| Pneumococcal infection | |
|---|---|
| Other names | Pneumococcosis |
| Specialty | Respirology, neurology |
Pneumococcal infection is an infection caused by the bacterium Streptococcus pneumoniae . [1]
S. pneumoniae is a common member of the bacterial flora colonizing the nose and throat of 5–10% of healthy adults and 20–40% of healthy children. [2] However, it is also a cause of significant disease, being a leading cause of pneumonia, bacterial meningitis, and sepsis. The World Health Organization estimates that in 2005, pneumococcal infections were responsible for the death of 1.6 million children worldwide. [3]
Pneumococcal pneumonia represents 15%–50% of all episodes of community-acquired pneumonia, 30–50% of all cases of acute otitis media, and a significant proportion of bloodstream infections and bacterial meningitis. [4]
As estimated by the WHO, in 2005 it killed about 1.6 million children every year worldwide with 0.7–1 million of them being under the age of five. The majority of these deaths were in developing countries. [3]
S. pneumoniae is normally found in the nose and throat of 5–10% of healthy adults and 20–40% of healthy children. [2] 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 (day-care centers, military barracks). It attaches to nasopharyngeal cells through interaction of bacterial surface adhesins. This normal colonization can become infectious if the organisms are carried into areas such as the Eustachian tube or nasal sinuses where it can cause otitis media and sinusitis, respectively. Pneumonia occurs if the organisms are inhaled into the lungs and not cleared (again, viral infection, or smoking-induced ciliary paralysis might be contributing factors). The organism's polysaccharide capsule makes it resistant to phagocytosis and if there is no pre-existing anticapsular antibody alveolar macrophages cannot adequately kill the pneumococci. The organism spreads to the blood stream (where it can cause bacteremia) and is carried to the meninges, joint spaces, bones, and peritoneal cavity, and may result in meningitis, brain abscess, septic arthritis, or osteomyelitis.[ citation needed ]
S. pneumoniae has several virulence factors, including the polysaccharide capsule mentioned earlier, that help it evade a host's immune system. It has pneumococcal surface proteins that inhibit complement-mediated opsonization, and it secretes IgA1 protease that will destroy secretory IgA produced by the body and mediates its attachment to respiratory mucosa.[ citation needed ]
The risk of pneumococcal infection is much increased in persons with impaired IgG synthesis, impaired phagocytosis, or defective clearance of pneumococci. In particular, the absence of a functional spleen, through congenital asplenia, surgical removal of the spleen, or sickle-cell disease predisposes one to a more severe course of infection (overwhelming post-splenectomy infection) and prevention measures are indicated. [ citation needed ]
People with a compromised immune system, such as those living with HIV, are also at higher risk of pneumococcal disease. [5] In HIV patients with access to treatment, the risk of invasive pneumoccal disease is 0.2–1% per year and has a fatality rate of 8%. [5]
There is an association between pneumococcal pneumonia and influenza. [6] Damage to the lining of the airways (respiratory epithelium) and upper respiratory system caused by influenza may facilitate pneumococcal entry and infection.
Other risk factors include smoking, injection drug use, hepatitis C, and COPD. [5]
S. pneumoniae expresses different virulence factors on its cell surface and inside the organism. These virulence factors contribute to some of the clinical manifestations during infection with S. pneumoniae.[ citation needed ]
Depending on the nature of infection an appropriate sample is collected for laboratory identification. Pneumococci are typically gram-positive cocci seen in pairs or chains. When cultured on blood agar plates with added optochin antibiotic disk they show alpha-hemolytic colonies and a clear zone of inhibition around the disk indicating sensitivity to the antibiotic. Pneumococci are also bile soluble. Just like other streptococci they are catalase-negative. A Quellung test can identify specific capsular polysaccharides. [12]
Pneumococcal antigen (cell wall C polysaccharide) may be detected in various body fluids. Older detection kits, based on latex agglutination, added little value above Gram staining and were occasionally false-positive. Better results are achieved with rapid immunochromatography, which has a sensitivity (identifies the cause) of 70–80% and >90% specificity (when positive identifies the actual cause) in pneumococcal infections. The test was initially validated on urine samples but has been applied successfully to other body fluids. [12] Chest X-rays can also be conducted to confirm inflammation though are not specific to the causative agent.[ citation needed ]
Due to the importance of disease caused by S. pneumoniae, several vaccines have been developed to protect against invasive infection. The World Health Organization recommend routine childhood pneumococcal vaccination; [13] it is incorporated into the childhood immunization schedule in a number of countries including the United Kingdom, [14] United States, [15] and South Africa. [16]
Throughout history treatment relied primarily on β-lactam antibiotics. In the 1960s nearly all strains of S. pneumoniae were susceptible to penicillin, but more recently there has been an increasing prevalence of penicillin resistance especially in areas of high antibiotic use. A varying proportion of strains may also be resistant to cephalosporins, macrolides (such as erythromycin), tetracycline, clindamycin and the fluoroquinolones. Notably, macrolide-resistant S. pneumoniae has been declared a medium-priority pathogen by the WHO due to its growing clinical and public health significance. [17] Penicillin-resistant strains are more likely to be resistant to other antibiotics. Most isolates remain susceptible to vancomycin, though its use in a β-lactam-susceptible isolate is less desirable because of tissue distribution of the medication and concerns of development of vancomycin resistance.[ citation needed ]
More advanced beta-lactam antibiotics (cephalosporins) are commonly used in combination with other antibiotics to treat meningitis and community-acquired pneumonia. In adults recently developed fluoroquinolones such as levofloxacin and moxifloxacin are often used to provide empiric coverage for patients with pneumonia, but in parts of the world where these medications are used to treat tuberculosis, resistance has been described. [18]
Susceptibility testing should be routine with empiric antibiotic treatment guided by resistance patterns in the community in which the organism was acquired. There is currently debate as to how relevant the results of susceptibility testing are to clinical outcome. [19] [20] There is slight clinical evidence that penicillins may act synergistically with macrolides to improve outcomes. [21]
Resistant pneumococci strains are called penicillin-resistant pneumococci (PRP), [22] penicillin-resistant Streptococcus pneumoniae (PRSP), [23] Streptococcus pneumoniae penicillin resistant (SPPR), [24] or drug-resistant Strepotococcus pneumomoniae (DRSP). [25]
In the 19th century it was demonstrated that immunization of rabbits with killed pneumococci protected them against subsequent challenge with viable pneumococci. Serum from immunized rabbits or from humans who had recovered from pneumococcal pneumonia also conferred protection. In the 20th century, the efficacy of immunization was demonstrated in South African miners.[ citation needed ]
It was discovered that the pneumococcus's capsule made it resistant to phagocytosis, and in the 1920s it was shown that an antibody specific for capsular polysaccharide aided the killing of S. pneumoniae. In 1936, a pneumococcal capsular polysaccharide vaccine was used to abort an epidemic of pneumococcal pneumonia. In the 1940s, experiments on capsular transformation by pneumococci first identified DNA as the material that carries genetic information. [26]
In 1900 it was recognized that different serovars of pneumococci exist and that immunization with a given serovar did not protect against infection with other serovars. Since then over ninety serovars have been discovered each with a unique polysaccharide capsule that can be identified by the quellung reaction. Because some of these serovars cause disease more commonly than others it is possible to provide reasonable protection by immunizing with less than 90 serovars; current vaccines contain up to 23 serovars (i.e., it is "23-valent").[ citation needed ]
The serovars are numbered according to two systems: the American system, which numbers them in the order in which they were discovered, and the Danish system, which groups them according to antigenic similarities.[ citation needed ]
Streptococcus is a genus of gram-positive 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, thus when growing they tend to form pairs or chains, which 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.
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.
Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic member of the genus Streptococcus. S. pneumoniae cells are usually found in pairs (diplococci) and do not form spores and are non motile. 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.
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.
Asplenia refers to the absence of normal spleen function and is associated with some serious infection risks. Hyposplenism is used to describe reduced ('hypo-') splenic functioning, but not as severely affected as with asplenism.
Bacterial pneumonia is a type of pneumonia caused by bacterial infection.
Mycoplasma pneumonia is a form of bacterial pneumonia caused by the bacterium Mycoplasma pneumoniae.
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.
Streptococcus agalactiae is a gram-positive coccus with a tendency to form chains. It is a beta-hemolytic, catalase-negative, and facultative anaerobe.
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.
The quellung reaction, also called the Neufeld reaction, is a biochemical reaction in which antibodies bind to the bacterial capsule of Streptococcus pneumoniae, Klebsiella pneumoniae, Neisseria meningitidis, Bacillus anthracis, Haemophilus influenzae, Escherichia coli, and Salmonella. The antibody reaction allows these species to be visualized under a microscope. If the reaction is positive, the capsule becomes opaque and appears to enlarge.
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.
Robert Austrian was an American infectious diseases physician and, along with Maxwell Finland, one of the two most important researchers into the biology of Streptococcus pneumoniae in the 20th century.
Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasionally photophobia. Other symptoms include confusion or altered consciousness, nausea, and an inability to tolerate light or loud noises. Young children often exhibit only nonspecific symptoms, such as irritability, drowsiness, or poor feeding. A non-blanching rash may also be present.
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.
The Pneumococcal Awareness Council of Experts (PACE) 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 pneumococcal disease, a leading infectious killer of children and adults worldwide. The Council works in collaboration and partnership with countries, NGOs, academia and industry.