MICR5832 L11: CNS and Ocular Infections 1/19/26

List all the Gram Positive bacteria that cause meningitis

1) S. pneumoniae (diplococci)

2) L. monocytogenes (bacilli)

List all the Gram Negative bacteria that cause meningitis

1) Neisseria meningitidis (diplococci)

2) E. coli, Enterobacter, Serratia, Proteus (bacilli)

2) Borrelia burgdorferi (spirochete)

Classify these CNS infections by site:

-BLANK

1) Meningitis

2) Encephalitis

3) Meningoencephalitis

4) Myelitis

5) Subdural empyema

5) Cerebral abscess/lesion

Why do CNS and ocular infections occur?

-Immune privilege

-Tropism

-Physical barriers disrupted (cornea, meninges, BBB)

What type of CNS infections are these?

-Meningococcal meningitis, HSV encephalitis

CNS infections in the otherwise well

What type of CNS infections are these?

-Toxoplasma encephalitis in HIV

-Cryptococcus meningitis in a renal transplant

CNS infections in the immunocompromised

What type of CNS infections are these?

-Streptococcys pneumoniae infection following base of skull fracture

-Enterobacter external ventricular device (EVD) infection

CNS infections in patients following trauma or neurosurgery (iatrogenic)

What type of CNS infections are these?

-S. aureus abscesses following infective endocarditis

-Invasive sinusitis

Secondary CNS infections

What type of CNS infections are these?

-Neurosyphilis, Lyme meningitis

CNS manifestations of systemic infections

What type of CNS infections are these?

-Acute demyelinating encephalomyelitis (ADEM)

-Subacute sclerosing panencephalitis (SSPE)

Post-infectious CNS complications

What type of CNS infections are these?

-Tetanus

Toxin-mediated CNS manifestations of non-CNS infections

What is this?

-Fever, headache, nausea, neck stiffness, altered mental status

-Focal neurological abnormalities, seizures

-Acute (meningococcal) or chronic (TB)

Meningitis

Which age group experiences these types of bacterial meningitis?

-S. galactiae (GBS)

-E. coli

-Gram Negative bacilli (Enterobacter, Serratia, Proteus)

-Listeria

Neonates

Which age group experiences these types of bacterial meningitis?

-N. meningitidis

-S. pneumoniae

-H. influenzae serogroup B

Children

Which age group experiences these types of bacterial meningitis?

-N. meningitidis

-S. pneumoniae

Young adults

Which age group experiences these types of bacterial meningitis?

-S. pneumoniae

-N. meningitidis

-Listeria

Older adults

What is this?

-Gram Negative diplococci

-Bacteremia associated with petechiae (non-blanching), purpura, ecchymoses (due to thrombocytopaenia)

-Nasopharyngeal carriage before invasive infection

Neisseria meningitidis

What serogroups cause most of Neisseria meningitidis disease?

Serogroups B and C

What serogroups does the Neisseria tetravalent vaccine protect against?

Groups A, C, W, Y

What is this?

-Gram Positive diplococci

-Most common bacterial cause of community-acquired pneumonia

-Nasopharyngeal carriage is very common

Streptococcus pneumoniae

Who is the pneumococcal vaccine (S. pneumoniae) scheduled for?

Infants, adults over 65

What is this?

-Gram Positive bacilli

-Asymptomatic or nonspecific, self-limiting febrile illness

-Rare in young healthy adults, more common after age 50

Listeria monocytogenes

What happens if a mother has Listeria infection?

-Amniotic infection

-Fetal loss

True or False: Listeria is not a commensal organism found in the normal flora

True

What are some foods that contain Listeria?

Vegetables, cold meats, salads, milk, cheese

What are all the bacteria that cause meningitis?

1) S. pneumoniae

2) Listeria monocytogenes

3) Mycobacterium tuberculosis

4) Borrelia burgdorferi

What are viral causes of meningitis?

1) Enterovirus

2) Parechovirus

3) HSV-2

4) VZV

5) Mumps

Which meningitis-related virus is this?

-Encompasses most viral meningitis cases

-May occur alone or with other manifestations of infection (eg. rash, myopericarditis)

Enterovirus

Name 3 examples of Enterovirus

Coxsackieviruses, echoviruses, enterovirus 71

Which meningitis-related virus is this?

- Usually in neonates

Parechovirus

Which meningitis-related virus is this?

-Usually with primary genital infection

-May cause recurrent meningitis

HSV-2

Which meningitis-related virus is this?

-Meningitis usually caused by reactivation (shingles)

VZV

Which meningitis-related virus is this?

-No longer common due to vaccine

Mumps

What are fungal/yeast causes of meningitis?

1) Cryptococcus neoformans

2) Cryptococcus gattii

3) Candida (post-surgical)

Which type of fungal meningitis is this?

-Worldwide distribution in soil and bird guano

Cryptococcus neoformans

Which type of fungal meningitis is this?

-Usually associated with red gum trees

-More common in Australia

Cryptococcus gattii

True or False: Cryptococcus does not cause disease in immunocompetent people

False

What are parasitic causes of meningitis?

1) Naegleria fowleri

2) Acanthamoeba

3) Balamuthia

4) Taenia solium

5) Angiostrongylus

6) Gnathostoma

What do amoebas like Naegleria fowleri, Acanthamoeba and Balamuthia invade directly across?

Cribiform plate

Where are amoeba that cause meningitis typically found?

Stagnant, underchlorinated water

What is this?

-Inflammation of the brain parenchyma

-Focal or diffuse

-Headache, fever, nausea, altered mental status, seizures, personality change, focal neurological abnormalities

Encephalitis

True or False: "Pure" encephalitis is usually viral

True

True or False: Encephalitis is more common than meningitis

False

What is the most common cause of sporadic encephalitis worldwide?

HSV-1

What Arboviruses cause encephalitis?

1) Murray Valley Encephalitis

2) Kunjin virus

3) JEV

4) West Nile Virus

Name all viruses that cause Encephalitis

-Murray Valley, Kunjin, JEV and West Nile Virus (Arboviruses)

-Hendravirus (Carried by macrobats)

-Rabies and ABLV (Lyssaviruses)

What hosts carry Lyssaviruses like Rabies and ABLV?

Bats and other mammals

What is this?

-Inflammation of the spinal cord

-Weakness, paralysis, paraesthesia

-Usually non-infectious, sometimes caused by viruses

-Caused by Polio and Flavivirus

Myelitis

What viruses cause Myelitis?

-Polio (enterovirus)

-Flavivirus

What is this?

-Collection of pus between dura mater/arachnoid layers

-Usually bacterial, rarely occurs spontaneously

-May complicate neurosurgery

Subdural empyema

What is this?

-Pus filled pocket of brain

-Usually bacterial

-S. aureus, Strep anginosus, Enterobacteriaceae, anaerobes, Nocardia

Cerebral abscess

What bacteria cause Cerebral abscess?

S. aureus, Strep anginosus, Enterobacteriaceae, anaerobes, Nocardia

What are some latent infections that can lead to CNS infections if reactivated?

1) Cryptococcus neoformans

2) EBV/CMV/HHV-6

3) JC Virus

4) Toxoplasma

How would you diagnose CNS infection?

1) CT scan

2) Lumbar puncture

3) CSF exam

4) Nucleic acid tests, cryptococcal tests

What CSF tests are available?

1) MC&S

2) Differential cell count

3) Protein and glucose

What does it mean if CSF is turbid instead of clear and colorless?

Pleocytosis (elevated white cell count)

How many white cells should CSF have normally?

-5 white cells

-20 in neonates

What does differential white cell count use to distinguish 1) Neutrophils and 2) Mononuclear cells?

Morphology

You perform differential white cell count after a CNS infection.

What does Neutrophilic pleocytosis suggest?

Bacterial infection

You perform differential white cell count after a CNS infection.

What does Mononuclear pleocytosis suggest?

Viral infection

True or False: Red cell count is typically raised in meningitis/encephalitis

False, it is not usually raised

What does it mean if you notice raised red cell count?

-"Bloody tap" or subarachnoid hemorrhage

-500:1 or 1000:1 red cells to white cells used to assess pleocytosis

What assay would you use for these meningitis-related viruses and bacteria?

-Enterovirus, HSV, VZV

-N. meningitidis, S. pneumoniae, Listeria

-CMV, toxoplasma

PCR assays

What is a drawback of using PCR assays after antibiotics have already been given?

Can't perform sensitivity testing

True or False: PCR assays have equal or greater sensitivity than culture

True

How soon are NAT results available?

2 to 24 hours

How does a Cryptococcal test work?

-India ink shows large polysaccharide capsule

-Latex agglutination test for antigens is more sensitive than culture/microscopy

What media would you use to culture Cryptococcus?

-Sabiuraud Dextrose Agar

-Bird Seed Agar

-CHROMagar

What makes Tuberculosis hard to diagnose?

-Culture has low sensitivity (requires 20 to 30 mL)

-PCR increases sensitivity

What type of meningitis can cause eosinophilic meningitis?

Parasitic

How would you diagnose Amoebic meningitis?

Live amoeba can be seen on microscope

Classify these ocular infections by site:

1) Conjunctivitis

2) Keratitis

3) Keratoconjunctivitis

4) Endophthalmitis

5) Uveitis

6) Chorioretinitis

What causes Conjunctivitis?

-Conjunctivitis: Pinkeye, inflamed conjunctiva

1) Staph aureus (+)

2) Strep pneumoniae (+)

3) H. influenzae (+)

4) Moxarella catarrhalis (+)

5) Neisseria gonorrhea (-)

6) Chlamydia trachomatis (-)

7) Adenovirus

What causes Keratitis in contact lens wearers?

-Keratitis: Inflamed cornea

1) S. aureus (+)

2) Pseudomonas aeruginosa (-)

3) HSV-1, VZV, Adenovirus

4) Fusarium

5) Acanthamoeba

What causes Endophthalmitis?

-Endophthalmitis: Infection inside eyeball

1) Staphylococci (coagulase negative, exogenous)

2) Staph aureus (coagulase positive, endogenous)

3) Candida, Cryptococcus (endogenous fungi)

4) Aspergillus, Fusarium (exogenous molds)

What causes Uveitis/Retinitis?

-Uveitis: Inflamed middle layer/uvea

-Retina: Inflamed retina

1) HSV, VZV (shingles), CMV (immunocompromised)

2) Toxoplasma, Syphilis, Bartonella

How would you diagnose Conjunctivitis?

-Swab and slide for MC&S

-Dry swab for PCR (ex: adenovirus)

How would you diagnose Keratitis?

-Corneal scrape

-Inoculate plates/slides at bedside

-Use special E. coli plate for Acanthamoeba

-Use dry swabs for PCR (ex: HSV or VZV)

How would you diagnose Endophthalmitis?

-Aqueous or vitreous aspirate via ophthalmology

-Fluid MC&S

-PCR if required (HSV/VZV, CMV, Toxoplasma, syphilis)