Lecture 61 Bacterial Meningitis Flashcards
Name the primary bacteria involved with meningitis
Haemophilus influenzae Listeria monocytogenes Neisseria meningitidis Streptococcus agalactiae Streptococcus pneumoniae
Bacterial meningitis has highest incidence rate in what groups?
Newborns and elderly
Developing countries
Community vs hospital acquired bacterial meningitis
Community acquired must be able to infect respiratory tract: S. pneumoniae, H. influenzae, N. meningitidis
Hospital: after iatrogenic procedures, include gram (-) rods, S. aureus, other Strep and Staph
Pathogenesis of bacterial meningitis
Infect mucosa –> enter blood –> penetrate BBB –> release inflammatory cytokines –> WBC diapedesis into CSF –> increase permeability of BBB –> Exudates and serum into brain => Edema, intracranial pressure, altered blood flow
Classic triad of symptoms for bacterial meningitis
Fever
Excruciating headache
Neck stiffness
Other symptoms for bacterial meningitis
Nausea, vomiting, confusion, irritability, delirium, sleepiness
H. influenza seasonality and age of incidence
Late winter, early spring
Infants 7-18 months
N. meningitidis seasonality and age of incidence
Winter
Infants and children 1 month to 19 years
S. pneumoniae seasonality and age of incidence
Winter
Infants and children 1 month to 4 years
Elderly
S. agalactiae seasonality and age of incidence
Winter
Neonates
Listeria monocytogenes seasonality and age of incidence
Summer
Newborns and predisposed adults
General diagnosis and treatment of bacterial meningitis
Many studies can be useful, but CSF analysis is most
Initiate treatment quickly if any sign of potential infection
Signs of neonatal meningitis
Hyperthermia (or hypothermia when close to death)
CNS manifestations: lethargy, seizures, irritability
GI: vomiting, diarrhea, anorexia, distension
Respiratory: dyspnea, apnea, cyanosis
Bulging fontanelle
Hypotonia
Primary bacteria that cause neonatal meningitis
S. agalactiae (most common)
E. coli
Listeria monocytogenes
Early vs late Neonatal Group B Strep
Early: within first 5 days, Ob complications common, bacteremia, pneumonia, meningitis
Late: 7 days – 3 months, Ob complications uncommon, bone/joint infections, bacteremia and fulminant meningitis
Other name for GBS (group B Strep)
Strep agalactiae
Diagnosis of S. agalactiae
Presumptive tests: CAMP factor looking at hemolysis, DNA probe
Definitive: isolation from infected site
E. coli and meningitis
Important in neonatal, but rare in adults–only after surgery that introduced bacteria
Encapsulated K1 strains, g(-)
Listeria monocytogens general characteristics
Gram (+) motile coccobacillus
Tumbling motility
Facultative intracellular–epithelial cells and macrophages
Listeria monocytogenes virulence factors
LPS-like surface component: inhibits phagocytosis Listeriolysin O (LLO): disrupts phagolysosome membrane, inhibits antigen processing, induces apoptosis
Listeriosis clinical manifestations
Neonates: if acquired in utero => death or pneumonia, seizures, skin lesions
Adults: leading cause of meningitis in cancer and renal transplant patients, brain stem encephalitis is classic feature
Haemophilus influenzae general characteristics
Also called HIB
Gram (-), non-motile coccobacillus
With or without a capsule
Has Lipooligosaccharide in cell wall (LOS)
Requires RBC factors for growth but isn’t hemolytic
Considered normal flora in 80%
Haemophilus influenzae virulence factors
LOS PRP: prevents killing by PMN's Nueraminidase IgA protease Fimbriae: attaching to nasopharynx
Common onset of HIB meningitis
Usually mild URI or otitis media several days before
Followed by deterioration and signs of meningitis
Pathogenesis of HIB meningitis
Infects respiratory epithelium
Penetrates epithelium
Enters blood and lymph
Spreads to CSF
Non-encapsulated strains have adhesins that allow attachment to mucins on ciliated cells
Causes loss of cilia, inflammation, and sloughing of damaged cells from action of LOS
Treatment of HIB meningitis
beta-lactams like amoxicillin/clavulanic acid
Or cephalosporins
Prevention of HIB
Vaccines
Strep pneumoniae general characteristics
Gram (+), lancet shaped diplococcus
Alpha-hemolytic–greenish colonies
Optochin sensitivity
Encapsulated strains are virulent
Occurs more often in colder and wetter months
Young children and adults over 65
Viral infections => inc risk of pneumococcal pneumonias
Organism is aspirated
Pneumococcal meningitis may follow?
May follow pneumococcal pneumonia or infections elsewhere in the body
What is the most common agent in recurrent meningeal infections?
S. pneumoniae
Pneumococcus virulence factors
IgA protease, H2O2, Pili
Peptidoglycan-teichoic acid complex–g(+)
Capsule
Autolysin–lyses itself to release pneumolysin in effort to dampen immune response
Pneumolysin–causes pores to form in target cell membrane => apoptosis, activates complement
S. pneumoniae diagnosis
Optochin sensitivity
Bile solubility test
S. pneumoniae treatment and prevention
Penicillin G
Fluorquinolones, vancomycin, linezolid
Vaccines exist and are recommended for elderly
Meningococcal meningitis general
Caused by Neisseria meningitidis Often in dorms and military recruits Gram (-) Kidney bean shaped diplococcus Encapsulated Serogroupds A,B,C,Y,W135 Acute meningococcemia=>meningitis
Meningococcal meningitis epidemiology
Humans only reservoir
Close contact required
Colonizes nasopharymx
Meningococcal meningitis manifestations
Presence of non-blanching rash–petichiea and pink macules
Meningococcal meningitis diagnosis
Gram stain CSF
Culture on chocolate agar, Thayer-Martin agar
Capsular polysaccharide in CSF
Meningococcal meningitis treatment
Penicillin G
Vaccine now available for all serotypes
