Microbiology - Meningitis Flashcards by Josh Broadman

What is meningitis?

Inflammation of the meninges (whereas encephalitis is inflammation of the brain).

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How does meningitis typically present? (4 main)

Headache
Fever
Nuchal Rigidity
Altered Mental Status

Nausea, vomiting, photophobia can also be seen.

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What are the three subdivisions of meningitis? Timing?

Acute - SX w/in 24 hrs
Subacute - SX w/in days-weeks
Chronic - SX present for > 4 weeks

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What is the pathophysiology of meningitis as seen in a) Strep Pneumonia b) Neisseria meningitidis and c) Haemophilus influenza

Pneumonia and Neiserria spread by normal flora of nasopharynx which invade bloodstream.

Haemophilus spread by respiratory droplets to nasopharynx.

They all have a polysaccharide capsule (avoid phagocytosis and complement). Infect the choroid plexus (which produces CSF) - SX will be caused by inflammatory response due to LPS/teichoic acids - increased cytokines and chemokines will be released.

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What is the pathophysiology of meningitis as seen in Strep agalactiae (Group B Strep - GBS)?

(-) cause of meningitis in adults, (+) cause of meningitis in neonates. Colonize genitourinary tract - vaginal carriage is up to 30% in pregnant women. Passed to neonate during birth (MCC of MENINGITIS IN NEONATES)

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What is the most common cause of meningitis in neonates? When does early onset disease present vs late onset?

Strep. agalactiae (Group B Strep).

Early onset: In first 7 days
Late onset: 1 week to 3 months after birth

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What is the pathophysiology of meningitis as seen in Listeria monocytogenes? Where do they replicate?

Infection is caused by consuming contaminated food. They replicate in phagocytes.

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Who is at risk to get listeria?

Pregnant women can pass to their children (in utero or during birth) and immunocompromised (old age, disease, etc - CMI deficient)

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What is the presentation of early vs. late onset disease in neonates (Listeria)? Timing of each?

Early onset disease (seen in the first 7 days) - the severe form presents with Granulomatosis infantiseptica (abscesses and granulomas) and there is a HIGH MORTALITY RATE.

Late onset disease (appears 1-3 weeks after birth) and the neonate presents with meningitis or meningoencephalitis with septicemia.

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How do you diagnose meningitis? What will be increased/decreased in ________?

Lumbar puncture is done (blood samples are second best). The CSF should have an INCREASE in the following:

INCREASED:

Pressure
WBC
Protein

DECREASED:

GLUCOSE

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What physical SX would help you differentiate meningitis caused by Neisseria meningitidis from other causes?

Nonblanching petechial or purpuric rash

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What is the treatment for meningitis? General tx? Specific tx?

Give empiric antibiotics w/in 60 minutes of presentation to emergency department.

General: START EMPIRIC ANTIBIOTICS IMMEDIATELY!

Specific: 3rd or 4th generation CEPHALOSPORIN (3rd gen - ceftriaxone or cefotaxime - can cross the BBB) + VANCOMYCIN

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How does Neisseria meningitidis stain (gram stain)? Is it aerobic or anaerobic?

GN Diplococcus. Aerobic

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Where is Neisseria meningitidis usually found? How does it spread?

Found: common in nasopharynx
Spread: respiratory droplets

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Time frame for Neisseria meningitidis?

Causes disease in susceptible individual in less than 4 days.

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What are Neisserias two virulence factors? (2)

Pilli - allow for colonization
Polysaccharide capsule

Note: Think DIPLOCOCCI = 2 cocci = 2 virulence factors and 2 diseases (meningitis and septicemia)

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What are the two most common diseases caused by Neisseria meningitidis? (2)

Meningitis and Septicemia (meningococcemia)

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How do you diagnose N. meningitidis? Skin? Gram Stain?

Rash (petechial/purpuric - separates it from other bacteria causing meningitis)
Gram strain - GN diplococcus
Culture and PCR

What is the treatment for N. meningitis?

3rd or 4th generation cephalosporins.

What is the physiology and structure of H. influenzae? Gram stain? Aerobe or anaerobe or facultative anaerobe? Growth factors? (2) Two group names? (2)

Gram strain: GN rod (bacillus)
Facultative anaerobe
Growth factor X and V
a) Type B (HiB) b) Nonencapsulated

What is the capsule of H. influenza type B?

Polyribosyl ribitol phosphate (PRP) capsule

Is H. influenza type B part of the normal flora and how is it spread? Is there a vaccine?

Not part of normal flora
Spread: Respiratory droplets
Vaccine exists (use PRP capsule)

What are the virulence factors of H. influenza Type B? (2)

Adhesins - allow for colonization

2. PRP capsule (polysaccharide capsule) - resist phagocytosis

What are the most common diseases caused by HiB? (2)

Meningitis and epiglottitis

How do you diagnose HiB?

Gram strain: Gram negative (GN) rod (bacillus)

What is the TX for HiB?

3rd or 4th generation cephalosporin

What is the physiology of nonencapsulated H. influenza ?

NO CAPSULE, DUH!

Is nonencapsulated H. influenza part of the normal flora and how is it spread?

Yes, it is part of the normal flora. | Spread: Respiratory droplets

What virulence factors do nonencapsulated H. influenza have? (1)

Adhesins - used for colonization

What is the physiology and structure of the Leptospira species? Gram strain?

Spirochete (with one or both ends having a hook shape) Grows slowly in culture NO GRAM STAIN - too thin to see.

What is the primary reservoir of Leptospira species?

Wild mammals (can also be cats, dogs and livestock)

How is Leptospira transmitted?

By urine, contaminated water and handling of infected tissue. Farm workers, veterinarians, pet shop owners, meat handlers, people engaged in water sports are at risk.

What disease is caused by Leptospira?

Leptospirosis

What is the incubation period for MILD leptospirosis?

1 - 30 days

What are the SX of MILD leptospirosis?

``` Fever Chills Headache Nausea Vomiting Abdominal Pain Myalgia *may have a rash ``` CAN LEAD TO MENINGITIS DURING THE IMMUNE PHASE.

Does MILD leptospirosis resolve on its own or requires treatment?

It spontaneously resolves in 7-10 days but can treat with DOXYCYCLINE or AMPICILLIN.

Where can leptospires be found during the first couple of days in MILD leptospirosis? Weeks to years?

Days: Blood and CSF. | Weeks to years: Urine

Treatment for MILD leptospirosis?

Doxycycline or ampicillin

What happens in SEVERE leptospirosis (Weil's syndrome)? Death due to? Diagnosis? Treatment?

Rare progression from mild disease. SX: hemorrhage, jaundice and acute kidney injury Death: Septic shock with multi-organ failure, severe bleeding DX: isolation of organism TX: IV penicillin

How are brain abscesses developed?

1. Direct spread from infection (sinusitis, otitis media, mastoiditis, dental infection), can be from 2. hematogenous spread (spread by blood - causing multiple abscesses) and 3. head trauma.

Name some bacteria that cause brain abscesses?

1. Streptococcus 2. Proteus 3. E. coli 4. Klebsiella 5. Bacteroides 6. Fusobacterium 7. Staphylococcus ALL PART OF NORMAL FLORA

How do brain abscess patients present?

They present with headache, fever and FOCAL NEUROLOGICAL DEFECTS NOTE: A focal neurological defect --> problem with nerve, spinal cord, or brain function. It affects a specific location, such as the left side of the face, right arm, or even a small area such as the tongue. Speech, vision, and hearing problems are also considered focal neurological deficits.

How do you diagnose a brain abscess?

MRI

What is the treatment for brain abscesses? (2)

Drainage of the abscess and empiric antibiotics (3rd or 4th generation cephalosporins)