Streptococcus pneumoniae
Encyclopedia
Streptococcus pneumoniae, or pneumococcus, is Gram-positive
, alpha-hemolytic
, aerotolerant anaerobic member of the genus
Streptococcus
. 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.
Despite the name, the organism causes many types of pneumococcal infection
s other than pneumonia
. These invasive pneumococcal diseases include acute sinusitis, otitis media
, meningitis
, bacteremia
, sepsis
, osteomyelitis
, septic arthritis
, endocarditis
, peritonitis
, pericarditis
, cellulitis
, and brain abscess
.
S. pneumoniae is one of the most common causes of bacterial meningitis in adults, along with Neisseria meningitidis
, and is the leading cause of bacterial meningitis in adults in the USA. It is also one of the top two isolates found in ear infection, otitis media. Pneumococcal pneumonia is more common in the very young and the very old.
S. pneumoniae can be differentiated from Streptococcus viridans
, 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, the so-called, "lancet-shaped" diplococci. They have a polysaccharide capsule that acts as a virulence factor for the organism; more than 90 different serotypes are known, and these types differ in virulence, prevalence, and extent of drug resistance.
.
The organism was termed Diplococcus pneumoniae from 1920 because of its characteristic appearance in Gram-stained sputum
. It was renamed Streptococcus pneumoniae in 1974 because of its growth in chains in liquid media.
S. pneumoniae played a central role in demonstrating 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. In 1944, Oswald Avery
, Colin MacLeod
, and Maclyn McCarty
demonstrated the transforming factor in Griffith's experiment
was DNA, not protein, as was widely believed at the time. Avery's work marked the birth of the molecular era of genetics.
S. pneumoniae is part of the normal upper respiratory tract flora, but, as with many natural flora, it can become pathogenic under the right conditions (e.g., if 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.
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
.
When both bacteria are placed together into the nasal cavity of a mouse, within 2 weeks, only H. influenzae survives. When both are placed separately into a nasal cavity, each one survives. Upon examining the upper respiratory tissue from mice exposed to both bacteria, an extraordinarily large number of neutrophil immune cells were found. In mice exposed to only one bacterium, the cells were not present.
Lab tests show neutrophils that were exposed to already-dead H. influenzae were more aggressive in attacking S. pneumoniae than unexposed neutrophils. Exposure to killed H. influenzae had no effect on live H. influenzae.
Two scenarios may be responsible for this response:
It is unclear why H. influenzae is not affected by the immune system response.
sensitive, although optochin resistance has been observed.
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...
, alpha-hemolytic
Hemolysis (microbiology)
Hemolysis is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on blood agar is used to classify certain microorganisms. This is particularly useful in classifying streptococcal species...
, aerotolerant anaerobic member of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Streptococcus
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
. A significant human pathogenic bacterium, S. pneumoniae was recognized as a major cause of pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
in the late 19th century, and is the subject of many humoral immunity
Humoral immunity
The Humoral Immune Response is the aspect of immunity that is mediated by secreted antibodies produced in the cells of the B lymphocyte lineage . B Cells transform into plasma cells which secrete antibodies...
studies.
Despite the name, the organism causes many types of pneumococcal infection
Pneumococcal infection
- Pathogenesis :S. pneumoniae is normally found in the nasopharynx of 5-10% of healthy adults, and 20-40% of healthy children. It can be found in higher amounts in certain environments, especially those where people are spending a great deal of time in close proximity to each other...
s other than pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
. These invasive pneumococcal diseases include acute sinusitis, otitis media
Otitis media
Otitis media is inflammation of the middle ear, or a middle ear infection.It occurs in the area between the tympanic membrane and the inner ear, including a duct known as the eustachian tube. It is one of the two categories of ear inflammation that can underlie what is commonly called an earache,...
, meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
, bacteremia
Bacteremia
Bacteremia is the presence of bacteria in the blood. The blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal....
, sepsis
Sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
, osteomyelitis
Osteomyelitis
Osteomyelitis simply means an infection of the bone or bone marrow...
, septic arthritis
Septic arthritis
Septic arthritis is the purulent invasion of a joint by an infectious agent which produces arthritis. People with artificial joints are more at risk than the general population but have slightly different symptoms, are infected with different organisms and require different treatment. Septic...
, endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
, peritonitis
Peritonitis
Peritonitis is an inflammation of the peritoneum, the serous membrane that lines part of the abdominal cavity and viscera. Peritonitis may be localised or generalised, and may result from infection or from a non-infectious process.-Abdominal pain and tenderness:The main manifestations of...
, pericarditis
Pericarditis
Pericarditis is an inflammation of the pericardium . A characteristic chest pain is often present.The causes of pericarditis are varied, including viral infections of the pericardium, idiopathic causes, uremic pericarditis, bacterial infections of the precardium Pericarditis is an inflammation of...
, cellulitis
Cellulitis
Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, blisters,...
, and brain abscess
Brain abscess
Brain abscess is an abscess caused by inflammation and collection of infected material, coming from local or remote infectious sources, within the brain tissue...
.
S. pneumoniae is one of the most common causes of bacterial meningitis in adults, along with Neisseria meningitidis
Neisseria meningitidis
Neisseria meningitidis, often referred to as meningococcus, is a bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life threatening sepsis. N. meningitidis is a major cause of morbidity and mortality during childhood in industrialized countries...
, and is the leading cause of bacterial meningitis in adults in the USA. It is also one of the top two isolates found in ear infection, otitis media. Pneumococcal pneumonia is more common in the very young and the very old.
S. pneumoniae can be differentiated from Streptococcus viridans
Streptococcus viridans
Viridans Streptococcus is a pseudotaxonomic non-Linnaenan term for a large group of commensal streptococcal bacteria that are either α-hemolytic, producing a green coloration on blood agar plates , or nonhemolytic...
, some of which are also alpha-hemolytic, using an optochin
Optochin
Optochin is a chemical used in cell culture techniques for the presumptive identification of Streptococcus pneumoniae, which is optochin-sensitive, from other alpha-hemolytic streptococci such as Streptococcus viridans which are resistant...
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
Coccus
Coccus can be used to describe any bacterium that has a spherical shape. It is one of the three distinct types of bacteria shapes, the other two being bacillus and spirillum cells...
bacteria have a distinctive morphology on Gram stain, the so-called, "lancet-shaped" diplococci. They have a polysaccharide capsule that acts as a virulence factor for the organism; more than 90 different serotypes are known, and these types differ in virulence, prevalence, and extent of drug resistance.
History
In 1881, the organism, discovered by Leo Escolar, then known as the pneumococcus for its role as an etiologic agent of pneumonia, was first isolated simultaneously and independently by the U.S Army physician George Sternberg and the French chemist Louis PasteurLouis Pasteur
Louis Pasteur was a French chemist and microbiologist born in Dole. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, and he created the first vaccine for rabies and anthrax. His experiments...
.
The organism was termed Diplococcus pneumoniae from 1920 because of its characteristic appearance in Gram-stained sputum
Sputum
Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....
. It was renamed Streptococcus pneumoniae in 1974 because of its growth in chains in liquid media.
S. pneumoniae played a central role in demonstrating genetic material consists of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
. In 1928, Frederick Griffith
Frederick Griffith
Frederick Griffith 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...
demonstrated transformation
Transformation (genetics)
In molecular biology transformation is the genetic alteration of a cell resulting from the direct uptake, incorporation and expression of exogenous genetic material from its surroundings and taken up through the cell membrane. Transformation occurs naturally in some species of bacteria, but it can...
of life, turning harmless pneumococcus into a lethal form by co-inoculating the live pneumococci into a mouse along with heat-killed, virulent pneumococci. In 1944, Oswald Avery
Oswald Avery
Oswald Theodore Avery ForMemRS was a Canadian-born American physician and medical researcher. The major part of his career was spent at the Rockefeller University Hospital in New York City...
, Colin MacLeod
Colin MacLeod
Colin Munro MacLeod was a Canadian-American geneticist.- Biography :Born in Port Hastings, Nova Scotia, Canada MacLeod entered McGill University at the age of 16 , and completed his medical studies by age 23.In his early years as a research scientist, MacLeod, together with Oswald Avery and...
, and Maclyn McCarty
Maclyn McCarty
Maclyn McCarty was an American geneticist.Maclyn McCarty, who devoted his life as a physician-scientist to studying infectious disease organisms, was best known for his part in the monumental discovery that DNA, rather than protein, constituted the chemical nature of a gene...
demonstrated the transforming factor in Griffith's experiment
Griffith's experiment
Griffith's experiment, reported in 1928 by Frederick Griffith, was one of the first experiments suggesting that bacteria are capable of transferring genetic information through a process known as transformation....
was DNA, not protein, as was widely believed at the time. Avery's work marked the birth of the molecular era of genetics.
Genetics
The genome of S. pneumoniae is a closed, circular DNA structure that contains between 2.0 and 2.1 million basepairs, 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.S. pneumoniae is part of the normal upper respiratory tract flora, but, as with many natural flora, it can become pathogenic under the right conditions (e.g., if the immune system of the host is suppressed). Invasins, such as pneumolysin
Pneumolysin
Pneumolysin is a putative virulence factor of the gram positive bacteria Streptococcus pneumoniae.It is a 53 kDa pore forming toxin composed of 471 amino acids...
, an antiphagocytic capsule, various adhesins and immunogenic cell wall components are all major virulence factors.
Interaction with Haemophilus influenzae
Both H. influenzaeHaemophilus influenzae
Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
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
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
.
When both bacteria are placed together into the nasal cavity of a mouse, within 2 weeks, only H. influenzae survives. When both are placed separately into a nasal cavity, each one survives. Upon examining the upper respiratory tissue from mice exposed to both bacteria, an extraordinarily large number of neutrophil immune cells were found. In mice exposed to only one bacterium, the cells were not present.
Lab tests show neutrophils that were exposed to already-dead H. influenzae were more aggressive in attacking S. pneumoniae than unexposed neutrophils. Exposure to killed H. influenzae had no effect on live H. influenzae.
Two scenarios may be responsible for this response:
- When H. influenzae is attacked by S. pneumoniae, it signals the immune system to attack the S. pneumoniae
- The combination of the two species sets off an immune system alarm that is not set off by either species individually.
It is unclear why H. influenzae is not affected by the immune system response.
Diagnosis
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, optochinOptochin
Optochin is a chemical used in cell culture techniques for the presumptive identification of Streptococcus pneumoniae, which is optochin-sensitive, from other alpha-hemolytic streptococci such as Streptococcus viridans which are resistant...
sensitive, although optochin resistance has been observed.
See also
- Child mortalityChild mortalityChild mortality, also known as under-5 mortality, refers to the death of infants and children under the age of five. In 2010, 7.6 million children under five died , down from 8.1 million in 2009, 8.8 million in 2008, and 12.4 million in 1990. About half of child deaths occur in Africa....
- Haemophilus influenzaeHaemophilus influenzaeHaemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
- MeningitisMeningitisMeningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
- Otitis mediaOtitis mediaOtitis media is inflammation of the middle ear, or a middle ear infection.It occurs in the area between the tympanic membrane and the inner ear, including a duct known as the eustachian tube. It is one of the two categories of ear inflammation that can underlie what is commonly called an earache,...
- PneumoADIPPneumoADIPPneumococcal vaccines Accelerated Development and Introduction Plan is a small, dedicated team based at Johns Hopkins Bloomberg School of Public Health and is supported by a $30 million grant from the Global Alliance for Vaccines and Immunization...
- Pneumococcal Awareness Council of ExpertsPneumococcal Awareness Council of ExpertsThe Pneumococcal Awareness Council of Experts is a project of the Sabin Vaccine Institute and is composed of global experts in infectious diseases and vaccines. Established in December 2006, The Council seeks to raise awareness among policymakers and aims to secure global commitments to prevent...
(PACE) - Pneumococcal conjugate vaccine
- Pneumococcal infectionPneumococcal infection- Pathogenesis :S. pneumoniae is normally found in the nasopharynx of 5-10% of healthy adults, and 20-40% of healthy children. It can be found in higher amounts in certain environments, especially those where people are spending a great deal of time in close proximity to each other...
- Pneumococcal polysaccharide vaccinePneumococcal polysaccharide vaccinePneumococcal polysaccharide vaccine — the latest version is known as Pneumovax 23 — is the first pneumococcal vaccine, the first vaccine derived from a capsular polysaccharide, and an important landmark in medical history...
- Pneumococcal vaccinePneumococcal vaccineA pneumococcal vaccine is a vaccine against Streptococcus pneumoniae.Types include:* Pneumococcal polysaccharide vaccine* Pneumococcal conjugate vaccine-Vaccination in the USA:...
- PneumoniaPneumoniaPneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
- SepsisSepsisSepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...