scholarly journals Identification of Virulence-Associated Properties by Comparative Genome Analysis of Streptococcus pneumoniae, S. pseudopneumoniae, S. mitis, Three S. oralis Subspecies, and S. infantis

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Mogens Kilian ◽  
Hervé Tettelin
Keyword(s):  
Streptococcus Pneumoniae ◽  
Virulence Factors ◽  
Genetic Stability ◽  
Common Ancestor ◽  
Striking Difference ◽  
Direct Impact ◽  
Streptococcus Mitis ◽  
Content Type ◽  
Commensal Microbiota ◽  
Successful Adaptation

ABSTRACT From a common ancestor, Streptococcus pneumoniae and Streptococcus mitis evolved in parallel into one of the most important pathogens and a mutualistic colonizer of humans, respectively. This evolutionary scenario provides a unique basis for studies of both infection-associated properties and properties important for harmonious coexistence with the host. We performed detailed comparisons of 60 genomes of S. pneumoniae, S. mitis, Streptococcus pseudopneumoniae, the three Streptococcus oralis subspecies oralis, tigurinus, and dentisani, and Streptococcus infantis. Nonfunctional remnants of ancestral genes in both S. pneumoniae and in S. mitis support the evolutionary model and the concept that evolutionary changes on both sides were required to reach their present relationship to the host. Confirmed by screening of >7,500 genomes, we identified 224 genes associated with virulence. The striking difference to commensal streptococci was the diversity of regulatory mechanisms, including regulation of capsule production, a significantly larger arsenal of enzymes involved in carbohydrate hydrolysis, and proteins known to interfere with innate immune factors. The exclusive presence of the virulence factors in S. pneumoniae enhances their potential as vaccine components, as a direct impact on beneficial members of the commensal microbiota can be excluded. In addition to loss of these virulence-associated genes, adaptation of S. mitis to a mutualistic relationship with the host apparently required preservation or acquisition of 25 genes lost or absent from S. pneumoniae. Successful adaptation of S. mitis and other commensal streptococci to a harmonious relationship with the host relied on genetic stability and properties facilitating life in biofilms. IMPORTANCE Streptococcus pneumoniae is one of the most important human pathogens but is closely related to Streptococcus mitis, with which humans live in harmony. The fact that the two species evolved from a common ancestor provides a unique basis for studies of both infection-associated properties and properties important for harmonious coexistence with the host. By detailed comparisons of genomes of the two species and other related streptococci, we identified 224 genes associated with virulence and 25 genes unique to the mutualistic species. The exclusive presence of the virulence factors in S. pneumoniae enhances their potential as vaccine components, as a direct impact on beneficial members of the commensal microbiota can be excluded. Successful adaptation of S. mitis and other commensal streptococci to a harmonious relationship with the host relied on genetic stability and properties facilitating life in biofilms.

scholarly journals Parallel Evolution of Streptococcus pneumoniae and Streptococcus mitis to Pathogenic and Mutualistic Lifestyles

mBio ◽  
2014 ◽  
Vol 5 (4) ◽  
Author(s):  
Mogens Kilian ◽  
David R. Riley ◽  
Anders Jensen ◽  
Holger Brüggemann ◽  
Hervé Tettelin
Keyword(s):  
Streptococcus Pneumoniae ◽  
Virulence Genes ◽  
Phylogenetic Analyses ◽  
Parallel Evolution ◽  
Structural Diversity ◽  
Capsular Polysaccharides ◽  
Streptococcus Mitis ◽  
Content Type ◽  
Genomic Plasticity ◽  
Reduced Genome

ABSTRACTThe bacteriumStreptococcus pneumoniaeis one of the leading causes of fatal infections affecting humans. Intriguingly, phylogenetic analysis shows that the species constitutes one evolutionary lineage in a cluster of the otherwise commensalStreptococcus mitisstrains, with which humans live in harmony. In a comparative analysis of 35 genomes, including phylogenetic analyses of all predicted genes, we have shown that the pathogenic pneumococcus has evolved into a master of genomic flexibility while lineages that evolved into the nonpathogenicS. mitissecured harmonious coexistence with their host by stabilizing an approximately 15%-reduced genome devoid of many virulence genes. Our data further provide evidence that interspecies gene transfer betweenS. pneumoniaeandS. mitisoccurs in a unidirectional manner, i.e., fromS. mitistoS. pneumoniae. Import of genes fromS. mitisand other mitis, anginosus, and salivarius group streptococci ensured allelic replacements and antigenic diversification and has been driving the evolution of the remarkable structural diversity of capsular polysaccharides ofS. pneumoniae. Our study explains how the unique structural diversity of the pneumococcal capsule emerged and conceivably will continue to increase and reveals a striking example of the fragile border between the commensal and pathogenic lifestyles. While genomic plasticity enabling quick adaptation to environmental stress is a necessity for the pathogenic streptococci, the commensal lifestyle benefits from stability.IMPORTANCEOne of the leading causes of fatal infections affecting humans,Streptococcus pneumoniae, and the commensalStreptococcus mitisare closely related obligate symbionts associated with hominids. Faced with a shortage of accessible hosts, the two opposing lifestyles evolved in parallel. We have shown that the nonpathogenicS. mitissecured harmonious coexistence with its host by stabilizing a reduced genome devoid of many virulence genes. Meanwhile, the pathogenic pneumococcus evolved into a master of genomic flexibility and imports genes fromS. mitisand other related streptococci. This process ensured antigenic diversification and has been driving the evolution of the remarkable structural diversity of capsular polysaccharides ofS. pneumoniae, which conceivably will continue to increase and present a challenge to disease prevention.

scholarly journals Identification of apheAGene Associated with Streptococcus mitis by Using Suppression Subtractive Hybridization

2012 ◽  
Vol 78 (8) ◽  
pp. 3004-3009 ◽  
Author(s):  
Hee Kuk Park ◽  
Hien Thanh Dang ◽  
Soon Chul Myung ◽  
Wonyong Kim
Keyword(s):  
Streptococcus Pneumoniae ◽  
Suppression Subtractive Hybridization ◽  
Subtractive Hybridization ◽  
Streptococcus Mitis ◽  
Content Type ◽  
Oral Environment

ABSTRACTWe performed suppression subtractive hybridization to identify genomic differences betweenStreptococcus mitisandStreptococcus pneumoniae. Based on thepheAgene, a primer set specific toS. mitisdetection was found in 18 out of 103S. mitis-specific clones. Our findings would be useful for discrimination ofS. mitisfrom other closely related cocci in the oral environment.

scholarly journals Highly Variable Streptococcus oralis Strains Are Common among Viridans Streptococci Isolated from Primates

mSphere ◽  
2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Dalia Denapaite ◽  
Martin Rieger ◽  
Sophie Köndgen ◽  
Reinhold Brückner ◽  
Irma Ochigava ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Virulence Factors ◽  
Gene Clusters ◽  
Genomic Islands ◽  
Genomic Diversity ◽  
Future Research ◽  
Viridans Streptococci ◽  
Content Type ◽  
Small Noncoding Rnas ◽  
Cas Gene

ABSTRACT Streptococcus pneumoniae is a rare example of a human-pathogenic bacterium among viridans streptococci, which consist of commensal symbionts, such as the close relatives Streptococcus mitis and S. oralis. We have shown that S. oralis can frequently be isolated from primates and a variety of other viridans streptococci as well. Genes and genomic islands which are known pneumococcal virulence factors are present in S. oralis and S. mitis, documenting the widespread occurrence of these compounds, which encode surface and secreted proteins. The frequent occurrence of CRISP-Cas gene clusters and a surprising variation of a set of small noncoding RNAs are factors to be considered in future research to further our understanding of mechanisms involved in the genomic diversity driven by horizontal gene transfer among viridans streptococci. Viridans streptococci were obtained from primates (great apes, rhesus monkeys, and ring-tailed lemurs) held in captivity, as well as from free-living animals (chimpanzees and lemurs) for whom contact with humans is highly restricted. Isolates represented a variety of viridans streptococci, including unknown species. Streptococcus oralis was frequently isolated from samples from great apes. Genotypic methods revealed that most of the strains clustered on separate lineages outside the main cluster of human S. oralis strains. This suggests that S. oralis is part of the commensal flora in higher primates and evolved prior to humans. Many genes described as virulence factors in Streptococcus pneumoniae were present also in other viridans streptococcal genomes. Unlike in S. pneumoniae, clustered regularly interspaced short palindromic repeat (CRISPR)–CRISPR-associated protein (Cas) gene clusters were common among viridans streptococci, and many S. oralis strains were type PI-2 (pilus islet 2) variants. S. oralis displayed a remarkable diversity of genes involved in the biosynthesis of peptidoglycan (penicillin-binding proteins and MurMN) and choline-containing teichoic acid. The small noncoding cia-dependent small RNAs (csRNAs) controlled by the response regulator CiaR might contribute to the genomic diversity, since we observed novel genomic islands between duplicated csRNAs, variably present in some isolates. All S. oralis genomes contained a β-N-acetyl-hexosaminidase gene absent in S. pneumoniae, which in contrast frequently harbors the neuraminidases NanB/C, which are absent in S. oralis. The identification of S. oralis-specific genes will help us to understand their adaptation to diverse habitats. IMPORTANCE Streptococcus pneumoniae is a rare example of a human-pathogenic bacterium among viridans streptococci, which consist of commensal symbionts, such as the close relatives Streptococcus mitis and S. oralis. We have shown that S. oralis can frequently be isolated from primates and a variety of other viridans streptococci as well. Genes and genomic islands which are known pneumococcal virulence factors are present in S. oralis and S. mitis, documenting the widespread occurrence of these compounds, which encode surface and secreted proteins. The frequent occurrence of CRISP-Cas gene clusters and a surprising variation of a set of small noncoding RNAs are factors to be considered in future research to further our understanding of mechanisms involved in the genomic diversity driven by horizontal gene transfer among viridans streptococci.

scholarly journals Draft Genome Sequence of a Potentially Novel Streptococcus Species Belonging to the Streptococcus mitis Group

2018 ◽  
Vol 6 (26) ◽  
Author(s):  
Ingerid Ø. Kirkeleite ◽  
Jon Bohlin ◽  
Lonneke Scheffer ◽  
Einar T. Weme ◽  
Didrik F. Vestrheim
Keyword(s):  
Species Identification ◽  
Genome Sequence ◽  
Common Ancestor ◽  
Draft Genome ◽  
Draft Genome Sequence ◽  
Recent Common Ancestor ◽  
Streptococcus Mitis ◽  
Content Type ◽  
Streptococcus Species ◽  
Most Recent Common Ancestor

We report here the draft genome sequence of a Streptococcus species belonging to the S. mitis group. While a clear species identification cannot be made for the isolate, it appears that its most recent common ancestor is the species S. pseudopneumoniae.

scholarly journals Inactivation of Transcriptional Regulator FabT Influences Colony Phase Variation of Streptococcus pneumoniae

mBio ◽  
2021 ◽  
Author(s):  
Jinghui Zhang ◽  
Weijie Ye ◽  
Kaifeng Wu ◽  
Shengnan Xiao ◽  
Yuqiang Zheng ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Cell Surface ◽  
Virulence Factors ◽  
Capsular Polysaccharide ◽  
Phase Variation ◽  
Transcriptional Regulator ◽  
Human Pathogen ◽  
Content Type ◽  
Reversible Phase

Streptococcus pneumoniae is a major human pathogen, and its virulence factors and especially the capsular polysaccharide have been extensively studied. In addition to virulence components that are present on its cell surface that directly interact with the host, S. pneumoniae undergoes a spontaneous and reversible phase variation that allows survival in different host environments.

scholarly journals M-Ficolin Binds Selectively to the Capsular Polysaccharides of Streptococcus pneumoniae Serotypes 19B and 19C and of a Streptococcus mitis Strain

2012 ◽  
Vol 81 (2) ◽  
pp. 452-459 ◽  
Author(s):  
Troels R. Kjaer ◽  
Annette G. Hansen ◽  
Uffe B. S. Sørensen ◽  
Anne T. Holm ◽  
Grith L. Sørensen ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Specific Binding ◽  
Opportunistic Pathogen ◽  
Lectin Pathway ◽  
Capsular Polysaccharides ◽  
Complement Factor ◽  
Streptococcus Mitis ◽  
Content Type ◽  
Phosphodiester Bond ◽  
Bacterial Surface

ABSTRACTThe three human ficolins (H-, L-, and M-ficolins) and mannan-binding lectin are pattern recognition molecules of the innate immune system mediating activation of the lectin pathway of the complement system. These four human proteins bind to some microorganisms and may be involved in the resolution of infections. We investigated binding selectivity by examining the binding of M-ficolin to a panel of more than 100 different streptococcal strains (Streptococcus pneumoniaeandStreptococcus mitis), each expressing distinct polysaccharide structures. M-ficolin binding was observed for three strains only: strains of the pneumococcal serotypes 19B and 19C and a singleS. mitisstrain expressing a similar polysaccharide structure. The bound M-ficolin, in association with MASP-2, mediated the cleavage of complement factor C4. Binding to the bacteria was inhibitable byN-acetylglucosamine, indicating that the interaction with the bacterial surface takes place via the fibrinogen-like domain. The commonN-acetylmannosamine residue present in the structures of the four capsular polysaccharides of group 19 is linked via a phosphodiester bond. This residue is apparently not a ligand for M-ficolin, since the lectin binds to two of the group 19 polysaccharides only. M-ficolin bound strongly to serotype 19B and 19C polysaccharides. In contrast to those of serotypes 19A and 19F, serotype 19B and 19C polysaccharides contain an extraN-acetylmannosamine residue linked via glycoside linkage only. Thus, this extra residue seems to be the M-ficolin ligand. In conclusion, we were able to demonstrate specific binding of M-ficolin to some capsular polysaccharides of the opportunistic pathogenS. pneumoniaeand of the commensal bacteriumS. mitis.

scholarly journals Intranasal Immunization with the Commensal Streptococcus mitis Confers Protective Immunity against Pneumococcal Lung Infection

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
Sudhanshu Shekhar ◽  
Rabia Khan ◽  
Karl Schenck ◽  
Fernanda Cristina Petersen
Keyword(s):  
Streptococcus Pneumoniae ◽  
Protective Effect ◽  
Protective Immunity ◽  
Lung Infection ◽  
Health Concern ◽  
Pneumococcal Vaccines ◽  
Pneumococcal Serotypes ◽  
Streptococcus Mitis ◽  
Content Type ◽  
Intranasal Immunization

ABSTRACT Streptococcus pneumoniae is a bacterial pathogen that causes various diseases of public health concern worldwide. Current pneumococcal vaccines target the capsular polysaccharide surrounding the cells. However, only up to 13 of more than 90 pneumococcal capsular serotypes are represented in the current conjugate vaccines. In this study, we used two experimental approaches to evaluate the potential of Streptococcus mitis, a commensal that exhibits immune cross-reactivity with S. pneumoniae, to confer protective immunity to S. pneumoniae lung infection in mice. First, we assessed the immune response and protective effect of wild-type S. mitis against lung infection by S. pneumoniae strains D39 (serotype 2) and TIGR4 (serotype 4). Second, we examined the ability of an S. mitis mutant expressing the S. pneumoniae type 4 capsule (S. mitis TIGR4cps) to elicit focused protection against S. pneumoniae TIGR4. Our results showed that intranasal immunization of mice with S. mitis produced significantly higher levels of serum IgG and IgA antibodies reactive to both S. mitis and S. pneumoniae, as well as enhanced production of interleukin 17A (IL-17A), but not gamma interferon (IFN-γ) and IL-4, compared with control mice. The immunization resulted in a reduced bacterial load in respiratory tissues following lung infection with S. pneumoniae TIGR4 or D39 compared with control mice. With S. mitis TIGR4cps, protection upon challenge with S. pneumoniae TIGR4 was superior. Thus, these findings show the potential of S. mitis to elicit natural serotype-independent protection against two pneumococcal serotypes and to provide the benefits of the well-recognized protective effect of capsule-targeting vaccines. IMPORTANCE Streptococcus pneumoniae causes various diseases worldwide. Current pneumococcal vaccines protect against a limited number of more than 90 pneumococcal serotypes, accentuating the urgent need to develop novel prophylactic strategies. S. pneumoniae and the commensal Streptococcus mitis share immunogenic characteristics that make S. mitis an attractive vaccine candidate against S. pneumoniae. In this study, we evaluated the potential of S. mitis and its mutant expressing pneumococcal capsule type 4 (S. mitis TIGR4cps) to induce protection against S. pneumoniae lung infection in mice. Our findings show that intranasal vaccination with S. mitis protects against S. pneumoniae strains D39 (serotype 2) and TIGR4 (serotype 4) in a serotype-independent fashion, which is associated with enhanced antibody and T cell responses. Furthermore, S. mitis TIGR4cps conferred additional protection against S. pneumoniae TIGR4, but not against D39. The findings highlight the potential of S. mitis to generate protection that combines both serotype-independent and serotype-specific responses.

scholarly journals Streptococcus pneumoniae Binds to Host Lactate Dehydrogenase via PspA and PspC To Enhance Virulence

mBio ◽  
2021 ◽  
Vol 12 (3) ◽  
Author(s):  
Sang-Sang Park ◽  
Norberto Gonzalez-Juarbe ◽  
Eriel Martínez ◽  
Joanetha Yvette Hale ◽  
Yi-Han Lin ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Amino Acid ◽  
Lactate Dehydrogenase ◽  
Virulence Factors ◽  
Lactate Production ◽  
Surface Protein ◽  
Host Cells ◽  
Metabolic Enzyme ◽  
Content Type ◽  
Rich Domain

ABSTRACT Pneumococcal surface protein A (PspA) and pneumococcal surface protein C (PspC, also called CbpA) are major virulence factors of Streptococcus pneumoniae (Spn). These surface-exposed choline-binding proteins (CBPs) function independently to inhibit opsonization, neutralize antimicrobial factors, or serve as adhesins. PspA and PspC both carry a proline-rich domain (PRD) whose role, other than serving as a flexible connector between the N-terminal and C-terminal domains, was up to this point unknown. Herein, we demonstrate that PspA binds to lactate dehydrogenase (LDH) released from dying host cells during infection. Using recombinant versions of PspA and isogenic mutants lacking PspA or specific domains of PspA, this property was mapped to a conserved 22-amino-acid nonproline block (NPB) found within the PRD of most PspAs and PspCs. The NPB of PspA had specific affinity for LDH-A, which converts pyruvate to lactate. In a mouse model of pneumonia, preincubation of Spn carrying NPB-bearing PspA with LDH-A resulted in increased bacterial titers in the lungs. In contrast, incubation of Spn carrying a version of PspA lacking the NPB with LDH-A or incubation of wild-type Spn with enzymatically inactive LDH-A did not enhance virulence. Preincubation of NPB-bearing Spn with lactate alone enhanced virulence in a pneumonia model, indicating exogenous lactate production by Spn-bound LDH-A had an important role in pneumococcal pathogenesis. Our observations show that lung LDH, released during the infection, is an important binding target for Spn via PspA/PspC and that pneumococci utilize LDH-A derived lactate for their benefit in vivo. IMPORTANCE Streptococcus pneumoniae (Spn) is the leading cause of community-acquired pneumonia. PspA and PspC are among its most important virulence factors, and these surface proteins carry the proline-rich domain (PRD), whose role was unknown until now. Herein, we show that a conserved 22-amino-acid nonproline block (NPB) found within most versions of the PRD binds to host-derived lactate dehydrogenase A (LDH-A), a metabolic enzyme which converts pyruvate to lactate. PspA-mediated binding of LDH-A increased Spn titers in the lungs and this required LDH-A enzymatic activity. Enhanced virulence was also observed when Spn was preincubated with lactate, suggesting LDH-A-derived lactate is a vital food source. Our findings define a role for the NPB of the PRD and show that Spn co-opts host enzymes for its benefit. They advance our understanding of pneumococcal pathogenesis and have key implications on the susceptibility of individuals with preexisting airway damage that results in LDH-A release.

scholarly journals Capsular Polysaccharide Expression in CommensalStreptococcusSpecies: Genetic and Antigenic Similarities toStreptococcus pneumoniae

mBio ◽  
2016 ◽  
Vol 7 (6) ◽  
Author(s):  
Uffe B. Skov Sørensen ◽  
Kaihu Yao ◽  
Yonghong Yang ◽  
Hervé Tettelin ◽  
Mogens Kilian
Keyword(s):  
Streptococcus Pneumoniae ◽  
Virulence Factors ◽  
Capsular Polysaccharide ◽  
Capsular Polysaccharides ◽  
Structural Polymorphism ◽  
Commensal Microbiota ◽  
Capsule Production ◽  
Genetic Mechanisms ◽  
Different Origins ◽  
Host Parasite

ABSTRACTExpression of a capsular polysaccharide is considered a hallmark of most invasive species of bacteria, includingStreptococcus pneumoniae, in which the capsule is among the principal virulence factors and is the basis for successful vaccines. Consequently, it was previously assumed that capsule production distinguishesS. pneumoniaefrom closely related commensals of the mitis group streptococci. Based on antigenic and genetic analyses of 187 mitis group streptococci, including 90 recognized serotypes ofS. pneumoniae, we demonstrated capsule production by the Wzy/Wzx pathway in 74% of 66S. mitisstrains and in virtually all tested strains ofS. oralis(subspeciesoralis,dentisani, andtigurinus) andS. infantis. Additional analyses of genomes ofS. cristatus,S. parasanguinis,S. australis,S. sanguinis,S. gordonii,S. anginosus,S. intermedius, andS. constellatusrevealed complete capsular biosynthesis (cps) loci in all strains tested. Truncatedcpsloci were detected in three strains ofS. pseudopneumoniae, in 26% ofS. mitisstrains, and in a singleS. oralisstrain. The level of sequence identities ofcpslocus genes confirmed that the structural polymorphism of capsular polysaccharides inS. pneumoniaeevolved by import ofcpsfragments from commensalStreptococcusspecies, resulting in a mosaic of genes of different origins. The demonstrated antigenic identity of at least eight of the numerous capsular polysaccharide structures expressed by commensal streptococci with recognized serotypes ofS. pneumoniaeraises concerns about potential misidentifications in addition to important questions concerning the consequences for vaccination and host-parasite relationships both for the commensals and for the pathogen.IMPORTANCEExpression of a capsular polysaccharide is among the principal virulence factors ofStreptococcus pneumoniaeand is the basis for successful vaccines against infections caused by this important pathogen. Contrasting with previous assumptions, this study showed that expression of capsular polysaccharides by the same genetic mechanisms is a general property of closely related species of streptococci that form a significant part of our commensal microbiota. The demonstrated antigenic identity of many capsular polysaccharides expressed by commensal streptococci andS. pneumoniaeraises important questions concerning the consequences for vaccination and host-parasite relationships both for the commensals and the pathogen.

scholarly journals Streptococcus pneumoniae serotypes that frequently colonise the human nasopharynx are common recipients of penicillin-binding protein gene fragments from Streptococcus mitis

2021 ◽  
Vol 7 (9) ◽  
Author(s):  
Akuzike Kalizang'oma ◽  
Chrispin Chaguza ◽  
Andrea Gori ◽  
Charlotte Davison ◽  
Sandra Beleza ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Type Species ◽  
Binding Protein ◽  
Pneumococcal Serotypes ◽  
Penicillin Binding Protein ◽  
Beta Lactam ◽  
Streptococcus Mitis ◽  
Content Type ◽  
Link Type ◽  
Close Relatives

Streptococcus pneumoniae is an important global pathogen that causes bacterial pneumonia, sepsis and meningitis. Beta-lactam antibiotics are the first-line treatment for pneumococcal disease, however, their effectiveness is hampered by beta-lactam resistance facilitated by horizontal genetic transfer (HGT) with closely related species. Although interspecies HGT is known to occur among the species of the genus Streptococcus , the rates and effects of HGT between Streptococcus pneumoniae and its close relatives involving the penicillin binding protein (pbp) genes remain poorly understood. Here we applied the fastGEAR tool to investigate interspecies HGT in pbp genes using a global collection of whole-genome sequences of Streptococcus mitis , Streptococcus oralis and S. pneumoniae . With these data, we established that pneumococcal serotypes 6A, 13, 14, 16F, 19A, 19F, 23F and 35B were the highest-ranking serotypes with acquired pbp fragments. S. mitis was a more frequent pneumococcal donor of pbp fragments and a source of higher pbp nucleotide diversity when compared with S. oralis . Pneumococci that acquired pbp fragments were associated with a higher minimum inhibitory concentration (MIC) for penicillin compared with pneumococci without acquired fragments. Together these data indicate that S. mitis contributes to reduced β-lactam susceptibility among commonly carried pneumococcal serotypes that are associated with long carriage duration and high recombination frequencies. As pneumococcal vaccine programmes mature, placing increasing pressure on the pneumococcal population structure, it will be important to monitor the influence of antimicrobial resistance HGT from commensal streptococci such as S. mitis .

Sign in / Sign up

Export Citation Format

Share Document