Streptococcus pneumoniae | |
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S. pneumoniae in spinal fluid. FA stain (digitally colored). | |
Scientific classification | |
Domain: | Bacteria |
Phylum: | Bacillota |
Class: | Bacilli |
Order: | Lactobacillales |
Family: | Streptococcaceae |
Genus: | Streptococcus |
Species: | S. pneumoniae |
Binomial name | |
Streptococcus pneumoniae (Klein 1884) Chester 1901 | |
Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic member of the genus Streptococcus. [1] They are usually found in pairs (diplococci) and do not form spores and are non motile. [2] As a significant human pathogenic bacterium S. pneumoniae was recognized as a major cause of pneumonia in the late 19th century, and is the subject of many humoral immunity studies.[ citation needed ]
Streptococcus pneumoniae resides asymptomatically in healthy carriers typically colonizing the respiratory tract, sinuses, and nasal cavity. However, in susceptible individuals with weaker immune systems, such as the elderly and young children, the bacterium may become pathogenic and spread to other locations to cause disease. It spreads by direct person-to-person contact via respiratory droplets and by auto inoculation in persons carrying the bacteria in their upper respiratory tracts. [3] It can be a cause of neonatal infections. [4]
Streptococcus pneumoniae is the main cause of community acquired pneumonia and meningitis in children and the elderly, [5] and of sepsis in those infected with HIV. The organism also causes many types of pneumococcal infections other than pneumonia. These invasive pneumococcal diseases include bronchitis, rhinitis, acute sinusitis, otitis media, conjunctivitis, meningitis, sepsis, osteomyelitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis, and brain abscess. [6]
Streptococcus pneumoniae can be differentiated from the viridans streptococci, some of which are also alpha-hemolytic, using an optochin test, as S. pneumoniae is optochin-sensitive. S. pneumoniae can also be distinguished based on its sensitivity to lysis by bile, the so-called "bile solubility test". The encapsulated, Gram-positive, coccoid bacteria have a distinctive morphology on Gram stain, lancet-shaped diplococci. They have a polysaccharide capsule that acts as a virulence factor for the organism; more than 100 different serotypes are known, and these types differ in virulence, prevalence, and extent of drug resistance.
The capsular polysaccharide (CPS) serves as a critical defense mechanism against the host immune system. It composes the outermost layer of encapsulated strains of S. pneumoniae and is commonly attached to the peptidoglycan of the cell wall. [7] It consists of a viscous substance derived from a high-molecular-weight polymer composed of repeating oligosaccharide units linked by covalent bonds to the cell wall. The virulence and invasiveness of various strains of S. pneumoniae vary according to their serotypes, determined by their chemical composition and the quantity of CPS they produce. Variations among different S. pneumoniae strains significantly influence pathogenesis, determining bacterial survival and likelihood of causing invasive disease. [8] Additionally, the CPS inhibits phagocytosis by preventing granulocytes’ access to the cell wall. [9]
In 1881, the organism, known later in 1886 as the pneumococcus [10] for its role as a cause of pneumonia, was first isolated simultaneously and independently by the U.S. Army physician George Sternberg [11] and the French chemist Louis Pasteur. [12]
The organism was termed Diplococcus pneumoniae from 1920 [13] because of its characteristic appearance in Gram-stained sputum. It was renamed Streptococcus pneumoniae in 1974 because it was very similar to streptococci. [10] [14]
Streptococcus pneumoniae played a central role in demonstrating that genetic material consists of DNA. In 1928, Frederick Griffith demonstrated transformation of life turning harmless pneumococcus into a lethal form by co-inoculating the live pneumococci into a mouse along with heat-killed virulent pneumococci. [15] In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty demonstrated that the transforming factor in Griffith's experiment was not protein, as was widely believed at the time, but DNA. [16] Avery's work marked the birth of the molecular era of genetics. [17]
The genome of S. pneumoniae is a closed, circular DNA structure that contains between 2.0 and 2.1 million base pairs depending on the strain. It has a core set of 1553 genes, plus 154 genes in its virulome, which contribute to virulence and 176 genes that maintain a noninvasive phenotype. Genetic information can vary up to 10% between strains. [18] The pneumococcal genome is known to contain a large and diverse repertoire of antimicrobial peptides, including 11 different lantibiotics. [19]
Natural bacterial transformation involves the transfer of DNA from one bacterium to another through the surrounding medium. Transformation is a complex developmental process requiring energy and is dependent on expression of numerous genes. In S. pneumoniae, at least 23 genes are required for transformation. For a bacterium to bind, take up, and recombine exogenous DNA into its chromosome, it must enter a special physiological state called competence. [20] Competence in S. pneumoniae is induced by DNA-damaging agents such as mitomycin C, fluoroquinolone antibiotics (norfloxacin, levofloxacin and moxifloxacin), and topoisomerase inhibitors. [21] Transformation protects S. pneumoniae against the bactericidal effect of mitomycin C. [22] Michod et al. [23] summarized evidence that induction of competence in S. pneumoniae is associated with increased resistance to oxidative stress and increased expression of the RecA protein, a key component of the recombinational repair machinery for removing DNA damage. On the basis of these findings, they suggested that transformation is an adaptation for repairing oxidative DNA damage. S. pneumoniae infection stimulates polymorphonuclear leukocytes (granulocytes) to produce an oxidative burst that is potentially lethal to the bacteria. The ability of S. pneumoniae to repair oxidative DNA damage in its genome caused by this host defense likely contributes to the pathogen's virulence. Consistent with this premise, Li et al. [24] reported that, among different highly transformable S. pneumoniae isolates, nasal colonization fitness and virulence (lung infectivity) depend on an intact competence system.
Streptococcus pneumoniae is part of the normal upper respiratory tract flora. As with many natural flora, it can become pathogenic under the right conditions, typically when the immune system of the host is suppressed. Invasins, such as pneumolysin, an antiphagocytic capsule, various adhesins, and immunogenic cell wall components are all major virulence factors. After S. pneumoniae colonizes the air sacs of the lungs, the body responds by stimulating the inflammatory response, causing plasma, blood, and white blood cells to fill the alveoli. This condition is called bacterial pneumonia. [25]
S. pneumoniae undergoes spontaneous phase variation, changing between transparent and opaque colony phenotypes. The transparent phenotype has a thinner capsule and expresses large amounts of phosphorylcholine (ChoP) and choline-binding protein A (CbpA), contributing to the bacteria’s ability to adhere and colonize in the nasopharynx. [26] The opaque phenotype is characterized by a thicker capsule, resulting in increased resistance to host clearance. [27] It expresses large amounts of capsule and pneumococcal surface protein A (PspA) which help the bacteria survive in the blood. [28] Phase-variation between these two phenotypes allows S. pneumoniae to survive in different human body systems.
Pneumonia is the most common of the S. pneumoniae diseases which include symptoms such as fever and chills, cough, rapid breathing, difficulty breathing, and chest pain. For the elderly, they may include confusion, low alertness, and the former listed symptoms to a lesser degree.[ citation needed ]
Pneumococcal meningitis is an infection of the tissue covering the brain and spinal cord. Symptoms include stiff neck, fever, headache, confusion, and photophobia.[ citation needed ]
Sepsis is caused by overwhelming response to an infection and leads to tissue damage, organ failure, and even death. The symptoms include confusion, shortness of breath, elevated heart rate, pain or discomfort, over-perspiration, fever, shivering, or feeling cold. [29]
Due to the importance of disease caused by S. pneumoniae, several vaccines have been developed to protect against invasive infection. The World Health Organization recommends routine childhood pneumococcal vaccination; [30] it is incorporated into the childhood immunization schedule in a number of countries including the United Kingdom, [31] the United States, [32] and South Africa. [33]
Currently, there are two vaccines available for S. pneumoniae: the pneumococcal polysaccharide vaccine (PPV23) and the pneumococcal conjugate vaccine (PCV13). PPV23 functions by utilizing CPS to stimulate the production of type-specific antibodies, initiating processes such as complement activation, opsonization, and phagocytosis to combat bacterial infections. It elicits a humoral immune response targeting the CPS present on the bacterial surface. [34] PPSV23 offers T-cell-independent immunity and requires revaccination 5 years after the first vaccination because of its temporary nature. [35] PCV13 was developed when determining its low efficacy in children and infants. PCV13 elicits a T-cell-dependent response and provides enduring immunity by promoting interaction between B and T cells, leading to an enhanced and prolonged immune response. [36]
Components from S. pneumoniae have been harnessed for a range of applications in biotechnology. Through engineering of surface molecules from this bacterium, proteins can be irreversibly linked using the sortase enzyme [37] or using the SnoopTag/SnoopCatcher reaction. [38] Various glycoside hydrolases have also been cloned from S. pneumoniae to help analysis of cell glycosylation. [39]
Historically, Haemophilus influenzae has been a significant cause of infection, and both H. influenzae and S. pneumoniae can be found in the human upper respiratory system. A study of competition in vitro revealed S. pneumoniae overpowered H. influenzae by attacking it with hydrogen peroxide. [40] There is also evidence that S. pneumoniae uses hydrogen peroxide as a virulence factor. [41] However, in a study adding both bacteria to the nasal cavity of a mouse within two weeks, only H. influenzae survives; further analysis showed that neutrophils exposed to dead H. influenzae were more aggressive in attacking S. pneumoniae. [42]
Diagnosis is generally made based on clinical suspicion along with a positive culture from a sample from virtually any place in the body. S. pneumoniae is, in general, optochin sensitive, although optochin resistance has been observed. [43]
The recent advances in next-generation sequencing and comparative genomics have enabled the development of robust and reliable molecular methods for the detection and identification of S. pneumoniae. For instance, the Xisco gene was recently described as a biomarker for PCR-based detection of S. pneumoniae and differentiation from closely related species. [44]
Atromentin and leucomelone possess antibacterial activity, inhibiting the enzyme enoyl-acyl carrier protein reductase, (essential for the biosynthesis of fatty acids) in S. pneumoniae. [45]
Resistant pneumococcal strains are called penicillin-resistant pneumococci (PRP), [46] penicillin-resistant Streptococcus pneumoniae (PRSP), [47] Streptococcus pneumoniae penicillin resistant (SPPR) [48] or drug-resistant Strepotococcus pneumoniae (DRSP). In 2015, in the US, there were an estimated 30,000 cases, and in 30% of them the strains were resistant to one or more antibiotics. [49]
Griffith's experiment, performed by Frederick Griffith and reported in 1928, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation. Griffith's findings were followed by research in the late 1930s and early 40s that isolated DNA as the material that communicated this genetic information.
Streptococcus is a genus of gram-positive coccus or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales, in the phylum Bacillota. Cell division in streptococci occurs along a single axis, so as they grow, they tend to form pairs or chains that may appear bent or twisted. This differs from staphylococci, which divide along multiple axes, thereby generating irregular, grape-like clusters of cells. Most streptococci are oxidase-negative and catalase-negative, and many are facultative anaerobes.
Oswald Theodore Avery Jr. was a Canadian-American physician and medical researcher. The major part of his career was spent at the Rockefeller Hospital in New York City. Avery was one of the first molecular biologists and a pioneer in immunochemistry, but he is best known for the experiment that isolated DNA as the material of which genes and chromosomes are made.
Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity of the condition is variable.
Frederick Griffith (1877–1941) was a British bacteriologist whose focus was the epidemiology and pathology of bacterial pneumonia. In January 1928 he reported what is now known as Griffith's Experiment, the first widely accepted demonstrations of bacterial transformation, whereby a bacterium distinctly changes its form and function.
Haemophilus influenzae is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria are mesophilic and grow best at temperatures between 35 and 37 °C.
Bacterial pneumonia is a type of pneumonia caused by bacterial infection.
The bacterial capsule is a large structure common to many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washed off, and it can be the cause of various diseases.
Pneumococcal polysaccharide vaccine, sold under the brand name Pneumovax 23, is a pneumococcal vaccine that is used for the prevention of pneumococcal disease caused by the 23 serotypes of Streptococcus pneumoniae contained in the vaccine as capsular polysaccharides. It is given by intramuscular or subcutaneous injection.
Community-acquired pneumonia (CAP) refers to pneumonia contracted by a person outside of the healthcare system. In contrast, hospital-acquired pneumonia (HAP) is seen in patients who have recently visited a hospital or who live in long-term care facilities. CAP is common, affecting people of all ages, and its symptoms occur as a result of oxygen-absorbing areas of the lung (alveoli) filling with fluid. This inhibits lung function, causing dyspnea, fever, chest pains and cough.
Pneumococcal pneumonia is a type of bacterial pneumonia that is caused by Streptococcus pneumoniae (pneumococcus). It is the most common bacterial pneumonia found in adults, the most common type of community-acquired pneumonia, and one of the common types of pneumococcal infection. The estimated number of Americans with pneumococcal pneumonia is 900,000 annually, with almost 400,000 cases hospitalized and fatalities accounting for 5-7% of these cases.
Pneumococcal conjugate vaccine is a pneumococcal vaccine made with the conjugate vaccine method and used to protect infants, young children, and adults against disease caused by the bacterium Streptococcus pneumoniae (pneumococcus). It contains purified capsular polysaccharide of pneumococcal serotypes conjugated to a carrier protein to improve antibody response compared to the pneumococcal polysaccharide vaccine. The World Health Organization (WHO) recommends the use of the conjugate vaccine in routine immunizations given to children.
Pneumococcal vaccines are vaccines against the bacterium Streptococcus pneumoniae. Their use can prevent some cases of pneumonia, meningitis, and sepsis. There are two types of pneumococcal vaccines: conjugate vaccines and polysaccharide vaccines. They are given by injection either into a muscle or just under the skin.
Pneumococcal infection is an infection caused by the bacterium Streptococcus pneumoniae.
Austrian syndrome, also known as Osler's triad, is a medical condition that was named after Robert Austrian in 1957. The presentation of the condition consists of pneumonia, endocarditis, and meningitis, all caused by Streptococcus pneumoniae. It is associated with alcoholism due to hyposplenism and can be seen in males between the ages of 40 and 60 years old. Robert Austrian was not the first one to describe the condition, but Richard Heschl or William Osler were not able to link the signs to the bacteria because microbiology was not yet developed.
Streptococcus pseudopneumoniae is a gram-positive coccus that may cause pneumonia in humans. It was first described in 2004. The organism is often mistaken for S. pneumoniae and its clinical importance is as yet uncertain. It seems likely that most cases of S. pseudopneumoniae pneumonia are misdiagnosed as S. pneumoniae.
In biology, a pathogen, in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ.
Necrotizing pneumonia (NP), also known as cavitary pneumonia or cavitatory necrosis, is a rare but severe complication of lung parenchymal infection. In necrotizing pneumonia, there is a substantial liquefaction following death of the lung tissue, which may lead to gangrene formation in the lung. In most cases patients with NP have fever, cough and bad breath, and those with more indolent infections have weight loss. Often patients clinically present with acute respiratory failure. The most common pathogens responsible for NP are Streptococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae. Diagnosis is usually done by chest imaging, e.g. chest X-ray, CT scan. Among these CT scan is the most sensitive test which shows loss of lung architecture and multiple small thin walled cavities. Often cultures from bronchoalveolar lavage and blood may be done for identification of the causative organism(s). It is primarily managed by supportive care along with appropriate antibiotics. However, if patient develops severe complications like sepsis or fails to medical therapy, surgical resection is a reasonable option for saving life.
Daniela M. Ferreira is a Brazilian British immunologist. She is a specialist in bacterial infection, respiratory co-infection, mucosal immunology and vaccine responses. She is currently Professor of Respiratory Infection and Vaccinology at the Oxford Vaccine Group in the Department of Paediatrics at the University of Oxford and the Director of the Liverpool Vaccine Group at the Liverpool School of Tropical Medicine. She leads a team of scientists studying protective immune responses against pneumococcus and other respiratory pathogens such as SARS-CoV2. Her team has established a novel method of inducing pneumococcal carriage in human volunteers. They use this model to:
Competence stimulating peptide (CSP), a chemical messenger assisting quorum sensing initiation, exists in many bacterial genera. Bacterial transformation of deoxyribonucleic acids (DNA) is driven by CSP coupled quorum sensing.