ACUTE BACTERIAL MENINGITIS FOR MICROBIOLOGY

Acute meningitis in microbiology
Types of meningitis

1. MENINGITIS Presented by: Kapil Kumar(51) Kavita Kurre(52) Komal Agrawal(53) Krishna Kumar Patel(54) Krishna Chandra(55) Guided by : Dr. Debashish Samal sir

2. CONTENTS : INTRODUCTION DEFINITION CLASSIFICATION OF MENINGITIS AGENTS OF MENINGITIS CLINICAL PRESENTATIONS

3. INTRODUCTION MENINGITIS DEFINITION: Meningitis is the inflammation of the leptomeninges (pia and archanoid matter) surrounding the brain and spinal cord, with involvement of the subarachnoid space. CLASSIFICATION OF MENINGITIS: Based on the onset ➤ Acute meningitis : Progresses in few hours Acute bacterial meningitis Acute viral meningitis ➤ Chronic meningitis: Progressively worsens over weeks (>4 weeks) Bacterial, viral, fungal and parasitic.

4. AGENTS OF MENINGITIS: BACTERIA Neonates and infants E.Coli Group B Streptococci (Streptococcus agalactice ) Staphylococcus aureus H.Influenzae Streptococcus pneumanice Klebsiella Listeria monocytogenes Children Haemophilus influenzae Neisseria meningitidis Streptococcus pneumoniae Adults Neisseria meningitidis Streptococcus pneumoniae Elderly Streptococcus pneumoniae Staphylococcus aureus Gram-negative enteric bacilli

5. VIRUS (ASEPTIC MENINGITIS) Enteroviruses (ECHO, Coxsackie, Polio) Paramyxoviruses (Mumps, Measles) Herpesviruses (Herpes simplex.Varicella zoster) Adenoviruses Arboviruses(Flavivirus, Buniyavirus )

6. FUNGI Cryptococcus neoformans Candida albicans Aspergillus species Histoplasma capsulatum Caccidioides immitis PARASITES Entamoeba histalytica Naegleria Acanthamoeba Toxoplasma gondii

7. CLINICAL PRESENTATION Symptoms: Headache, fever, altered sensorium Signs: Neck rigidity and positive signs for meningism such as Kernig's and Brudinsky's sign; older children and adults develop a stiff neck, usually with fever and headache. Infants and young children may have a high or low body temperature, be irritable or drowsy, or have a poor appetite.

8. ACUTE BACTERIAL MENINGITIS

9. Acute Bacterial Meningitis It is also called as pyogenic meningitis , is an acute purulent infection within the subarachnoid space. It is characterized by elevated polymorphonuclear cells in CSF. The causative agents may vary according to the ages.

10. Overall : most common cause is Streptococcus pneumoniae (-50%). Other agents include Meningococcus (-25%), Streptococcus agalactiae (-15%), Listeria (-10%) and Haemophilus influenzae (<10%) Neonates: Streptococcus agalactiae, Gram-negative bacilli such as Escherichia coli and Klebsiella, and Listeria monocytogenes Elderly (>60 years): Streptococcus agalactiae and Listeria monocytogenes.

11. Pathogenesis • Mode of transmission -droplets from respiratory secretions, prolonged and close contacts. • Routes of infection: Hematogenous spread - most common, through choroid plexus Direct spread - otitis media, sinusitis, mastoiditis. Anatomical defect in CNS- due to surgery, trauma, congenital defects.

12. Predisposing factors Age: neonates - highest prevalence of meningitis; due to Immature immune system Acquiring organism from mother’s Birth canal Increased permeability to BBB. Vaccination: reduces incidence of H. influenza meningitis due to implementation of Hib vaccine.

13. Presence of CSF shunts also facilitate pathogens entry into meninges, e.g. staphylococci, Pseudomonas, Acinetobacter, etc. Breach in the blood-brain barrier (BBB): Organism can gain access through BBB by: ■ Loss of capillary integrity by disrupting the tight junctions ■ Transport within circulatory phagocytes Crossing the endothelial cells by transport within the endothelial cell vacuoles.

14. Clinical Manifestations : average incubation period :4 days range : 2 to 10 days. Important symptoms include: fever, vomiting, intense headache, altered consciousness and occasionally photophobia .

15. signs of meningism (meningeal irritation) such as: „ Nuchal rigidity (“stiff neck”) : pathognomonic sign of meningeal irritation, present when the neck resists passive flexion.

16. „ Kernig’s sign: Severe stiffness of the hamstrings causes an inability to straighten the leg when the hip is flexed to 90°.

17. „ Brudzinski’s sign: When the neck is passively flexed, results in spontaneous flexion of the hips and knees.

18. In infants: slower onset, signs may be nonspecific, and neck stiffness may not be present. Babies usually present with fever, irritability and bulging fontanelle. Complications: meningoencephalitis—that may result in decreased consciousness, seizures, raised intracranial pressure, and stroke. Organism specific finding—e.g. purpuric rashes seen in meningococcal meningitis .

19. Laboratory Diagnosis Specimen Collection and Transport ideal specimen: CSF Blood culture is another useful specimen for culture. ™ CSF collection: by lumbar puncture under strict aseptic conditions. It is divided into three sterile containers; one each for cell count, biochemical analysis and bacteriological examination

20. ™ CSF transport: CSF should never be refrigerated as delicate pathogens such as H. influenzae, pneumococci or meningococci may die. if delay is expected, kept in an incubator at 37°C

21. Other useful specimens ™ Blood culture: Blood should be collected in automated blood culture bottles such as BacT /ALERT. ™ For suspected meningococcal meningitis: nasopharyngeal swabs, pus or scrapings from rashes ; carried in transport media (such as Stuart’s medium ). These specimens are inoculated onto selective media, such as Thayer Martin medium or New York City medium, to suppress the growth of normal flora.

22. Cytological and Biochemical Analysis

23. CSF Microscopy (Gram Staining) It gives clue about the etiological agent of pyogenic meningitis based on the morphology of the bacteria.

24. ™ Heaped smear : As the bacterial load in CSF may be very low, to increase the sensitivity, several drops of CSF should be placed at the same spot on the slide, each drop being allowed to air dry before the next is added . ™ Centrifugation : CSF can be centrifuged (by cytospin ) and the deposit is examined for Gram staining.

25. Direct Antigen Detection From CSF: After centrifugation of CSF, the supernatant can be used for antigen detection. Latex agglutination test is performed using latex beads coated with anti-capsular antibodies. ™ It is available for detection of capsular antigens such as of S. pneumoniae, S. agalactiae, N. meningitidis, H. influenzae or E. coli.

26. From urine: Antigen detection in urine is useful for pneumococcal meningitis . Immunochromatographic test (ICT) is available to detect the C-polysaccharide antigen of S. pneumoniae in urine.

27. Culture Ideal media for bacteriological culture of CSF are enriched media like chocolate agar and blood agar, and differential media like MacConkey agar. ™ Enriching: As the bacterial load is very low, a part of the CSF can be inoculated into enriched media such as blood culture bottles or brain heart infusion (BHI) broth in the laboratory. ™ Blood culture collected in BHI broth/agar or preferably in automated blood cultures (e.g. BacT /ALERT). ™ Culture plates (blood agar and chocolate agar) are incubated at 37°C, preferably in candle jar (provides 5%-10% CO2 ) for 48 hours.

28. ™ Antimicrobial susceptibility test done to initiate definitive antimicrobial therapy. It is carried out by disk diffusion test or by automated MIC based methods such as VITEK. ™ Sensitivity: CSF and blood cultures may take >48 hours for organism identification and are positive in 70-85% of patients with bacterial meningitis. ™ Therefore , rapid diagnostic tests such as antigen detection or molecular test should be considered to determine the bacterial etiology of pyogenic meningitis.

29. Serology Antibodiesto capsular antigens of meningococci can be detected in patient’s serum by ELISA. Molecular Methods highly sensitive , detect even few bacteria in CSF with less turnaround time than culture and also help in serogroup identification. ™ Formats: Multiplex PCR and multiplex real-time PCR can be used for simultaneous detection of common agents of pyogenic meningitis. ™ BioFire Film Array is an automated nested multiplex PCR commercially available, which can simultaneously detect 14 common agents of meningitis (both pyogenic and viral) in CSF, with a turnaround time of 1 hour.

30. ™ Common genes targeted include: „ For meningococcus: ctrA (capsule transport gene) and sodC (Cu-Zn superoxide dismutase gene) . „ For pneumococcus: lytA (autolysin gene), ply ( pneumolysin ) and psaA (pneumococcus surface antigen A). „ For H. influenzae: Conserved capsular gene bexA .

31. Treatment of Pyogenic meningitis Empirical therapy comprises of: ‰ Adult: IV cefotaxime or ceftriaxone and vancomycin is the recommended regimen. If Listeria is suspected, IV ampicillin can be added to the regimen. ‰ For neonates: IV ampicillin plus gentamicin is the recommended regimen. ‰ IV dexamethasone is added to the regimen to reduce intracranial pressure. Definitive therapy: After the culture report is available, the empirical therapy is modified based on the organism isolated and its antimicrobial susceptibility pattern.