JH IM Board Review - Infectious Disease VI Flashcards
Meningitis - Definition:
Inflammation of the LEPTOMENINGES = Tissue surrounding the brain and spinal cord.
Aseptic meningitis is defined as:
Meningeal inflammation with an absence of bacteria on CSF exam and culture.
Some pathogens may cause chronic meningitis, in which symptoms are present for …?
4 or more weeks.
==> Cryptococcal meningitis (Rarely in seemingly healthy individuals).
==> TB meningitis.
In meningitis, unlike encephalitis, …?
Brain function is normal.
==> Mental status changes and seizures can occur.
Meningitis - PEx may reveal signs of meningeal irritation, but these findings occur in less than …?
5% of patients.
==> Kernig = Pain in the back is elicited with passive extension of the knee while the hip is flexed.
==> Brudzinski = Passive flexion of the neck results in spontaneous flexion of the hips and knees.
Meningitis - Dx:
- Blood cultures should be obtained IMMEDIATELY.
- Dx relies on exam of the CSF.
- Neuroimaging with CT or MRI is only needed in select situations before performing a LP.
- If neuroimaging is needed, empiric abx (and dexamethasone if indicated) should be started BEFORE scanning.
Bacterial meningitis - Empirical Tx - <1month:
Ampicillin + cefotaxime OR Ampicillin + aminoglycoside.
Bacterial meningitis - Empirical Tx - 1month-50yr:
Vanco + 3rd gen cephalosporin (ceftriaxone or cefotaxime).
Bacterial meningitis - Empirical Tx - >50yr:
Ampicillin (to cover Listeria spp.) + Vanco + 3rd gen cephalosporin.
Bacterial meningitis - Empirical Tx - Penetrating head trauma, post-neurosurgery, CSF shunt:
Vanco + Cefepime, ceftazidime, or meropenem.
Meningitis - Tx - Role of adjunctive dexamethasone:
Recommended in adults with suspected or proven pneumococcal meningitis.
==> 1st dose IDEALLY given 10-20min before the first dose of abx.
==> If not given before the first dose of abx, then give concomitantly with the 1st dose.
==> Dosing: 0.15mg/kg IV every 6h for 2-4 days.
Common etiologic agents causing acute bacterial meningitis in adults - S.pneumo:
- MC etiologic agent in the USA.
- Mortality 19-26%.
- Sometimes associated with other foci of infection (eg pneumonia, endocarditis).
Common etiologic agents causing acute bacterial meningitis in adults - S.pneumo - Tx:
Vanco + 3rd gen cephalosporin until antimicrobial susceptibility is known.
==> Some experts add rifampin if dexamethasone is given.
Common etiologic agents causing acute bacterial meningitis in adults - N.meningitidis:
- Affects mostly children and young adults.
- Patients with terminal complement deficiency are at increased risk.
- Maculopapular rash progresses to petechiae on the trunk, extremities, and mucous membranes.
Common etiologic agents causing acute bacterial meningitis in adults - N.meningitidis - Tx:
3rd gen cephalosporin.
==> Switch to penicillin G or ampicillin once confirmed to be highly sensitive.
N.meningitidis - Chemoprophylaxis:
Rifampin (or ciproflox or ceftriaxone) recommended for household contacts, day care center members, those directly exposed to oral secretions.
Common etiologic agents causing acute bacterial meningitis in adults - H.flu:
- Mostly occurs in children.
- Disease in adults usually associated with:
==> Sinusitis, otitis media, pneumonia, sickle cell disease, splenectomy, DM, immunodeficiency, head trauma with CSF leak, or alcoholism.
Common etiologic agents causing acute bacterial meningitis in adults - H.flu - Tx:
3rd gen cephalosporin.
Common etiologic agents causing acute bacterial meningitis in adults - Listeria:
- Disease of neonates, older adults, and immunocompromised (incl. poorly controlled diabetics and pregnant women).
- Outbreaks associated with contaminated produce, coleslaw, milk, cheese.
- Associated with hematologic malignancy, steroid use, iron overload.
Common etiologic agents causing acute bacterial meningitis in adults - Listeria - Tx:
Ampicillin (or PCN G) +/- aminoglycoside.
Common etiologic agents causing acute bacterial meningitis in adults - S.aureus:
Usually seen after head trauma, in post-op settings, or when hardware is present.
Common etiologic agents causing acute bacterial meningitis in adults - S.aureus - Tx:
Nafcillin or oxacillin (if methicillin-susceptible).
==> Vanco +/- rifampin (if methicillin-resistant).
Causes of aseptic meningitis - Categories:
- Viral.
- Bacterial.
- Fungal.
- Miscellaneous infections.
- Non infectious diseases.
- Drugs.
Causes of aseptic meningitis - Viral:
- Enteroviruses.
- Mumps.
- Echovirus.
- Poliovirus.
- Coxsackie.
- HSV.
- CMV.
- VZV.
- Arbo.
- Acute HIV.
- Influenza.
Causes of aseptic meningitis - Bacterial:
- TB.
- Rickettsiae.
- Syphilis.
- B.burgdorferi.
Causes of aseptic meningitis - Fungal:
- Cryptococcus.
- Coccidioides.
- Histoplasma.
- Candida.
- Molds (aspergillus, exserohilum).
Causes of aseptic meningitis - Miscellaneous infections:
- Toxo.
- Malaria.
- Whipple.
- Leptospira.
Causes of aseptic meningitis - Noninfectious disease:
- Brain tumors.
- Sarcoidosis.
- Lupus.
- Meningeal carcinomatosis.
Causes of aseptic meningitis - Drugs:
- TMP-SMX.
- Ibuprofen.
- Carbamazepine.
Encephalitis frequently occurs with …?
MENINGITIS ==> Meningoencephalitis.
MYELITIS ==> Encephalomyelitis.
In pts who had a recent viral illness or vaccination and who present with encephalitis, consider …?
A diagnosis of acute disseminated encephalomyelitis (ADEM).
West Nile virus may be associated with …?
FLACCID WEAKNESS + Reduced or absent reflexes.
Encephalitis - Dx - CSF PCR:
- HSV.
- CMV.
- EBV.
- VZV.
- JC virus.
- West Nile virus.
- Enteroviruses.
Encephalitis - Dx - CSF serology is useful for …?
Detection fo ARBOviruses.
Encephalitis - Dx - Serum +/- CSF serologic testing and PCRs can help diagnose:
Tick-borne + Spirochetal disease.
Encephalitis - Dx - Brain Bx when?
ONLY needed in pts who continue to deteriorate on acyclovir and who have a negative Dx workup.
Encephalitis - Dx - CSF culture is useful for:
- Fungal.
- Mycobacterial.
- Bacterial.
causes of encephalitis.
Encephalitis - Dx - Perform respiratory viral panel testing if …?
There is a suspicion of resp. viral disease.
Encephalitis - Dx - MRI?
ALWAYS. If not possible, then CT.
Indications for head CT before LP when acute bacterial meningitis is suspected - Immunocompromised host:
- HIV/AIDS.
- Transplant patient.
- Patient on immunosuppressive medications.
Indications for head CT before LP when acute bacterial meningitis is suspected - Hx of CNS disease:
- Mass lesion.
- Stroke.
- Focal infection.
Indications for head CT before LP when acute bacterial meningitis is suspected - Papilledema:
Especially if no venous pulsations.
Indications for head CT before LP when acute bacterial meningitis is suspected - New-onset seizure:
Onset within 1 week of presentation.
Indications for head CT before LP when acute bacterial meningitis is suspected - Focal neurologic deficit:
- Dilated nonreactive pupil.
- Ocular motility abnormalities.
- Abnormal visual fields.
- Gaze palsy.
- Arm or leg drift.
Indications for head CT before LP when acute bacterial meningitis is suspected - Abnormal level of consciousness:
Inability to follow 2 consecutive commands or answer 2 consecutive questions.
Selected pathogens causing encephalitis - West Nile:
- Transmission ==> Mosquito.
- Dx ==> PCR and IgM in CSF or serum/ Convalescent titers in serum.
- Tx ==> Supportive.
==> Most infected pts present with febrile illness/ Advanced age is GREATEST risk factor for severe disease.
Skin and soft tissue infections - Basic info:
- Range from minor superficial infections to life-threatening conditions, such as necrotizing fasciitis.
- Generally categorized into purulent vs non purulent infections ==> Purulence usually denotes Staph.
- Incr. incidence of infections caused by CA-MRSA.
Skin and soft tissue infections - CP:
- Most present with isolated skin or soft tissue findings.
- Some develop necrotizing pneumonia, necrotizing fasciitis, endocarditis, osteomyelitis, sepsis.
- Erythema without pain, fever, warmth, or leukocytosis should lead to consideration of alternative diagnoses.
Skin and soft tissue infections - Tx - MRSA:
- Incision + Drainage is the primary treatment for cutaneous abscesses.
- Vanco is the DoC for hospitalized pts. Linezolid is an alternative.
- Many CA-MRSA strains may be sensitive to TMP-SMX. Other options for outpatients include clindamycin (although resistance can be inducible) and doxycycline.
- Newer agents ==> Daptomycin, telavancin, ceftaroline can be considered.
Skin and soft tissue infections - Tx - NON purulent:
Most are caused by beta-hemolytic strep, making beta-lactam Tx (eg amoxicillin) the Tx of choice.
Acute bacterial arthritis - Organisms:
- N.gono ==> <30.
- S.aureus.
- S.pneumo.
- Mycoplasma spp. ==> 1o Ig deficiency.
- Salmonella spp. ==> HIV/SCA.
- P.multocida ==> Cat bites or scratches.
- Other Gram(-) bacilli.
Acute bacterial arthritis - S.aureus - Risk factors:
- Glucocorticoid Tx.
- RA.
- DM.
- Post-op.
- Injection drug use.
Acute bacterial arthritis - S.pneumo - Risk factors:
- HIV.
- Alcohol.
- SCA.
==> LESS THAN HALF have another focus of S.pneumo infection.
Acute bacterial arthritis - Other gram(-) bacilli - Risk factors:
- Injection drug use.
- Immunodeficiency.
- Neonates.
- Elderly.
- Nursing home residents.
Acute bacterial arthritis - Dx:
ASPIRATION OF SYNOVIAL FLUID IS ESSENTIAL.
==> US/CT/MRI may be helpful for detection and aspiration with involvement of certain joints (eg hip, sacroiliac).
==> WBC in the fluid >50.000 with >75% neutros.
==> Glucose is <40mg/dL.
Acute bacterial arthritis - Dx - The presence of crystals …?
DOES NOT R/O INFECTION.
==> Crystal-induced arthritis and septic arthritis can occur together.
Acute bacterial arthritis - Dx - Gram stain:
Positive in 1/3.
Acute bacterial arthritis - Dx - Synovial fluid cultures:
Positive in up to 90% of nongonococcal bacterial arthritis, but in less than 50% of gono arthritis.
Acute bacterial arthritis - Dx - What is often needed to confirm GC arthritis?
Genital or pharyngeal culture +/- NAA to confirm GC, or NAA on joint fluid or urine.
Acute bacterial arthritis - Dx - Blood cultures:
SHOULD BE OBTAINED.
==> Up to 60% positive in S.aureus cases. LESS Se in Dx other pathogens.
Acute bacterial arthritis - Tx - Empirical abx after blood cultures and joint aspiration largely depends on gram stain:
- If GC arthritis is suspected ==> CEFTRIAXONE.
- If S.aureus is suspected ==> Vanco (if MSSA then oxacillin/nafcillin).
- If Streptococcal disease is suspected ==> Penicillin/ampicillin.
- If gram(-) is suspected ==> Ceftazidime or cefepime are appropriate empiric choices.
Acute bacterial arthritis - Tx - Indications for surgical drainage:
- Hip joint involvement (except in cases of GC).
- Delay of therapy (>1week after onset of symptoms).
- Loculated infection or exudate too thick to aspirate.
- Poor response to Tx (eg failure to decr. synovial WBC).
- Prosthetic joint infection.
Viral arthritis:
- Caused by direct invasion of the synovium OR by an immune reaction involving certain joints.
- USUALLY Migratory polyarthritis.
Viral arthritis - Many viruses implicated:
- Rubella.
- Mumps.
- B19.
- Hep B.
Rubella arthritis:
- Can occur following infection or immunization.
- Usually seen in women.
- Disease typically self-limited but can rarely persists for years.
Mumps arthritis:
- More common in men.
2. Develops within 2 weeks of parotitis.
B19 arthritis:
- Small joints of the hands most frequently invovled.
- Infection in adults can occur without fever or rash.
- Self-limited: usually resolves within 8-10 weeks.
HBV arthritis:
- Can manifest as arthralgias or symmetrical arthritis.
2. Symptoms (arthralgias or arthritis) occur before jaundice and resolve when jaundice develops.
Prosthetic joint infection - Early infection:
- Within 1-3 months.
- Acquired at surgery.
- Acute symptoms (cellulitis, erythema, pain, drainage).
==> Usually caused by S.aureus, Gram(-) bacilli, anaerobes, or polymicrobial.
Prosthetic joint infection - Delayed infection:
- 3-12months.
- Acquired at surgery.
- Indolent symptoms of joint pain and/or loosening of prosthesis.
==> Usually low-virulence pathogens (eg Propionibacterium acnes, CN staph, enterococci).
Prosthetic joint infection - Late infection:
After 12 months, commonly via hematogenous seeding.
==> Usual pathogens are S.aureus, beta-hemolytic strep, gram(-) bacilli.
Prosthetic joint infection - Dx and Tx:
Definitive Dx made by arthrocentesis or surgival debridement.
Most successful Tx is removal of entire prosthesis with 6 weeks of abx therapy.
Osteomyelitis - 2 basic types:
- Hematogenous.
2. Contiguous.
Osteomyelitis - Hematogenous source - Etiology:
- Seeding of the bone during bacteremia.
- Primarily occurs in children and older adults.
- Injection drug users.
Osteomyelitis - Hematogenous - Involvement:
- Vertebrae.
- Sternoclavicular.
- Sacroiliac joints.
- Syphysis pubis.
Osteomyelitis - Hematogenous - Organisms:
- S.aureus (MC).
- Pseudomonas.
- Serratia.
- Eikenella.
Osteomyelitis - Pts with SCA:
- S.aureus.
2. Salmo.
Osteomyelitis - Hematogenous - Vertebral involvement:
- S.aureus.
- Gram(-) bacilli.
- TB.
- Candida.
Osteomyelitis - Contiguous source:
- Most cases in adults.
- Infections from adjacent soft tissue, injury, or surgery.
- Presentation is more indolent than with hematogenous spread.
- DM foot ulcers + decubitus ulcers are common sources.
==> S.aureus MC, although most are POLYMICROBIAL. Pseudomonas ==> Puncture wound of the foot.
Osteomyelitis - Dx - Blood studies:
- ESR/CRP elevated.
2. Blood cultures more likely to be positive in cases of hematogenous spread.
Osteomyelitis - Dx - Radiologic and imaging studies - Plain radiographs:
- May show periosteal elevation, soft tissue swelling, or lytic changes.
- Findings may not be present during early or acute infection, but if seen are adequate for diagnosis.
Osteomyelitis - Dx - Radiologic and imaging studies - MRI:
- Best identifies early changes consistent with acute osteomyelitis ==> Such as bone marrow edema.
- Test of choice for vertebral osteomyelitis because it better defines the surrounding soft tissue.
Osteomyelitis - Dx - Radiologic and imaging studies - CT:
Can be helpful if hardware present.
Osteomyelitis - Dx - Radiologic and imaging studies - Tc bone scan:
- Can detect early lesions with high sens.
- Can be falsely negative in acute and chronic infection.
- Best when bone was previously normal (false positive common with previously abnormal bone).
- Cannot distinguish infection from tumor, fracture, or infarction.
Osteomyelitis - Dx - Bone Bx for culture:
Is recommended to make a definitive diagnosis if blooc cultures are negative.
Osteomyelitis - Dx - Swab cultures of sinus tract or ulcer base:
UNRELIABLE for making a microbiologic Dx.
==> However they can be useful if treatment is to be empiric to determine if therapy needs to include coverage against virulent pathogens such as S.aureus, P.aeruginosa.
Osteomyelitis - Tx - Acute event:
Tx of acute osteomyelitis usually consists of 6 WEEKS of IV abx directed by the culture results.
==> Depending on the organism and antimicrobial susceptibilities, oral Tx after an initial 2 weeks of IV abx may be considered in select cases if the abx to be used has adequate bioavailability and bone penetration.
Osteomyelitis - Tx - Chronic:
- Often requires surgical debridement to remove devitalized bone ore restore vascular supply in conjunction with antimicrobial therapy.
- Antimicrobial therapy in the absence of debridement is suppressive, not curative.
==> Monitoring of CRP/ESR over time is helpful.
Classification of FUO:
- Classic FUO.
- Nosocomial FUO.
- Neutropenic FUO.
- HIV-associated FUO.
Classic FUO - Def:
- Fever >38.3 for 3 weeks.
- Blood cultures negative.
- Lack of Dx with 3 outpatient visit or 3 inpatient days.
Classic FUO - Etiology:
- Infection.
- Malignancy.
- Collagen vascular diseases.
- Granulomatous disease.
Nosocomial FUO - Definition:
Hospitalized patient with NO fever on admission.
==> 3 days of investigation + 2 days of negative incubating cultures.
Nosocomial FUO - Etiology:
- C.diff.
- Phlebitis or venous thromboembolism.
- Sinusitis.
- Drug fever.
Neutropenic FUO - Definition:
Absolute neutros <500.
==> 3 days of investigation.
==> 2 days of negative incubating cultures.
Neutropenic FUO - Etiologies:
- Perianal infection.
- Aspergillus spp.
- Candida spp.
HIV-associated FUO - Def:
HIV(+).
==> Fever > 3weeks in outpatients or >3days for inpatients.
==> 3 days of investigation.
==> 2 days of negative incubating cultures.
HIV-associated FUO - Etiology:
- Mycobacteria, incl. TB.
- Lymphoma.
- Drug fever.
- CMV.
- PCP.
Etiologic considerations for classic FUO - Foreign-born:
Extrapulmonary TB.
Etiologic considerations for classic FUO - Age >50:
- Malignancy.
- Giant cell arteritis.
- Polymyalgia rheumatica.
Etiologic considerations for classic FUO - High fevers with arthralgias/arthritis and rash:
Adult Still disease.
Etiologic considerations for classic FUO - Medical background with undocumented fever:
Factitious fever.
Etiologic considerations for classic FUO - Returning traveler:
From endemic countries:
- Plasmodium spp.
- Dengue.
- Salmonella spp.
- Tick-borne diseases.
Etiologic considerations for classic FUO - Recurrent episodic fevers:
Hereditary periodic fevers.
FUO - Dx - Hx/PEx:
A thorough Hx including travel, hobbies, history of TB exposure, HIV, risk factors, medications, should be obtained to guide the evaluation.
==> Repeated PEx may be necessary to detect slowly progressing diseases.
FUO - Basic testing should include the following:
- CBC.
- Comprehensive metabolic panel.
- Urinalysis.
- ESR/CRP.
- Blood cultures (greater than 3 sets).
- CXR.
- ANA.
- HIV.
FUO - Dx - IGRA and PPD:
Should be considered.
FUO - Dx - CT:
CT scan of the chest, abdomen, and pelvis should be considered in the absence of other localizing signs.
FUO - Dx - Administration of NAPROXEN …?
May help distinguish between neoplasia and infection.
==> The fever from neoplasms is thought to be more responsive to the medication.
FUO - Dx - Empirical abx:
Try to avoid empirical abx.
==> They may suppress an occult infection without curing it, and may interfere with the ability to make a diagnosis.
FUO - Drug-induced fever:
Should be considered a Dx of exclusion.
==> It is confirmed by stopping the potentially offending agent.
Drug-induced fever - Features:
- Usually pts do not appear as toxic as with other causes of FUO.
- RASH + EOSINOPHILIA are sometimes present, but their ABSENCE does NOT rule out drug fever.
==> Common causes ==> Sulfonamides, beta-lactam abx, phenytoin, amiodarone, nitrofurantoin.
FUO - The cause of may NOT be found in approx. …?
30% of adults.
==> Most of those without a Dx have a good prognosis.