Introduction
Although they usually populate the respiratory mucosa without causing damage, pneumococci, finding the optimal conditions for them, can replicate themselves disproportionately, transforming themselves from commensal microorganisms to terrible opportunistic pathogens, capable of triggering diseases of varying size.
In the previous discussion we described the pneumococcus from a microbiological point of view, also focusing on the epidemiological aspects; in the following discussion, the topic will be examined from the point of view of diseases, thus examining the pathogenesis, the symptomatological framework and the available treatments.
- Pneumococcal infections: pathogenesis
- Pneumococcus pneumoniae and Haemophilus influenzae
- Pneumococcal infections: Symptoms
- Symptoms INVASIVE pneumococcal infection
- Symptoms of pneumococcal pneumonia
- Symptoms NON-invasive pneumococcal infection
- Pneumococcal infections: diagnosis
- Pneumococcus: therapies
Causes
Pneumococcal cells reach the alveolar level through inhalation of infected saliva microdroplets; only minimally can the bacilli spread by hematogenous route.
TO DEVELOP DISEASE, THE PNEUMOCOCCO MUST EXTEND THE MUCOSE BARRIERS OF THE GUEST; to remember, moreover, that only the pneumococci with capsules are virulent.
After passing the mucosa of the respiratory tract, the pneumococcus can reach the sinuses and the middle ear ; if the bacterium is able to overcome even the body's defenses, thus escaping the action of the immune system, it can spread to create pneumonia, meningitis and mastoiditis (inflammation of the mastoid cells as a result of infection at the level of the middle ear) . Subsequently, from the pulmonary lesions the pneumococcus can infect the mediastinal lymph nodes, pass into the thoracic duct and, finally, into the blood circulation (bacteremia). If the infection proceeds, the vital organs can also be affected, such as the heart: here, the pneumococcus can determine endocarditis and pericarditis . In some patients, the infection occurs at the level of the joint cavities.
Inhalation of infected secretions is slowed down by the normal closure of the epiglottis during swallowing; also the movements of the eyelashes arranged along the airways can defend the organism from the attacks of the pneumococcus, since they can convey the mucous secretions infected from the lower tract of the respiratory tract towards the pharynx and the middle ear.
A healthy subject is normally able to block infection in the bud; furthermore, it has been observed that the co-presence of other bacilli on the respiratory mucosa, such as Haemophilus influenzae, severely (or even blocks) the replication of the pneumococcus.
Deepening: Pneumococcus pneumoniae and Haemophilus influenzae Haemophilus influenzae is also involved in infectious diseases affecting the respiratory tract and, similarly to the pneumococcus (and meningococcus), it can also cause damage to the meninges. It is not uncommon for the two pathogens to be simultaneously in the same location; in such circumstances, however, only one bacterium survives: between the two, the pneumococcus is destined to succumb. If the two microorganisms (H. influenzae and pneumococcus) were SEPARATELY located in the nasal cavities, a similar situation would not occur, and both would be able to create damage. How to explain this phenomenon? In the laboratory, some experiments on animal guinea pigs have led to surprising results: by analyzing the respiratory tissue of a mouse exposed to both bacteria, an exaggerated number of neutrophils, an expression of the mobilization of the cells of the immune system, was observed. However, when the respiratory tissue of the mouse was exposed only to one of the two bacteria it triggered a much lower immune response.
What conclusions can be drawn? The mechanism that regulates this particular competition has not yet been clarified with certainty; however, two hypotheses have been formulated:
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Polysaccharide capsule antigens are indispensable elements to ensure pneumococcal virulence; moreover, the antigens guarantee to the microorganism a certain protection from macrophages and polynuclear cells, which could phagocytise - therefore inactivate - the pathogen.
Young children, under the age of two, are particularly susceptible to pneumococcal infections, since the body is not yet able to produce antibodies to polysaccharide antigens.
General symptoms
Pneumococcal infections are classified into two categories: invasive and non-invasive. In the first category, pneumococcal infection is completed within a vital organ or in the blood, and the damage is extremely serious; non-invasive forms occur outside the locations just described, and generally create limited damage and are easy to resolve.
The table summarizes the symptoms that distinguish the various invasive infections mediated by pneumococcus.
Table of symptoms
INVASIVE pneumococcal infection | Symptoms |
Septic arthritis (infection in a joint) | Fever, intense pain, inability / inability to control the joint involved in the infection |
Bacteremia (spread of bacteria in the blood) | Presence of bacteria (pneumococcus, in this case) in the blood, with fever and other non-specific symptoms |
Meningitis (inflammation of the meninges) | Anorexia, changes in the menstrual cycle, widespread chills, convulsions, joint and muscle pain, headache, high fever, photophobia, irritability, nausea, cough and vomiting |
Osteomyelitis (bone and bone marrow infection) | Redness and swelling of the affected area, difficulty in moving the injured area, acute pain, fever and potential swelling. Possible formation of cutaneous fistulas with pus emission |
Pneumonia (lung infection) | Omnipresent symptoms: chills, severe chest pains and cough. Pneumonia is also characterized by: halitosis, weakness, dyspnea, muscle pain, headache, sweating, accelerated breathing |
Septicemia (alarming and exaggerated Systemic Inflammatory Response following a pneumococcal bacterial insult - in this case) | Hypothermia / high fever, increased respiratory rate, tachycardia + cardiac dysfunction, gangrene, hypotension, leukopenia, spots on the skin, loss of organ functions, thrombocytopenia, widespread thrombus, death. |
Pneumococcal pneumonia
The most widespread disease triggered by pneumococcus is POMMONITE, often preceded by purely flu symptoms. The intensity of the symptoms depends on the patient's general health and on the pneumococcal serotype involved in the infection. Even the onset of symptoms is not always constant and some patients develop mild symptoms at first, which complicates the diagnosis, making the disease even more dangerous and devious.
Severe pneumonia usually begins with a very high fever, which can reach even 40-41 ° C in a few hours; clearly, the exaggerated thermal increase also involves the development of diffuse chills (the so-called shaking shiver ). Some patients with pneumococcal pneumonia also complain of chest pain, dyspnea, cyanosis, polypnea and tachycardia. The omnipresent cough is initially dry and snappy, and then turns into a fat cough, producing a blood-streaked sputum with a yellow-greenish color. Also possible secondary symptoms, such as asthenia, arthritis, diarrhea, abdominal distention, nausea and vomiting.
It is not uncommon for the patient to contract Herpes labialis in association with pneumonia.
The table shows the characteristic symptoms of non-invasive pneumococcal infections.
NON-invasive pneumococcal infection | Symptoms |
BRONCHITE (bronchial infection) | Difficulty in swallowing, dyspnoea, joint pain, greenish-white sputum emission, pharyngitis, fever, flu, cold, hoarseness. |
Conjunctivitis (conjunctiva infection) | Redness and swelling of the conjunctiva, lacrimation, ocular itching, conjunctival hyperemia, lymphadenopathy |
OTITUS MEDIA (infection of the middle ear, typical of children under the age of 10) | Auricular pain to the touch (otitis externa), emission of purulent material from the ear canal associated with pain (otitis media), sore throat, fever, low-grade fever, stuffy nose, cough |
SINUSITIS (infection of the paranasal sinuses, small cavities filled with air, located posteriorly to the cheekbones and forehead) | Nasal obstruction with emission of yellowish or greenish mucus + alteration of the perception of food taste, halitosis, nasal congestion, weakness, dyspnea, facial and tooth pain, fever, swollen eyes, closed ears, rhinorrhea and cough |
Diagnosis of infections
Before embarking on a therapeutic strategy for treating the infection, it is necessary to ascertain the pathogen involved in the disease: the samples on which it is possible to isolate the bacterium are blood (for blood culture) and sputum (for cultivation analysis and microscopic). Many streptococci are morphologically similar, so it is easy to confuse one strain with another; for this reason, the culture of the bacterium is always indispensable. However, the microscopic analysis of a sample of purulent material, liquor or sputum is useful to suspect pneumococcal infection and possibly start a targeted therapy while waiting for the results of the culture analysis.
The optochin (a-ethylidrocupreine) test identifies and distinguishes pneumococcal colonies from other viridating streptococci, very similar from a morphological point of view: unlike the other streptococci, the pneumococcus appears to be sensitive to optochin.
Furthermore, the bile salt sensitivity test is used for diagnostic purposes to highlight the pneumococci: in the presence of bile salts (0.05% sodium deoxycholate), pathogens belonging to this category undergo lysis in a very short time.
The test of agglutination with Omniserum (a particular capsular swelling reaction), is instead used to agglutinate all types of pneumococcus.
For a more in-depth diagnostic investigation, it is necessary to make use of the so-called TIPIZZAZIONE, therefore the exact identification of the type of pneumococcus involved in the infection: for this investigation, it is possible to make use of the Neufeld reaction (or of capsular swelling) or of the agglutination on slide .
Contrary to what one might think, the search for antibodies against antigens is not used among diagnostic techniques, since the types of antigens that may be involved in pneumococcal infection are numerous.
It seems, however, that the best diagnostic investigation for an invasive pneumococcal infection is the polymeric reaction chain (or more simply PCR), although this technique is not very widespread.
The search for pneumococcal polysaccharide in a urine sample is not recommended: in fact, this diagnostic investigation turned out to be not very specific for pneumococcal infections.
Care
The pneumococcus shows a reasonable sensitivity to some antibiotics, in particular to penicillins, erythromycin and tetracyclines. Despite what has been said, there is no lack of reports of drug resistance, especially to penicillins: in the USA, it is estimated that 5-10% of the pneumococci responsible for infection are completely resistant to these drugs, while 20% are considered moderately resistant.
Penicillin resistance is a consequence of the alteration of the proteins that bind the drug, not so much of the synthesis of beta lactamase.
In general, pneumococcal infections should be treated with the amoxicillin + clavulanic acid combination; cephalosporins are also drugs used to eradicate pneumococcal infections.
