Meningitis
A quick presentation of its
bacterial form.
- A Brief History Meningitis is caused by various types of
microorganisms:
•
•
•
•
•
Bacterial
Viral
Fungal
Parasitic
Non-infectious
Meningitis has been described by many people over the
years and even dating back to Hippocrates over 25
centuries ago. In 1805, in Geneva, Switzerland, the first
ever outbreak was recorded by Gaspard Vieusseux (17461814) and Andre Matthey (1778-1842) and the first in
Africa was in 1840. However, it took another 40+ years
before bacteria was linked to a cause of meningitis, by
Anton Weichselbaum, an Austrian bacteriologist.
In 1906, Simon Flexner, an American
scientist, attempted a study using an
anti-serum from horses, to treat
meningitis and showed good success.
With the development of penicillin,
1944 brought about a study confirming
penicillin as a very effective treatment.
Three major causes of bacterial meningitis
include Streptococcus pneumoniae,
Neisseria meningitides, Haemophilus
influenzae type b.
-A Recent Outbreak of Bacterial MeningitisSince January 13, 2015, six undergraduate
students at the University of Oregon had come
down with Meningococcal meningitis, type b.
Recently, a 52 year old father visiting the campus
has now tested positive. One of the
undergraduate students passed away from the
disease, but the other five students have since
recovered. The sixth case was a 20 year old
student who reported to an outpatient clinic
with flu-like symptoms. The school has been
attempting to vaccinate all their undergraduate
students. As of June 2, 2015, only 10, 000 of the
22, 000 students have received the vaccine.
With the recent infection of a girl’s father, it’s
evidence that the disease is still present and
that’s why the school is pushing for everyone to
get vaccinated.
Description of the Etiologic
Agents and Virulence Factors
As stated before, the three types
of bacteria causing meningitis are:
1. Streptococcus pneumonia
2. Neisseria meningitides
3. Haemophilus influenzae type b
Streptococcus pneumoniae:
Virulence Factors:
This is a lancet shaped gram-positive
coccus that come in pairs or short
chains and is the most common cause
of bacterial meningitis, affecting
mainly the elderly. They are usually
anywhere from 0.5-1.2um.
They are non-motile bacteria
and our usually cultured on a
blood agar plate. The cultures
grow best at 35-37 ⁰C and will
show small, grey, moist
colonies and usually contain a
zone of alpha-hemolysis.
This bacteria has three main factors:
This
cerebrospinal
fluid from a
child with
meningitis
contains
many
neutrophils
and oval
gram-positive
cocci singly
and in pairs.
•
Cell wall – this serves to protect the
bacteria from phagocytosis by white
blood cells.
•
Pneumolysin – this does a variety of
things, but including inhibits
lymphocytes and antibody
proliferation.
•
IgA protease – counteracts mucosal
defenses.
Growth of N.
meningitidis on lower
left and S. pneumoniae
on upper left of a BAP
Neisseria meningitides
This is a gram-negative, coffee
bean shaped diplococcus.
They are roughly 0.6-1.0um.
This particular bacteria
typically causes meningitis in
adolescents and young adults.
They are nonmotile, aerobic
bacteria. It is
fastidious and
grows best under
35-37⁰C. The
cultures are usually
grown on a blood
agar plate and tend
to present grey,
round, smooth, and
smooth with
defined edges.
Virulence Factors:
•
Cell wall - this serves to protect
the bacteria from phagocytosis
by white blood cells.
•
Capsule/Slime layer – this layer
makes it more difficult for the
phagocytes to engulf the
bacteria.
•
IgA protease – counteracts
mucosal defenses.
•
Endotoxin – lipopolysaccharides
cause the white blood cells to
release cytokines into the blood
leading to vascular collapse and
hemorrhages.
Growth of N. meningitidis on
lower left, S. pneumoniae on
top, and H. influenzae on lower
right of a CAP
Haemophilus influenzae type b.
This is a pleomorphic, Gram-negative
bacilli or coccobacilli. It can grow as
facultative anaerobe, but usually via
aerobic. It lacks motility. Type b
occurs mainly in children 5 and under
and accounts for 95% of invasive
disease.
Haemophilus influenzae type b
cultures appear as large, round,
smooth, convex, colorless-to-grey,
opaque colonies on a chocolate
agar plate (the preferred medium).
Virulence Factors:
• Polyribosyl Ribitol Phosphate (PRP) capsule – Makes
bacteria resistant to phagocytosis.
• Cell wall – contains lipooligosaccharide which is
similar to lipopolysaccharide, but shorter.
• IgA protease – inhibits mucosal defenses.
• Pili – these help the bacteria to bind to other cells
and surfaces.
This
cerebrospinal
fluid contains
many
neutrophils
and gramnegative
coccobacilli,
primarily in
the cytoplasm
of the white
cells.
Meningitis: A Brief Description
Bacterial meningitis is an infection
that causes an inflammation of the
meninges. The meninges are the
membranous layers surrounding
and protecting the brain and spinal
cord. People often present with
head aches, neck pain, fever, and
nausea.
Who is affected by which bacteria:
• Children under 5 years of age –
Haemophilus influenzae
• Adolescents/young adults - Neisseria
meningitides
• Elderly - Streptococcus pneumoniae
Steps to Invasion:
1)
2)
3)
4)
Bacteria invades through the
nasal mucosa
Colonizes in the nasopharynx
Disrupts the cilia and epithelial
cells and invades the
bloodstream
Crosses the blood-brain barrier
and enters the meninges of the
brain and spinal cord.
- Signs and Symptoms As stated before, the main symptoms
are headache, sore/stiff neck, fever,
and nausea. According to the Mayo
Clinic they can also include:
• Confusion
• Difficulty sleeping
• Sleepiness
• Sensitivity to light
*** In the case of Neisseria
meningitides, the patient may develop
skin rashes called petechiae.
With babies these symptoms can also
include poor eating, excessive crying,
and a bulge in the soft spot at the top
of a baby’s head.
The cerebral spinal fluid of the
meninges are a great place for
bacteria to grow, due to lots of
nutrients and few phagocytic cells.
The bacteria help to damage the
blood brain barrier allowing for
cerebral edema, increased
intracranial pressure. The meninges
becomes inflamed and
accumulating neutrophils have the
capacity to destroy brain tissue,
nerves, and blood vessels.
Potential complications (according to
Risk Factors:
the Mayo Clinic:
• Skipping Vaccinations
• Hearing loss
• Age (under 20 years old)
• Brain damage
• Living in a community setting (i.e. college dorms)
• Kidney failure
• Compromised immune system
• Shock
• Death
Incubation Times:
Neisseria meningitides - The average incubation period is 4
days, but can range between 2 and 10 days.
Haemophilus influenzae - The incubation period is not
certain, but could be as short as a few days.
Streptococcus pneumoniae - The incubation period of
pneumococcal pneumoniae is short, about 1 to 3 days.
The germs that cause bacterial
meningitis can be contagious. Some
bacteria can spread through the
exchange (e.g., by kissing) of
respiratory and throat secretions (e.g.,
saliva or mucus).
Fortunately, most of the bacteria that
cause meningitis are not as
contagious as viruses that cause the
common cold or the flu.
Also, the bacteria are not spread by
casual contact or by simply breathing
the air where a person with
meningitis has been. Other
meningitis-causing bacteria are not
spread person-to-person, but can
cause disease because the person has
certain risk factors (such as a weak
immune system or head trauma)
Healthy people can carry
the bacteria in their
nose or throat without
getting sick. Rarely,
these bacteria can
invade the body and
cause disease. Most
people who ‘carry’ the
bacteria never become
sick.
Diagnostic Process:
Four Main Ways to Diagnose Meningitis:
•
Blood Cultures – blood is drawn and cultured to see if
microorganisms, and in particular bacteria, are growing.
•
Imaging – CT scans and MRIs can help detect inflammation in the
head, sinuses, and spine.
•
Cerebrospinal Tap – The definitive diagnosis of meningitis requires an
analysis of your cerebrospinal fluid (CSF), which is collected during a
procedure known as a spinal tap. In people with meningitis, the CSF
fluid often shows a low sugar (glucose) level along with an increased
white blood cell count and increased protein. This test can also help
distinguish which bacteria is causing meningitis.
•
Nasal swab – samples from the nasopharyngeal area are swabbed
and stained.
*** Gram staining is the stain used for diagnosis.
MRI scan of
frontal
sinusitis,
empyema,
and abscess
formation in a
patient with
bacterial
meningitis.
- Treatment and Prevention Prevention:
•
There are various vaccines for each bacterial strain that
causes meningitis –
1. Neisseria meningitides – conjugated vaccine
(also may use rifampin or tetracycline). The CDC
recommends all college students be vaccinated
for this bacterial strain.
2. Streptococcus pneumoniae – Prevnar 13
(children) and Pneumovax (adults)
3. Haemophilus influenzae – Hib vaccine (routine
child vaccination)
Other Precautions:
1.
2.
3.
4.
Wash your hands
Practice good hygiene
Stay healthy
Cover mouth when coughing and sneezing
Treatment:
For bacterial meningitis, antibiotics are effective. Often
times, suspected bacterial meningitis will be treated
with broad-spectrum antibiotics before confirming
diagnosis. Meningococcal meningitis is of biggest
concern and is often treated until ruled out.
Cefotaxime is usually effective in all three bacteria, but
Penicillin can be used with Neisseria meningitides.
- Number of Cases Total in the United States -
Due to Neisseria meningitides:
Due to Haemophilus influenzae:
Strain:
2010
2011
2012
2013
A, C, Y, W-135
280
257
161
115
Other serogroups
12
20
20
12
Type B
135
159
110
68
Unknown
406
323
260
310
2010
2011
2012
2013
23
14
30
19
*** Contrast this to the Democratic Republic of Congo, who the National Meningitis
Association reported that there were 9339 cases of Meningococcal meningitis in
2013.
*** According to the Centers for Disease Control.
- Local Cases of Meningitis State of Oregon:
Type:
2013
Neisseria meningitides
12
Haemophilus influenzae
138 (not necessarily caused meningitis
Marion County:
Type:
2013
Neisseria meningitides
3
Haemophilus influenzae
4
*** According to the Oregon Department of Health
Why Should we spend money on research and prevention/treatment?
Although other types of meningitis are usually less severe, it is
important that we are up to date on our knowledge of bacterial
meningitis (especially due to Neisseria meningitides). As stated
before, if untreated, meningitis can cause hearing loss, brain damage,
kidney failure, and even death. Bacteria have the capability to
mutate over time and therefore keeping up with newer and more
effective vaccines are extremely important.
In sub-Saharan Africa, many of these countries have deaths due to
meningitis in much greater numbers than the United States.
Spending money to help vaccinate more people is also of vital
importance.
References:
De Velasco, Alonso. (December 1995). Streptococcus pneumoniae: Virulence Factors, Pathogenesis, and Vaccines.
Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC239389/pdf/590591.pdf
Identification and Characterization of Streptococcus pneumoniae.
Retrieved from http://www.cdc.gov/meningitis/lab-manual/chpt08-id-characterization-streppneumo.pdf
Identification and Characterization of Neisseria meningitidis.
Retrieved from http://www.cdc.gov/meningitis/lab-manual/chpt07-id-characterization-nm.html
Identification and Characterization of Haemophilus influenzae.
Retrieved from http://www.cdc.gov/meningitis/lab-manual/chpt09-id-characterization-hi.html
Community Acquired Pneumonia.
Retrieved from https://meded.ucsd.edu/isp/1999/CAP/hflu.html
Mayo Clinic Staff. (March 19, 2013). Diseases and Conditions: Meningitis.
Retrieved from http://www.mayoclinic.org/diseases-conditions/meningitis/basics/definition/con-20019713
Bacterial Meningitis. (April 1, 2014).
Retrieved from http://www.cdc.gov/meningitis/bacterial.html
Epidemiology of Meningitis Caused by Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenza. (April 1, 2014).
Retrieved from http://www.cdc.gov/meningitis/lab-manual/chpt02-epi.html
Cowan, Marjorie Kelly. Microbiology Fundamentals: A Clinical Approach. (2013). pp. 464-467.
Meningococcal Meningitis. (February 2015).
Retrieved from http://www.who.int/mediacentre/factsheets/fs141/en/
References Continued:
Haemophilus influenzae Disease: Causes and Transmission. (April 2, 2014).
Retrieved from http://www.cdc.gov/hi-disease/about/causes-transmission.html
Pneumoccal Disease: Clinical Features. (June 10, 2015).
Retrieved from http://www.cdc.gov/pneumococcal/clinicians/clinical-features.html
2015 Meningococcal Update. (May 29, 2015).
Retrieved from https://public.health.oregon.gov/DiseasesConditions/DiseasesAZ/MeningococcalDisease/Pages/Meningococcal-Update.aspx