Bacterial Pathogens of Central Nervous System ID UNIT 2

Meninges

Dura

Arachnoid mater

Pia mater

Endothelial cells

tight junctions

Why the blood-brain barrier matters?

Blocks bacteria, immune cells and antibiotics

Inflammation → ↑ intracranial pressure

Meningitis

infection of meninges (arachnoid and pia mater)

Meningoencephalitis

both brain and meninges

Encephalitis

brain

Poliomyelitis

illness caused by a virus that mainly affects nerves in the spinal cord or brain stem

Aseptic (viral)

• Most common

• Enteroviruses

• HSV-2 (recurrent)

• HIV early infection

Infant / Neonatal

• Group B Strep (S. agalactiae)

• E. coli

• Listeria monocytogenes

Bacteria are common causes of infant meningitis in

children <1 month of age (28 days)

Acute bacterial

A life-threatening infection; needs urgent and specific treatment

Neonates acquire

Group B Strep & E. coli during passage down the birth canal

neonatal meningitis symptoms

• Poor feeding

• High fever

• Bulging fontanelle

• Floppy baby

• Seizures

Organism of children

S. pneumoniae, N. meningitidis, Haemophilus influenzae type B (HIB)

Organism of teens/young adults

S. pneumoniae, N. meningitidis

Organism of adults

S. pneumoniae, N. meningitidis, Listeria

most common cause of bacterial meningitis in infants, young children and adults in the United States

Streptococcus pneumoniae

Risk Factors for Acute Bacterial Meningitis

• Infants

• College dorms

• Military bases

• Pregnancy (Listeria)

• Immunocompromised

• Skipping vaccines

Signs & Symptoms in >2 yr old

• Fever

• Neck stiffness

• Altered mental status

Brudzinski sign

Flex neck → hips/knees flex

Kernig sign

Pain when extending knees

if there is meningitis, there will be

inflammation around the nerve routes, and this causes pain upon

stretching.

N. meningitidis/ H. influenzea

Capsule

igA protease

Pilli

Endotoxin

Yes

Yes

Yes

Yes

S. pnuenmoniae

Capsule

igA protease

Pilli

Endotoxin

Yes

Yes

No

No

Most common cause of Chronic Meningitis is

Mycobacterium tuberculosis

2nd cause of Chronic Meningitis in AIDS

Cryptococcus neoformans

Chronic Meningitis

Develops slowly (weeks)

Gram-negative diplococci →

Neisseria meningitidis

Gram-positive diplococci →

S. pneumoniae

Gram-positive rods →

Listeria

S. pneumoniae is

spread person to person by respiratory droplets

L. monocytogenes is

ingestion of commonly contaminated foods (dairy, meat)

How acute Bacterial Meningitis happens

1. Colonization (nose/throat, lungs, GI)

2. Enters bloodstream (bacteremia)

3. Bacteria penetrates the dura and arachnoid

4. Multiplies in CSF (Cerebrospinal fluid)

5. Inflammation → ↑ pressure → brain damage