Acute Bacterial Meninigitis

7/31/2019 Acute Bacterial Meninigitis

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ACUTE BACTERIAL MENINIGITIS

Dr. A. T. Olayinka

Dept of Medical MicrobiologyABUTH - ZARIA



Introduction

• Infection of the meninges and CSF.

• Could be acute or chronic

• Caused by a variety of organisms



Acute forms

In neonates

• Group B Streptococci

• Listeria monocytogenes

• Escherihia coli & othercoliforms

• Salmonella spp

• Klebsiella pneumonia

• Staphylococcus aureus

• Staph epidermidis

In the older ages

• Neisseria meningitidis

• Haemophilus influenza

• Streptococcus pneumonia

• Listeria monocytogenes

• Burkholderia psuedomallei

• Fusobacterium

necrophorum



Neonatal factors

• Deficient immunity (humoral and CMI)

• Ineffective phagocytes

•

Complement activity is 50% of adult activity• IgM production less than 20% of adult level

• IgG production about 5% of adult levels

• IgA production begins at birth



Epidemiology

• Typically occurs in the dry season

• Meningitic belt: Senegal –Sudan, Ethiopia,

also some parts of East/South Africa.

• Mean annual rainfall 300-1100mm

• Epidemics occur in 5-10year cycles.

•

In epidemics 400/100,000 population• Hyperendemic rate ≈ 40/100,000 population.



Bacteriology: N. meningitidis

• GNDC with contiguous sides flattened (bean-shaped)

• Capsulated and piliated

•

9 capsular sero-groups at least: A, B, C, D, X, Y, Z,W-135, 29-E

• Serotypes B, C and Y a(resource rich countries)

• A (especially clones III – I) andW-135 - common in

less developed countries.• Groups A and C are associated with epidemics

• Group B in sporadic endemic cases.



Virulence factors

• Capsule

• IgA protease

•

Pili• Endotoxin

• Outer membrane proteins





Bacteriology: H. influenzae

• Pleomorphic non-motile Gram negative

coccobacillus

• 6 types designated a-f,

• Capsular type b produces invasive disease in

the immune-competent host.

• It possesses a polyribitol phosphate capsule.

• requires X-haematin, V-NAD factors



Related factors

• Maternal antibodies protect the baby till 3 –

4months of age

• Rare above 7 years of age though may occur in

adults



Bacteriology - Streptococcus pneumoniae

• Lanceolate gram positive capsulated cocci

usually occurring in pairs.

• draughtsman appearance and α-haemolysis

• More than 85 capsular types,

• Sensitive to optochin

•

Produce exotoxin - pneumolysin



Predisposing factors

• Children less than 2yrs of age or the elderly.

• Splenectomized patients

•

Sickle cell disease• Following previous head trauma

• Debilitation



Clinical features

• Signs of meningeal irritation

• More associated with focal signs on admission

•

Symptoms and signs tend to be worse than formeningococcus and H. influenzae



Pathogen Host Impt CF Mortality Sequelae

N. meningitidis Children &

adolescents

Acute (6-24hrs) 7 – 10 <1

H. Influenzae Children < 5yrs Less acute (1-

2ds)

5 9

S. Pneumoniae All ages esp

<2yrs, elderly

Usu 20 to ilness 2 0- 30 15-20



Virulence factor Bacterial Pathogen

N. meningitidis H. Influenzae S. Pneumoniae

Capsule + + +

IgA Protease + + +

Pili + + -

Endotoxin + + -

OMPs + + -



Bacteriology -Listeria monocytogenes

• Small Gram positive motile rods

•

β -Haemolytic on sheep or horse blood agar• Grow at selective incubation temp of 40C

• Organism is motile at 250C and non-motile at

370

C• In immunocompromised adults, renal

transplants, cancer patients



Transmission - Generally

• Facilitated by droplet contact

• Saliva exchange

• Close household contacts



Pathogenesis

• Colonization of the nasopharynx

• Pili by which it attaches to the mucosa

•

Capsule allows evasion of phagocytic killingenabling longer survival of the organism

• Translocates to enter the circulation.

•

Localizes in the pia and arachnoid mater andsets up an inflammatory response in the

meninges & CSF.



Diagnosis

• Gram stain

• Culture: selective media

•

CSF chemistry and cell count• Agglutination (latex or haem)

• CCIE

• Molecular diagnosis – PCR• Serology not useful – acute disease





NORMAL PURULENT ASEPTIC

Appearance Clear Turbid Clear/Opalescnt

Pressure mm/H20 <180-200 Raised Normal

Protein g/l 0.15 – 0.4 0.5 – 6.0 0.5 – 1.0

Neutrophils( 106/l) 0 100-6000 <15

Mononuclear cells 0 – 5 Can be raised 15 – 500

Glucose (mmol) 2.2 – 3.3 0 – 2.2 2.2 – 3.3



Pathogen Capsule Important types Vaccine

N. meningitidis Polysaccharide A,B,C,Y,W-135 A&C –good

B-poor

H. Influenzae Polysaccharide B Hib vaccine <1yr

olds

S. Pneumoniae Polysaccharide Many Pneumovax (23-

valent)

Grp B

Streptococcus

Polysaccharide rich

in sialic acid

(Ia,Ib,II) III in

neonatal

meningitis

-

E. Coli KI in meningitis -



Treatment

• Empirical – important

• Penicillin

•

Chloramphenicol• Cephalosporins



Prevention

• Chemoprophylaxis

– Preemptive therapy

– Eradication of NP carriage

• Vaccination

– Hib

– Conjugate group A/Conjugate Group C

– Conjugate polysaccharide

– 23-valent pneumococcal polysaccharide vaccine



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Acute Bacterial Meninigitis