Infectious Disease Flashcards
What are risk factors for true bacteremia?
Old age Lines and catheters Steroid use Immune suppression Chronic liver and kidney disease Neutropenia Parenteral nutrition
What are the most common bacterial contaminants in blood cultures?
Skin flora: Bacillus Coag negative staph Propionibacterium Strep viridans
What bacteria is the leading cause of hospital infections? What are common infections that it causes?
Pseudomonas Ventilator associated pneumonia Catheter associated UTI’s Most common pathogen isolated from cystic fibrosis patients
What are some pathogens that when isolated in blood cultures are likely true positives?
S. aureus S. pneumo Pseudomonas Candida Enterobacteriaceae (E. coli, shigella, klebsiella, salmonella)
Which antibiotics provide coverage for P. aeruginosa?
Cefepime Ceftazidime (3rd gen. Ceph.) Zosyn Ciprofloxacin
Which foodbourne illness is associated with an increased risk of pre-term labor?
Listeria monocytogenes
Listeria infection is most commonly associated with what activity?
Eating unpasteurized dairy and deli products
What is the treatment of choice for Listeria?
Ampicillin or Pen G
Listeria infection Source, presentation, associations, treatment
Unpasteurized dairy and deli Fever, myalgia, vomiting, non-bloody diarrhea Causes pre-term labor, and sepsis/meningitis in elderly or immune compromised Treated only in severe cases with ampicillin or Pen G
What bacteria cause foodbourne illness through pre-formed toxins?
B. cereus and S. aureus
When empirically treating meningitis, when do you need to provide coverage for Listeria?
Immune compromised and >50 years
What are the broad classifications of the stages of Syphilis?
Primary, Secondary, Latent, Tertiary
What are the defining features of primary syphilis? What happens if not treated?
Painless chancre If untreated, can develop secondary syphilis weeks to months later
What are the defining features of secondary syphilis?
Weeks to months after primary infection develop: Generalized lymphadenopathy Diffuse maculopapular rash classically involving the palms and soles Mucus membrane lesions Systemic symptoms Condyloma lata (moist, flat, broad based papular lesions of the anogenital region)
What are the features of tertiary syphilis?
Cardiovascular involvement including aortitis and aortic aneurysms Gummatous disease: unique granulomatous disease forming gumma in the liver (most common), heart, brain, skin, bone, testis and other tissues
Which STI’s cause a rash on the palms and soles?
Secondary Syphilis and Gonococcemia
A patient is noted to have a diffuse macular rash and moist broad-based papular lesions on her external genitalia. What STI is possible?
Syphilis Condyloma lata
Explain the diagnostic tests for syphilis
Dark field microscopy: best in primary stage, but limited by performer and collector RPR/VDRL: decreased sensitivity in early and late syphilis therefore best for secondary, positive 4-6 weeks after infection, only 70–80% sensitive, must be followed by a more sensitive and specific test, many false positives Treponemal specific: EIA, TPHA, FTA-abs: used to confirm diagnosis after positive VDRL/RPR
What is the treatment for syphilis?
Primary/Secondary: IM benzathine pen G X 1 dose Tertiary: IM benzathine pen G qweek X 3 weeks
What disease process is this and what is the treatment?
Toxoplasmosis as suggested by the ring enhancing lesions. AIDS-defining illness. Caused by toxoplasmosis gondii, a parasite that is common and best known to be in cat feces.
Treated with IV pyrimethamine and sulfadiazine (must also give leukovorin (folinic acid) to prevent toxic effects of methotrexate and pyrimethamine)
Neurocysticercosis also has ring enhancing lesions in the brain, but the rings tend to be grape-like in size and are more symmetrically round
The most common CNS infection of untreated AIDS patients?
Toxoplasmosis
An AIDS patient that has not been treated presents with headache, fever, and new-onset seizure. What should you suspect?
Toxoplasmosis infection of the CNS
What are two AIDS-defining CNS infections and how are they different?
Toxoplasmosis: CD4 counts less than 100, ring enhancing lesions on head CT
Cryptococcal meningitis: CD4 counts less than 50, no CT head findings
What is the treatment for cryptococcal meningitis?
Amphotericin B and oral flucytosine
What is the common imaging finding for neurocysticercosis and what other disease has a similar finding?
Round, ring-enhancing lesions of the brain
Toxoplasmosis also has ring-enhacing brain lesions, but they are larger and more irregularly shaped
What is the treatment for neurocysticercosis and what is the source of this disease?
Praziquantel
Tapeworm in the brain from undercooked pork
What is the prophylactic medication for toxoplasmosis in HIV patients and when is it given?
sulfamethoxazole-trimethoprim (Bactrim) after CD4 counts are less than 100
Who are the patients that the CDC recommends treating with Tamiflu?
Patients at higher risk of complications:
>65yr, <2yr, pregnant or up to 2 weeks postpartum, immune compromise, residents of nursing homes, individuals with chronic illnesses including pulmonary disease, significant cardiac disease not including hypertension, malignancy, renal insufficiency, liver disease, diabetes, sickle cell disease, immunosuppression, and any neurological condition that compromises respiratory function, morbidly obese patients, and Native Americans
Better if within 48 hours of onset, but still administer at anytime if otherwise indicated
Patients who report improvement in symptoms are not likely to benefit from treatment
What are the most common symptoms of the flu?
Fever, Headache, myalgias, cough, sore throat, fatigue/malaise, GI symptoms
What is the most common cause of viral pneumonia in adults?
Influenza
Antiviral treatment has been shown to be beneficial in which type of flu?
Type A (pandemic type)
In herpes, lesions on what part of the face have a higher risk of ophthalmic involvement and why?
Vesicular lesions on the tip of the nose carry a higher risk of eye involvement because of the nasociliary branch of the trigeminal nerve that innervates both the nose and the globe. Called Hutchinson’s sign.
What is the treament for herpes ophthalmicus?
Oral antivirals and topical steroids. If immunecompromised or other severe disease, IV antivirals should be given.
Ophthalmology consult urgent/emergently
Patient has left sided facial paralysis, left ear pain and tinitus and is found to have vesicles in the left ear canal. What could be causing this?
Herpes zoster infection of the left middle/inner ear.
What is the first-line vasopressor in septic shock and why is it better compared to the other options? (Epinephrine, Dopamine, Phenylephrine, Dobutamine, Vasopressin)
Norepinephrine
Has B1 and A1 activity increasing cardiac output and vascular resistance.
Dopamine has more cardiac and less vessel effects and causes more dysrhythmias than NE
Phenylephrine doesn’t increase cardiac output
Vasopressin can be used as an adjunct, but not alone in sepsis
When are vasopressors used in sepsis?
After failure of fluid resuscitation of 30cc/kg bolus given rapidly and MAP<65
What are the 3 most common ways of getting botulism and what are the presenting symptoms?
Infant: most common, from honey or corn syrup
Food ingestion: poorly preserved foods, canned foods
Wound: contamination, iatrogenic from ingections
Symptoms: symmetric descending paralysis, cranial nerve defecits causing diplopia, dilated and non-reactive pupils, ptosis, dysphonia, dysphagia, dysarthria, poor gag reflex, decreased muscle strength and DTR’s but intact sensation, respiratory failure, parasympathetic blockade
What is the treatment for botulism?
Infants<1yr give human derived immune globulin
>1yr give equine derived immune globulin
How might botulism and an ischemic stroke be differentiated?
Stroke causes assymetrical weakness and sensation loss
Botulism is symmetrical and causes non-reactive pupils
What is one big difference between the symptoms of botulism vs myasthenia gravis?
Botulism causes non-reactive pupils whereas pupils are normal in MG
What is the most common cause of infectious food-bourne illness?
Viruses, with Norovirus causing more than 50%
Foodbourne illness is usually from fecally contaminated foods…, but viral enteritis can also come from person-person contact and aerosolization
What are the symptoms of viral enteritis?
diarrhea, nausea, vomiting, loss of taste
Viral courses are more mild than bacterial enteritis
What is the most common extra-pulminary presentation of tuberculosis?
Scrofula (painless lymphadenitis)
Cervical is most common
What are these tender nodules and the most common causes?
Erythema Nodosum
Thought to be a delayed hypersensitivity reaction causing inflammatory and painful nodules of the subcutaneous fat
Most common cause is strep throat, but also caused by tuberculosis, mycoplasma pneumo, histoplasma capsulatum, EBV, cat scratch, valley fever, autoimmune disorders such as sarcoidosis, and many others
When is a PPD test positive for TB?
15mm induration for those with no increased risk of disease
10mm for homeless, healthcare workers, IVDU, foreign-born
5mm for immune compromised, recent TB contact, steroid use, positive CXR
What is the name for the lesions seen in the lungs in TB?
Ghon focus
It is a calcified lesion if a cavitary lesion has not healed
How is TB diagnosed?
Primary or latent: PPD
Active/reactivated: Sputum looking for acid-fast bacilli
What is the treatment for TB?
Latent TB: INH for 6 or 9 months, rifampin for 4 months, or INH/rifapentine for 3 months
Active/reactivation TB: rifampin, INH, pyrazinamide, ethambutol (RIPE)
What are the most common encapsulated bacteria?
mnemonic: SHiNE SKiS
Strep. pneumo
H. flu B
Neisseria meningitidis
E.coli
Salmonella
Klebsiella pneumo
Strep (group B)
Kids with sickle cell disease are most likely to be bactermic from what organism?
Strep. pneumo
Young patient with sickle cell disease presents with a fever. What should you do?
Any patient with sickle cell disease that presents with a fever should be assumed to be bacteremic and septic and treated very aggressively as they are 100’s of time more susceptible to bacteremia.
Obtain blood and urine cultures immediately and start empiric antibiotics until cultures are negative.
What is the treatment for uncomplicated chlamydia infection?
Azithromycin
What is the treatment for gonoccocal infection?
Ceftriaxone 250mg IM
What is the treatment for syphilis?
Primary and secondary: single dose of pen g
Tertiary: IM pen g once weekly for 3 weeks
Describe the VZV virus and herpes zoster and the diseases they cause and why the virus is named the way it is.
Varicella = chicken pox
Zoster = shingles
Single herpes virus causes both conditions and it is called the Varicella-Zoster Virus (VZV)
Herpes Zoster is the disease known as shingles that this virus causes
How are acyclovir and valacyclovir related?
valacyclovir is a prodrug form and is converted into acyclovir in the body and apparently is more potent.
How toxic is acyclovir/valacyclovir?
Apparently virtually non-toxic to normal cells with little to no adverse effects
IV administration has more side-effects of nausea, diarrhea and headache
Can acyclovir and valacyclovir be used in pregnancy?
Yes
What diseases are acyclovir and valacyclovir most effective against?
Herpes infections
Less effective for zoster but still some activity
What is the drug of choice for treating CMV infection?
IV therapy with ganciclovir
Oral therapy with valganciclovir
These drugs have more toxic side-effects than acyclovir but are much more effective in this case.
What disease is this and what are the primary features of the rash?
Herpes
Grouped vesicles on an erythematous base
What disease is this and what is the causative agent and treatment?
Impetigo
Staph aureus and sometimes Strep A
Isolated lesions treated with topical mupirocin
Keflex if MRSA not suspected
If MRSA: bactrim, doxy or clinda
What disease and causative agent?
Hand-foot-mouth disease
Caused by coxackie virus
Which agents are active against MRSA?
Mupirocin (topical and uncomplicated)
Doxycycline, Vancomycin, Bactrim, Daptomycin, Linezolid
Clindamycin has some activity
Patient returns from travel to south america with mild fever, red maculopapular rash on trunk and face that is pruritic, joint pain in hands and feet, and conjunctival injection. What viral infection may she have? What are the complications of this disease?
Zika
Notable symptoms are: mild fever, pruritic rash, small joint pain, conjunctival involvement
Complications: microcephaly, pregnancy loss, Guillain-Barre syndrome
Pt returns from south america with a cyclical fever, anemia, nausea, and muscle aches. What is a likely illness?
Malaria
Pt returns from south america with high fever, severe myalgias, and a headache. What is a likely cause?
Dengue fever
Known for high fever and severe myalgias
Zika is different for more mild symptoms and conjunctival involvement
What are the common features of Yellow Fever and where in the world is it endemic?
Hepatic and renal failure with coagulopathy
South america and sub-saharan Africa
18 month old child, had high fever near 104, fussy, but otherwise doing well, fever breaks and macular rash appears that blanches and is non-pruritis or painful. What is the likely cause?
Roseola Infantum
Common disease of children less than 2 years.
High fevers that can lead to seizures. Fever then rash after fever breaks. Kids usually appear well. Disease is self-limiting requiring support only with tylenol.
Caused by HHV 6
What are the classic features of scarlet fever and what is the treatment?
Pharyngitis, macular rash that is sandpaper like, and a fever.
Treated with penicillin
What are the defining criteria of SIRS?
2 of the following:
Heart rate >90
Temperature >38C or less than 36C
Respiratory rate >20 or pCO2<32
WBC >12,000 or <4,000
What is the definition of sepsis?
Severe sepsis?
Septic shock?
Sepsis = SIRS + source
Severe = sepsis + organ dysfunction, lactic acidosis, hypotension (SBP<90)
Shock = severe + unresponsive to fluids
What is the regimen for post-rabies exposure prophylaxis?
Rabies Ig injected at the wound lite + the vaccine on days 0, 3, 7, 14
If previously vaccinated, give just the vaccine on days 0, 3
Describe tetanus prophylaxis
Clean wounds: Tdap if never vaccinated or more than 10 yeara ago
Dirty wound: Tdap if vaccine >5yr; Tdap + Ig if never immunized
What are the “atypical” bugs that require special agents for coverage and which agents are used?
Mycoplasma pneumoniae, Legionella, rickettsia
Doxycycline, Azithromycin, Cipro and Levofloxacin
What is the treatment for newborn chlamydia conjunctivitis?
Oral erythromycin (topical does not work)
What is a side effect of giving erythromycin to infants <2weeks old?
Hypertrophic pyloric stenosis
What is the treatment for mucormycosis and the causative agent?
Rhizopus-oryzae fungal infection
Amphotericin B is the only treatment
Hyphae get into vasclature causing necrosis
Elevated serum levels of what substance promote fungal growth in serum and tissues and increases the risk of mucormycosis?
Iron
What diseases can cause non-tender lymphadenitis like this in children?
Nontuberculous mycobatcterium
Cat scratch disease
Brucellosis
Mononucleosis
Toxoplasmosis
Tularemia
Lymphoma
What are the different stages of Lyme Disease?
Early Localized: 7–14 days after infection, local erythema migrans, non-specific symptoms of fever, fatigue, anorexia, headache, myalgias, neck stiffness
Early Disseminated: multiple sites of erythema migrans, delayed neurologic and cardic sequelae including peripheral neuropathies, cranial nerve palsies, bilateral Bell’s palsy, heart block and myopericarditis
Late Lyme: large joint arthritis and mild encephalopathy
What are the treatments for early Lyme disease for all populations?
Doxycycline is the drug of choice for 10–21 days
Amoxicillin is used for kids under 8 and pregnant women due to teeth side effects
What are the most common side effects of doxycycline treatment for Lyme?
Teeth discoloration for kids under 8 and pregnant women
Photosensitivity, prevented with sunscreen
What is a common reaction that happens in the first 24 hours when treating spirochete infections?
Jarisch-Herxheimer reaction
As spirochetes die they release their inner contents and the patient feels worse at first with fever and other symptoms
Patient has been traveling to countries along the equator and complains of cough, intermittent fevers, nausea, lethargy, and chills. What is the likely diagnosis?
Malaria
Suspect anytime there is a travel history and irregular fevers
How is malaria diagnosed?
Thick and thin blood smears
What is the cause of malaria? What are the types and which is the most severe?
Parasite infection transmitted most commonly by mosquito
Plasmodium falciparum (most severe)
P. vivax
P. ovale
P. malariae
What are common complaints with malaria? What severe symptoms are possible with P. falciparum?
intermittent fevers, upper respiratory symptoms, anemia, lethargy, nausea, abdominal pain, headache (fevers are every other day, or every third day)
P. falciparum can cause severe organ failure and death, encephalopathy, hypoglycemia, metabolic acidosis, severe anemia, renal failure, pulmonary edema, disseminated intravascular coagulation
What are the treatments for malaria?
Uncomplicated and in areas that are not resistant: chloroquine
Complicated or in areas of resistance: doxycycline + quinidine
Bilateral facial nerve palsy is virtually pathognomonic for…?
Lyme disease
How is the facial paralysis of Bell’s palsy differentiated from a central cause of paralysis?
Forehead muscles are involved with bell’s palsy (peripheral cause) and spared in a stroke
This is because the forehead has bilateral innervation from both sides of the brain so only a peripheral lesion can disrupt fibers from both sides of the brain
What are the signs/symptoms, source, treatment of hantavirus infection?
Hantavirus comes from rodents—feces, urine, saliva that is aerosolized and inhaled
Causes a prodromal viral illness followed by a cardiopulmonary phase with bilateral pleural edema that progresses rapidly with hypoxia
Hemorrhagic fever with renal syndrome, oliguria and diuresis
Treat with supportive care including mechanical ventilation, ICU care, and possibly ECMO
What is the treatment for the different stages of syphilis?
Primary and secondary: one dose of IM PenG
Tertiary: IM penG once a week for 3 weeks
What is the most common finding for septic arthritis?
Pain with joint motion
What is the most common bacteria in septic arthritis and how does the bacteria get in the joint?
Staph aureus
Hematogenous spread
How is syphilis treated in pregnant patients who are allergic to penicillin?
Penicillin is the only treatment, so patients have to be admitted for desensitization prior to treatment
What is the pattern of paralysis progression in botulism? What effects does botulism have on the GI and GU tracts?
Descending paralysis starting with the cranial nerves
Causes ileus and urinary retention (parasympathetic blockade from prevention of Ach release)
What CXR findings are highly suggestive of TB?
Upper lobe cavitary lesions with hilar or mediastinal lymphadenopathy
Hilar adenopathy is the most common CXR finding
The most common symptom is fever
How is TB diagnosed?
Latent/primary: PPD
Active/reactivation: sputum smears or culture
Which causes of food-bourne illness are more likely to cause watery diarrhea?
Vibrio, shiga-toxin producing E. coli, shigella, Staph aureus, B cereus, C. perfringens, viral
What bugs cause hemorrhagic diarrhea?
salmonella, campylobacter, enteroinvasive E. coli
What bug is associated with traumatic myonecrosis, or gas gangrene?
Clostridium perfringens
Clostridium septicum causes spontaneus clostridial myonecrosis
What is the treatment for campylobacter and salmonella enterocolitis?
Treatment is supportive, even with bloody diarrhea.
Treatment for salmonella with antibiotics may be considered in immunecompromised, and those over 50 or under 3 months or in severe disease
Which cause of food-bourne illness causes a pseudoappendicitis?
Campylobacter
What is a potential late complication of campylobacter enteritis?
reactive arthritis
Guillain barre
What CBC lab finding is associated with Coccidioides immitis?
Eosinophilia
Describe the spectrum of activity of fluoroquinolones
In general, known for activity against gram negative enterobacteriacieae with Cipro as the first. Also great against Haemophilus and M. catarrhalis making it good for respiratory infections.
Levo and Moxi have increased effect on gram positives including S. pneumo
Moxi covers anaerobes somewhat
Only Cipro covers pseudomonas
What is the primary use of macrolides and what antibiotics are in this class?
Erythromycin, Azithromycin, Clarithromycin
Azithro and Clarithro used commonly for respiratory infections
What is the spectrum of activity of Azithromycin and CLarithromycin? How does this differ from erythromycin?
Used best for upper respiratory infections
Activity against: S. pneumo, M. catarrhalis, Haemophilus
And also against atypicals: Chlamydia, Mycoplasma, Legionella
Also usually active against strep and staph aureus
Erythro does not cover H. flu and the newer agents have enhanced gram negative activity
Why is azithro chosen over clarithro or erythromycin for treating respiratory infections?
Azithromycin has the best activity against H. influenzae
