Invasive Group B Streptococcus Isolates Research Articles

Genomic Traits Associated with Virulence and Antimicrobial Resistance of Invasive Group B Streptococcus Isolates with Reduced Penicillin Susceptibility from Elderly Adults.

ABSTRACTThis study aimed to investigate genomic traits underlying the antimicrobial resistance and virulence of multidrug-resistant (MDR) group B streptococci with reduced penicillin susceptibility (PRGBS) recovered from elderly patients with bloodstream infections, which remain poorly characterized. The pangenome was found to be open, with the predicted pan- and core genome sizes being 3,531 and 1,694 genes, respectively. Accessory and unique genes were enriched for the Clusters of Orthologous Groups (COG) categories L, Replication, recombination, and repair, and K, Transcription. All MDR PRGBS isolates retained a core virulence gene repertoire (bibA, fbsA/-B/-C, cspA, cfb, hylB, scpB, lmb, and the cyl operon), supporting an invasive ability similar to that of the other invasive GBS, penicillin-susceptible GBS (PSGBS), and noninvasive PRGBS isolates. The putative sequence type 1 (ST1)-specific AlpST-1 virulence gene was also retained among the serotype Ia/ST1 PRGBS isolates. In addition to tet(M) and erm(B), mef(A)-msr(D) elements or the high-level gentamicin resistance gene aac(6′)-aph(2″), which are both rare in PSGBS, were detected among those MDR PRGBS isolates. In the core single-nucleotide polymorphism (SNP) phylogenetic tree, all invasive ST1 PRGBS isolates with serotypes Ia and III were placed together in a clade with a recombination rate of 3.97, which was 36 times higher than the value found for a clade formed by serotype V/ST1 PSGBS isolates derived mostly from human blood. ST1 has been the predominant sequence type among the PRGBS isolates in Japan, and serotypes Ia and III have been very rare among the ST1 PSGBS isolates. Thus, these lineages that mostly consisted of serotypes Ia/ST1 and III/ST1 PRGBS could possibly emerge through recombination within the ST1 populations.IMPORTANCE Streptococcus agalactiae, or group B Streptococcus (GBS), is recognized as the leading cause of neonatal invasive infections. However, an increasing incidence of invasive GBS infections among nonpregnant adults, particularly the elderly and those with underlying diseases, has been observed. There is a trend toward the increasing occurrence of penicillin nonsusceptibility among GBS clinical isolates, from 4.8% in 2008 to 5.8% in 2020 in Japan. Also, in the United States, the frequency of adult invasive GBS isolates suggestive of β-lactam nonsusceptibility increased from 0.7% in 2015 to 1.0% in 2016. In adults, mortality has been significantly higher among patients with bacteremia than among those without bacteremia. Our study revealed that invasive GBS with reduced penicillin susceptibility (PRGBS) isolates harbor major virulence and resistance genes known among GBS, highlighting the need for large population-based genomic surveillance studies to better understand the clinical relevance of invasive PRGBS isolates.

Serotyping of invasive and colonizing group B Streptococcus (GBS) isolates at selected hospitals in Sri Lanka: a multicenter study.

Group B Streptococcus (GBS) causes significant morbidity and mortality in neonates, pregnant women and patients with underlying comorbidities. Intrapartum antibiotic prophylaxis (IAP) is currently the mainstay of prevention and effective vaccine against invasive GBS disease is under clinical trial. To describe the serotype distribution of invasive and colonizing GBS isolates in Sri Lanka. Probable GBS isolates from high vaginal swabs (HVS) and sterile body sites were collected from eight selected hospital laboratories. Following confirmation of the identification as group B Streptococcus by phenotypic methods including Lancefield grouping test (Plasmatic UK), isolates were tested for serotyping by latex agglutination test kit (STATEN serum institute, Denmark). Out of the 145 probable GBS isolates only 100 from HVS and 37 from sterile body sites were confirmed as GBS. Serotype III was the most predominant in invasive GBS isolates followed by Ia, Ib, VI, II and V in the descending order of frequency. Serotype VI was the most predominant in HVS isolates followed by serotype III, V, Ia, II, Ib and IV. Difference of GBS serotype distribution between the invasive and HVS group was statistically significant (P value = 0.038). Serotype distribution pattern of the study isolates was comparable to most of the other developing and developed countries and hence will be beneficial in future vaccine introduction. GBS vaccine which is currently under clinical trial (Ia, Ib and III) is potentially effective for preventing 68% of the early onset disease in neonates in this study setting.

Serotyping and Antibiotic Susceptibility of Invasive Streptococcus agalactiae in Egyptian Patients with or without Diabetes Mellitus.

Streptococcus agalactiae serotype distribution and its antibiotic susceptibility affect disease prevention strategies, but the serotype distribution varies among patient groups. The objectives of this study were to establish the group B Streptococcus (GBS) serotype distribution in patients from Egypt and to assess antibiotic sensitivity of invasive GBS isolates. A total of 490 patients participated in this multicenter study; 160 had urinary tract infection, 115 complained of diabetic foot ulcers, 125 men had genital tract infections, and 30 women females had genital tract infections. Others had bronchopneumonia, otitis media, synovitis, or meningitis. Serotyping of the isolated GBS was performed at the CDC in the United States. Antibiotic sensitivity patterns were determined using the disk diffusion method. In men, the most common serotypes were II, III, and V, whereas types Ia, II, III, and V were isolated from women. Macrolides (erythromycin) resistance occurred in 4.1% of the isolates; 10.2% were resistant to both clindamycin and inducible resistance of macrolides, lincomycin, and streptogramin; 17.3% were resistant to quinolones; and 95.9% were resistant to tetracyclines. GBS primarily infected the urinary tract, skin, soft tissue, and genital tract in both genders. Isolates were sensitive to beta-lactam drugs, vancomycin, and linezolid; 14.0% were resistant to macrolides with or without clindamycin. Only 6.0% of the strains were sensitive to tetracyclines. Although GBS causes invasive infections in Egyptian adults, it rarely causes neonatal meningitis or sepsis. Future studies should determine whether GBS isolates are transmitted sexually, by performing a follow-up study of the partner of the infected patient.

Emergence of Multi-Drug Resistance and Its Association With Uncommon Serotypes of Streptococcus agalactiae Isolated From Non-neonatal Patients in Thailand.

Group B streptococcus (GBS) or Streptococcus agalactiae is an opportunistic pathogen that causes serious illness in newborns, pregnant women, and adults. However, insufficient detection methods and disease prevention programs have contributed to an increase in the incidence and fatality rates associated with this pathogen in non-neonatal patients. This study aimed to investigate factors of the observed increased incidence by investigation of serotype distribution, virulence factors, and antimicrobial susceptibility patterns from invasive GBS disease among non-neonatal patients in Thailand. During 2017–2018, a total of 109 S. agalactiae isolates were collected from non-pregnant patients. There were 62 males and 47 females, with an average age of 63.5 years (range: 20 – 96). Serotypes were determined by latex agglutination assay and multiplex polymerase chain reaction (PCR)-based assay. Among those isolates, seven virulence genes (rib, bca, pavA, lmb, scpB, cylE, and cfb) were detected by PCR amplification, and were determined for their susceptibility to 20 antimicrobial agents using a SensititreTM Streptococcus species STP6F AST plate. Among the study isolates, serotype III was predominant (52.3%), followed by serotype V and serotype VI (13.8% for each), serotype Ib (11.9%), and other serotypes (8.2%). Of the seven virulence genes, pavA was found in 67.0%. Except for one, there were no significant differences in virulence genes between serotype III and non-serotype III. Study isolates showed an overall rate of non-susceptibility to penicillin, the first-line antibiotic, of only 0.9%, whereas the resistance rates measured in tetracycline, clindamycin, azithromycin, and erythromycin were 41.3, 22.0, 22.0, and 22.0%, respectively. Strains that were resistant to all four of those drugs were significantly associated with non-serotype III (p < 0.001). Using multi-locus sequence typing (MLST), 40.0% of the four-drug-resistant isolates belonged to serotype VI/ST1, followed by serotype Ib/ST1 (35.0%). Cluster analysis with global GBS isolates suggested that the multiple drug-resistant isolates to be strongly associated with the clonal complex (CC) 1 (p < 0.001). Compared to the 2014 study of 210 invasive GBS isolates conducted in 12 tertiary hospitals in Thailand, the proportion of serotype III has dramatically dropped from nearly 90% to about 50%. This suggests that resistances to the second-line antibiotics for GBS might be the selective pressure causing the high prevalence of non-serotype III isolates.

Pathogenesis and in vivo interactions of human Streptococcus agalactiae isolates in the Galleria mellonella invertebrate model

Group B Streptococcus (GBS) is a gram positive bacterium colonizing the gastrointestinal and urogenital tracts in humans. However under certain conditions GBS invades leading to severe infections in neonates, pregnant women, immunocompromised patients and the elderly people. The precise mechanisms involved in the transition from colonizer to pathogen remain to be elucidated, however it has been suggested that environmental determinants may regulate gene expression resulting in GBS invasion. We have assessed the potential of the moth Galleria mellonella as a model to study the in vivo virulence and GBS interactions of invasive and noninvasive human isolates from our population. Temperature, pH and bacterial competition effects were examined in the model as well as the response of Galleria hemocytes to GBS infection. GBS strains were able to effectively grow and infect G. mellonella in a dose dependent manner with a (half-lethal dose) LD50 1 × 107 CFU after 24 h. GBS infection induced larva melanization with hemocyte vacuolation and depletion. Larval killing increased with environmental conditions such as temperature (37 °C) and pH (≥5.5–7.2). Bacterial interference assays showed a remarkable antagonistic effect of Lactobacillus gasseri (cells and filtrates) on GBS infection and significantly improved Galleria survival. The protective effect of L. gasseri was observed even at ratios similar to those of GBS colonization suggesting that L. gasseri modulation by its metabolic products is relevant. Exposure to L. gasseri acidic filtrates induced growth inhibition and prevented larva killing after infection with the hypervirulent GBS clone (a multiresistant clinical ST 17 strain). We showed that mechanisms mediating these effects are mainly pH dependent, however other mechanisms may have a role depending on inocula. We also found that G. mellonella infected with invasive human GBS isolates showed differential killing curves with higher killing rates after 24 h when compared to those considered colonizers or noninvasive isolates.Overall it has been shown that G. mellonella may be a representative in vivo model for baseline GBS studies. Given the potential effects over the hypervirulent strain, our findings support the use of L. gasseri in the GBS control strategies based on Lactobacillus formulations.

In vitro synergistic activity of erythromycin and nisin against clinical Group B Streptococcus isolates.

This study investigated the potential synergy between erythromycin and nisin against clinical Group B Streptococcus (GBS) strains. The combination of erythromycin and nisin was examined for synergistic activity using checkerboard and time-kill assays against invasive and colonizing GBS strains. Additionally, the immunological effect of the antibiotic combination was investigated in vitro using human U937 cells and ELISA analysis. Checkerboard assays confirmed an additive effect when the antimicrobials were combined, while time-kill assays demonstrated a synergistic effect when antimicrobials were combined for invasive GBS isolates. Furthermore, a significantly lower TNF-alpha response (P<0·05) was observed in U937 cells challenged with GBS when erythromycin and nisin were used in combination. The results suggest that erythromycin and nisin can act synergistically to inhibit the growth of GBS. Group B Streptococcus is the leading cause of invasive neonatal disease worldwide and is becoming increasingly more prevalent in adults. Resistance to some conventionally used antibiotics, such as erythromycin and clindamycin, continue to rise among GBS, indicating a need for alternative treatments. This study demonstrates the potential of an erythromycin-nisin combination for treatment of GBS infections and encourages further investigation of this treatment option.

Fluoroquinolone-Resistant Streptococcus agalactiae Invasive Isolates Recovered in Argentina.

Background: Streptococcus agalactiae or group B Streptococcus (GBS) is an important pathogen in neonates and nonpregnant individuals. Epidemiological studies of GBS resistance to fluoroquinolones (FQs) in Latin America are scarce. This study aimed to determine the local prevalence of FQ resistance in the frame of a national, prospective multicenter study of invasive GBS infections and to investigate mechanisms of resistance, serotype distribution, and clonal relationships among resistant isolates. Methods: From July 2014 to July 2015, 162 invasive GBS isolates were collected from 86 health care centers in 32 Argentinean cities. All isolates were screened for FQ nonsusceptibility using a five-disc scheme: levofloxacin (LVX), ciprofloxacin, norfloxacin (NOR), ofloxacin, and pefloxacin (PF). LVX minimal inhibitory concentration (MIC) was determined by the agar dilution method. Sequencing of internal regions of gyrA and parC genes was performed. Capsular typing and genetic characterization of nonsusceptible isolates were assessed by latex agglutination, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing. Results: Twenty-four of one hundred sixty-two GBS isolates exhibited no inhibition zones to all tested FQs with an MIC range of 16-32 mg/L for LVX, and one isolate with MIC = 1 mg/L showed no inhibition zones around NOR and PF discs. In all resistant isolates, point mutations were detected in both genes. Serotype Ib was prevalent (88%). One PFGE type accounted for 84% of the FQ-resistant isolates and belonged to serotype Ib, sequence type 10. Conclusions: The prevalence of FQ resistance was 14.8% likely to be associated with dissemination of an ST10/serotype Ib clone. The unexpected high rate of resistance emphasizes the relevance for continuous surveillance of GBS epidemiology and antibiotic susceptibility.

Serotype distribution, antimicrobial resistance, and molecular characterization of invasive group B Streptococcus isolates recovered from Chinese neonates

Group B Streptococcus (GBS) is an important neonatal pathogen associated with high morbidity and mortality in developed countries. However, data describing neonatal GBS disease in developing countries, particularly in Asia, are largely incomplete. The aim of this study was to determine the serotype distribution, antimicrobial resistance, and molecular characteristics of invasive GBS isolates recovered from Chinese neonates. From 2008 to 2013, 40 GBS isolates were recovered from infected neonates less than 3 months of age. All isolates were identified with the CAMP test and commercially available techniques. Serotyping was performed by latex agglutination. Antibiotic susceptibility was tested with Etest strips and the disk diffusion method. Multilocus sequence typing and erythromycin resistance gene detection (ermB and mefA) were performed by PCR. Four serotypes were identified. Serotype III (85%) was the most prevalent, followed by Ia (7.5%), Ib (5%), and V (2.5%). All isolates were sensitive to penicillin, ceftriaxone, and levofloxacin. However, resistance to erythromycin (92.5%), clindamycin (87.5%), and tetracycline (100%) was observed. Among erythromycin-resistant isolates, 73.0% carried the ermB gene alone, 5.4% carried the mefA gene alone, and 21.6% expressed both ermB and mefA genes. A total of seven sequence types (STs) were identified; the most prevalent was ST17, accounting for 80% of all isolates. Further, serotype III isolates contained ST17 (94.2%), ST19 (2.9%), and ST650 (2.9%). Serotype distribution, antimicrobial susceptibility, and sequence type characterization in Asia and in other global regions may contribute to improve the prevention and treatment of neonatal GBS infections.

Genetic Differences Between Invasive and Noninvasive Neonatal Group B Streptococcal Isolates

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. 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. 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%). 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.

Serotype distribution and invasive potential of group B streptococcus isolates causing disease in infants and colonizing maternal-newborn dyads.

BackgroundSerotype-specific polysaccharide based group B streptococcus (GBS) vaccines are being developed. An understanding of the serotype epidemiology associated with maternal colonization and invasive disease in infants is necessary to determine the potential coverage of serotype-specific GBS vaccines.MethodsColonizing GBS isolates were identified by vaginal swabbing of mothers during active labor and from skin of their newborns post-delivery. Invasive GBS isolates from infants were identified through laboratory-based surveillance. GBS serotyping was done by latex agglutination. Serologically non-typeable isolates were typed by a serotype-specific PCR method. The invasive potential of GBS serotypes associated with sepsis within seven days of birth was evaluated in association to maternal colonizing serotypes.ResultsGBS was identified in 289 (52.4%) newborns born to 551 women with GBS-vaginal colonization and from 113 (5.6%) newborns born to 2,010 mothers in whom GBS was not cultured from vaginal swabs. The serotype distribution among vaginal-colonizing isolates was as follows: III (37.3%), Ia (30.1%), and II (11.3%), V (10.2%), Ib (6.7%) and IV (3.7%). There were no significant differences in serotype distribution between vaginal and newborn colonizing isolates (P = 0.77). Serotype distribution of invasive GBS isolates were significantly different to that of colonizing isolates (P<0.0001). Serotype III was the most common invasive serotype in newborns less than 7 days (57.7%) and in infants 7 to 90 days of age (84.3%; P<0.001). Relative to serotype III, other serotypes showed reduced invasive potential: Ia (0.49; 95%CI 0.31–0.77), II (0.30; 95%CI 0.13–0.67) and V (0.38; 95%CI 0.17–0.83).ConclusionIn South Africa, an anti-GBS vaccine including serotypes Ia, Ib and III has the potential of preventing 74.1%, 85.4% and 98.2% of GBS associated with maternal vaginal-colonization, invasive disease in neonates less than 7 days and invasive disease in infants between 7–90 days of age, respectively.

Variation in erythromycin and clindamycin resistance patterns between New Zealand and Australian group B streptococcus isolates

Intrapartum chemoprophylaxis for group B streptococcus (GBS) carriers reduces the risk of early-onset neonatal GBS infection. For women with β-lactam allergy, either erythromycin or clindamycin are administered. Recent reports worldwide suggest that GBS resistance to these antibiotics is increasing. To compare erythromycin and clindamycin resistance phenotypes in invasive neonatal GBS isolates across New Zealand and Australia over the past two decades and to determine whether regional variation in resistance patterns exist. Invasive neonatal GBS isolates were collected from laboratories across New Zealand (n=107) and Australia (n=74) over two time periods (1992-1994 and 2002-2004 in New Zealand; 1982-2001 and 2002-2006 in Australia) and subjected to standard antibiotic susceptibility testing. A nested sub-study in New Zealand examined antibiotic susceptibilities of 112 maternal colonising GBS isolates during 2003-2004. Erythromycin resistance among invasive neonatal GBS isolates increased across both countries over the past decade, with similar rates of resistance in New Zealand (9%) and Australia (6%) in recent years. New Zealand erythromycin-resistant GBS isolates commonly displayed cross-resistance to clindamycin. Also, there were significantly higher rates of isolated clindamycin resistance in GBS isolates from New Zealand than Australia (P=0.034). Maternal GBS isolates from New Zealand showed similar resistance patterns to neonatal isolates. Erythromycin and clindamycin resistance among invasive neonatal GBS isolates has emerged in both New Zealand and Australia over the past decade and is consistent with global trends in GBS resistance patterns. Although regional variations exist, these findings should be considered when implementing intrapartum GBS prevention strategies.

Antimicrobial resistance in group B streptococcus: the Australian experience

Intrapartum chemoprophylaxis for pregnant group B streptococcus (GBS) carriers reduces vertical transmission, with a resultant decrease in neonatal as well as maternal morbidity from invasive GBS infection. Current Australian guidelines recommend penicillin for intrapartum prophylaxis of GBS carriers, with erythromycin or clindamycin for those with a β-lactam allergy. Recent reports globally suggest that resistance to erythromycin and clindamycin may be increasing; hence, a study was undertaken to promote an evidence base for local clinical guidelines. Samples collected for standardized susceptibility testing included 1160 invasive GBS isolates (264 isolates retrospectively from 1982 to 2001 and prospectively from 2002 to 2006, plus 896 prospectively collected colonizing GBS isolates gathered over a 12 month period from 2005 to 2006) from 16 laboratories around Australia. All isolates displaying phenotypic macrolide or lincosamide resistance were subsequently genotyped. No isolates showed reduced susceptibility to penicillin or vancomycin. Of the invasive isolates, 6.4 % demonstrated phenotypic erythromycin resistance and 4.2 % were clindamycin resistant. Of the erythromycin-resistant isolates, 53 % showed cross-resistance to clindamycin. Very similar results were found in colonizing specimens. There was no statistically significant change in macrolide-resistance rates over the two study periods 1982-2001 and 2002-2006. Genotyping for macrolide and lincosamide-resistant isolates was largely consistent with phenotype. These findings suggest that penicillin therapy remains an appropriate first-line antibiotic choice for intrapartum GBS chemoprophylaxis, with erythromycin and/or clindamycin resistance being low in the Australian population. It would, nevertheless, be appropriate for laboratories screening for GBS in obstetric patients to consider macrolide sensitivity testing, particularly for those with β-lactam allergy, to ensure appropriate chemoprophylaxis.

Molecular Epidemiology of Invasive Neonatal Streptococcus agalactiae Isolates in Germany

Streptococcus agalactiae [group B streptococcus (GBS)] is a well-known cause of invasive infections leading to sepsis and meningitis in neonates. A comprehensive nationwide active surveillance study over 2 years was performed in Germany to describe the molecular epidemiology among 296 invasive neonatal GBS isolates. Isolates were typed by pulsed-field gel electrophoresis (PFGE). Typing results were compared with serotypes as well as to clinical data on disease onset, meningitic involvement, and outcome. A remarkable clustering was found with about 60% of all typeable invasive isolates being annotated to one of 7 major PFGE groups, and clusters being nationally widely spread over the whole time period. Despite heterogenic elements, certain PFGE groups were closely related to singular serotypes, especially serotypes V (82%), Ia (84%), and Ib (77%). PFGE groups and serotypes were also partly related to clinical presentation as either early onset disease or late onset disease, and either meningitis or nonmeningitic GBS disease, but not to outcome. There is a remarkable clonality among invasive GBS isolates that are widely spread geographically and in time; however, no specific clonal lines could be correlated to disease severity and outcome.

Combining Microarray Technology and Molecular Epidemiology to Identify Genes Associated with Invasive Group BStreptococcus

Many bacterial species function as both commensals and pathogens; we used this dual nature to develop a high-throughput molecular epidemiological approach to identifying bacterial virulence genes. We applied our approach to Group B Streptococcus (GBS). Three representative commensal and one invasive GBS isolates were selected as tester strains from a population-based collection. We used microarray-based comparative genomic hybridization to identify open reading frames (ORFs) present in two sequenced invasive strains, but absent or divergent in tester strains. We screened 23 variable ORFs against 949 GBS isolates using a GBS Library on a Slide (LOS) microarray platform. Four ORFs occurred more frequently in invasive than commensal isolates, and one appeared more frequently in commensal isolates. Comparative hybridization using an oligonucleotide microarray, combined with epidemiologic screening using the LOS microarray platform, enabled rapid identification of bacterial genes potentially associated with pathogenicity.

Multilocus Sequence Typing of Swedish Invasive Group B Streptococcus Isolates Indicates a Neonatally Associated Genetic Lineage and Capsule Switching

Streptococcus agalactiae, also designated group B streptococcus (GBS), is an important pathogen in neonates, pregnant women, and nonpregnant adults with predisposing conditions. We used multilocus sequence typing (MLST) to characterize 158 GBS isolates that were associated with neonatal and adult invasive disease and that were collected in northern and western Sweden from 1988 to 1997. Five major genetic lineages (sequence type [ST] 19, ST-17, ST-1, ST-23, and ST-9 complexes) were identified among the isolates, including serotype Ia, Ib, and II to V isolates, indicating a highly clonal population structure among invasive GBS isolates. A number of STs were found to contain isolates of different serotypes, which indicates that capsule switching occurred rather frequently. Two distantly related genetic lineages were identified among isolates of serotype III, namely, clonal complex 19 (CC19), and CC17. CC19 was equally common among isolates from adult and neonatal disease (accounting for 10.3% of GBS isolates from adult disease and 18.7% from neonatal disease), whereas CC17 significantly appeared to be associated with neonatal invasive disease (isolated from 21.9% of neonatal isolates but only 2.6% of adult isolates). The distribution of the mobile elements GBSi1 and IS1548 reveals that they can act as genetic markers for lineages CC17 and CC19, respectively.