intrapartum antibiotic prophylaxis (IAP) given to women who are GBS positive at prenatal screening or women with risk factors for EOD. Although successfully implemented, IAP has not fully eradicated EOD, and incidence rates of late-onset disease remain unchanged. Furthermore, antibiotic resistance may result from widespread antibiotic use. New prophylactic strategies are therefore of critical importance. A vaccine active against GBS, administered during pregnancy and combined with targeted IAP, could overcome these problems and reduce the mortality and morbidity associated with invasive diseases.

Characteristics of group B Streptococcus isolated from infants with invasive infections: a population-based study in Japan

Group B Streptococcus (GBS) is one of the leading causes of neonatal bacterial infections. Population-based surveillance of GBS-related invasive diseases among newborns and infants from 10 prefectures in Japan was performed between 2007 and 2012. The characteristics of cases and isolated GBS are described in this study. The incidence rate of GBS-related invasive diseases was 0.13 per 1,000 live births. Analysis of GBS samples obtained from 60 invasive cases showed that the most frequent serotypes were III (48.3%), Ia (30.0%), and Ib (10.0%). All isolates were susceptible to penicillin G, ampicillin, cefotaxime, imipenem, and panipenem. However, 14, 2, and 7 isolates were resistant to erythromycin, clindamycin, and both erythromycin and clindamycin, respectively. Multilocus sequence typing revealed that GBS sequence type (ST) 23, ST17, and ST335 caused higher incidences of meningitis. These data show that serotypes III, Ia, and Ib together caused more than 80% of invasive infections in Japanese infants, and that GBS strains are still susceptible to β-lactam antibiotics.

Molecular characterization of Streptococcus agalactiae isolates harboring small erm(T)-carrying plasmids

Among 1,827 group B Streptococcus (GBS) strains collected between 2006 and 2013 by the French National Reference Center for Streptococci, 490 (26.8%) strains were erythromycin resistant. The erm(T) resistance gene was found in six strains belonging to capsular polysaccharides Ia, III, and V and was carried by the same mobilizable plasmid, which could be efficiently transferred by mobilization to GBS and Enterococcus faecalis recipients, thus promoting a broad dissemination of erm(T).

Group B streptococcal epidemiology and vaccine needs in developed countries

Development of a group B streptococcal vaccine (GBS) vaccine is the most promising approach for the prevention of GBS infections in babies, given the potential adverse effects of intrapartum antibiotic prophylaxis as well as the need for effective prevention of both adult and late perinatal disease. There are numerous prevention strategies at this time but none are 100% effective in the eradication of neonatal early onset GBS disease and there are no preventative strategies for late onset disease. The need for a GBS vaccine is therefore, of utmost importance. Efforts applying genomics to GBS vaccine development have led to the identification of novel vaccine candidates. The publication of GBS whole genomes coupled with new technologies including multigenome screening and bioinformatics has also allowed researchers to overcome the serotype limitation of earlier vaccine preparations in the search of a universal effective vaccine against GBS. This review brings together the key arguments concerning the potential need of a GBS vaccine in developed countries and describes the current status with GBS epidemiology and microbiology in these countries.

Serotype IV and invasive group B Streptococcus disease in neonates, Minnesota, USA, 2000-2010

Serotype predominance has shifted, and drug resistance is emerging.

Group B streptococcal colonization in 160 mother-baby pairs: a prospective cohort study

OBJECTIVES

To identify the source of postnatal colonization with group B Streptococcus (GBS) and to evaluate the impact of intrapartum antibiotic prophylaxis (IAP) administration in newborn infant transmission.

STUDY DESIGN

A prospective, longitudinal study evaluated GBS colonization in 160 mother-baby pairs. Specimens were collected from the time of delivery to 8 weeks post-partum, from rectum, vagina, and milk of mothers, and from throat and rectum of neonates. Women were grouped according to their GBS status at discharge from the hospital: culture-positive carriers (n = 83), culture-negative carriers (n = 26), and noncarriers (n = 51). Newborns were considered colonized if GBS was yielded from at least 1 site.

RESULTS

A total of 35 (21.9%) neonates were colonized; 30 were born to culture-positive carriers, 2 to culture-negative carriers, and 3 to noncarriers. Infants of culture-positive carriers exposed to IAP were less likely to be colonized (15/57 vs 15/26, P = .01), or heavily colonized, (7/57 vs 9/26, P = .04). Of all newborns, those exposed to IAP and discharged GBS-free from hospital, often became colonized subsequently (12/57 vs 1/26, P = .09). Molecular typing analysis (available for 30 of 32 carrier mothers and their infants) confirmed an identical strain of GBS in all mother-baby pairs. Six of 83 culture-positive carrier mothers had a positive milk culture. Their respective neonates all were heavily colonized.

CONCLUSIONS

Newborns exposed to IAP and GBS-free at hospital discharge subsequently acquire GBS from their mothers. Culture-positive milk is associated with heavy neonatal colonization.

Neonatal infectious diseases: evaluation of neonatal sepsis

Neonatal sepsis remains a feared cause of morbidity and mortality in the neonatal period. Maternal, neonatal, and environmental factors are associated with risk of infection, and a combination of prevention strategies, judicious neonatal evaluation, and early initiation of therapy are required to prevent adverse outcomes. This article reviews recent trends in epidemiology and provides an update on risk factors, diagnostic methods, and management of neonatal sepsis.

Distribution of serotypes and evaluation of antimicrobial susceptibility among human and bovine Streptococcus agalactiae strains isolated in Brazil between 1980 and 2006

Streptococcus agalactiae is a common agent of clinical and subclinical bovine mastitis and an important cause of human infections, mainly among pregnant women, neonates and nonpregnant adults with underlying diseases. The present study describes the genetic and phenotypic diversity among 392 S. agalactiae human and bovine strains isolated between 1980 and 2006 in Brazil. The most prevalent serotypes were Ia, II, III and V and all the strains were susceptible to penicillin, vancomycin and levofloxacin. Resistance to clindamycin, chloramphenicol, erythromycin, rifampicin and tetracycline was observed. Among the erythromycin resistant strains, mefA/E, ermA and, mainly, ermB gene were detected, and a shift of prevalence from the macrolide resistance phenotype to the macrolide-lincosamide-streptogramin B resistance phenotype over the years was observed. The 23 macrolide-resistant strains showed 19 different pulsed-field gel electrophoresis profiles. Regarding macrolide resistance, a major concern in S. agalactiae epidemiology, the present study describes an increase in erythromycin resistance from the 80s to the 90s followed by a decrease in the 2000–2006 period. Also, the genetic heterogeneity described points out that erythromycin resistance in Brazil is rather due to horizontal gene transmission than to spreading of specific macrolide-resistant clones.

Group B streptococcus late-onset disease: 2003-2010

BACKGROUND

There is insufficient population-based data on group B streptococcus (GBS) late-onset disease (LOD). Risk factors and routes of GBS transmission are poorly understood.

METHODS

A prospective, cohort study was conducted to collect incidence data on LOD and evaluate GBS infections over an 8-year period (2003-2010). Starting from January 2007, maternal rectovaginal and breast milk cultures were routinely collected on confirmation of the LOD diagnosis to assess maternal GBS culture status.

RESULTS

The incidence rate of LOD was 0.32 per 1000 live births (1.4 and 0.24 per 1000 live births for preterm and term newborns, respectively). The registered cases of LOD (n = 100) were classified as sepsis (n = 57), meningitis (n = 36), or focal infection (n = 7). Thirty neonates were preterm (2 had recurrent infection); 68 were term. Four infants died (3 early preterm, 1 term). At the time the LOD diagnosis was confirmed, 3 (6%) of 53 mothers had GBS mastitis, and 30 (64%) of 47 carried GBS at the rectovaginal site. Early (7-30 days) LOD presentation was associated with neonatal brain lesions or death (odds ratio: 0.96 [95% confidence interval: 0.93-0.99]). Intrapartum antibiotic exposure was significantly associated with mild (12 of 22) rather than severe (11 of 45; P = .03) LOD.

CONCLUSIONS

Preterm neonates had the highest rates of LOD and mortality. Most mothers carried GBS at the time of the LOD diagnosis, whereas 6% had mastitis. Intrapartum antibiotics were associated both with delayed presentation of symptoms and milder LOD.