Streptococcus agalactiae

From MicrobeWiki, the student-edited microbiology resource
Jump to: navigation, search

A Microbial Biorealm page on the genus Streptococcus agalactiae

Classification

Higher order taxa

Cellular organisms

Kingdom: Bacteria

Phylum: Firmicutes

Class: Bacilli

Order: Lactobacillales

Family: Streptococcaceae

Genus: Streptococcus

Species: Streptococcus agalactiae

Species

NCBI: Taxonomy Genome: Streptococcus agalactiae

Streptococcus agalactiae

Description and significance

Streptococcus is a genus that is classified based on the hemolytic properties into three types: Alpha-Hemolytic Streptococci, Beta-Hemolytic Streptococci, and Non-Hemolytic Streptococci. Streptococcus agalactiae, often referred as Group B Streptococcus (GBS), is one of four Beta-Hemolytic streptococci, which results in complete rupture of blood cells shown in wide and clear areas surrounding bacterial colonies on blood agar. [1]

Appearance: S. agalactiae is a diplococcal (a pair of cocci, circular, pair) gram-positive, non acid-fast bacterium (~2.0µm) that does not form spores, is not motile, and is catalase-free, which is an enzyme that catalyzes the reduction of hydrogen peroxide). It occurs in pairs or short chains and has group B Lancefield antigen present. [2][3]

Habitat: S. agalactiae , originally discovered as a cause of bovine mastitis, is part of the normal bacterial flora colonizing the gastrointestinal(GI) tract and genitourinary tract of a significant proportion of the human population. However, it occasionally become a infectious pathogen colonizing the uterus, blood, brain, and meninges. [4]

Significance : This pathogen is one of the leading causes of invasive infections in non-pregnant immunocompromised individuals and also causes bacteremia, septicaemia, meningitis, and pneumonia. Colonization of the rectum and vagina of pregnant women with GBS is correlated with GBS sepsis in newborn infants with early onset disease.[4] S. agalactiae is also subclassified into nine serotypes depeding on the immunologic reactivity of the polysaccharide capsule and among nine serotypes, only types Ia, Ib, II, III, and V are discovered to be responsible for invasive human disease. [5]

Isolation: S. agalactiae can be isolated in infected site of human or in secretions from infected mammary gland of female cattle and related ungulates. In some samples these bacteria are numerous and easily found in stained films; in other cases they may be so scarce that they can be located only with great difficulty. Also, most stains can be used to stain GBS to locate them, since the GBS is gram-positive and readily stained.[4]

Genome project: S. agalactiae poses a serious threat to lives of neonates, responsible for 2-3 cases per 1000 live birth and to lives of human, especially elderly persons and those with weakened immune systems. This microorganism is considered one of the major causes of economic losses to dairy producers without a control program. Because of its significance as an threat to both human and related ungulates, such as cow, its genome was sequenced and still being studied to gain more insight into the virulence factor and to develop treatments and preventive prophylactic antibodies. [5]

Genome structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the or ganism's lifestyle?

The genome of three strains in Streptococcus agalactiae (GBS) have been completely sequenced: S. agalactiae NEM 316, S. agalactiae 2603V/R, and S. agalactiae A909. The genome of two plasmids also have been completely sequenced: S. agalactiae plasmid pGB3631 and S. agalactiae plasmid pGB354. The genome of known five strains in S. agalactiae have not yet been completely sequenced: S. agalactiae 515, S. agalactiae CJB111, S. agalactiae COH1, S. agalactiae H36B, S. agalactiae 18RS21.[6]

Size of genome: S. agalactiae NEM 316 is the serotype III strain.[7] Complete genome sequence of this strain is a circular dsDNA chromosome with 2,211,485 nt (GC content of 35%, coding content of 87%) and contains 2235 genes, 2094 protein coding genes, 101 structural RNAs, and 40 pseudogenes. Genome sequence was completed in 2002/11/15.[8] S. agalactiae 2603V/R is the serotype V strain.[9] Complete genome sequence of this strain is a circular dsDNA chromosome with 2,160,267 nt (GC content of 35%, coding content of 86%) and contains 2271 genes, 2124 protein coding genes, 96 structural RNAs, and no pseudogenes. Genome sequence was completed in 2002/08/28.[10] S. agalactiae A909 is the serotype Ic strain.[11] Complete genome sequence of this strain is a circular DNA chromosome with 2,127,839 nt (GC content of 35%, coding content of 86%) and contains 2136 genes, 1996 protein coding genes, 102 structural RNAs, and 32 pseudogenes. Genome sequence was completed in 2005/10/03.[12]

S. agalactiae A909 is the serotype Ic strain.[11] Complete genome sequence of this strain is a circular DNA chromosome with 2,127,839 nt (GC content of 35%, coding content of 86%) and contains 2136 genes, 1996 protein coding genes, 102 structural RNAs, and 32 pseudogenes. Genome sequence was completed in 2005/10/03.[12]



Analysis of NEM316 genome predicted and identify locus responsible for extracellular products like capsular polysaccharide, surface proteins, and secreted proteins, which are involved in virulence and contributing to pathogenesis. Strain contains 17 genes (cpsA-L, neuBCDA) along with the transcriptional gene cpsY for sialyated capsular polysacchraide, 30 genes (gbs 0391, 0392, 0393, and 27 more genes) for surface proteins containing cell wall, and various genes responsible for 71 secreted proteins.

In strain NEM315, it was observed that there are 12 genes encoding proteins related to plasmid functions, which are replication, partition or transfer, and genes were found in the vicinity of integrase genes.

Streptococcus agalactiae contains two completely sequenced plasmids, pGB 354 and pGB3631. pGB 354 is a circular DNA plasmid with 6,437 nt (GC content of 32% and coding content of 62%) and contains 5 genes, 5 protein coding genes, no structural and pseudo genes. Genome sequence was completed 1997/03/04. pGB 3631 is also a circular DNA plasmid with 5,842 nt (GC content of 33% and coding content of 62%) and contains 9 genes, 6 protein coding genes, no structural and pseudo genes, and 4 other genes. Genome sequence was completed 1994/07/13.

In genomic analysis of NEM315, it was revealed to have stress adaption by encoding Clp proteins (gbs 1634, 1383, 1869, 1367, 0535), which is ATP-dependent protease playing a role in virulence. Also, the genome was analyzed to have several chromosal islands, which is unique feature different from other streptococcus, but rather similar to pathogenic Escherichia coli . This unexpected similarity built hypothesis that virulence factor was on the unique chromosomal island for both species and evolve them into pathogens. But this hypothesis was not yet tested.

Cell structure and metabolism

Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.


carbon? hetero auto? energy -CHEKC

Cellular Features: Streptococcus agalactiae is a non-acid fast Gram-positive baterium (cell wall?? exaplain?). This species is non-motile, catalase (an enzyme that catalyzes the reduction of hydrogen peroxide) - free diplococcal (a pair of cocci, circular, pair) (~2.0 µm) that occur in pairs or short chains. It also does not form spores and often known as Group B Streptococcus due to the presence of group B Lancefield antigen. This species is also B-hemolytic (determined base on hemolysis on blood agar plates). virulence factor - surface protein. - genes or pseudogenes epxressing surface prtotein to adhere to mucosal surfacs and evade host defense.

Environment: Streptococcus agalactiae is host-associated facultative anaerobe, (generation of ATP?explain). The optimal temperature for this species is at 37 Celcius degree (mesophile).

Glucose Oxidation: Oxidative phosphorylation: able to synthesize ATP by oxidative phosphorulation. structural genoes for cytochrome bd quinol oxidase (high affinity for oxygen and a low energetic yield) and NADH dehydrogenase. enzymes contributing to aerobic growth of this species. no gene involved in heme synthesis --> could use external source of heme, but no corresponding transporter detected.

able to ferment different carbon sources to multiple by-products, lactate, acetate, ethanol, formate or acetoin

worth noting that bioenergetic mecahnism of this more related to L. lactis than other pathogenic streptococci - seen in genes coding for bd oxidase and some feremnt pathwyas have ortholog (explain) only in gene seq. of L alctise .

capacity to import a broad range of carbon souces 17 sugar-specific phosphoenolpyruvate-dependent phosphotransferase system (PTS) enyzme II complex identified. specificity including cellobioise, beta-glucoside, trehalose, mannose, lactose, fructose, mannitol, N-acetylgalactosamine, and glucose.

4 sugar-specific ABC transporter, 3 glycerol permeases and one glycerol-phosphate permease. 68% similiar to that of Shigella flexneri - horizonal gene tranfer between two enteric bacteria.

enezymes necessary glycolysis all present and that pentose phosphate pathway is only involved in pentose and gluconate utilization but not by-pass glysolysis (penotose-phosphate cycle_. --> broad catabolic capacity, may reflect its ability to adapt to various env.


require a great number of AA for grwoth. missing TCA cycle - depriving from ability to synthesize the precursors of most AA. only biosynthetic pathwyas for Ala, Ser, Gly, Glutamine, asparatate, asparagine, and threonine - present

addition of proline not required although missing genes.

auxotropic for most AA. needs to importe compoounds from exogenous sources. support by 8 ABC transporter and permease specific for AA.

another source - degradation of peptides by peptidase 4 genes encoding exported peptidase, 3 ABC transporters specific for oligopeptides, 21 genes for intracellular peptidase (some known to play a role in virulence)

zinc metalopetidase??

high number of transporters related to AA

but also a broad tranport capacity 255 genes most abundant class ABC tranposete

no complete vitamin biosyntheic some permease? with not yet unknown fxn.

a larger set of transporters for different inorganic componds, like two phosphate and two iron ABC tranporters and several cation tranport systmes.

diverse -->? surive and multiply in diff env and cause disease.

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Streptococcus agalactiae colonizes in the body of some animals, including cow, sheep, and humans without causing any harm. The habitat of this microorganism is largely confined to the intestine and vagina in human and the mammary gland of cows and sheep. This microorganism also colonizes in the genital and/or intestinal tract of about 10-30% of pregnant women.

However, some can actually cause diseases in their neonates or immunocompromised mammals. S. agalactiae is the common cause of inflammation or fibrosis of mammary glands and adjacent areas in cows and sheep colonizing the surface of the teat and duce sinuses. In human neonates, this species is and of bacterial sepsis and meningtis colonizing different location including the fauces, the nose, the umbilical cord, the ears, feces.

Infection is spread between cows and/or sheep through the milker's hand, contaminated instrument, and the mouth of calves. Once infected, this mammals are likely to lose their reproductive capacity due to blocked milk channels through inflammation. Infection in human is through genital and/or intestinal tract of pregnant women either during pregnancy or delivery and from other neonates or members of the hospital staff in the maternity hospital.

"The interaction of this bacteria with host protein and and the entry into host cells thereby represent important virulence traits."

Although Streptococcal diseases are very serious once developed, luckily only small percentage of neonates develop those even if their mother carry the bacteria (0.25 per 1000 lives with absence of clinical risk factors and 1-4 per 1000 birth with the presence of clinical risk factors).

This microorganism is considered one of the major causes of economic losses to dairy producers without a control program and poses great threats to neonates and some population of adult.

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

S. agalactiae causes various diseases both in ungulates such as cows and sheep and in humans. Originally discovered as a cause of bovine mastitis, S.agactiae has also revealed to cause invasive bacterial infections in mostly neonates and rarely immunocompromised adults, most notably septicemia, pneumonia, and meningitis. In ungulates -

Since S.agalactiae is normally present in the vaginal and intestinal tract of 15-40% of adult women without causing any harm, the reason and mechanism of this microorganism causing diseases in neonates is still not fully known. However, neonates is thought to be infected by being exposed to this microorganism through the birth canal or by spread from the maternal genital tract before birth and during early neonatal period. Infections due to this microorganism can be divided into two types depending on when infections take a place in neonates. Most common early-onset infections take places before the end of the first week and less common late-onset between 1 week and 3 months after birth.

Experimental study of early-onset infection suggests that this bacteria to invade fetal epithelial and endothelial cells and certain macrophages and the mortality rates for early-onset is 4-6%. This invasion is confirmed to play important role in its pathogenesis through the ability of S. agalactiae in the monkey model. Ability to invade and transcytosse, this bacteria can enter into the respiratory tract causing pneumonia or further into the blood causing septicemia. Bloodstream enables this bacteria to reach different sites of body causing meningitis and osteomyelitis.

The little pathogenesis of late-onset infection is known. But it is suggested to be vertically transmitted from mother or horizontally transferred from nursery personnel. The mortality rate of this infections is relatively lower than that of early-onset infection, 2-6%. This infections is likely to cause meningtitis and bacteremia.

Several factors are currently identified to increase the risk of infection, including rupture of cell membrane before rupture before labor and increased interval between rupture and delivery and it can also be affected by small amount of antibiotics against the virulence factor of S. agalactiae . Anticapsular vaccine, erythromycin, ampicillin, penicillin, cephalosporin, and vancomycin can be treated to prevent this infection.


The pathogenesis for infections in adults are not yet known.

S. agalactiae expresses several extracellular products including capsular polysaccharide, surface proteins and secreted protein that are studied in some animal models (mouse,rat) to be the virulence factor.


The symptoms of different disease caused by this bacteria is following: Neonatal septicemia includes lethargy, fever, jaundice, hypotension, hypothermia, tachypnea, bacteremia, and low Apgar scores. Neonatal pneumonia includes low Apgar scores, lethargy fever, apnea,tachypnea, cyanosis, cough, pulmonary infiltrates, rales Neonatal meningitis (10 -60 days of age) lethargy fever jaundice hypotension hypothermia stiff neck nuchal rigidity seizures

Osteomyelitis fever bone pain chills erythema swelling inflammation

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

S. agalactiae produces some antibiotics in mouse,Mouse Anti-Streptococcus agalactiae Monoclonal Antibody and can be further used to develop new antibiotics. ---?

Ideal vaccine is likely to include one surface protein that elicits host's immune system and present in all clinical isolates (strains). S.agalactiae are studied to contain several surface proteins having properties as ideal vaccine component for not only this species, but also for other gram-positive pathogens.

Surface proteins of members of Alp family, which elicit immune system in a mouse, in this microorganism is studied as a potential vaccine component. Vaccine containing two surface proteins (Rib and a) of this family would possibly protect against the majority of S. agalactiae infection without adjuvant, which is extra agents modifying and catalyzing the effect of vaccine. Another surface proteins is Sip protein, which also is ideal vaccine component, because it is highly conserved and elicit immune system against antigens from different types of strains of this microorganism. Additional surface proteins that are not yet fully studied, including C5a peptidase(ScpB) and beta protein. Especially ScpB has high potential of being ideal vaccine component, since it is present in all strains and highly conserved. However, the immunization with ScpB-based vaccine has not yet been tested.

Also the polysaccharide capsule of S. agalactiae, which is another virulence factor, is currently studied to develop a multivalent vaccine conjugated to S. agalactiae protein as carrier. The development of multivalent vaccines are important and necessary because of possibly of antigenic variation and protein-based vaccine is not sufficient alone. Conjugated vaccine of type III polysaccharide and beta surface protein or other surface protein do elicit immune system for strains expressing either of surface protein or polysaccharide. However, protection against infection has not yet been tested.


An antibiotic is a chemical compound that inhibits or abolishes the growth of microorganisms, such as bacteria, fungi, or protozoans. >

This application relates to Group B Streptococcus ('GBS') vaccines comprising combinations of GBS polypeptide antigens where the polypeptides contribute to the immunological response in a recipient. Preferably, the compositions of the invention comprise a combination of two or more GBS antigens, wherein said combination includes GBS 80 or a fragment thereof. In one embodiment, the combination may consist of two to thirteen GBS antigens selected from an antigen group consisting of GBS 80, GBS 91, GBS 104, GBS 184, GBS 276, GBS 305, GBS 322, GBS 330, GBS 338, GBS 361, GBS 404, GBS 690, and GBS 691.

Current Research

After S. agalactiae is discovered to be pathogenic not only to ungulates including cows and sheep, but also to neonates and immunocompromised adults, research has focused on virulence factors that are contributing to its pathogenesis and corresponding mechanisms.

In recently research at Institute of Biotechnology, University of Helsinki, structure of the S. agalactiae family II inorganic pyrophosphatase was crystallized and solved by molecular replacement refining at 2.8 A. This pyrophosphatase is one of targets in a serine/threonine protein kinase (STK) signaling cascade which phosphorylates serine/threonine residues and is studied to contribute to virulence of S.agactiae. The structure of pyrophosphatase is revealed to consist of two domains (residues 1-191 and 198-311) with active site between two domains and suggests the likely target of both kinase and phosphate to be Ser150, Ser194, Ser195, and Ser296. Those targets were found to be surface-accessible and present in either the active site or the hinge region between two domain. The target of bacterial Ser/Thr phosphorylation can be used to study to block the transduction of signals within S. agalctiae and to control its virulence. Drugs targeting signaling enzymes and its targets can be designed to cure severe disease, such as septs and meningitis caused by these pathogens. Further study is currently in process to identify exact target to control its pathogenesis. [7]

Another recent research focused on S. agalactiae CAMP factor/protein B to discover that it does not bind to human IgG. CAMP factor, an extracellular cytolytic protein, was called protein B, because it has been believed to bind the Fc fragment of IgG and this interaction is suggested to inhibit the hemolytic activity of CAMP factor/protein B. However, the CAMP factors are examined to react with only specific IgG through Fab domain, through the study with sera of infected adults and neonates and of non-infected. None of sera of infected adults reacted with CAMP factor and only 2 of sera of non-infected, indicating that CAMP factor is not binding to Fc domain of IgG and that this interaction is not involved in inhibiting hemolytic activity of CAMP factor. Since human IgG is not binding CAMP factor, protein involved in hemolytic activity, further study is necessary to find antibody that will inhibit its activity. [8]

Researchers also have studied for spreadable mobile genetic mobile element that largely contributes to increased resistance of S. agalactiae to various antibiotics. Study recently done at Universite ́ de Caen Basse-Normandie in France characterized a small mobilizable transposon, MTnSag1, identified in clinical strain of S. agalctiae. This transposon, containing two open fram, ORF1 and ORF2, encoding an Is1-like transposage gene and a lincosamide o-nucleotidyltransferase coferring resisntace to antibiotic, lincomycin, respectively. MTnSag1 can be conjugated to other transposon Tn916 to spread into other recipient. Most S. agactiae harbors Tn916-like element, so MTnSag1 is likely to be acquired and spread antibiotic resistance efficiently across S. agalactiae. This suggests that lincomycin can be less likely to be effective in treating infection caused by MTnSag1-carrying S.agalctiae, thus necessitate further antibiotic studies. [9]

References

  1. M. J. Patterson, S. Baron, et al, eds. Streptococcus. Baron's Medical Microbiology, Section 1, Chapter 13, pp. 1 (on website), 4th ed. (1996), Univ of Texas Medical Branch.
  2. J. Timoney, J. Gillespie, F. Scott, and J. Barlough. Hagan and Bruner's Microbiology and Infectious Diseases of Domestic Animals, Chapter 19, pp. 181-186, 8th ed., 1973.
  3. Entrez Genome. Streptococcus agalactiae NEM316 genome project. Project ID: 33, pp.1 (on website), Institut Pasteur.
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. M. K. Rantanen, L. Lehtiö, L. Rajagopal, C. E. Rubens and A. Goldman. "Structure of the Streptococcus agalactiae family II inorganic pyrophosphatase at 2.80 Å resolution." Acta Crystallographica Section D, Volume 63, Part 6, pp738-743, June 2007.
  10. W. El-Huneidi1, R. Mui1, T. H. Zhang1 and M. Palmer. "Streptococcus agalactiae CAMP factor/protein B does not bind to human IgG." Medical Microbiology and Immunology, Volume 196, Number 2, pp73-77, June 2007.
  11. A. Achard and R. Leclercq. "Characterization of a Small Mobilizable Transposon, MTnSag1, in Streptococcus agalactiae". Journal of Bacteriology, Volume 189, Number 11, pp4328-4331, June 2007.

[Ferretti, J.J., McShan, W.M., Ajdic, D., Savic, D.J., Savic, G.,Ferretti, J.J., McShan, W.M., Ajdic, D., Savic, D.J., Savic, G., M1 strain of Streptococcus pyogenes. Proc Natl Acad Sci USA 98: 4658–4663.]

[Tettelin, H., Nelson, K.E., Paulsen, I.T., Eisen, J.A., Read, T.D., Peterson, S., et al. (2001) Complete genome sequence of a virulent isolate of Streptococcus pneumoniae. Science 293: 498–506.]

[www.cdc.gov/ncidod/eid/vol10no8/pdfs/03-0917.pdf John F. Bohnsack,* April A. Whiting,* Gabriela Martinez,† Nicola Jones,‡ Elisabeth E. Adderson,§ Shauna Detrick,* Anne J. Blaschke-Bonkowsky,* Naiel Bisharat,‡ and Marcelo Gottschalk† " Serotype III Streptococcus agalactiaefrom Bovine Milk and Human Neonatal Infections".Emerging Infectious Diseases • Vol. 10, No. 8, August 2004]

MATERIAL SAFETY DATA SHEET - INFECTIOUS SUBSTANCES: Streptococcus agalactiae

Edited by Ha Bean Kim,student of Rachel Larsen and Kit Pogliano