Premise
In international cases, pneumococcus is portrayed as the etiopathological factor most involved in the onset of pneumonia.
The current scientific name of the pneumococcus is Streptococcus pneumoniae, while in the past it was better known as Diplococcus pneumoniae, in reference to the peculiar morphology of the bacterium: in fact, observed under an optical microscope, the pneumococcus appears as two joined cocci, apparently fused at one end, which gives the characteristic "flame" shape.
Microbiological analysis
In addition to being the protagonist of pneumonia par excellence, the pneumococcus - entered into the body through inhalation of microgells of infected saliva - is also involved in other highly invasive diseases and in other minor disorders. The pneumococcus, together with Nisseria meningitidis (meningococcus), is for example involved in the manifestation of bacterial meningitis, a potentially fatal disease which consists of an acute, sudden and violent inflammatory process of the meninges.
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Streptococcus pneumoniae is a gram positive haemolytic alpha-type bacterium in an aerobic and beta-haemolytic type under anaerobic conditions. Belonging to the genus Streptococcus, the pneumococcus has a circular genome, containing 2.0-2.1 million base pairs; there are 1553 genes in the nucleus, of which 154 contribute to virulence and 176 retain an invasive phenotype.
Some strains of pneumococcus, especially those with capsulapolisaccaride, are particularly virulent; it is precisely the capsular polysaccharide that confers virulence on the pathogen, given that this external coating protects the microorganism from phagocytosis and, at the same time, increases its pathogenicity.
The pneumococcal cell wall consists largely of the M protein and the C antigen, which in turn is composed of teicoic acid, choline and galactosamine-6-phosphate.
The pneumococcus undergoes autolysis phenomena, after which it tends to originate non-capsulated bacterial colonies, far less virulent than the previous forms (capsulated).
The pneumococcus is a fermenting bacterium, capable of forming lactic acid from glucose: this capacity heavily affects the choice of the culture medium, which must be composed of a negligible quantity of glucose; in fact the pneumococcus, cultivated on blood agar soil enriched with glucose, would quickly transform this sugar into lactic acid, which would lead to a lowering of the pH, consequently the growth of the microorganism would be compromised by the excessive acidity of the soil. The ideal culture medium for the pneumococcus is blood agar embellished with ox heart or with soy protein, clearly poor in glucose.
Even if the pneumococcus is a commensal microorganism, normally present in the mucous membranes of the respiratory tract, under optimal conditions it can replicate indiscriminately, becoming an opportunistic pathogen .
To date, there are over 90 Pneumococcal serum groups, most of which are capable of triggering infections, especially of the respiratory system and the nervous system. Among these, the serotypes 1, 3, 4, 5, 7, 8, 12, 14 and 19 are those that are common to most pneumococcal infections.
Incidence of infections
Pneumococcal infections are a serious public health problem everywhere, even if the damage that the bacterium can develop is heavily influenced by the country's hygienic conditions; just think of the danger that a pneumococcal infection can create in developing nations. The pathogen preferentially affects (although not exclusively) children under the age of 5 (especially from 6 months of age), causing approximately one million deaths annually: pneumococcal deaths are observed mainly in those countries in where health resources (medicines and hospitals) are scarce, and personal and environmental hygiene leave something to be desired.
Children are the bacterium's preferred targets, probably because they are not yet able to develop antibodies to the polysaccharide antigens of the pneumococcus; to this first factor is also added the high frequency of bacterial colonization in children, which could explain both the susceptibility to pneumococcal attack, and the poor efficacy of unconjugated polysaccharide vaccines.
In general, pneumococcus is the etiological element most involved in pneumonia, otitis media and occult bacteremia; in Italy, the frequency of pneumococcal infections is similar to that of meningococcus.
DATA:
Data in hand, it has been observed that the major infections mediated by the pneumococcus are supported by some specific serum groups: this means that not all pneumococci tend to develop severe damage. Considering infected patients of all ages, it is estimated that 80% of pneumococcal infections are sustained by one or more pneumococci belonging to 12 serum groups (1, 3, 4, 5, 6, 7, 8, 9, 14, 18, 19, 23); children under the age of 6, on the other hand, are more affected by 6 serum groups (4, 6, 9, 14, 18, 23).
In general terms, it is estimated that the pneumococcus affects 5, 2-15, 2 inhabitants per 100, 000.
The number of patients treated for pneumococcal infections increases if the target is narrowed: in children between the ages of 0 and 5, pneumococcal infections are believed to occur in 10.1-24.2 cases per 100, 000 children.
Risk factors
RISK FACTORS : it has been observed that pneumococcal infections are more frequent among males, species of black race; for example, blacks in America, Australian aborigines and American Indians tend to be affected 2 to 10 times more than healthy white children.
Among the most common risk factors that can promote pneumococcal infections, we cannot forget cigarette smoking, bronchial asthma and flu illnesses. Still, other pathologies can predispose the patient to pneumococcal insults: congenital or acquired immunodeficiencies (AIDS), deficiencies of complement factors, Diabetes Mellitus, congestive heart failure, chronic lung disease, nephrotic syndrome and thalassemia major.
Also the intake of drugs and drugs can reduce the phagocytic activity of macrophages (defense function), as well as the cough reflex, which can favor the inhalation of pneumococci.
