Epidemiology, clinical profile and role of rapid tests in the diagnosis of acute bacterial meningitis in children (aged 1-59 months)
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.236972
Source of Support: None, Conflict of Interest: None
Keywords: Acute bacterial meningitis, latex particle agglutination, neurological sequelae, polymerase chain reaction
Acute bacterial meningitis (ABM) is a devastating disease that is associated with substantial morbidity and mortality. There is a need for periodic review worldwide as the pathogens responsible vary with time, geography, immune status, and age of the patient. The community incidence of ABM in India is not known. The reported frequency of occurrence of ABM in hospital admissions among children in India below 5 years of age is 0.5–2.5%. Most Indian studies have reported a high incidence of pneumococcal meningitis both in adults and children., Despite the availability of newer potent antibiotics, the mortality rate remains significantly high and approaches nearly 100% in untreated cases.,
In neonatal meningitis, group B Streptococci, Escherichia More Details coli K1 and Listeria monocytogenes are the predominant causes, while in the postneonatal period, Hemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria More Details meningitidis are the commonly documented pathogens. The diagnosis of meningitis is established by gram stain and culture; the diagnostic yield of these investigations is, however, affected in many clinical situations by the use of antibiotics administered prior to the lumbar puncture. Moreover, in many instances, antimicrobial therapy must be started empirically because no causative agent can be identified in the early stage of the disease.
The latex particle agglutination (LPA) test is highly sensitive and specific, simple to perform test that requires no special equipment and is technically easy. The results of this test are available in 10 min. Additionally, the use of polymerase chain reaction (PCR) for the rapid diagnosis of ABM has the potential to overcome the poor sensitivity of culture when antibiotic have already been introduced.,
The rapid detection and estimation of the severity of the disease are important factors, both in guiding the treatment as well as for the formulation of vaccination policies. There are limited studies from India regarding the etiology and epidemiological factors associated with ABM.
The aim of this study was to study the clinical profile of ABM in children aged between 1-59 months, and to investigate the role of rapid tests in establishing its diagnosis.
This prospective study was conducted over a period of 1 year on 250 cerebrospinal fluid (CSF) samples obtained from pediatric patients (1–59 months) admitted with suspected ABM in the Department of Pediatrics in a tertiary care hospital at Shimla (Himachal Pradesh), India. Out of the cohort from whom CSF samples were collected, blood samples could be collected from 187 patients only.
The data collected was a subset from the project on surveillance for meningitis due to H. influenzae type b, S. pneumoniae, and N. meningitidis in children of the age group 1–59 months, assigned by the Indian Council of Medical Research.
The clinical parameters included the age (1–59 months), duration of illness (<7 days), clinical features, antimicrobial treatment used, outcome at discharge, and follow-up, which was conducted until 6 months after the discharge.
The inclusion criteria for suspected ABM included the presence of fever, with one, or more than one, of the following symptoms such as neck stiffness, bulging fontanel, altered or reduced level of consciousness, lethargy, convulsions in a child without a documented seizure disorder, and the clinical suspicion of meningitis by the treating physician.
The study was approved by the Ethical Committee of the institution and a written informed consent was obtained from the parents or the legal guardians.
All samples were collected preferably prior to the initiation of antimicrobial therapy. However, history of any prior antibiotic intake or immunization against S. pneumoniae, H. influenzae type b and N. meningitidis was also documented in all patients. Lumbar puncture was performed under aseptic conditions and the CSF samples collected were subjected to laboratory examination, including the white cell count, sugar and protein levels, gram stain, bacteriological culture, antimicrobial sensitivity testing, antigen detection tests, and real-time polymerase chain reaction (RT-PCR).
CSF was centrifuged in a sterile/conical centrifuge tube at 3000 rpm for 30 min. Gram stain and culture were performed on the centrifuged deposit, and the culture media was provided by HIMEDIA, Mumbai.
Bacterial antigen detection in the CSF was done by treating the supernatant with the BD Directigen ™ Meningitis Combo Test Kit (Becton, Dickinson and Company, USA) and Binax NOW Kit (Binax Inc.). The methods given in the literature of commercial kits were followed for performing the tests.
Under the surveillance project, RT-PCR was available only for S. pneumoniae, N. meningitidis ACYW135, N. meningitidis type b, and H. influenzae type b. Blood samples were processed for serum glucose levels, culture, and antimicrobial sensitivity testing.
The criteria for establishing a confirmed diagnosis included the following: A case of clinically suspected meningitis was subjected to laboratory tests, including CSF and/or blood culture. A positivity on culture for an organism known to cause meningitis, or the identification of the pathogen by gram stain or by antigen detection methods established the diagnosis of ABM.
PCR was also used in the diagnosis because it acts as a complementary tool to the classic phenotype-based methods such as culture, gram stain and latex agglutination test, and often enhances the diagnostic yield of ABM.,
The results were analysed for sensitivity, specificity and were evaluated according to the standard statistical methods using the Statistical Package for the Social Sciences (SPSS) software version 17.
Two hundred and fifty patients matched the inclusion criteria for clinically suspected meningitis in the specified age group (1–59 months).
Fever <7 days and temperature ≥38.0°C (based on the axillary measurement) were present in 100% (250) of the cases studied. Other clinical features recorded in descending order were lethargy, convulsions, altered sensorium, neck stiffness, and bulging anterior fontanel in 53.2% (n = 133), 28.8% (n = 72), 26.2% (n = 67), 16.4% (n = 41), and 15.6% (n = 39) patients, respectively. Two patients had a purulent ear discharge, while funduscopic changes and cranial nerve palsy were also noted in a patient (0.40%).
In accordance with the National Program of Immunization, 97.60% children were completely immunized for their age; however, none had received immunization for H. influenzae b, S. pneumoniae, and N. meningitidis. Before being referred to the tertiary care hospital, 85.2% had received prior antibiotic treatment from some peripheral institutions. The most commonly used antibiotic was third-generation cephalosporin (either ceftriaxone or cefotaxime) followed by amikacin, gentamicin, and cotrimoxazole.
Eighty one patients were diagnosed as confirmed cases. Out of these (n = 81), 65.4% (n = 53) were detected to be positive on antigen detection tests (LPA + immunochromatography); and among these, 40 were positive for Group B Streptococcus (GBS), 6for S. pneumoniae, 4 for H. influenzae type b, 2 for N. meningitidis B /E. coli K1, and 1 for N. meningitidis ACYW135. In the six patients in whom S. pneumoniae was present, three were also found to be positive by the immunochromatographic test.
RT-PCR detected the pathogens in 25.9% (21) patients. Seventeen samples were positive for S. pneumoniae, 3 for H. influenzae type b, and 1 for N. meningitides ACY135.
Only five samples demonstrated the presence of the pathogens on CSF gram staining and culture. Among the two samples with gram-positive diplococci sensitivity, the culture was positive for S. pneumoniae in both, while among the three samples positive for gram-negative bacilli, two were detected to be having H. influenzae, while the last one was positive for E. coli. All CSF samples that were detected as being positive for a specific organism on culture were also found to be positive on LPA and RT-PCR for the same organism. The blood culture was positive in 20.9%(17) patients. Various organisms isolated on blood culture were S. pneumoniae (n = 1), E. coli (n = 5), Klebsiella pneumoniae (n = 5), and S. aureus (n = 6). Other than S. pneumoniae, other isolates obtained on blood culture are not classically associated with ABM in this age group. S. pneumoniae was found to be 100% sensitive to cotrimoxazole, erythromycin, cefotaxime, chloramphenicol, and linezolid; and, H. influenzae was 100% susceptible to ampicillin, cotrimoxazole, and chloramphenicol.
Considering the diagnostic criteria, GBS was the most common pathogen detected in 49.4% (n = 40), followed by S. pneumoniae, S. aureus, H. influenzae type b, E. coli, K. pneumoniae, and N. meningitides ACYW135 in 23.4% (n = 19), 7.4% (n = 6), 6.1% (n = 5), 6.1% (n = 5), 6.1% (n = 5), and in 1.2% (n = 1) patients, respectively [Table 1].
While studying for complications during hospitalization in these patients (n = 81), seizures were found in 23.4% (n = 19), increased intracranial pressure in 20.9% (n = 10), infarct on imaging in 4.9% (n = 4), coma in 4.9% (n = 4), respiratory compromise leading to ventilatory support in 3.7% (n = 3), hydrocephalus in 2.4% (n = 2), and subdural effusion in 2.4% (n = 2) cases, respectively. Seventy patients got discharged, 4 left against medical advice and 7 died, reflecting a fatality rate of 8.6%. The follow-up until 6 months after discharge was possible in 32 patients and cranial nerve palsies, hemiparesis, seizures, vision impairment, hearing deficit, and extrapyramidal movements were documented in 28.1% (n = 9), 25% (n = 8), 15.6% (n = 5), 9.3% (n = 3), 9.3% (n = 3), and 6.2% (n = 2) patients, respectively [Table 2].
The sensitivity of detection of ABM in the CSF PCR, and LPA tests were compared against CSF culture. The LPA and PCR tests showed a sensitivity of 100% by positively identifying all the culture and smear positive isolates. The specificity of these tests was 80.08 and 93.46%, respectively [Table 3].
Bacterial meningitis continues to be an important cause of mortality and morbidity in neonates and children throughout the world. In children <5 years of age, the diagnosis and treatment may be delayed due to nonspecific and subtle symptoms. Although bacterial culture is considered to be the standard method for establishing the presence of ABM, the negative effects of prior antimicrobial medication on the sensitivity of its detection necessitates the usage of nonculture techniques for establishing the diagnosis of ABM., In the present study (n = 81), gram stain and CSF culture were positive in 6.1% (n = 5) cases only, while the nonculture techniques detected such pathogens in 91.3% (n = 74) patients. The reasons, as reviewed in other studies, for a low diagnostic yield on gram stain and CSF culture are a low bacterial load, the use of antimicrobial agents prior to CSF collection,,,, as well as poor culture facility such as non-availability of special media, the storage of serum fluids in unsatisfactory conditions, the presence of autolytic enzymes, samples being refrigerated before their plating, a delayed and faulty inoculation, lack of transport media, and inadequacy in processing of CSF specimens., The reason for the low culture yield in the present study may be explained by the fact that the maximum number (85.20%) of patients had received prior antibiotics from other peripheral institutions.
Various authors have advocated the usefulness of rapid diagnostic tools such as bacterial antigen detection test and PCR. These tests are highly sensitive and specific especially in situ ations where the patient has received prior antibiotics.,,, The PCR assay could pick 13 additional cases which could not be diagnosed by the conventional techniques. This re-emphasizes the need for a molecular technique that does not require the organism to be viable and can detect even a low quantity of the bacteria.,
The LPA test showed a sensitivity of 100% and a specificity of 80.08%. PCR had a sensitivity of 100% and a specificity of 93.46%. Using CSF culture as the gold standard for calculating sensitivity and specificity has its own limitations. CSF culture is less sensitive compared to these rapid tests, and moreover, these tests are not designed to detect all the organisms. Hence, a culture negative, and a LPA test or a PCR test positive result, that is taken as false positive could actually be a true positive test, and vice versa, which could influence the sensitivity and specificity adversely. Further reports from various studies indicate that in a significant proportion of CSF samples, the amplification process is problematic due to the presence of PCR inhibitors as there may be increased levels of proteins and cell numbers in the CSF samples.
In view of their higher costs, the indiscriminate use of these rapid tests without consideration of the chemical and cytological profiles of the CSF is a misuse of valuable resources.,
In the present study (n = 81), LPA detected 49.3% (n = 40) cases to be positive for GBS and out of these, 75% (n = 30) were above 3 months of age. Our results correlate with the study done by some other Indian authors, who reported 27 (15.97%) of 169 CSF samples of patients in the age group 1–18 months to be positive for GBS by LPA, with 59% (n = 16) children being above 3 months of age. Florindo et al., reported GBS as the causative agent responsible for sixty episodes of meningitis in children aged 3 months to 12 years from Angola, during a study conducted from 2004 to 2005.
S. pneumoniae was detected in 23.4%, H. influenzae type b in 6.1%, and N. meningitides ACYW135 in 1.2% patients. Most Indian studies have quoted low isolates of H. influenzae.,, Whether this is because the organism is difficult to grow or the incidence is genuinely low is still not clear. A low incidence of infection with N. meningitidis and a relatively high incidence of pneumococcal infection has been noted by other Indian workers., The complication rate of ABM is very high in spite of its aggressive management. In our study, 54.3% of patients developed one or more of the acute complications. Similar rates have been reported in other studies.,
Case fatality rate was documented in 8.88% cases and one-third of the deaths occurred during the first 48 h, reflecting the critical condition of the patients at admission. The mortality rate recorded for ABM is approximately 27%, and up to 50% of the patients develop psycho-neurological sequelae due to damage to the hippocampal nuclei and other neurological structures. Data regarding the sequelae could be recorded only in 39.5% of the positive cases which was one limitation of this study. Neurological sequelae occur in a substantial amount of patients following bacterial meningitis. The most frequently reported sequelae are focal neurological deficits, hearing loss, cognitive impairment, and epilepsy.,, Such data from India is lacking.
GBS has emerged to be an important cause of paediatric morbidity and mortality, hence a continued surveillance with more detailed studies are warranted to assess the actual magnitude of the problem and the spectrum of diseases caused by this pathogen in our setting. Further, the incidence of ABM and the complication rates associated with it remain high in our country. As a result, an immediate diagnosis and treatment are recommended, which will help in improving the outcome.
Financial support and sponsorship
ICMR (Indian Council of Medical Research).
Conflicts of interest
There are no conflicts of interest.
[Table 1], [Table 2], [Table 3]