Meningococcal meningitis is a rare (but very serious) condition that affects the meninges. It is estimated that at least 2 people in the United States develop the disease each year. Failure to properly treat the disease causes death of the sick person or serious damage to the body. Even proper treatment does not always guarantee a full recovery.
Meningococcal meningitis – symptoms
Suspicion of meningitis should arouse severe and increasing headaches accompanied by nausea and vomiting. Photophobia is observed in some patients. Physical examination shows neck stiffness and other meningeal symptoms. Moreover, there are various degrees of disturbances in consciousness, rapid progression of the disease is possible, expressed in the increase of disturbances of consciousness.
In adult patients, convulsions and symptoms of focal CNS damage are observed less frequently than in other purulent meningitis. In young children, and especially in infants, the initial symptoms may be non-specific, including:
- lack of appetite
- vomiting,
- diarrhea,
- irritability,
- lack of interest in the environment,
- excessive sleepiness,
- tearfulness.
Later symptoms include a tense and pulsating fontanel, opisthotonus. This non-specific and mildly symptomatic onset of meningococcal meningitis contributes to delayed diagnosis. Parents often seek medical attention only when there are disturbances in consciousness or seizures.
Diagnosis of meningococcal meningitis
1. Laboratory research
In laboratory studies of patients with meningococcal meningitis, we observe abnormalities similar to those seen in other severe bacterial infections. Most patients develop leukocytosis with the rejuvenation of white blood cells and the presence of toxic granules in the neutrophil cytoplasm. There are high values of inflammatory markers – procalcitonin (PCT) and C-reactive protein (CRP). Patients with DIC have a reduced number of platelets, increased concentrations of D-dimers and fibrinogen degradation products (FDP), and decreased coagulation factors.
In patients with severe sepsis and septic shock, biochemical features of organ damage due to accompanying disorders in tissue flow are visible. The following ailments may appear:
- high bilirubin concentration,
- hypocapnia,
- lactic acidosis,
- overactivity of transaminases,
- hypoxaemia,
- high levels of creatinine.
In patients with meningococcal meningitis, the diagnosis is based on a general and microbiological examination of the cerebrospinal fluid. The general examination shows changes typical of purulent meningitis. The cerebrospinal fluid is usually cloudy and flows out under increased pressure during the lumbar puncture. The number of cells usually ranges from several hundred to several thousand per mm3, the smear is dominated by neutrophils (often accounting for 100%), there is a significantly elevated protein concentration and reduced, often to very low values, glucose concentration.
2. Microbiological, serological and genetic tests
In establishing the etiology of meningococcal meningitis infection, it remains the gold standard cultivation of the microorganism from material taken from the patient. Therefore, material for microbiological testing should be collected in any case of suspected invasive meningococcal disease. The material for culture should be collected before starting antibiotic treatment, because the chances of obtaining positive results decrease drastically after the implementation of antibiotic therapy.
In any case of suspicion of IChM, it should be strictly performed blood cultures. Blood cultures should also be collected from patients with meningitis. Despite the fact that the basic material for microbiological tests in them is the cerebrospinal fluid, in about half of the patients in the first phase of the disease, meningococcus can also be grown from blood. Blood is the primary breeding material when septicemia is suspected.
When infection is accompanied by symptoms of a hemorrhagic rash, harvesting may be performed for establishment of the culture swabs from characteristically altered places on the skin. The material must be collected by biopsy or by incision of the changed skin fragment and taking a smear from its inside. Execution may be helpful in determining the etiological factor of the infection nasopharyngeal swabj patient, since any case of meningococcal meningitis is preceded by carriage of the meningococcus in the nasopharynx.
In the case of non-invasive infections, appropriate material should be collected according to the location of the infection. The collected materials should be used for microscope slides stained with the Gram method and methylene blue according to Loefler. N. meningitidis grows better on solid than liquid media. It is used for the final identification of the bacteria biochemical tests. Among the non-breeding techniques, they are commonly used, they are convenient to use due to the possibility of obtaining the result in a very short time, latex tests. They can detect pathogenic microorganisms even after antimicrobial treatment, when the culture results are already negative, because they detect enveloped antigens also from damaged and killed bacteria.
WARNING! However, it should be emphasized that the manufacturers of latex tests themselves emphasize that they are only a preliminary and auxiliary stage of identification, and their results must be absolutely confirmed by other methods.
The meningococcal serogroups can be defined by slide agglutination using a set of specific sera, but this test is generally only performed by reference laboratories. Full serological typing also includes the identification of the serotype, serological subtype and possibly immunotype. The most common is ELISA methodusing the whole cell ELISA (WCE) antigen, although immunoblotting is also used.
Diagnostic methods in which they are used are increasingly used molecular biology methods. They are used in the study of virtually any material collected from the patient. The most common is polymerase chain reaction – PCR (polymerase chain reaction), which allows to detect DNA specific for a specific bacterial species, as well as serological group in the material collected from the patient. The PCR technique can also be used to determine the infectious agent in postmortem material.
Methods of typing isolates
In the epidemiological investigation, typing of isolates is performed. The typing methods used should answer the question of whether isolates causing infections are the same or different (local epidemiology) and whether isolates responsible for local infections are related to isolates causing infections in a given area at another time or in other parts of the world (long-term epidemiology and global).
Until recently, the study of the relationship of strains involved the study of restriction fragments lenght polymorphism (RFLP) of genomic DNA separated by electrophoresis in a pulsed-field gel electrophoresis (PFGE) and the analysis of polymorphism of the polymerase chain reaction products using primers with arbitrarily selected DNA sequence (randomly amplified polymorphic DNA – RAPD).
Currently, it is increasingly used for typing N. meningitidis isolates sequencing techniques. Their result is reproducible, comparable between different laboratories, does not depend on the method of performing the experiment and the interpretation of the person who conducts it, and all isolates containing a given gene are typical. Another very important and invaluable benefit of sequencing techniques is their applicability to meningococcal DNA sequencing directly in a clinical specimen collected from a patient with suspected meningococcal meningitis, in the absence of culture or its negative result.
It is commonly used in typing isolates of N. meningitidis MLST technique (multilocus sequence typing) and more and more often sequencing of various coding genes, incl. outer membrane proteins: porA and fetA. In the MLST technique, internal fragments of genes encoding proteins of basic metabolism (so-called housekeeping genes) are sequenced. The different nucleotide sequences of a particular loci are referred to as different alleles. Based on the allelic profile of all 7 analyzed loci, the so-called sequence type (ST).
Source: J. Cianciara, J. Juszczyk, Infectious and parasitic diseases; Czelej Publishing House