Chapter 7 - ID Flashcards
Which organisms are most likely to cause serious bacterial illness, namely sepsis or meningitis, in the following age groups and what are the empiric antibiotics of choice based on this?
- 0 to 1 month
- 1 to 3 months
- 3 to 36 months
- 3 years and older
- 0-1 month: GBS, E. coli, Listeria - treat with ampicillin + gentamicin or cefotaxime
- 1-3 months: GBS, S. pneumoniae, Listeria - treat with ampicillin + cefotaxime + vancomycin if bacterial meningitis is suspected
- 3-36 months: S. pneumoniae, H. influenza type b, N. meningitidis - treat with cefotaxime + vancomycin if bacterial meningitis is suspected
- older: S. pneumoniae, N. meningitidis - treat with cefotaxime + vancomycin if bacterial meningitis is suspected
What is fever of unknown origin?
a fever lasting longer than 8 days to 3 weeks without a primary diagnosis
Bacterial Meningitis
- risk factors are young age, especially in the first month of life, immunodeficiency, and anatomic defects
- GBS, E. coli, Listeria, S. pneumoniae, H. influenzae type b, and N. meningitidis are the most common organisms depending on age
- infants and young children may have nonspecific signs with an absent or minimal fever and bulging fontanelle
- older children often present with fever, altered consciousness, nuchal rigidity, seizures, photophobia, emesis, and headache
- children with suspected bacterial meningitis should receive a lumbar puncture, blood culture, and CT scan with contrast to evaluate for brain abscesses
- CSF culture may be sterile if antibiotics have been started, but the biochemical profile should be unchanged
- elevated WBC with predominately PMNs, high protein, low glucose, and a positive culture/gram stain
- treat with empiric antibiotics based on age and likely organism, corticosteroids to reduce the incidence of hearing loss in HIB meningitis, and supportive care
- most often complicated when due to a gram-negative or S. pneumoniae; may be complicated by hearing loss, global brain injury, SIADH, seizures, hydrocephalus etc.
What are the primary complications of bacterial meningitis?
- hearing loss
- global brain injury
- SIADH
- seizures
- hydrocephalus
Describe the CSF profile in someone with the following types of meningitis:
- acute bacterial
- partially treated bacterial
- viral
- tuberculosis
- fungal
- parameningeal focus
- acute bacterial: elevated WBC with predominately PMNs, high protein, low glucose, and positive culture/stain
- partially treated bacterial: elevated WBC with predominately monocytes, normal to high protein, low glucose, and a negative culture/stain
- viral: PMNs early, then monocytes and lymphocytes, normal to high protein, normal glucose; enterovirus may be cultured, HSV encephalitis may show RBCs
- tuberculosis: slightly elevated WBC with predominately lymphocytes, very high protein content, low glucose
- fungal: slightly elevated WBC with predominately lymphocytes
- normal to high protein, low glucose
Aseptic Meningitis
- inflammation of the meninges with a CSF lymphocytic pleocytosis
- viral meningitis is the most common form with enteroviruses being the predominate agent
- clinical features resemble bacterial meningitis with fever, altered consciousness, nuchal rigidity, seizures, photophobia, emesis, and headache
- typically CSF WBC is elevated but to a lesser extent than in bacterial cases and there are predominately PMNs early but then monocytes and lymphocytes; protein is normal or high and glucose is normal
- most cases are self-limited and require only supportive therapy
M. tuberculosis Meningitis
- an aseptic bacterial meningitis
- most common in children younger than 5 years old
- presents with lethargy or irritability which progresses rapidly to cranial nerve deficits, altered consciousness, coma, paraplegia, and death
- has a slightly elevated WBC with predominately lymphocytes, protein is high, and glucose is low
- likely to find a characteristic basilar enhancement on neuroimaging and a positive culture or PCR
- treated with RIPE therapy
Simple Upper Respiratory Infection
- also known as the common cold, which can be caused by a number of viruses including rhinovirus, parainfluenza, and coronavirus
- presents with low-grade fever, rhinorrhea, cough, and sore throat, which resolve within 7-10 days; persistent symptoms beyond 10 days warrant evaluation for bacterial superinfection
- treat with hydration and exclusion of more serious disorders
Describe development of the sinuses.
- the ethmoid and maxillary sinuses are present at birth
- the sphenoid sinuses develop between 3-5 years of age
- frontal sinuses arise between 7-10 years of age
Sinusitis
- most often caused by S. pneumoniae, H. influenzae, or M. catarrhalis
- clinical features help classify it as acute persistent, acute severe, subacute, or chronic
- acute severe presents with purulent nasal discharge for 3-5 days and has a high fever
- acute persistent presents with nasal discharge and cough for 10-30 days and may also have headache, malodorous breath, facial pain, or low-grade fever
- subacute has these same symptoms for 30-90 days and chronic lasts more than 90 days
- chronic should be evaluated for an underlying condition like CF or involvement of S. aureus or an anaerobe
- acute and subacute are treated with amoxicillin, amoxicillin-clavulanate, or second generation cephalosporin for 10-14 days
- chronic is typically treated with a trial of broad-spectrum oral antibiotics and CT imaging
Viral Pharyngitis
- there are many causes including those involved in simple URI
- presents with low-grade fever, rhinorrhea, cough, and sore throat in addition to tonsils exudates
- specifically, EBV pharyngitis may present with enlarged posterior cervical lymph nodes, malaise, and hepatosplenomegaly; coxsackievirus pharyngitis presents with herpangina
- managed with supportive care, analgesics, and maintenance of adequate hydration; EBV pharyngitis may require corticosteroids
Strep Pharyngitis
- caused by S. pyogenes (GABHS)
- presents with a lack of other URI symptoms, petechiae on the soft palate, strawberry tongue, and enlarged tender anterior cervical lymph nodes, fever, and scarlatiniform rash
- culture is the gold standard for diagnosis but is slow so antigen testing is a common substitute in the short-term
- treated with oral penicillin, single dose IM penicillin, or oral erythromycin or macrolides
Corynebacterium diphtheriae
- gram positive rods which are club-shaped, contain metachromatic granules, and form V or Y shapes
- spread via respiratory droplets, colonize the oropharynx, and may spread in the blood
- they produce an extoxin encoded by beta-prophage, which ADP-ribosylates and inactivates EF-2, inhibiting protein production by host cells
- the bacteria cause “bull neck” lymphadenopathy, pseudomembrane formation in the oropharynx, a potentially fatal myocarditis with heart block and arrhythmia, and nerve deficits beginning in the posterior pharyngeal wall
- diagnosis is made by culture on cystine-tellurite or Loeffler’s medium in combination with the Elek’s test to distinguish toxigenic species from nontoxigenic ones
- treated with oral erythromycin or parenteral penicillin
- toxoid vaccine is available (DTaP)
Acute Otitis Media
- an acute infection of the middle ear space
- most commonly caused by S. pneumoniae, non-tapeable H. influenzae, or Moraxella catarrhalis
- presents with fever, ear pain, and decreased hearing; there may be drainage if the tympanic membrane perforates
- diagnosis requires identification of fluid in the middle ear space with symptoms; fluid is most reliably detected using a pneumatic otoscope since erythema and loss of tympanic membrane landmarks are unreliable
- treated with amoxicillin, amoxicillin-clavulanic acid, or cephalosporin
What is an otitis media with effusion?
defined as fluid within the middle ear space without symptoms of infection
Otitis Externa
- risk factors are those that interfere with the protective mechanisms of the outer ear: cerumen removal, trauma, maceration of the skin from swimming, or excessive moisture
- P. aeruginosa, S. aureus, and Candida albicans are the most common organisms
- presents with pain, tenderness on palpation or movement of the tragus, itching, and drainage; systemic symptoms are usually absent
- diagnosis is based on erythema and edema of the external auditory canal
- treated with restoration of the canal’s acidic environment: use acetic acid solution for mild cases and add topical antibiotics for more severe cases
- if a perforated AOM is complicated by OE, treat with both oral and topical antibiotics
Cervical Lymphadenitis
- present as enlarged, tender, warm, and mobile nodes with overlying erythema in the cervical area
- S. aureus is the most common bacterial agent but S. pyogenes, mycobacterium, and B. henselae are also seen
- other causes include reactive lymphadenitis, viral lymphadenitis, Kawasaki disease, or T. gondii
- managed with empiric antibiotics directed toward S. aureus and S. pyogenes, including a first-generation cephalosporin or anti-staph penicillin
What is cervical reactive lymphadenitis?
an enlarged, inflamed, tender lymph node in the cervical area that occurs in response to infections of the pharynx, teeth, or soft tissues of the head and neck
What typically distinguishes Kawasaki disease-related lymphadenitis from other causes?
Kawasaki disease usually presents with unilateral cervical lymphadenitis rather than bilateral
Parotitis
- an inflammation of the parotid salivary glands
- bilateral cases are usually caused by mumps and other viruses while bacterial parotitis caused by S. aureus, S. pyogenes, and M. tuberculosis result in unilateral parotitis
- presents with swelling centered above the angle of the jaw, fever, and sometimes pus expressed from Stensen’s duct
- diagnosed based on culture from the Stensen’s duct drainage in the case of bacterial parotitis and by viral serology in viral parotitis
- treated with supportive care, analgesics, and antibiotics if bacterial
- may be complicated by meningoencephalitis, orchitis, epididymitis, or pancreatitis as well as abscess and osteomyelitis of the jaw