L16: Meningitis Flashcards
Meningitis is infection of the
subarachnoid space
higher incidence of meningitis
infants, elderly, developing countries
pathogens considered community acquired meningitis (3)
S Pneumoniae
H influenzae
N meningitidis
normally able to colonize respiratory tract
pathogens considered hospital acquired meningitis
G- rods
S aureus
other strep and staph
iatrogenic procedures, immunocompromised
3 pathways to gain access to the CNS
- Invasion of bloodstream and seeding of CNS (most common)
- Retrograde neuronal pathway (ex Naegleria)
- Direct contagious spread: infection, congenital malformation, trauma
Meningitis presentation
Triad: Fever+Headache+Neck stiffness
+/- N/V, sleepiness, confusion, irritability, delirium
Encephalitis is
inflammation of the parenchyma
increases the permeability of the blood brain barrier
release of inflammatory cytokines→ WBC diapedesis into CSF
Neonatal factors that predispose for meningitis
immaturity of host defense mechanisms or organ systems, low birth weight
Maternal factors that predispose for meningitis
premature rupture of membranes, urogenital infection during late term, intrauterine infection during early term, invasion of the uterine space
3 causative agents of neonatal meningitis
Strep agalactiae
E coli
Listeria monocytogenes
Presentation of neonatal meningitis
Bulging fontanelle, high pitched cry, hypotonia, paradoxical irritability (crying when held)
Other:
Hyperthermia (more common, could be hypothermic), V/D/A, distention, lethargy, irritability, seizures, dyspnea/apnea, cyanosis
Prevention of neonatal meningitis
Universal prenatal screening for vaginal/rectal colonization with group B strep at 35-37 weeks gestation
if the mother is (+) for group B strep
antibiotic prophylaxis unless:
- C-section planned
- Membranes have ruptured/labor begun
Strep agalactiae morphology
G+ coccus
Capsular polysaccharide
Strep agalactiae produces
Hyaluronidase
Collagenase
Hemolysin
Strep agalactiae occurs during ____ in ____
Winter, neonates and adults
Strep agalactiae in neonates is usually transmitted
during delivery
Early onset Strep agalactiae symptoms
maternal obstetric complications, symptoms during first 5 days of life.
Bacteremia, pneumonia, meningitis.
Late onset Strep agalactiae symptoms
maternal obstetric complications uncommon. Symptoms develop 7 days-3 months of age.
Bone/joint infections, bacteremia with concomitant/fulminant meningitis
Labs for Strep agalactiae
(+) CAMP factor: accentuation of hemolysis due to interaction w/staph beta lysin
Culture of Strep agalactiae
Isolate organism from:
1. Normally sterile areas: CSF, blood→ definitive
2. Mixed flora areas: vagina, skin
Gray-white colonies with a narrow zone of beta-hemolysis
Accuprobe can detect
Strep agalactiae
Listeria monocytogene
E coli morphology
G- enteric bacillus
Encapsulated K1 strains
who/how get E coli meningitis
Rectal colonization of mother’s vagina
NOT an endogenous infection
Rare in adults, can follow neurosurgical trauma
Most common bacterial cause. Most common cause in recurrent infections.
Streptococcus Pneumoniae
Streptococcus Pneumoniae presentation
Acute purulent meningitis may follow pneumococcal pneumonia, infection at other site, or appear with no antecedent infection
Streptococcus Pneumoniae risk
Risk: All ages, elderly. Multiple myeloma, sickle cell, cardiorespiratory disease, congenital defects
Streptococcus Pneumoniae occurs in the ____ in _____
Winter, infant, children, adults (elderly)
Haemophilus influenzae morphology
Nonmotile, G- coccobacillus
Lipooligosaccharide (LOS)
Haemophilus influenzae presentation
Prior URI/otitis media → deterioration, meningitis
Haemophilus influenzae occurs in the _____ in ____
Hib: later winter/early spring, infants
Listeria monocytogene morphology
G+ motile coccobacillus
Numerous serotypes, 3 in most cases
Listeria monocytogene is a _______
Facultative intracellular pathogen: in epithelial cells, macrophages, monocytes
Listeria monocytogene virulence factors
LPS like surface component: antiphagocytic.
→ induces complement dependent hemolytic antibodies
Listeriolysin O: disrupts the phagolysosome membrane, inhibits antigen processing, induces apoptosis
the one pathogen more common in summer
Listeria monocytogene
Listeria monocytogene is seen in the _____ and _____
summer, newborns and predisposed adults
Listeria monocytogene sources
Worldwide, plants, soil, feces, vegetable and animal food sources
Human and animal carriers
Listeria monocytogene presentation in a normal patient
eliminated by immune system
Listeria monocytogene presentation in an immunocompromised patient
intra and extracellular multiplication → systemic disease
cancer/renal transplant→ leading cause of meningitis→ brain stem encephalitis
Listeria monocytogene can cause
Sepsis or meningitis
Listeria monocytogene in utero
tillbirth, abortion, death OR pneumonia, seizures, skin lesions→ high mortality if undiagnosed
Listeria monocytogene from mother’s genital tract
neonatal meningitis
culturing Listeria monocytogene
Requires reduced oxygen tension for in vitro growth
Nonfastidious, grows from 0-50 C
Pleomorphic, grown on blood agar
→ 60% of meningitis cases are negative
→ Tissues must be homogenized before culture
“Tumbling” motility in hanging drop preparation
Listeria monocytogene
meningococcal means
Neisseria meningitidis
Neisseria meningitidis morphology
G-, kidney bean shaped diplococci
Encapsulated
Disease causing serotypes: A, B, C, Y, W135
most important serotype of Neisseria meningitidis
B
Trumemba prevents
Neisseria meningitidis (in everyone)
Neisseria meningitidis reservoir
Human reservoir
Asymptomatic/slightly symptomatic nasopharyngeal carriers: Chronic, Immune, Nonimmune
Infection by close contact
Neisseria meningitidis is seen during the _____ in _____
winter, infants/children
Skin rash: widespread petechiae, pink macules within hour
+/- DIC, G- shock
Neisseria meningitidis
Neisseria meningitidis presentation
Transient bacteremia+fever→ spontaneous resolution in 1-2 days Acute meningococcemia (rash)→ meningitis
how Neisseria meningitidis causes disease
- Entry through oropharynx
- Spread through blood (hematogenous)
- Diseases: meningitis or other sites
- Exit through oropharynx
Neisseria meningitidis at home diagnostics
Tumbler test: press a glass tumbler to rash:
- Does not change color → contact doctor: meningitis
- Fades/loses color under pressure→ unlikely to be meningitis
Neisseria meningitidis culture/detection
Gram stain CSF
Culture: blood, CSF
Detect capsular polysaccharide in CSF
agars for Neisseria meningitidis
Fastidious, culture blood, CSF:
chocolate agar
Thayer-martin agar: Mueller Hinton supplemented with sheep RBC, abx: vancomycin, colistin, nystatin, bactrim
