Latex particle agglutination test in the diagnosis of Haemophilus influenzae type B, Streptococcus pneumoniae and Neisseria meningitidis A and C meningitis in infants and children

Diagnostic value of latex agglutination test in diagnosis of acute bacterial meningitis

Objectives:

To know the incidence of bacterial meningitis in children below five years of age. To compare conventional culture and antigen detection methods (Latex agglutination test).

Materials and Methods:

100 CSF samples of clinically suspected meningitis cases in children below 5 years of age were included. The samples were subjected to cell count, Gram stain, culture and LAT. The organisms isolated in the study were characterized according to standard procedures.

Results:

Of the 100 cases studied, 31 cases were diagnosed as ABM by Gram stain, culture and latex agglutination test as per WHO criteria. The hospital frequency of ABM was 1.7%. 15 (48.38) cases were culture positive. Gram stain was positive in 22(70.96) cases and LAT in 17(54.83) cases. Haemophilus influenzae was the most common causative agent of acute bacterial meningitis followed by S.pneumoniae. Case fatality rate was 45.16%. The sensitivity and specificity of LAT was 66.66% and 87.91% respectively.

Conclusion:

Bacterial meningitis is a medical emergency and early diagnosis and treatment is life saving and reduces chronic morbidity. LAT was more sensitive compared to conventional Gram stain and Culture technique in identifying the fastidious organisms like H.influenzae, S.pneumoniae and Group B Streptococcus. However, the combination of Gram stain, Culture and LAT proved to be more productive than any of the single tests alone.

Probable acute disseminated encephalomyelitis due to Haemophilus influenzae meningitis

We report the case of a 17-year-old male on long-term steroid therapy for minimal lesion glomerulopathy who, after an upper respiratory infection, presented with Haemophilus influenzae type b meningitis. Twenty-four hours later he developed depression of consciousness which progressed to coma and left hemiparesis. Brain magnetic resonance imaging (MRI) revealed multiple lesions (hyperintense on T2 and slightly hypointense on Tl) involving mainly white matter suggestive of inflammation. MRI features were compatible with acute disseminated encephalomyelitis (ADEM), although a differential diagnosis included cerebritis or vasculitis, secondary to bacterial meningitis. The patient was treated with high-dose steroids which resulted in a gradual improvement followed by complete clinical recovery. We propose a diagnosis of ADEM was the best diagnosis because of the radiological features and response to steroids. The occurrence of ADEM associated with acute meningitis, however rare, represents an important diagnostic challenge for the clinician.

Biological diagnosis of meningococcal meningitis in the African meningitis belt: Current epidemic strategy and new perspectives

Laboratory diagnosis is an essential component in surveillance of meningococcal epidemics, as it can inform decision-makers of the Neisseria meningitidis serogroup(s) involved and the most appropriate vaccine to be selected for mass vaccination. However, countries most affected face real limitations in laboratory diagnostics, due to lack of resources. We describe current diagnostic tools and examine their cost-effectiveness for use in an epidemic context. The conclusion is that current WHO recommendations to use only the latex agglutination assay (Pastorex) at epidemic onset is cost-effective, but recently developed rapid diagnostic tests for the major epidemic-causing meningococcal serogroups may prove a breakthrough for the future.

Evaluation of the Pastorex meningitis kit for the rapid identification of Neisseria meningitidis serogroups A and W135

The recent emergence of Neisseria meningitidis W135 as a cause of epidemic bacterial meningitis and the availability of a trivalent ACW135 vaccine have created a need for accurate and timely meningococcal serogroup determination for organization of epidemic vaccine response. The sensitivity and specificity of the Pastorex meningitis kit (Bio-Rad) to identify serogroups A and W135 in the African meningitis belt was assessed using PCR testing as the gold standard. The sensitivity and specificity for serogroups A and W135 were 87 and 85%, respectively, while the specificities were 93 and 97%. The positive and negative likelihood ratios for A were 12 and 0.14 and for W135 were 33 and 0.16. The positive and negative predictive values, computed to simulate an epidemic of meningococcal meningitis with an estimated 70% prevalence of N. meningitidis among suspected cases, were 97% and 75% for A and 99% and 73% for W135. In remote locations of the African meningitis belt, latex agglutination is the only currently available test that can rapidly determine meningococcal serogroup. This study showed that latex agglutination performs well and could be used during the epidemic season to determine appropriate vaccine response.

Antigen detection for the diagnosis of pneumonia

Streptococcus pneumoniae and Haemophilus influenzae type b are the main agents of bacterial community-acquired pneumonia in developing countries, although a definite etiologic diagnosis cannot be established in most cases. This study was carried out to assess the performance of a latex particle agglutination test (LPAT) from a commercial kit (Slidex Méningite Kit trade mark, BioMérieux, France) in diagnosing pneumococcal and H. influenzae type b pneumonia. One hundred and seven children (45 ill subjects and 62 healthy controls) were enrolled. All 45 cases had a presumptive diagnosis of bacterial pneumonia based on clinical (WHO criteria), laboratory (white blood cell count > or = 15.000/mm3, polymorphonuclear leukocytes > or = 70%, bands > or = 500/mm3, and C-reactive protein > or = 40 mg/l), and radiological findings, i.e., two or more positive points in the scoring system described by Khamapirad and Glezen (Semin Respir Infect 1987;2:130-144). Clinical, laboratory, and radiological assessments were performed in a blinded manner. LPAT was performed in urine samples after concentration through an ethanol-acetone solution. Sensitivity, specificity, and positive and negative predictive values were 77.3% (95% CI, 61.8-88.0%), 90.3% (95% CI, 79.5-96.0%), 85.0% (95% CI, 69.5-93.8%), and 84.8% (95% CI, 73.4-92.1%), respectively. Results suggest that LPAT is a useful diagnostic tool for the etiologic diagnosis of S. pneumoniae and H. influenzae type b pneumonia, especially in the developing world.

Opportunities for Control of Meningococcal Disease in the United States

The United States currently has relatively low rates of meningococcal disease caused by Neisseria meningitidis. Serogroups Y, C, and B are most common. Although most cases are sporadic, a minority are associated with outbreaks. Pediatric populations have disproportionately higher rates of disease, but nearly two thirds of all cases occur in persons aged 15 years and older. The major challenge to control of domestic meningococcal disease is the absence of a vaccine to prevent sporadic cases spanning many age groups. The quadrivalent A/C/Y/W-135 meningococcal polysaccharide vaccine is licensed in the United States, but because of its limited efficacy in children under two years of age, it is recommended for high-risk groups and outbreak response rather than routine childhood immunization. New conjugate meningococcal vaccines have successfully reduced endemic disease in the United Kingdom, and similar vaccines promise to have a dramatic impact on the burden of meningococcal disease in the United States.

Use of the NOW Streptococcus pneumoniae urinary antigen test in cerebrospinal fluid for rapid diagnosis of pneumococcal meningitis

Streptococcus pneumoniae is one of the most common pathogens in bacterial meningitis. Rapid diagnosis is critical for effective treatment. The aim of this study was to assess the accuracy of the NOW S. pneumoniae Urinary Antigen Test, (Binax, Portland, ME, USA) originally developed for urine testing, in detecting the S. pneumoniae antigen in cerebrospinal fluid (CSF). The study included 519 patients with suspected meningitis. CSF, blood and urine samples were cultured according to standard methods. CSF viral culture was also performed. CSF and urine specimens were tested for pneumococcal antigen with the NOW S. pneumoniae test.S. pneumoniae was isolated from the CSF of 22 patients. The direct antigen test was positive in CSF in 21/22 patients (95.4% sensitivity), and in urine, in 12/21 (57.1% sensitivity). Direct CSF smear was positive in 15/22 (68% sensitivity). CSF samples that cultured negative for S. pneumoniae (n = 470) or positive for other bacteria (n = 27) were also negative on the NOW test (100% specificity). By contrast, urine samples of 63/470 of patients with negative CSF culture were positive on the NOW test, as were 5/27 urine samples of patients with CSF culture positive for other bacteria (p = 0.45). The NOW S. pneumoniae antigen test in CSF yields a rapid and very reliable diagnosis of pneumococcal meningitis, enabling prompt and adequate treatment. Its low sensitivity in urine indicates that this mode of testing is not useful for the diagnosis of pneumococcal meningitis. These data have been included in the FDA application for approval of the NOW test for use in the CSF for the diagnosis of pneumococcal meningitis.

Cerebrospinal fluid

A quick and accurate diagnosis of maladies affecting the central nervous system (CNS) is imperative. Procurement and analysis of cerebrospinal fluid (CSF) are paramount in helping the clinician determine a patient's clinical condition. Various staining methods, measurement of white blood cell counts, glucose and protein levels, recognition of xanthochromia, and microbiologic studies are CSF parameters that are collectively important in the ultimate determination by a clinician of the presence or absence of a catastrophic CNS condition. Many of these CNS parameters have significant limitations that should be recognized to minimize under treating patients with catastrophic illness.