Infectious Disease Flashcards
Bug associations
Human bite
Reptile bite
Cat bites
- Human bite: Eikenella
- Reptile bite: Salmonella
- Cat bites: Pasteurella multocida (prophylactic antibiotics)
Lyme disease
agent
vector
rash
•Caused by spirochete Borrelia burgorferi
Vector = deer tick = Ixodes
•Erythema migrans = skin lesions (usually 7-10 days after bite) from local spread of the organisms in the skin (typically can be annular lesions with bright red borders and cleared centers – can also be uniformly red or with red center), occur in majority of cases (75%)
Lyme disease
differential
treatment
Differential: GC, septic arthritis, rheumatic fever, rheumatoid arthritis, reactive arthritis (Reiter’s Syndrome)
Treatment: doxycycline, amoxicillin, erythromycin and others
Erythema migrans of Lyme disease
Malaria
vector
pathogen and worst subtypes
diagnostic options (three)
Female Anopheles mosquito
plasmodium falciparum and vivax
thick and thin blood smear, antigen based rapid diagnostic tests, PCR
Malaria
fever pattern
pathogen location
•every two days (vivax and ovale) and every 3 days for falciparum
complications: cerebral malaria and Blackwater fever (renal involvement) both from microvascular sludging
pathogen location: inside RBCS
Dengue Fever
vector
symptoms with eponym
complication
vector: Aedes aegypti
symptoms with eponym: flulike illness with severe myalgias “break bone fever”, measles like rash
MOST often mild 80%
complication: •dengue hemorrhagic fever – bleeding, low platelets (due to viral destruction of bone marrow), plasma leakage and shock
Dengue Fever
phases with symptoms
HIV drug categories (5)
treatment principle
Categories: protease inhibitors, NRTIs. NNRTIs, entry inhibitors, integrates inhibitors
treatment principle: patients need drugs from three or more classes (many pills combined multiple drugs in one pill)
HIV PEP
risk of seroconversion after needlestick
treatment (3)
Risk: 0.3%
treatment options:
- Tenofovir 300mg QD
- Emtricitabine 200mg QD
- Raltegravir 400mg BID or Dolutegravir 50mg QD
HIV related emergencies, descriptions
lactic acidosis
immune reconstitution syndrome
•Lactic Acidosis
–Certain anti-HIV drugs (nucleoside reverse transcriptase inhibitors-NRTIs) can cause mitochondrial damage inhibiting cellular energy production resulting in lactic acidosis
–May start suddenly or gradually
–Symptoms include abdominal pain, weight loss, malaise, fatigue, rapid breathing, tachycardia
–Stop the drugs, bicarbonate, glucose, riboflavin
–Mortality can be as high as 60%
•Immune Reconstitution Syndrome
–Highly active antiretroviral therapy (HAART) can be associated with the reconstitution of the immune system and an exaggerated immune response to occult opportunistic or recent prior infections characterized by inflammation / fever.
–Can be seen most commonly with subclinical TB (fever, SOB, enlarged lymph nodes, cerebral masses [tuberculomas]), cryptococcal meningitis, CMV, hepatitis C
–Treat the infection / steroids
HIV medication issues, describe and drug type
hypersensitivity
nephrolithiasis (and pearl)
Stephen Johnson’s
hypersensitivity: NRTIs
nephrolithiasis: Indinavir -> stones are radio Lucent
Stephen Johnson’s NNRTIs
HIV emergencies
ocular emergencies (2)
Varicella zoster and Cytomegalovirus retinitis
–Cytomegalovirus retinitis
- The most common vision-threatening condition in HIV
- T-cell counts typically below 50
- Blind spots, visual field losses, flashing lights, floaters, decreased VA
- Treatment with anti-CMV meds (ganciclovir, foscarnet, cidofovir)
–Varicella zoster
- Second most common eye condition in HIV (shingles, 3-4% of patients)
- Can involve the retina with retinitis and necrosis (70% get retinal detachment with the necrosis)
- Treatment is acyclovir for 10-14 days
HIV emergencies
pulmonary: leading AIDS defining condition -?
CD4 <
Tx
PCP: Pneumocystis jiroveci pneumonia
CD4 < 200
Tx: •Trimethoprim/sulfamethoxazole and steroids
HIV emergencies - CNS (2)
Cerebral toxoplasmosis and Cryptococcal meningitis
–Cerebral toxoplasmosis
- A protozoan (hosted by cats) infection usually caused by ingestion of undercooked meats (lamb and pork) that causes focal brain lesions (be careful with cat litter!!)
- Most cases occur with T-cells less than 50
- Headache, confusion, altered mental status, fever, seizures (up to 50%) and strokes (exceed seizures)
- Diagnosis by CT (ring-enhancing lesions) and positive IgG antibodies to Toxoplasma
–Cryptococcal meningitis
- Most common systemic HIV fungal infection
- Typical signs and symptoms of meningitis but may be slower in presenting and more indolent
- LP looking for cryptococcal antigen and fungal culture
Ring-enhancing lesions of toxoplasma gondii: think HIV and kitty litter
HIV emergency, GI
Common symptom and general etiologies
Symptom: diarrhea,
etiologies: opportunistic, non-opportunistic, drug-related
Diarrhea
dx pearl
Most common agents including #1 in kids, cruise ships
Viral causes (most common) will not have stool WBC or blood
- Rotavirus, adenovirus, calicivirus, enterovirus, Norwalk virus (“RACE to Norwalk”)
- Norovirus (Norwalk-like) virus is the leading cause of gastroenteritis in the US – cruise ships
- Rotavirus is the most common cause of diarrhea in children
E Coli O157 H7
sources (4)
Complication peds and adult and trigger
–Undercooked hamburger, petting zoos, raw milk, untreated water
–Causes HUS (in children), TTP (in elderly)
–Antibiotics may increase risk of HUS
Diarrhea with high fever, bloody, seizures
Tx
Shigella
Cipro
Diarrhea with
Watery or mucoid stools
Sources: Cafeteria food, pet turtles, amphibians, eggs, chickens
Complication in specific underlying chronic disease
Treatment
Salmonella
Complication: osteomyelitis in sicklers
Treatment: cipro
Most common cause of bacterial diarrhea
Contaminated food/water, backpacker’s diarrhea
Tx peds and adults
Complication
Campylobacter (“you get it camping”)
Tx: Erythromycin (children), fluoroquinolones (adults)
Complication: Acute infection is associated with development of Guillain-Barré syndrome
Diarrhea from raw oysters, clams, shrimp (2)
Vibrio Parahaemolyticus and Vulnificus (increased morbidity with preexisting liver disease)
Diarrhea more often mimicking appy
colicky abdominal pain
special dx test
tx (2)
Yersinia enterocolitica
Fecal Wright stain
Treatment: supportive if uncomplicated, quinolones or TMP-SMX if complicated
Most common cause of water-borne diarrheal outbreak in US
Less typical sources (2)
Stools charcteristics
Tx
Giardia
Less typical source: daycare, STDs
Stool: floating, frothy, foul smelling
Metronidazole, Furazolidone
Diarrhea that
–Spreads between family members and sexual partners
–Fecal-oral contact and anal intercourse
–Diarrhea can be bloody
Extra-intestinal manifestations
Amebiasis (Entamoeba histolytica)
–Extra-intestinal manifestations: liver abscess, pericarditis, pleuropulmonary disease,cerebral amebiasis
–Wide variety of presentations,rom asymptomatic cyst-passer to colitis to fatal cerebral amebiasis
Diarrhea that is:
–Intestinal protozoan parasite
–Most common cause of chronic diarrhea in AIDS
Contracted from:
At risk:
Tx (2):
Cryptosporidium
Contracted from: infected water
At risk: children, animal handlers, IC
Tx (2): Paromomycin + Azithro
Diarrhea that:
–Contaminated foods (dairy, meat, poultry, eggs, potato salads, cream-filled pastries)
–Nausea, vomiting, diarrhea
–Most common cause of food-borne disease- Large outbreaks
Symptoms within 6 hours of ingestion
Staph
Diarrhea that is:
–Common, large outbreaks (buffets, schools)
–Casseroles, stews, gravies, steam table meats
–Spores survive cooking, then produce toxins
–6-24 hour onset
–Watery diarrhea, no fever or vomiting
–Fecal WBCs and RBCs negative
Treatment: ?
Clostridium perfringens
fluids (antibiotics not helpful)
Diarrhea with:
–Copious watery “rice water” diarrhea
Complications
Tx (3)
Vibrio cholera
Complications: severe fluid and electrolyte issues
Tx (3): WHO ORT, TMP-SMX, Cipro
Diarrhea that is:
–Common in fried rice (Chinese restaurants), starchy foods, vegetables, meat
–Spores germinate when boiled rice not refrigerated
Forms
Tx
Bacillus cereus
Forms: violent vomitting within 2-3 hours or diarrhea
Tx: supportive
Scombroid
Fish type
Etiology (2)
–Deep ocean fish (tuna, mackerel, mahi-mahi)
–Heat-stable toxin from bacterial action on dark meat fish not promptly refrigerated
–Histamine-like toxin, rapid symptom onset (30 minutes)
After eating *** type of fish:
–Muscle weakness, paresthesias (perioral, burning hands and feet), distorted or reversed temperature sensation, vomiting, diarrhea
Tx:
Complication:
Ciguatera (Gambierdiscus toxicus)
–Reef fish (groupers, red snapper, barracuda) which eat dinoflagellates containing ciguatoxins which accumulate in food chain
Tx: mannitol, amitriptyline, diphenhydramine
Complication: chornic sx lasting years
C diff
Alternative name
types (3)
Tx (2)
Alternative name: Pseudomembranous Enterocolitis
types (3): neonatal, post-op, antibiotic-related
Tx (2): oral vanc or metronidazole
Mononucleosis
agent
pathogmnemonic findings PEX/lab (1+2)
rash?
EBV
posterior cervical lymphadenopathy, atypical large lymphocytes, transaminitis
If given ampicillin, 95% get EBV-induced antibodies to it and a rash
Exited of pharyngitis/fever/ha/sandpaper rash, strawberry tongue -> Dx?
Cause
Pastia’s lines
Tx
Scarlet fever
erythrogenic toxin from Group A step
linear rash accentuated in flexure creases
antibiotics/penicillin
Strep pharyngitis
rationale for treatment
Prevents rheumatic fever when started < 9 days
does NOT prevent glomerulonephritis
Ulcerative infections to remember (4) - pain?
dx (3) + caveat
secondary syphilis: timing, classic features (3)
“LuSCH”: painless-> lymphogranuloma veneruem, syphilis (primary, single), painful -> herpes, chancroid (unilateral)
painless
dark-field microscopy of primary or secondary lesions (80% sens), VDRL/RPR can be neg in early syphillis, FTA-ABS/MHA-TP best sens/spec
secondary: 2 to 10 weeks after chancre
rash affecting palms and soles, painless lymphadenopathy, condyloma lata (smooth, moist flat warts)
Tertiary syphilis
timing
symptom categories (4)
Tx
3 to 25 years
neurologic - dementia, meningitis, neuropathy
cardiac-thoracic aneurysm, aortic insufficiency
skin lesions - gummas (can be anywhere in body; granulomas)
bone and joint - Charcot’s joint (degenerative arthritis from loss of sensation)
Tx: PCN benzathine 2.4 million units (alternatives inferior)
Jarisch-Herxheimer reaction - what?
Pictured painful lesion
agent
classic finding
tx
Jarisch-Herxheimer reaction: Release of endotoxin from spirochete death (fever, arthralgias, headache, myalgias; several hours after antibiotics); 50% in primary; 90% in secondary, Also seen treating in Lyme disease (14%)
chancroid - painful vesicular pustular lesion
tender unilateral adenopathy with bubo formation
tx: CTX or azithro
Pictured lesion
etiology
classic phases (2)
Tx
Lymphogranuloma veneruem
chlamydia trachomatis
painless genital vesicles/papules, painful bubo (inguinal node weeks to months later) with groove sign (above and below inguinal ligament)
doxycycline x 3 weeks
Most common STD
treatment (2 options)
common co-infection, bacteria type
standard treatment
Chlamydia (intracellular)
azithromycin/doxycycline
gonorrhea - Gram negative diplococci
ceftriaxone 250 mg IM plus azithromycin 1 g OR Doxy times 7 days
Non-genital gonococcal infections
locations (4)
most common cause of what age < 50
dx caveat
classic associated skin finding
Conjunctivitis, pharyngitis, rectal/proctitis AND
disseminated (skin, arthritis, endocarditis, meningitis)
septic arthritis
joint fluid culture often negative
<20 necrotic pustules on erythematous base
Skin lesions of gonnococemia - <20 necrotic pustules on erythematous base
Bone and joint infections, common causes
- Neonates
- IVDA
- Sickle cell
- Foot puncture wounds
- Cat bites
- Fresh water wounds
- Diabetic foot
- Human bites
- Reptile bites
- Neonates: group B Streptococcus
- IVDA: Pseudomonas osteomyelitis
- Sickle cell: Gram negative osteomyelitis, Salmonella
- Foot puncture wounds: Pseudomonas
- Cat bites: Pasteurella multocida
- Fresh water wounds: Aeromonas
- Diabetic foot: polymicrobial
- Human bites: Eikenella corrodens, Staph,
Strep, anaerobes
•Reptile bites: Salmonella
