Multilocus sequence types, serotypes, and variants of the surface antigen PspA in Streptococcus pneumoniae isolates from meningitis patients in Poland

Serotype Distribution and Multi Locus Sequence Type (MLST) of Erythromycin-Resistant Streptococcus Pneumoniae Isolates in Tehran, Iran

Background

The number of erythromycin-resistant Streptococcus pneumoniae has significantly increased around the world. The present study aimed to determine the serotype distribution and molecular epidemiology of the erythromycin-resistant Streptococcus pneumoniae (ERSP) isolated from patients with invasive disease.

Methods

A total of 44 Streptococcus pneumoniae isolates were tested for susceptibility to several antimicrobial agents. Additionally, the polymerase chain reaction (PCR) was applied to evaluate ERSP isolates in terms of the presence of erythromycin resistance genes (e.g., ermB and mefA). The isolates were serotyped using the sequential multiplex-PCR method, and molecular epidemiology was assessed through the multilocus sequence typing (MLST) analysis.

Results

The results represented multidrug resistance (MDR) in approximately half of the pneumococcal isolates. Among 22 ERSP isolates, 20 (90.9%) and 12 (56%) ones contained ermB and mefA, respectively. Further, 14 (31.8%), 3 (22.7%), and 19A (18.1%) were the common serotypes among the isolates. No significant correlation was observed between serotypes and erythromycin resistance genes. Furthermore, the MLST results revealed 18 different sequence types (STs), the top ones of which were ST3130 (3 isolates) and ST166 (3 isolates). Population genetic analysis disclosed that CC63 (32%), CC156 (18%), and CC320 (18%) were identified as the predominant clonal complexes.

Conclusions

The ERSP isolates exhibited high genetic diversity. The large frequency of MDR isolates suggests the emergence of high resistant strains, as well as the need to implement vaccination in the immunization schedule of Iran. These accumulating evidences indicate that 13-valent pneumococcal conjugate vaccines provided higher serotype coverage in the ERSP isolates.

A Jack of All Trades: The Role of Pneumococcal Surface Protein A in the Pathogenesis of Streptococcus pneumoniae

Streptococcus pneumoniae (Spn), or the pneumococcus, is a Gram-positive bacterium that colonizes the upper airway. Spn is an opportunistic pathogen capable of life-threatening disease should it become established in the lungs, gain access to the bloodstream, or disseminate to vital organs including the central nervous system. Spn is encapsulated, allowing it to avoid phagocytosis, and current preventative measures against infection include polyvalent vaccines composed of capsular polysaccharide corresponding to its most prevalent serotypes. The pneumococcus also has a plethora of surface components that allow the bacteria to adhere to host cells, facilitate the evasion of the immune system, and obtain vital nutrients; one family of these are the choline-binding proteins (CBPs). Pneumococcal surface protein A (PspA) is one of the most abundant CBPs and confers protection against the host by inhibiting recognition by C-reactive protein and neutralizing the antimicrobial peptide lactoferricin. Recently our group has identified two new roles for PspA: binding to dying host cells via host-cell bound glyceraldehyde 3-phosphate dehydrogenase and co-opting of host lactate dehydrogenase to enhance lactate availability. These properties have been shown to influence Spn localization and enhance virulence in the lower airway, respectively. Herein, we review the impact of CBPs, and in particular PspA, on pneumococcal pathogenesis. We discuss the potential and limitations of using PspA as a conserved vaccine antigen in a conjugate vaccine formulation. PspA is a vital component of the pneumococcal virulence arsenal - therefore, understanding the molecular aspects of this protein is essential in understanding pneumococcal pathogenesis and utilizing PspA as a target for treating or preventing pneumococcal pneumonia.

Association Between Pneumococcal Surface Protein A Family and Genetic/Antimicrobial Resistance Traits of Non-Invasive Pneumococcal Isolates from Adults in Northern Japan

Pneumococcal isolates from adult patients in northern Japan in 2016 were subjected to molecular investigation related to pneumococcal surface protein A (PspA) and drug resistance determinants. Of the 51 isolates, serotype 3/ST180 was the most prevalent (17.6%), followed by 35B (ST2755/ST558) (11.8%) and 15A (ST63/ST7874/ST13068/ST13785) (9.8%). Coverage of serotypes by 13-valent conjugate vaccine and 23-valent polysaccharide vaccine was 27.5% and 49%, respectively. All the isolates expressed PspA family 1 or 2 (51% and 49%, respectively). Each serotype was associated with either of the PspA families (e.g., serotype 3, PspA family 1; serotypes 35B and 15A, PspA family 2). Multidrug resistance (MDR) was found in 84.3% of the isolates. Minimum of one altered penicillin-binding protein gene was detected in 82.4% of isolates, indicating 25.5% non-susceptibility to penicillin. Serotypes 15A and 35B were predominant and demonstrated MDR. An isolate of serotype 15A/ST13785 (single-locus variant of ST242) was resistant to fluoroquinolones associated with double mutation in the quinolone resistance-determining regions of gyrA and parC. The present study indicates the spread of MDR pneumococci represented by isolates of serotypes 3, 15A, and 35B, and prevalence of both PspA family 1 and 2 in isolates obtained from adult patients.

PspA family distribution, antimicrobial resistance and serotype of Streptococcus pneumoniae isolated from upper respiratory tract infections in Japan

Background

The protection against pneumococcal infections provided by currently available pneumococcal polysaccharide conjugate vaccines are restricted to the limited number of the serotypes included in the vaccine. In the present study, we evaluated the distribution of the pneumococcal capsular type and surface protein A (PspA) family of pneumococcal isolates from upper respiratory tract infections in Japan.

Methods

A total of 251 S. pneumoniae isolates from patients seeking treatment for upper respiratory tract infections were characterized for PspA family, antibiotic resistance and capsular type.

Results

Among the 251 pneumococci studied, the majority (49.4%) was identified as belonging to PspA family 2, while most of the remaining isolates (44.6%) belonged to family 1. There were no significant differences between the distributions of PspA1 versus PspA2 isolates based on the age or gender of the patient, source of the isolates or the isolates’ susceptibilities to penicillin G. In contrast, the frequency of the mefA gene presence and of serotypes 15B and 19F were statistically more common among PspA2 strains.

Conclusion

The vast majority of pneumococci isolated from the middle ear fluids, nasal discharges/sinus aspirates or pharyngeal secretions represented PspA families 1 and 2. Capsular serotypes were generally not exclusively associated with certain PspA families, although some capsular types showed a much higher proportion of either PspA1 or PspA2. A PspA-containing vaccine would potentially provide high coverage against pneumococcal infectious diseases because it would be cross-protective versus invasive disease with the majority of pneumococci infecting children and adults.

Characterization of the antibody response elicited by immunization with pneumococcal surface protein A (PspA) as recombinant protein or DNA vaccine and analysis of protection against an intranasal lethal challenge with Streptococcus pneumoniae

Pneumococcal surface protein A (PspA) is an important candidate for a vaccine against pneumococcal infections. DNA vaccines expressing PspA were shown to protect mice against intraperitoneal and colonization challenge models in mice. We now show that a DNA vaccine expressing PspA from clade 4 (pSec-pspA4Pro) is also able to elicit protection against an intranasal lethal challenge model at levels similar to the recombinant protein PspA4Pro adjuvanted with alum. PspA4Pro + alum induced an IgG response characterized by a high IgG1/IgG2a ratio, leading to a lack of binding of anti-PspA IgG2a antibodies to intact pneumococci in vitro, which is in contrast to the response elicited by pSec-pspA4Pro. Epitopes recognized by the sera were mapped and antibodies induced by immunization with PspA4Pro + alum showed positive reaction with several synthetic peptides, mostly located in the first half of the protein. On the other hand, antibodies induced by the DNA vaccine showed reactivity with only two peptides. Though both strategies were protective against the intranasal lethal challenge model, the elicited humoral responses differ significantly, with the detection of important differences in the Fc (IgG1/IgG2a ratios) and Fab (recognized epitopes) regions of the induced antibodies.

A new variant of the capsule 3 cluster occurs in Streptococcus pneumoniae from deceased wild chimpanzees

The presence of new Streptococcus pneumoniae clones in dead wild chimpanzees from the Taï National Park, Côte d'Ivoire, with previous respiratory problems has been demonstrated recently by DNA sequence analysis from samples obtained from the deceased apes. In order to broadenour understanding on the relatedness of these pneumococcal clones to those from humans, the gene locus responsible for biosynthesis of the capsule polysaccharide (CPS) has now been characterized. DNA sequence analysis of PCR fragments identified a cluster named cps3(Taï) containing the four genes typical for serotype 3 CPS, but lacking a 5'-region of ≥2 kb which is degenerated in other cps3 loci and not required for type 3 biosynthesis. CPS3 is composed of a simple disaccharide repeat unit comprising glucose and glucuronic acid (GlcUA). The two genes ugd responsible for GlcUA synthesis and wchE encoding the type 3 synthase are essential for CPS3 biosynthesis, whereas both, galU and the 3'-truncated gene pgm are not required due to the presence of homologues elsewhere in the genome. The DNA sequence of cps3(Taï) diverged considerably from those of other cps3 loci. Also, the gene pgm(Taï) represents a full length version with a nonsense mutation at codon 179. The two genes ugd(Taï) and wchE(Taï) including the promoter region were transformed into a nonencapsulated laboratory strain S. pneumoniae R6. Transformants which expressed type 3 capsule polysaccharide were readily obtained, documenting that the gene products are functional. In summary, the data indicate that cps3(Taï) evolved independent from other cps3 loci, suggesting the presence of specialized serotype 3 S. pneumoniae clones endemic to the Taï National Park area.

First report of Streptococcus pneumoniae serotype 6D isolates from invasive infections

We report the first invasive Streptococcus pneumoniae isolates of serotype 6D and the first occurrence of this serotype in Europe. Till now, the appearance of serotype 6D pneumococci in nasopharyngeal carriage has been speculated to be associated with a selective pressure from vaccination with the conjugated 7-valent antipneumococcal vaccine. Our observations indicate that this serotype is present also among unvaccinated individuals in the population where mass infant vaccination has not yet been introduced. Importantly, these strains were isolated from invasive infections, indicating the full virulence potential of pneumococci belonging to serotype 6D and its importance for future vaccine formulations.

The relBE2Spn toxin-antitoxin system of Streptococcus pneumoniae: role in antibiotic tolerance and functional conservation in clinical isolates

Type II (proteic) chromosomal toxin-antitoxin systems (TAS) are widespread in Bacteria and Archaea but their precise function is known only for a limited number of them. Out of the many TAS described, the relBE family is one of the most abundant, being present in the three first sequenced strains of Streptococcus pneumoniae (D39, TIGR4 and R6). To address the function of the pneumococcal relBE2Spn TAS in the bacterial physiology, we have compared the response of the R6-relBE2Spn wild type strain with that of an isogenic derivative, Delta relB2Spn under different stress conditions such as carbon and amino acid starvation and antibiotic exposure. Differences on viability between the wild type and mutant strains were found only when treatment directly impaired protein synthesis. As a criterion for the permanence of this locus in a variety of clinical strains, we checked whether the relBE2Spn locus was conserved in around 100 pneumococcal strains, including clinical isolates and strains with known genomes. All strains, although having various types of polymorphisms at the vicinity of the TA region, contained a functional relBE2Spn locus and the type of its structure correlated with the multilocus sequence type. Functionality of this TAS was maintained even in cases where severe rearrangements around the relBE2Spn region were found. We conclude that even though the relBE2Spn TAS is not essential for pneumococcus, it may provide additional advantages to the bacteria for colonization and/or infection.

Molecular characterization of invasive penicillin non-susceptible Streptococcus pneumoniae from Denmark, 2001 to 2005

The aim of this study was to characterize invasive penicillin non-susceptible pneumococci (PNSP) isolated in Denmark from 2001 to 2005, describe the genetic changes in the penicillin-binding proteins (PBPs) and compare the isolates to the international recognized PNSP clones. All isolates were characterized using serotyping; 43 isolates were also characterized by multilocus sequence typing (MLST) and sequence determination of the PBP genes, pbp1a, pbp2b and pbp2x. In addition, isolates were tested for susceptibility to various antimicrobial agents. From 2001 to 2005, 178 invasive PNSP isolates were found among all invasive isolates. Of these, 13% were penicillin-resistant pneumococci (PRP). The PRP isolates were different to the penicillin intermediate-resistant pneumococci (PIRP) as they were co-resistant to a higher number of antimicrobial agents, and the serotype diversity was lower for the PRP isolates compared to the PIRP isolates. Changes in the PBPs were found to be the same as those observed in other studies. Most PRP isolates were found to belong to the clonal complex CC156 of which most were ST156 serotype 9V or 14. ST156 is a well known multiresistant widespread international PMEN (Pneumococcal Molecular Epidemiology Network) clone, Spain(9V)-3, which is also present as one of the dominant clones in our neighbour countries of Sweden, Norway and Germany.

An unusual pneumococcal sequence type is the predominant cause of serotype 3 invasive disease in South Africa

We reviewed pneumococcal serotype 3 cases reported from 2000 through 2005 to a laboratory-based surveillance system for invasive pneumococcal disease in South Africa. The prevalence of serotype 3 invasive isolates was compared to their prevalence in carriage isolates to determine the odds of invasiveness due to serotype 3 among South African children. Three groups of serotype 3 strains were characterized by pulsed-field gel electrophoresis (PFGE) or Box element PCR (BOX-PCR), randomly selected invasive isolates from one province, isolates from a carriage study involving children in the same province, and antimicrobial-resistant invasive isolates collected nationally. Examples of the PFGE types identified were further characterized by multilocus sequence typing. In total, 15,980 viable isolates causing invasive disease were submitted, of which 661 (4%) were serotype 3, mostly from adults (85% [489/575]). Fewer serotype 3 isolates were nonsusceptible to antimicrobial agents tested (40/661 [6%]) than non-serotype 3 isolates (8,480/15,319 [55%]) (P < 0.001). Compared to non-serotype 3 cases, there was no association with HIV coinfection (2,212/2,569 [86%] versus 72/78 [92%]; P = 0.1) or increased case fatality ratio (1,190/4,211 [28%] versus 54/154 [35%]; P = 0.7). Serotype 3 in children had a low but statistically insignificant invasive disease potential (odds ratio [OR] of 0.15; 95% confidence interval [CI] of 0.01 to 1.06). Strains were grouped into 3 PFGE clusters, with the largest, cluster A, representing 54% (84/155), including 14 isolates confirmed as sequence type 458 (ST458). It was confirmed that 3 isolates from cluster B, which represented only 12% (18/155) of the isolates, were the serotype 3 global strain, ST180. We have therefore identified ST458 as predominating in South Africa, but with an invasive potential similar to that of the predominant global clone ST180.

Diversity of pneumococcal surface protein A (PspA) among prevalent clones in Spain

BACKGROUND

PspA is recognized as a major pneumococcal virulence factor and a possible vaccine candidate. The aim of this study was to analyze the PspA family and clade distribution among 112 Spanish pneumococci representatives of dominant clones among patients with invasive disease (n = 66) and nasopharyngeal healthy carriage in children (n = 46).

RESULTS

PspA family 2 was predominant among invasive (63.6%) and carriage (54.3%) pneumococcal isolates. No PspA family 3 isolates were detected and only one strain was PspA negative. Although four clonal complexes contained strains of different clades, a clear association between clade and multi locus sequence typing results was found. Clades 1, 3 and 4 were associated with a wide variety of sequence types (ST) related to multiresistant and antibiotic-susceptible worldwide-disseminated clones. Clade 1 was associated with Spain 6B-ST90, Spain 14-ST18, Colombia 5-ST289, Sweden 1-ST306, Denmark 14-ST230 and Sweden 1-ST304 clones. Clade 3 was associated with Spain 23F-ST81, Spain 9V-ST156, Tennessee 14-ST67, Netherlands 3-ST180 and Netherlands 7F-ST191 clones. Clade 4 was related to Sweden 15A-ST63, Netherlands 18C-ST113 and Greece 21-ST193 clones. In contrast, PspA clade was not related to serotype, age or clinical origin of the isolates.

CONCLUSION

PspA clades were associated with genotypes. PspA family 2 and family 1 were dominant among major Spanish pneumococcal clones isolated from patients with invasive disease and nasopharyngeal carriage in children.

Development of antibodies to PspA families 1 and 2 in children after exposure to Streptococcus pneumoniae

Pneumococcal surface protein A (PspA) is an important virulence factor of Streptococcus pneumoniae. PspA exists as two major families, which include variable but serologically cross-reactive proteins. Previous studies with a family 1 PspA antigen suggested that children develop low concentrations of anti-PspA after pneumococcal carriage or infection. In this study, antibody to PspA families 1 and 2 was measured by an enzyme immunoassay of the serum and saliva of children with a history of culture-proven pneumococcal colonization and/or acute otitis media and in the serum and saliva of adults. The PspA families of the pneumococcal strains isolated from children were determined. The majority of the children had high serum and salivary anti-PspA concentrations to the PspA family they had encountered and low concentrations to the other, whereas adults had high antibody concentrations to both PspA families, both in serum and in saliva. The results suggest that children have a relatively family-specific antibody response to the PspA family they have been exposed to and that any PspA vaccine for children should contain members of both major PspA families.

Distribution of pneumococcal surface protein A families 1 and 2 among Streptococcus pneumoniae isolates from children in finland who had acute otitis media or were nasopharyngeal carriers

PspA is a structurally variable surface protein important to the virulence of pneumococci. PspAs are serologically cross-reactive and exist as two major families. In this study, we determined the distribution of PspA families 1 and 2 among pneumococcal strains isolated from the middle ear fluid (MEF) of children with acute otitis media and from nasopharyngeal specimens of children with pneumococcal carriage. We characterized the association between the two PspA families, capsular serotypes, and multilocus sequence types (STs) of the pneumococcal isolates. MEF isolates (n = 201) of 109 patients and nasopharyngeal isolates (n = 173) of 49 children were PspA family typed by whole-cell enzyme immunoassay (EIA). Genetic typing (PCR) of PspA family was done for 60 isolates to confirm EIA typing results. The prevalences of PspA families 1 and 2 were similar among pneumococci isolated from MEF (51% and 45%, respectively) and nasopharyngeal specimens (48% each). Isolates of certain capsule types as well as isolates of certain STs showed statistical associations with either family 1 or family 2 PspA. Pneumococci from seven children with multiple pneumococcal isolates appeared to express serologically different PspA families in different isolates of the same serotype; in three of the children the STs of the isolates were the same, suggesting that antigenic changes in the PspA expressed may have taken place. The majority of the isolates (97%) belonged to either PspA family 1 or family 2, suggesting that a combination including the two main PspA families would make a good vaccine candidate.

Recognition of pneumococcal isolates by antisera raised against PspA fragments from different clades

Pneumococcal surface protein A (PspA) is an important vaccine candidate against pneumococcal infections, capable of inducing protection in different animal models. Based on its structural diversity, it has been suggested that a PspA-based vaccine should contain at least one fragment from each of the two major families (family 1, comprising clades 1 and 2, and family 2, comprising clades 3, 4 and 5) in order to elicit broad protection. This study analysed the recognition of a panel of 35 pneumococcal isolates bearing different PspAs by antisera raised against the N-terminal regions of PspA clades 1 to 5. The antiserum to PspA clade 4 was found to show the broadest cross-reactivity, being able to recognize pneumococcal strains containing PspAs of all clades in both families. The cross-reactivity of antibodies elicited against a PspA hybrid including the N-terminal region of clade 1 fused to a shorter and more divergent fragment (clade-defining region, or CDR) of clade 4 (PspA1–4) was also tested, and revealed a strong recognition of isolates containing clades 1, 4 and 5, and weaker reactions with clades 2 and 3. The analysis of serum reactivity against different PspA regions further revealed that the complete N-terminal region rather than just the CDR should be included in an anti-pneumococcal vaccine. A PspA-based vaccine is thus proposed to be composed of the whole N-terminal region of clades 1 and 4, which could also be expressed as a hybrid protein.

Phenotypic and molecular analysis of penicillin-nonsusceptible Streptococcus pneumoniae isolates in Poland

beta-Lactams are the drugs of choice for the treatment of infections caused by the important bacterial pathogen Streptococcus pneumoniae. The recent growth of resistance of this organism to penicillin observed worldwide is of the highest concern. In this study, using 887 surveillance pneumococcal isolates recovered in Poland from 1998 to 2002, we observed the increase in penicillin nonsusceptibility from 8.7% to 20.3%. All of the 109 penicillin-nonsusceptible S. pneumoniae (PNSP) isolates identified, together with 22 archival PNSP isolates from 1995 to 1997, were subsequently analyzed by susceptibility testing, serotyping, profiling of pbp genes, pulsed-field gel electrophoresis, and multilocus sequence typing (MLST). Four predominant serotypes, serotypes 6B, 9V, 14, and 23F, characterized 85.5% of the isolates. MLST revealed the presence of 34 sequence types, 15 of which were novel types. Representatives of seven multiresistant international clones (Spain(23F)-1, Spain(6B)-2, Spain(9V)-3, Taiwan(23F)-15, Poland(23F)-16, Poland(6B)-20, and Sweden(15A)-25) or their closely related variants comprised the majority of the study isolates. The spread of Spain(9V)-3 and its related clone of serotype 14/ST143 has remarkably contributed to the recent increase in penicillin resistance in pneumococci in the country.