Infectious and immunology Flashcards
Pathophys of bacterial meningitis
- Damage caused by the host response to infection
- Release of inflammatory mediators and activated leucocytes
- Endothelial damage
- -> Cerebral edema, raised ICP, decreased cerebral blood flow
- Vasculopathy –> cerebral cortical infarction –> fibrin deposits block resorption of CSF –> hydrocephalus
Pathogens causing bacterial meningitis
- Neonate - 3 months:
- Group B streptococcus (Strep. Agalactiae)
- E. coli
- Listeria monocytogens
- 1 month - 6 years
- Neisseria meningitides
- Strep. pneumoniae
- H. influenza
- > 6 years
- N. meningitides
- Strep. pneumonia
Clinical features of bacterial meningitis
- Nonspecific signs in infants
- Fever
- Headache
- Photophobia
- Lethargy
- Poor feeding/vomiting
- Irritability
- Hypotonia
- Drowsiness
- Loss of consciousness
- Seizures
- Late signs: bulging fontanelle, neck stiffness, arched back (opisthotonos)
Contraindications to lumbar puncture
- Cardiorespiratory instability
- Focal neurological signs
- Increased ICP
- Coagulopathy
- Thrombocytopenia
- Local infection at the site of LP
- If it causes undue delay in starting antibiotics
Cerebral complications after bacterial meningitis
- Hearing impairment
- Local vasculitis
- Local cerebral infarction
- Subdural effusion
- Hydrocephalus
- Cerebral abscess
Viruses causing meningities
More than 2/3 of CNS infections are viral
- Enteroviruses
- EBV
- Adenoviruses
- Mumps
Encephalitis may be cause by
- Direct invasion of the brain by neurotoxic virus (e.g. HSV)
- Delayed brain swelling following a dysregulated neuroimmunological response to an Ag (post infectious encephalopathy)
- Slow virus infection (e.g. HIV or subacute sclerosing panencephalitis from measles)
Clinical features of encephalitis
- Fever
- Altered consciousness
- Often seizures
Most common cause of encephalitis
Viruses: - Enteroviruses - Influenza viruses - Herpesviruses (HSV, VZV, HHV-6) Mycoplasma B. burgdorferi (Lyme) Bartonella Rickettsial infections Arboviruses
Pathogens responsible of Toxic shock syndrome
- S. aureus
- Group A streptococci
Clinical characteristics of Toxic shock syndrome
- Fever >39 C
- Hypotension
- Diffuse erythematous, macular rash
Organ dysfunction in Toxic shock syndrome
Toxin acts as superantigen
- Mucositis - conjunctivae, orla mucosa, genital mucosa
- GI dysfunction - diarrhea, vomiting
- Renal impairment
- Liver impairment
- Clotting abnormalities and thrombocytopenia
- CNS - altered consciousness
What happens after 1-2 weeks in Toxic shock syndrome?
Desquamation of the palms, soles, finger and toes
What is PVL?
Panton-Valentine leukocidin
= Toxin produced by 2% of S. aureus
Causing recurrent skin and soft tissue infections, can also cause necrotizing fasciitis and necrotizing hemorrhagic pneumonia
Pathogens causing necrotizing fasciitis/cellulitis
- S. aureus
- Group A strep.
What are the characteristic feature of meningococcal meningitis?
- Septicemia accompanied by a purpuric rash
- May start anywhere on the body, spread
- Lesions are nonblanching on palpation, irregular in size and outline, may have necrotic centre
Which type of N. meningitidis cause the majority of meningitis?
Group B meningococci
S. pneumonia may cause which diseases?
- Pharyngitis
- Otitis media
- Conjunctivitis
- Sinusitis
- Invasive diseases: pneumonia, sepsis, meningitis
Pathogen responsible for Impetigo
- S. aureus
- Group A Strep.
Clinical features of Impetigo
- More common i children with preexisting skin disease, e.g. atopic dermatitis
- Skin infection on the face, neck, and hands
- Begin as erythematous macules that may become vesicular/pustular og bullous
- Honey-colored crusted lesions (rupture of vesicles)
What is Nikolsky sign?
When areas of epidermis separate on gentle pressure, leaving denuded areas of skin, which subsequently dry and heal, generally without scarring.
- In staphylococcal scalded skin syndrome
Most common presentation of herpes simplex virus infection
- Gingivostomatitis
- Usually occurs from 10 months - 3 years of age
- Vesicular lesions on lips, gums, and anterior surfaces of the tongue and hard palate
Which disease does HHV-6 and 7 cause?
Roseola infantum = exanthema subitum
Clinical features of Roseaola
High fever - then - rash
- Fever with malaise
- Generalized macular rash (appears as the fever wanes)
- Rash first appear on trunk, then extend to extremities and face
