Bacterial meningitis Flashcards
What is meningitis?
Inflammation of the meninges of the brain typically as a result of an infective cause like bacterial, fungal, viral, or aseptic
What are the main causative agents of bacterial meningitis specifically meningococcal meningitis?
Neisseria meningitidis
Streptococcus pneumoniae
What types of meningitis are present and what is their mortality rate?
- Pneumococcal meningitis= up to 20%
2. Meningococcal meningitis c. = 10%
Describe the microbiology of Neisseria meningitidis?
Gram -ve diplococcus Divided based on capsular group 12 types Common= B, C, W, Y A, B, and C are responsible for 90% of disease globally
Where does Neisseria meningitidis inhabit?
Upper respiratory tract
Throat
Middle meatus
Describe the initial colonisation of Neisseria meningitidis?
Nasopharyngeal carriage
Age , behaviour, and population are important factors in carriage
How is Neisseria meningitidis transmitted?
Aerosol droplets
What are the innate defense mechanism of the upper respiratory tract which prevent Neisseria meningitidis development?
- Mucociliary pathway
- Nitric oxide= produce antimicrobials
- Colonisation resistance= bacteria already in nasal cavity, take up a lot of available nutrients so reduces competition
- Lactoferrin
What groups of people carry Meningococcal?
19-20 years
Describe the carriage of Neisseria meningitidis?
Carriage in a healthy host exists before invasive infection
Facilitated by down regulation or loss of capsule expression
If Neisseria meningitidis enters blood how does it survive?
Uses virulence factors
Expression of polysaccharide capsule- allows it survival in blood
Nm capsules inhibit opsonophagocytosis through charge
Capsule serotype B mimics host as it is identical to NCAM (neural cell adhesion molecule)
Eventually host is damaged following immune system activation- blebbing of cell wall
Uncontrolled growth in blood can lead to meningococcal septicaemia
How does Neisseria meningitidis move across the blood brain barrier and cause infection?
If bacteria is present in hosts blood
Adheres to brain endothelial cells need for BBB crossing
Tight junction depletes
Paracellular movement occurs
Endotoxin produced and host inflammatory response after the migration of Polymorphonuclear neutrophils across BBB causes CNS injury
Infection of the meninges of the brain by Neisseria meningitidis = meningococcal meningitis
What are the signs and symptoms of bacterial meningitis?
Non-blanching rash stiff neck altered mental status bulging fontanelle photophobia
What are the signs of septic shock which can be caused by bacterial meningitis?
- Tachycardia
- Breathing difficulty
- Leg pain
- Cold hands and feet
- Altered mental state
- Poor urine output
What are the vaccination measures taken to prevent meningococcal meningitis?
8 weeks old= Men B vaccine= bexsero
16 weeks old= Men B vaccine
12 months old= HiB/Men C vaccine= menitorix and the Men B booster= bexsero
14 years old and eligible up to 25 years old= Men ACWY vaccine= nimenrex or Menveo
What are the NICE guidelines for treating bacterial meningitis?
Transfer to secondary care as 999 emergency
Secondary care
Antibiotic treatment promptly
Suspected bacterial meningitis
3m+ of immediate IV ceftriaxone if 7 days confirmed meningococcal or 14 days confirmed Sp
Less than 3m= cefotaxime + amoxicillin/ampicillin
What does Streptococcus pneumoniae cause?
Pneumococcal meningitis and community acquired pneumonia
Describe the microbiology of Streptococcus pneumoniae?
Gram +ve coccus
Non-motile
Has polysaccharide capsule
What virulence factors does Streptococcus pneumoniae use to evade immune response?
polysaccharide capsule Neuraminidase= reduces viscosity of mucous
IgA protease= cleaves IgA
What virulence factors does Streptococcus pneumoniae use to survive in the blood?
Polysaccharide capsule= the charge protects it from opsonophagocytosis as macrophage and the bacteria repel due to their charges
Massive activation of host cell complement and coagulation systems
Host cell mediated damage and Pneumolysin- allow and aid it to cross BBB
Neutrophil recruitment in CNS= leads to neurological sequelae
Where does Streptococcus pneumoniae inhabit?
Nasal cavity
Nasopharynx
Pharynx
What are the vaccination measures taken to prevent Streptococcus pneumoniae?
12 weeks old= PCV pneumococcal vaccine
12 months old= booster of the PCV
Eligible paediatric groups= live attenuated flu vaccine which is annual
65 years= PPV pneumococcal vaccine
65 years >= inactivated annual flu vaccine
Describe the PCV vaccine in more detail?
Prevenar 13= pneumococcal conjugate vaccine (PCV)
13 valent conjugate vaccine used in 2 yrs. or younger
Valent conjugates= 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 23F
Increase in invasive disease is due to non-vaccine serotypes occurring
How many serotypes does the PPV vaccine have?
23
