Biomarkers for Diagnosis of meningitis

The supernatant part of centrifuged CSF tested for glucose , protein , lactate , C-Reactive protein , adenosine deaminase (ADA) content , estimation of the level of cytokines ,

lysozyme tests,total and differential leucocytic count ( Salmaso et al ., 1997).

(a)- Glucose content :

Simultaneous estimation of blood and CSF glucose levels is the most discriminatory test of the nonspecific CSF parameters to differentiate between bacterial and viral meningitis. CSF contain 2.2-4 mmol glucose/liter .Normal CSF glucose is about 60% of serum glucose value. If CSF glucose is <50% of serum glucose this will raise the possibility of bacterial meningitis. Glucose level is usually reduced in bacterial meningitis but may be normal or slight decreased in viral meningitis (Cinque et al ; 1996) . (b)- Protein content : Protein concentration which is below 0.4 g/L in normal CSF is usually more elevated in bacterial meningitis but may be normal or mild elevated in viral meningitis. In purulent (septic) meningitis , the glucose concentration is reduced and the protein concentration increased but in AM , the glucose concentration is normal and the protein concentration either normal or raised a little ( Cinque et al ; 1996). (c)- CSF lactate : The best test to differentiate bacterial from viral meningitis is the measurement of CSF lactate . Lactate levels are particularly important when CSF Gram staining is negative and there is a predominance of PMNs with low glucose in the CSF. CSF lactate concentrations greater than 3.5 mmol/L are characteristic of acute bacterial meningitis. As the lactate concentration in the CSF is independent of that of serum, there is no necessity to test the serum level (Cunha,2004). (d)- Acute phase reactants : Hansson et al.( 1993) found that determination of concentrations of alpha-¬1-acid glycoprotein (AAG) and C-reactive protein (CRP) in serum and alpha-2-ceruloplasmin (CER) in CSF are useful in differentiation between bacterial and viral meningitis. In children younger than 6 years of age , a discriminatory level of serum CRP of 20 mg/L can be used to distinguish between bacterial and viral meningitis but for older patients, a discriminatory level of 50 mg/L is more appropriate. Determination of AAG, CRP in serum are good markers for treatment efficacy and infectious complications in case of bacterial meningitis (Kwaik et al; 1995 and Paradowski et al; 1995) . (e)-Estimation of cytokines : Interleukin 6 (IL6) in CSF was reported to be as a diagnostic marker in the differential diagnosis of meningitis.It can be measured using monoclonal antibody enzyme immunoassay or Radioimmunoassay(RIA). CSF IL6 concentrations were found to be elevated in pyogenic meningitis in 100% of cases and in >50% of viral and other subarachnoid space infections and rarely in patients without CNS infections. Though, patients affected by pyogenic meningitis show the highest levels of CSF IL6 (Lopez-Cortes et al;1997).

(f)- Lysozyme test :

The principle of this test is to add polymexin M sulfate into
the gel bacterial medium. Rapid differential diagnosis of bacterial and viral meningitis with the use of this test is based on different time of the appearance of the lyses areas in bacterial meningitis. The CSF lysozyme activity is detectable within 15-120 min whereas in viral meningitis it manifests 40-50 min later or does not manifest at all. The results are dependant on the time of the CSF collection as more positive results are obtained when CSF samples are early collected (Babich et al ;1992).

Sepsis in Children with Oncohematological Malignancies, old Problem Revisited

   Though the use of aggressive treatment protocols that combine chemotherapy, radiation, and surgery, the prognosis for patients with childhood malignancies has improved substantially. However, these intensive treatment regimens can cause life-threatening complications, the

most prominent of which are infections that result from treatment-associated immunosuppression.

Historically, sepsis and septic shock in pediatric oncology patients have carried a poor prognosis. Earlier studies, however, used a variety of criteria to define sepsis and septic shock, and most included relatively small numbers of children. Some studies even excluded patients who had received bone marrow transplants (BMT).

Sepsis is a leading cause of death in critically ill patients despite the use of modern antibiotics and resuscitation therapies. The septic response is an extremely complex chain of events involving inflammatory and anti-inflammatory processes, humoral and cellular reactions and circulatory abnormalities. The diagnosis of sepsis and evaluation of its severity is complicated by the highly variable and non-specific nature of the signs and symptoms of sepsis. However, the early diagnosis and stratification of the severity of sepsis is very important, increasing the possibility of starting timely and specific treatment.

    A rapid microbiological diagnosis could therefore confirm an infectious cause of fever and aid in the choice of a specific therapy. Among the infectious causes, bacteria and fungi are the leading threats, with high infection-related mortality rate, especially for polymicrobial infections and moulds. The current gold standard for the detection of bacterial pathogens in blood is blood culture. However, all blood culture systems suffer from several limitations, such as lack of rapidity and low sensitivity, especially when the patient has already received antibiotics and when fastidious micro-organisms are involved. From this perspective, the diagnosis of bloodstream infections could prove really challenging in oncohaematological patients, who routinely receive prophylactic antibiotics and whose blood cultures therefore often remain negative. Even after the detection of growth in cultured blood (usually not before 6–12 h of incubation), conventional blood cultures require at least a further 24–48 h for the definitive identification of the pathogen and the evaluation of its sensitivity to antibiotics. Other parallel approaches are therefore needed, and among them well-designed molecular assays could prove really useful. Several molecular techniques have already been successfully used in routine microbiology laboratories for direct detection of viral, bacterial, mycotic and protozoan pathogens. However, their use on whole blood samples for detection of sepsis has been hampered by several factors, including insufficient sensitivity, presence of PCR inhibitors in blood, and the difficulty of setting up an assay capable of detecting a wide range of potential pathogens.

  Another advance in diagnosis of sepsis is the use of biomarkers. Biomarkers can have an important place in this process because they can indicate the presence or absence or severity of sepsis. A biomarker is defined as ‘‘a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention.’’.

 Beside rapid diagnosis of sepsis, other potential uses of biomarkers include roles in prognostication, guiding antibiotic therapy, evaluating the response to therapy and recovery from sepsis, differentiating Gram-positive from Gram-negative microorganisms as the cause of sepsis, predicting sepsis complications and the development of organ dysfunction (heart, kidneys, liver or multiple organ dysfunction). However, the exact role of biomarkers in the management of septic patients remains undefined. C-reactive protein (CRP) has been used for many years but its specificity has been challenged. Procalcitonin (PCT) has been proposed as a more specific and better prognostic marker than CRP, although its value has also been challenged. It remains difficult to differentiate sepsis from other non-infectious causes of systemic inflammatory response syndrome, and there is a continuous search for better biomarkers of sepsis.

Lectures on applied clinical microbiolog...

(ASIN: B004Y0XF54) http://www.amazon.com/Lectures-applied-clinical-microbiology-ebook/dp/B004Y0XF54

Sepsis in Children with Oncohematological Malignancies

Though the use of aggressive treatment protocols that combine chemotherapy, radiation, and surgery, the prognosis for patients with childhood malignancies has improved substantially. However, these intensive treatment regimens can cause life-threatening complications, the


most prominent of which are infections that result from treatment-associated immunosuppression.

Historically, sepsis and septic shock in pediatric oncology patients have carried a poor prognosis. Earlier studies, however, used a variety of criteria to define sepsis and septic shock, and most included relatively small numbers of children. Some studies even excluded patients who had received bone marrow transplants (BMT).

Sepsis is a leading cause of death in critically ill patients despite the use of modern antibiotics and resuscitation therapies. The septic response is an extremely complex chain of events involving inflammatory and anti-inflammatory processes, humoral and cellular reactions and circulatory abnormalities. The diagnosis of sepsis and evaluation of its severity is complicated by the highly variable and non-specific nature of the signs and symptoms of sepsis. However, the early diagnosis and stratification of the severity of sepsis is very important, increasing the possibility of starting timely and specific treatment.

A rapid microbiological diagnosis could therefore confirm an infectious cause of fever and aid in the choice of a specific therapy. Among the infectious causes, bacteria and fungi are the leading threats, with high infection-related mortality rate, especially for polymicrobial infections and moulds. The current gold standard for the detection of bacterial pathogens in blood is blood culture. However, all blood culture systems suffer from several limitations, such as lack of rapidity and low sensitivity, especially when the patient has already received antibiotics and when fastidious micro-organisms are involved. From this perspective, the diagnosis of bloodstream infections could prove really challenging in oncohaematological patients, who routinely receive prophylactic antibiotics and whose blood cultures therefore often remain negative. Even after the detection of growth in cultured blood (usually not before 6–12 h of incubation), conventional blood cultures require at least a further 24–48 h for the definitive identification of the pathogen and the evaluation of its sensitivity to antibiotics. Other parallel approaches are therefore needed, and among them well-designed molecular assays could prove really useful. Several molecular techniques have already been successfully used in routine microbiology laboratories for direct detection of viral, bacterial, mycotic and protozoan pathogens. However, their use on whole blood samples for detection of sepsis has been hampered by several factors, including insufficient sensitivity, presence of PCR inhibitors in blood, and the difficulty of setting up an assay capable of detecting a wide range of potential pathogens.

Another advance in diagnosis of sepsis is the use of biomarkers. Biomarkers can have an important place in this process because they can indicate the presence or absence or severity of sepsis. A biomarker is defined as ‘‘a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention.’’.

Beside rapid diagnosis of sepsis, other potential uses of biomarkers include roles in prognostication, guiding antibiotic therapy, evaluating the response to therapy and recovery from sepsis, differentiating Gram-positive from Gram-negative microorganisms as the cause of sepsis, predicting sepsis complications and the development of organ dysfunction (heart, kidneys, liver or multiple organ dysfunction). However, the exact role of biomarkers in the management of septic patients remains undefined. C-reactive protein (CRP) has been used for many years but its specificity has been challenged. Procalcitonin (PCT) has been proposed as a more specific and better prognostic marker than CRP, although its value has also been challenged. It remains difficult to differentiate sepsis from other non-infectious causes of systemic inflammatory response syndrome, and there is a continuous search for better biomarkers of sepsis.

In the present chapter we will try to explore the occurrence of sepsis in children with oncohematological disorders under chemotherapy with emphasis on rapid diagnosis and recent therapy.

Keywords: Sepsis, Oncohematological malignancies, biomarkers, children.