Infectious Disease Flashcards by JONATHAN VLAHOS

Bug associations

Human bite

Reptile bite

Cat bites

Human bite: Eikenella
Reptile bite: Salmonella
Cat bites: Pasteurella multocida (prophylactic antibiotics)

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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%)

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Lyme disease
differential
treatment

Differential: GC, septic arthritis, rheumatic fever, rheumatoid arthritis, reactive arthritis (Reiter’s Syndrome)

Treatment: doxycycline, amoxicillin, erythromycin and others

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Erythema migrans of Lyme disease

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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

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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

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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

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Dengue Fever

phases with symptoms

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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)

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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

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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

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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

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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

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HIV emergencies

pulmonary: leading AIDS defining condition -?

CD4 <

PCP: Pneumocystis jiroveci pneumonia

CD4 < 200

Tx: •Trimethoprim/sulfamethoxazole and steroids

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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

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Ring-enhancing lesions of toxoplasma gondii: think HIV and kitty litter

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HIV emergency, GI

Common symptom and general etiologies

Symptom: diarrhea,
etiologies: opportunistic, non-opportunistic, drug-related

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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

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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

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 ## Footnote –Spreads between family members and sexual partners –Fecal-oral contact and anal intercourse –Diarrhea can be bloody Extra-intestinal manifestations

Amebiasis (Entamoeba histolytica) ## Footnote –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: ## Footnote –Intestinal protozoan parasite –Most common cause of chronic diarrhea in AIDS Contracted from: At risk: Tx (2):

Cryptosporidium ## Footnote Contracted from: infected water At risk: children, animal handlers, IC Tx (2): Paromomycin + Azithro

Diarrhea that: ## Footnote –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: ## Footnote –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: ## Footnote –Copious watery “rice water” diarrhea Complications Tx (3)

Vibrio cholera ## Footnote Complications: severe fluid and electrolyte issues Tx (3): WHO ORT, TMP-SMX, Cipro

Diarrhea that is: ## Footnote –Common in fried rice (Chinese restaurants), starchy foods, vegetables, meat –Spores germinate when boiled rice not refrigerated Forms Tx

Bacillus cereus ## Footnote 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: ## Footnote –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 ## Footnote * 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