Test characteristics and interpretation of cerebrospinal fluid gram stain in children

Molecular diagnostics in cerebrospinal fluid for the diagnosis of central nervous system infections

SUMMARYCentral nervous system (CNS) infections can be caused by various pathogens, including bacteria, viruses, fungi, and parasites. Molecular diagnostic methods are pivotal for identifying the different causative pathogens of these infections in clinical settings. The efficacy and specificity of these methods can vary per pathogen involved, and in a substantial part of patients, no pathogen is identified in the cerebrospinal fluid (CSF). Over recent decades, various molecular methodologies have been developed and applied to patients with CNS infections. This review provides an overview of the accuracy of nucleic acid amplification methods in CSF for a diverse range of pathogens, examines the potential value of multiplex PCR panels, and explores the broad-range bacterial and fungal PCR/sequencing panels. In addition, it evaluates innovative molecular approaches to enhance the diagnosis of CNS infections.

Diagnostic Accuracy of Cerebrospinal Fluid Multiplex Polymerase Chain Reaction Panel Testing in Patients With Suspected Central Nervous System Infections: A Multi-Center Study in the United Arab Emirates

Background Delays in diagnosis and treatment of central nervous system (CNS) infections can lead to significant morbidity and mortality among children and adults. Prior antibiotic treatment is a major hurdle to accurate diagnosis due to falsely negative cerebrospinal fluid (CSF) cultures in partially treated patients. Increasingly, molecular diagnostic methods using multiplex polymerase chain reaction (mPCR) testing on CSF samples are being utilized in clinical practice for timely and accurate diagnosis. However, there is no data regarding the diagnostic accuracy or clinical impact of CSF mPCR testing in the Middle East region. We sought to compare the diagnostic accuracy of an automated mPCR CSF panel with routine CSF culture, the current gold standard, in the United Arab Emirates (UAE).  Methods This single-gated, multi-center, diagnostic accuracy study included patients from birth onwards who were admitted to any of the three participating hospitals with an initial diagnosis of meningitis or encephalitis, between January 2017 and March 2021, and had CSF samples collected for mPCR and culture. Sociodemographic, clinical, and molecular data were collected for all. Results A total of 353 CSF samples were collected from patients from 0-90 years old hospitalized for suspected CNS infection. Children constituted 51% of the study population, and males were slightly over-represented (55.2%). Pathogens were detected by mPCR in 78 (22%) CSF samples, of which 19 (24%) were bacteria and 59 (76%) were viruses. No fungal pathogens were detected. Enteroviruses were the most prevalent CNS pathogen among our cohort (40%), followed by herpes simplex virus type 2 (HSV-2) (12.5%). Children constituted 69% of positive samples for enterovirus, while HSV-2 was exclusively detected among adults. Using CSF culture as the diagnostic gold standard, the mPCR panel demonstrated high specificity (100%) and sensitivity (96.3%) in diagnosing CNS infection among all age groups. mPCR testing demonstrated a high overall percentage of agreement (OPA) with CSF culture (98.9%). Patients with bacterial meningitis had a significantly longer hospitalization (p=0.004) and duration of antibiotic therapy (p=0.001) compared to those with viral meningitis. Three CSF samples were negative on mPCR testing but positive on culture. These pathogens included: methicillin-sensitive Staphylococcus aureus(MSSA), Bacillus cereus, and Mycobacterium Tuberculosis (MTB). In addition, 13 patients had negative CSF cultures but tested positive on CSF mPCR. These pathogens included Streptococcus pneumoniae (seven patients), Haemophilus influenzae (three patients), Streptococcus agalactiae (two patients), and Escherichia coli (one patient). All discordant results were confirmed by reviewing the patient's clinical presentation, CSF analysis, clinical course, and final diagnosis. Conclusion CSF mPCR panel is a highly sensitive and specific diagnostic tool for the diagnosis of CNS infections among all age groups in the UAE. Routine use of CSF mPCR panels can decrease healthcare costs by reducing the length of stay and can also aid antibiotic stewardship efforts by reducing antibiotic overuse in patients with viral CSF infections. CSF culture and mPCR complement each other by identifying CNS pathogens in patients with prior antibiotic exposure who would otherwise be missed if relying on CSF culture alone. However, concomitant CSF culture samples should be sent to avoid missing unusual CNS pathogens.

Validation of Septic Knee Monoarthritis Prediction Rule in a Lyme Disease Endemic Area

OBJECTIVE

In Lyme disease endemic areas, Lyme and septic arthritis often present similarly. A published septic knee arthritis clinical prediction rule includes 2 high-risk predictors: absolute neutrophil count of 10,000 cells/mm3 or greater and erythrocyte sedimentation rate of 40 mm/h or greater. The objective of the study was to externally validate this prediction rule in a multicenter prospective cohort.

METHODS

We enrolled a prospective cohort of children with knee monoarthritis undergoing evaluation for Lyme disease at 1 of 8 Pedi Lyme Net emergency departments located in endemic areas. We defined a case of septic arthritis with a positive synovial fluid culture or a synovial fluid white blood cell count of 50,000 or greater per high powered field with a positive blood culture and Lyme arthritis with a positive or equivocal C6 EIA, followed by a positive supplemental immunoblot. Other children were classified as having inflammatory arthritis. We report the performance of the septic arthritis clinical prediction rule in our study population.

RESULTS

Of the 543 eligible children, 13 had septic arthritis (2.4%), 234 Lyme arthritis (43.1%), and 296 inflammatory arthritis (54.5%). Of the 457 children (84.2%) with available laboratory predictors, all children with septic arthritis were classified as high risk (sensitivity, 100%; 95% confidence interval [CI], 77.2%-100%; specificity, 68.1%; 95% CI, 63.6-73.3; negative predictive value, 278/278 [100%]; 95% CI, 98.6%-100%). Of the 303 low-risk children, 52 (17.2%) underwent diagnostic arthrocentesis.

CONCLUSIONS

The septic knee arthritis clinical prediction rule accurately distinguished between septic and Lyme arthritis in an endemic area. Clinical application may reduce unnecessary invasive diagnostic procedures.

How and when to use CSF to investigate neonates and children with possible central nervous system infection

A child presented to the emergency department with fever, reduced consciousness, irritability and reduced oral intake. Infective meningitis and encephalitis were within the differential diagnoses. Is a lumbar puncture (LP) indicated and, if so, what is the optimal timing of LP? Will antimicrobial pretreatment affect the cerebrospinal fluid (CSF) results? How can clinicians optimise diagnostic stewardship to benefit individual patients and society at large? Interpretation of rapidly available CSF biochemical tests (protein, glucose and lactate levels) and microscopy can provide a prompt insight into the infective aetiology and inform treatment and further diagnostic testing strategies. Diagnosis of an aetiological pathogen in a patient presenting with central nervous system (CNS) infection has clinical, infection control and public health implications. A plethora of tests are available to enable CSF analysis in patients with possible CNS infection. We aimed to summarise current evidence and guidance to ensure the best possible use of the diagnostics available.

Challenges in the Management of Gram-Negative Bacterial Infections in Patients With Ventriculoperitoneal Shunt

Gram-negative bacterial infections of the central nervous system (CNS) have worse clinical outcomes. The most common bacteria include Escherichia Coli, Citrobacter species, Enterobacter species, Serratia species, and Pseudomonas aeruginosa. There are multiple risk factors for CNS infection after shunt insertion, including younger age, obstructive hydrocephalus, shunt revision surgery, and trauma. The clinical presentation of a ventriculoperitoneal (VP) shunt infection includes the signs and symptoms of meningitis to fever with abdominal pain and peritonitis. Apart from cerebrospinal fluid (CSF) analysis, microbiological cultures and radiological studies are key diagnostic tools. Initial empirical intravenous antimicrobial therapy is preferably broad spectrum with appropriate coverage for resistant Gram-negative pathogens and the duration of treatment depends upon pathogenesis, host factors, and clinical response to the therapy.

Considering the importance of this disease and associated clinical outcomes, in this review article, we have summarized the epidemiology, clinical features, management, and prevention of Gram-negative VP shunt infections in adults.

Test Characteristics of Cerebrospinal Fluid Gram Stain to Identify Bacterial Meningitis in Infants Younger Than 60 Days

ABSTRACT

In our cohort of 20,947 infants aged 60 days or younger, cerebrospinal fluid Gram stain had a sensitivity of 34.3% (95% confidence interval, 28.1%-41.1%) and a positive predictive value of 61.4% (95% confidence interval, 52.2%-69.8%) for positive cerebrospinal fluid culture, suggesting that Gram stain alone may lead to both underdiagnosis and overdiagnosis of bacterial meningitis.

Point-of-care cerebrospinal fluid Gram stain for the management of acute meningitis in adults: a retrospective observational study

Background

Gram stain of cerebrospinal fluid (CSF) is widely used in the diagnosis of acute meningitis, however, it is often conducted in the laboratory, as only some hospitals have access to point-of-care Gram stain (PCGS). The purpose of this study was to demonstrate the clinical impact and utility of PCGS in diagnosing and treating both bacterial and aseptic meningitis in adults.

Methods

This was a hospital-based, retrospective observational study at a referral center in Okinawa, Japan. We reviewed the records of all patients aged 15 years or older who were admitted to the Division of Infectious Diseases between 1995 and 2015 and finally diagnosed with bacterial (n = 34) or aseptic meningitis (n = 97). For bacterial meningitis, we compared the treatments that were actually selected based on PCGS with simulated treatments that would have been based on the Japanese guidelines. For aseptic meningitis, we compared the rates of antibiotic use between real cases where PCGS was available and real cases where it was not.

Results

PCGS was the most precise predictor for differentiating between bacterial and aseptic meningitis (sensitivity 91.2%, specificity 98.9%), being superior in this regard to medical histories, vital signs and physical examinations, and laboratory data available in the emergency room (ER). In bacterial meningitis, PCGS reduced the frequency of meropenem use (1/34 = 3.0%) compared with simulated cases in which PCGS was not available (19/34 = 55.9%) (p< 0.001). In aseptic meningitis cases, the rate of antibiotic administration was lower when PCGS was used (38/97 = 39.2%) than when it was not (45/74 = 60.8%) (p = 0.006).

Conclusions

PCGS of CSF distinguishes between bacterial and aseptic meningitis more accurately than other predictors available in the ER. Patients with bacterial meningitis are more likely to receive narrower-spectrum antimicrobials when PCGS is used than when it is not. PCGS of CSF thus can potentially suppress the empiric use of antimicrobials for aseptic meningitis.

Clinical utility of anaerobic culture of cerebrospinal fluid

Anaerobic meningitis is a rare serious clinical condition which mainly affects vulnerable populations and patients with predisposing factors such as head trauma, prior neurosurgical procedures or implantable medical devices such as ventriculoperitoneal shunts or ventricular drains. In this study we retrieved data from aerobic and anaerobic cultures of cerebrospinal (CSF) or ventricular fluid ordered over a 5 year period at our institution. A total of 8868 aerobic and 594 anaerobic cultures were performed from 2013 to 2017. 24/594 (4%) anaerobic cultures from 14 patients were positive for anaerobes. Only 3 of those patients were diagnosed clinically with anaerobic meningitis, each with predisposing factors, while anaerobes (Cutibacterium acnes and Clostridium perfringens) recovered from the remaining 21 patients were regarded as contaminants. 129/8868 (1.45%) aerobic CSF cultures were positive for anaerobes. 120/129 (93%) cultures recovered C. acnes while non-C. acnes anaerobes were recovered in the remaining 9 cultures and were deemed to be contaminants. In the majority of situations, recovery of C. acnes from CSF or ventricular fluid was regarded as contamination. Our cohort included 18 patients with a ventriculoperitoneal shunt or ventricular drain, 17 of whom had C. acnes recovered from either aerobic or anaerobic culture, and 10 were treated with targeted antibiotics and surgical replacement of the shunt or drain. Anaerobic culture of the CSF or ventricular fluid aided in identification of two patients with anaerobic meningitis and an additional two patients with shunt infection. Anaerobe culture of CSF is important in identification of anaerobic meningitis, as growth of anaerobes other than C. acnes is rare from aerobic CSF culture.

Evaluation of the BioFire FilmArray meningitis/encephalitis panel for the detection of bacteria and yeast in Chinese children

Background

Meningitis and encephalitis are life-threatening syndromes with high morbidity and mortality in children. Due to limitations of traditional laboratory approaches in etiological diagnosis, the rate of misdiagnoses is unacceptably high.

Methods

We retrospectively compared the potential clinical impact of the FilmArray meningitis/encephalitis (ME) panel vs. conventional cerebrospinal fluid (CSF) culture in children with central nervous system (CNS) infections. Sixty-eight pediatric patients (<18 years of age) with an initial diagnosis of meningitis or encephalitis were enrolled at 2 children's hospital from January to October 2017.

Results

Fifteen specimens were found to be positive after CSF culture, with a positive rate of 22.1% (15/68). For the FilmArray ME panel, 26 bacteria and fungi from 25 samples were detected, and the positive rate was 36.8% (25/68). The FilmArray ME panel identified 14 pathogens in previously pathogen-negative patients.

Conclusions

This study demonstrated the capability of the FilmArray ME panel in the diagnosis of bacterial and fungal meningitis and therefore its potential use in facilitating enhanced patient care.

New molecular tools for meningitis diagnostics in Ethiopia - a necessary step towards improving antimicrobial prescription

BACKGROUND

Meningitis remains a top cause of premature death and loss of disability-adjusted life years in low-income countries. In resource-limited settings, proper laboratory diagnostics are often scarce and knowledge about national and local epidemiology is limited. Misdiagnosis, incorrect treatment and overuse of antibiotics are potential consequences, especially for viral meningitis.

METHODS

A prospective study was conducted over three months in a teaching hospital in Ethiopia with limited laboratory resources. Cerebrospinal fluid (CSF) samples from patients with suspected meningitis were analysed using a multiplex PCR-based system (FilmArray, BioFire), in addition to basic routine testing with microscopy and culture. Clinical data, as well as information on treatment and outcome were collected.

RESULTS

Two hundred and eighteen patients were included; 117 (54%) neonates (0-29 days), 63 (29%) paediatrics (1 month-15 years) and 38 (17%) adults (≥16 years). Of 218 CSF samples, 21 (10%) were PCR positive; 4% in neonates, 14% in paediatrics and 18% in adults. Virus was detected in 57% of the PCR positive samples, bacteria in 33% and fungi in 10%. All CSF samples that were PCR positive for a bacterial agent had a white cell count ≥75 cells/mm³ and/or turbid appearance. The majority (90%) of patients received more than one antibiotic for treatment of the meningitis episode. There was no difference in the mean number of different antibiotics received or in the cumulative number of days with antibiotic treatment between patients with a microorganism detected in CSF and those without.

CONCLUSIONS

A rapid molecular diagnostic system was successfully implemented in an Ethiopian setting without previous experience of molecular diagnostics. Viral meningitis was diagnosed for the first time in routine clinical practice in Ethiopia, and viral agents were the most commonly detected microorganisms in CSF. This study illustrates the potential of rapid diagnostic tests for reducing antibiotic usage in suspected meningitis cases. However, the cost of consumables for the molecular diagnostic system used in this study limits its use in low-income countries.

Modalities and accuracy of diagnosis of external ventricular drainage-related infections: a prospective multicentre observational cohort study

BACKGROUND

Device infection is a major complication of placement external ventricular drains (EVD). Diagnostic features are often masked by underlying disease or cerebrospinal fluid (CSF) contamination by blood. We aim to assess which diagnostic modalities are applied for EVD-related infection (ERI) diagnosis and evaluate their accuracy.

METHODS

This observational prospective study included 187 adult patients with an EVD. Modalities of clinical diagnosis of ERI diagnosed by treating physicians on clinical grounds and blood and CSF analysis (clinically diagnosed ERI (CD-ERI)) were assessed prospectively. Additionally, the diagnostic accuracy of clinical and laboratory parameters for the diagnosis of culture proven ERI (CP-ERI) was evaluated, using data of the study patients and including a retrospective cohort of 39 patients with CP-ERI.

RESULTS

Thirty-one CD-ERIs were diagnosed in the prospective cohort. Most physicians used CSF analysis to establish the diagnosis. ROC analysis revealed an AUC of 0.575 (p = 0.0047) for the number of positive SIRS criteria and AUC of 0.5420 (p = 0.11) for the number of pathological neurological signs for diagnosis of CP-ERI. Diagnostic accuracy of laboratory values was AUC 0.596 (p = 0.0006) for serum white blood cell count (WBCC), AUC 0.550 (p = 0.2489) for serum C-reactive protein, AUC 0.644 (p < 0.0001) for CSF WBCC and AUC 0.690 for CSF WBC/red blood cell count ratio (both p < 0.0001). Neither a temporal trend in potential predictors of CP-ERI nor a correlation between clinical diagnosis and proven CSF infection was found.

CONCLUSIONS

Clinicians base their diagnosis of ERI mostly on CSF analysis and occurrence of fever, leading to over-diagnosis. The accuracy of the clinical diagnosis is low. Commonly used clinical and laboratory diagnostic criteria have a low sensitivity and specificity for ERI.

Central Nervous System Infections

This chapter provides an overview of infectious syndromes, pathogens, and diagnostic testing modalities for central nervous system infections in the immunocompromised host.

Comparative evaluation of the FilmArray meningitis/encephalitis molecular panel in a pediatric population

We compared an FDA cleared molecular meningitis/encephalitis panel to lab developed viral PCRs and bacterial culture. Of the 67 viral PCR or bacterial culture-positive samples, 92.5% were positive for the same target by the panel. Of the 66 negative samples tested, no targets were detected by the panel, for an agreement of 96.2%.

Indicators of external ventricular drainage-related infections--a retrospective observational study

BACKGROUND

External ventricular drainage (EVD) is frequently used in different groups of patients in neurocritical care. Despite the frequent use of EVD, no consensus regarding the diagnosis of EVD-related infection currently exists, and diagnosis is commonly based on criteria for the diagnosis of non-EVD-related CNS infections. This study evaluates the diagnostic accuracy of clinical and laboratory parameters for the prediction of EVD-related infection in patients with proven EVD-related infection.

METHODS

In two tertiary care centers, data on EVD insertions were matched with a microbiologic database of cultured microorganisms and positive Gram stains of cerebrospinal fluid (CSF) to identify patients with EVD-related infections. Available clinical data and results of blood tests and CSF analysis were retrospectively collected. Predefined potential clinical and laboratory predictors of EVD-related infection were compared between three time points: at the time EVD insertion and 48 h before and at the time of occurrence of EVD-related infection.

RESULTS

Thirty-nine patients with EVD-associated infection defined by positive CSF culture or positive CSF Gram stains and concomitant clinical signs of infection were identified. At the time of infection, a significantly higher incidence of abnormal temperature, high respiratory rate, and a slightly but significantly higher incidence of decreased mental state were observed. The assessed blood and CSF parameters did not significantly differ between the different assessment time points.

CONCLUSIONS

Our analysis of 39 patients with culture positive EVD-related infection showed that commonly used clinical and laboratory parameters are not reliable infection predictors.

A versatile PDMS/paper hybrid microfluidic platform for sensitive infectious disease diagnosis

Bacterial meningitis is a serious health concern worldwide. Given that meningitis can be fatal and many meningitis cases occurred in high-poverty areas, a simple, low-cost, highly sensitive method is in great need for immediate and early diagnosis of meningitis. Herein, we report a versatile and cost-effective polydimethylsiloxane (PDMS)/paper hybrid microfluidic device integrated with loop-mediated isothermal amplification (LAMP) for the rapid, sensitive, and instrument-free detection of the main meningitis-causing bacteria, Neisseria meningitidis (N. meningitidis). The introduction of paper into the microfluidic device for LAMP reactions enables stable test results over a much longer period of time than a paper-free microfluidic system. This hybrid system also offers versatile functions, by providing not only on-site qualitative diagnostic analysis (i.e., a yes or no answer), but also confirmatory testing and quantitative analysis in laboratory settings. The limit of detection of N. meningitidis is about 3 copies per LAMP zone within 45 min, close to single-bacterium detection sensitivity. In addition, we have achieved simple pathogenic microorganism detection without a laborious sample preparation process and without the use of centrifuges. This low-cost hybrid microfluidic system provides a simple and highly sensitive approach for fast instrument-free diagnosis of N. meningitidis in resource-limited settings. This versatile PDMS/paper microfluidic platform has great potential for the point of care (POC) diagnosis of a wide range of infectious diseases, especially for developing nations.

Improved detection of bacterial central nervous system infections by use of a broad-range PCR assay

A universal PCR assay for bacteria and fungi detected meningitis pathogens in 65% of 20 cerebrospinal fluid (CSF) samples from patients with suspected central nervous system (CNS) infections compared to a 35% detection rate by culture and/or microscopy methods. Thus, the PCR assay can improve the diagnosis rate of infective meningitis when standard methods provide a negative result.

The bacterial meningitis score to distinguish bacterial from aseptic meningitis in children from Sao Paulo, Brazil

In a retrospective cohort of 494 children with meningitis in Sao Paulo, Brazil, the Bacterial Meningitis Score identified all the children with bacterial meningitis (sensitivity 100%, 95% confidence interval: 92-100% and negative predictive value 100%, 95% confidence interval: 98-100%). Addition of cerebrospinal fluid lactate to the score did not improve clinical prediction rule performance.

Bacterial meningitis post-PCV7: declining incidence and treatment

The epidemiology of bacterial meningitis in the United States has changed tremendously in the past 20 years. Since the introduction of the Haemophilus influenzae type b vaccine in 1988, the incidence of H. influenzae type b meningitis has declined by at least 97%, and Streptococcus pneumoniae has emerged as the most common etiologic agent. The PCV7 (7-valent pneumococcal conjugate vaccine [Prevnar]; Wyeth Pharmaceuticals) vaccine, which targets 7 pneumococcal serotypes, was introduced in 2000 and has had an enormous impact on both the incidence and epidemiology of bacterial meningitis. This article reviews the impact of the PCV7 vaccine and the most up-to-date evidence on diagnosis and empiric therapy of suspected bacterial meningitis in the current day.

The clinical and laboratory diagnosis of acute meningitis and acute encephalitis

INTRODUCTION

Acute bacterial meningitis (ABM) is a life-threatening infectious disease requiring prompt antimicrobial therapy. ABM must be differentiated from systemic disorders with CNS manifestations that may mimic ABM. ABM should also be differentiated from acute meningoencephalitis (AME) and acute viral encephalitis (AVE). Nonviral causes of AME are treatable. Among the causes of AVE, Herpes simplex encephalitis (HSE) is treatable. This article reviews the clinical diagnostic approach to ABM, AME and AVE.

AREAS COVERED

The differential diagnostic (DDx) approach to ABM, AME and AVE is based on clinical and laboratory findings. A specific pathogen diagnosis is based on serum/cerebrospinal fluid (CSF) tests. This overview presents the diagnostic approach to ABM, AME and AVE in normal hosts (excluding brain abscesses and chronic CNS infections).

EXPERT OPINION

It is time critical to diagnose ABM and begin empiric antimicrobial therapy based on the known/most likely pathogen. The diagnosis of ABM depends on clinical features and the CSF profile. The CSF Gram stain and CSF lactic acid (LA) levels provide the most rapid, reliable and cost-effective tests to diagnose ABM. CSF LA levels are also the best way to diagnose partially treated acute bacterial meningitis (PTABM). In those cases of AME/AVE due to viruses with a CSF profile mimicking ABM, for example, HSE, unelevated CSF LA levels rapidly/reliably rule out ABM as a diagnostic possibility.

Central Nervous System Infections

Central nervous system (CNS) infections—i.e., infections involving the brain (cerebrum and cerebellum), spinal cord, optic nerves, and their covering membranes—are medical emergencies that are associated with substantial morbidity, mortality, or long-term sequelae that may have catastrophic implications for the quality of life of affected individuals. Acute CNS infections that warrant neurointensive care (ICU) admission fall broadly into three categories—meningitis, encephalitis, and abscesses—and generally result from blood-borne spread of the respective microorganisms. Other causes of CNS infections include head trauma resulting in fractures at the base of the skull or the cribriform plate that can lead to an opening between the CNS and the sinuses, mastoid, the middle ear, or the nasopharynx. Extrinsic contamination of the CNS can occur intraoperatively during neurosurgical procedures. Also, implanted medical devices or adjunct hardware (e.g., shunts, ventriculostomies, or external drainage tubes) and congenital malformations (e.g., spina bifida or sinus tracts) can become colonized and serve as sources or foci of infection. Viruses, such as rabies, herpes simplex virus, or polioviruses, can spread to the CNS via intraneural pathways resulting in encephalitis. If infection occurs at sites (e.g., middle ear or mastoid) contiguous with the CNS, infection may spread directly into the CNS causing brain abscesses; alternatively, the organism may reach the CNS indirectly via venous drainage or the sheaths of cranial and spinal nerves. Abscesses also may become localized in the subdural or epidural spaces. Meningitis results if bacteria spread directly from an abscess to the subarachnoid space. CNS abscesses may be a result of pyogenic meningitis or from septic emboli associated with endocarditis, lung abscess, or other serious purulent infections. Breaches of the blood–brain barrier (BBB) can result in CNS infections. Causes of such breaches include damage (e.g., microhemorrhage or necrosis of surrounding tissue) to the BBB; mechanical obstruction of microvessels by parasitized red blood cells, leukocytes, or platelets; overproduction of cytokines that degrade tight junction proteins; or microbe-specific interactions with the BBB that facilitate transcellular passage of the microorganism. The microorganisms that cause CNS infections include a wide range of bacteria, mycobacteria, yeasts, fungi, viruses, spirochaetes (e.g., neurosyphilis), and parasites (e.g., cerebral malaria and strongyloidiasis). The clinical picture of the various infections can be nonspecific or characterized by distinct, recognizable clinical syndromes. At some juncture, individuals with severe acute CNS infections require critical care management that warrants neuro-ICU admission. The implications for CNS infections are serious and complex and include the increased human and material resources necessary to manage very sick patients, the difficulties in triaging patients with vague or mild symptoms, and ascertaining the precise cause and degree of CNS involvement at the time of admission to the neuro-ICU. This chapter addresses a wide range of severe CNS infections that are better managed in the neuro-ICU. Topics covered include the medical epidemiology of the respective CNS infection; discussions of the relevant neuroanatomy and blood supply (essential for understanding the pathogenesis of CNS infections) and pathophysiology; symptoms and signs; diagnostic procedures, including essential neuroimaging studies; therapeutic options, including empirical therapy where indicated; and the perennial issue of the utility and effectiveness of steroid therapy for certain CNS infections. Finally, therapeutic options and alternatives are discussed, including the choices of antimicrobial agents best able to cross the BBB, supportive therapy, and prognosis.

Comparison of cerebrospinal fluid in newborns and in infants ≤ 2 months old with or without meningitis

BACKGROUND

The aim of the present study was to evaluate the characteristics and accuracy of cerebrospinal fluid (CSF) parameters for neonatal meningitis, by comparing CSF data in newborns and in infants ≤ 2 months of age, with or without meningitis.

METHODS

This case-control study was performed on 120 newborns and infants ≤ 2 months old. 60 patients with meningitis were considered as the case group and 60 ill patients without meningitis were defined as the control group. Each of the two groups was divided into 0-1 months and 1-2 months old. CSF characteristics were compared in newborns in the case and control groups; in infants ≤ 2 months old in the case and control groups; and in healthy newborns and healthy infants ≤ 2 months old.

RESULTS

The mortality rate was 16.7% in the case group. The differences of CSF parameters in the case and control groups were mostly not significant, except for CSF glucose only in term newborns <7 days old (P= 0.04), and white cell count (WBC) only in 0-7-day-old term and preterm neonates (P= 0.04 and P= 0.01, respectively). Polymorphonuclear leukocyte (PMNL) level in the case group was significantly higher than in the control group (P= 0.02). CSF characteristics in healthy newborns were nearly the same as in healthy infants ≤ 2 months old. Prevalence of positive CSF culture was 31.7% in the case group. The most common pathogen was Neisseria meningitidis in the two age groups. The concomitant positive blood culture in the case group was 26.3%.

CONCLUSION

In the case of meningitis with negative CSF culture and Gram stain, diagnosis can be made on CSF parameters, clinical and laboratory findings and suspicion of meningitis. Therefore, a clinical prediction rule to classify risk for bacterial meningitis on evaluation of CSF parameters in any region should be established. More regional trials are needed to enhance the probability of diagnosis according to CSF parameters.

Diagnostic accuracy of cerebrospinal fluid gram stain in children with suspected bacterial meningitis

This cross-sectional study included 1938 children undergoing lumbar puncture; 21 (1.1%) cases were classified as definite (n = 17) or probable (n = 4) bacterial meningitis. Gram stain sensitivity was 94.1% (95% confidence interval, 71.3%-99.9%) for those with definite meningitis; the positive predictive value was 47.1% (95% confidence interval, 29.8%-64.9%). The sensitivity was 95.2% for those with definite or probable meningitis. Antibiotic pretreatment did not affect results.

Use of quantitative broad-based polymerase chain reaction for detection and identification of common bacterial pathogens in cerebrospinal fluid

BACKGROUND

Conventional laboratory diagnosis of bacterial meningitis based on microscopy followed by culture is time-consuming and has only moderate sensitivity.

OBJECTIVES

The objective was to define the limit of detection (LOD), analytic specificity, and performance characteristics of a broad-based quantitative multiprobe polymerase chain reaction (PCR) assay for rapid bacterial detection and simultaneous pathogen-specific identification in patients with suspected meningitis.

METHODS

A PCR algorithm consisting of initial broad-based detection of Eubacteriales by a universal probe, followed by pathogen identification using either pathogen-specific probes or Gram-typing probes, was employed to detect pathogens. The 16S rRNA gene, which contains both conserved and variable regions, was chosen as the target. Pathogen-specific probes were designed for Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes. Gram-positive and -negative typing probes were designed based on conserved regions across all eubacteria. The LOD and time to detection were assessed by dilutional mocked-up samples. A total of 108 convenience cerebrospinal fluid (CSF) clinical samples obtained from the Johns Hopkins Hospital (JHH) microbiology laboratory were tested, and results were compared with hospital microbiologic culture reports.

RESULTS

The LOD of the assay ranged from 10(1) to 10(2) colony-forming units (CFU)/mL. Pathogen-specific probes showed no cross-reactivity with other organisms. Time to detection was 3 hours. In clinical specimens, the universal probe correctly detected 16 of 22 culture-positive clinical specimens (sensitivity = 72.7%; 95% confidence interval [CI] = 49.8% to 89.3%), which were all correctly characterized by either pathogen-specific or Gram-typing probes. Adjusted sensitivity after removing probable microbiologic laboratory contaminants was 88.9% (95% CI = 65.3% to 98.6%). The universal probe was negative for 86 of 86 culture-negative specimens.

CONCLUSIONS

A broad-based multiprobe PCR assay demonstrated strong analytic performance characteristics. Findings from a pilot clinical study showed promise in translation to human subjects, supporting potential utility of the assay as an adjunct to traditional diagnostics for early identification of bacterial meningitis.

Cerebrospinal fluid pleocytosis in children in the era of bacterial conjugate vaccines: distinguishing the child with bacterial and aseptic meningitis

Although bacterial meningitis remains an important cause of childhood morbidity and mortality, the incidence of bacterial meningitis has greatly decreased with the advent of polysaccharide-protein conjugate vaccines in the past 2 decades. Most children with cerebrospinal fluid pleocytosis have aseptic rather than bacterial meningitis, raising the possibility that some patients may be managed as outpatients. In this article, we review the changing epidemiology of bacterial meningitis as well as the available clinical decision rules that may assist the clinician in distinguishing aseptic from bacterial meningitis in patients with cerebrospinal fluid pleocytosis.