Infectious Diseases Flashcards
Microorganisms responsible for most cases of prolonged, profuse, watery diarrhea
- Cryptosporidium parvum
- Cyclospora
- Giardia
Clinical hallmark of necrotizing fasciitis
Rapidly progressive erythema with pain and tenderness significantly out of proportion of physical findings
Most important and definitive treatment of necrotizing fasciitis
Surgical debridement
Risk factors to develop shingles
- Advancing age
- Immunosuppression
- Trauma to the skin
How do you confirm gonococcal proctitis?
Nucleic acid amplification testing of rectal swab
What is Ludwig angina? Clinical presentation.
- Rapidly progressive cellulitis of the submandibular space→most cases arise from dental infections
- Rapidly systemic symptoms→fever, chills, malaise
- Local compressive→mouth pain, drooling, dysphagia, muffled voice, airway compromise
Findings in the physical examination of Ludwig angina
Mass effect from edema; tender, indurated submandibular area; elevated floor of the mouth; tongue displaced; crepitus
Major risks factors for Clostridium difficile infection
- Recent antibiotic use (fluoroquinolones, clindamycin, cephalosporins, penicillins)
- Advanced age (>65 years)
- Gastric acid suppression (Ex, PPI)
Gold standard for diagnosis Herpes encephalitis
PCR of HSV DNA in CSF
*Highly sensitive and specific. Replacing brain biopsy.
Most appropriate next step when suspect clinically amebic liver abscess
EIA test - antibodies for Entamoeba histolytica
*The role of microscopic stool examination is limited. Less than 30-40% of patients with amebic liver abscess have concomitant intestinal amebiasis, and 10% of the population is infected with the nonpathogenic strain of E. dispar
Most likely causal organism of a macular rash involving abdomen, chest, back, extremities and soles without fever and pruritus
Treponema pallidum
Most important clues to recognize a Valley Fever. Which is the etiology?
- Valley Fever
1. Desert Southwest (Ex, Arizona or California)
2. Symptoms onset 7-14 days after inoculation, subclinical, >50% Community acquired pneumonia (fever, chest pain, dry or productive cough, lobar infiltrate)
3. Often accompanied: arthralgias, erythema nodosum or erythema multiforme - Coccidioides immitis
Causal agent and treatment of Bacillary angiomatosis
- Bartonella
- Oral Erythromycin
Most common cause of endocarditis in a patient with associated nosocomial urinary tract infection
Enterocci species, Ex Enterococcus faecalis
*Recent instrumentation can yield the bacteremia
Which germs that cause endocarditis or bacteremia are associated with colon pathology? What test you should perform?
- Clostridium septicum>Streptococcus bovis
- Perform colonoscopy➡rule out colon cancer
*Tumor cells undergo anaerobic glycolysis➡adequate environment for C. septicum spores germination; damage colonic mucosa➡bacteria transcolation into bloodstream
How do you treat endocarditis secondary to staphylococcus aureus on a protestic valve?
Oxacilin, Nafcilin or Cefazolin + Rifampin for 6 weeks
Strongest indication of surgery in acute endocarditis
Acute valve rupture and congestive heart failure
Most common bacteria causing endocarditis when culture is negative
- Coxiella
- Bartonella
Pathognomonic sign of syphilis
Epitrochlear lymphadenopathy→2-handed “sailor’s handshake”
When do you consider an adequate or successful treatment of syphilis?
4-fold decrease in serologic titers at 6-12 months
What is the endemic typhus? Clinical presentation.
Louse-borne rickettsial infection→abrupt onset of fever, severe headache, malaise and centrifugally-spreading macular or maculopapular rash (sparing palms and soles)
How is the rash of the Rocky mountain spotted fever?
Maculopapular rash that spreads centripetally toward the trunk. Includes palms and soles. Petechial over time.
Treatment of tertiary syphilis
Intravenous Penicillin for 10-14 days
*Desensitize if penicillin allergy
What must you do with a pregnant woman with syphilis or a patient with neurosyphilis to treat them?
Penicillin desensitization
Diagnosis of Hepatitis C Virus chronic infection
- Hepatitis C virus antibody→Positive serology
- HCV PCR→confirmatory molecular test (Do this because HCV may clear in up to half of patients)
Systemic manifestations of Blastomycosis
- Skin compromise➡multiple, well-circumscribed, verrucous, crusted, ulcerated lesions
- Lytic bone lesions
*In addition of chronic pulmonary symptoms: productive cough, low grade fever, night sweats, weight loss
Treatment of choice for pulmonary and disseminated nocardiosis
Trimethoprim-sulfamethoxazole (generally by 6-12 mo)
*Carbapenems may be added when brain is involved (brain abscess)
How do you distinguish Nocardia from Mycobacterium tuberculosis?
Nocardia➡Gram-positive, partially acid-fast rods
*Mycobacterium tuberculosis➡acid-fast rods, do not Gram stain
Treatment for necrotizing (malignant) otitis externa
- Intravenous antipseudomonal antibiotic (Ciprofloxacin)
- ±Surgical debridement
Most common organism causing deep infections following puncture wound (through the sole of a shoe)
Staphylococcus aureus and Pseudomonas aeruginosa
*Risk of osteomyelitis
Treatment for HIV cachexia
Synthetic cannabinoids (dronabinol)
Antibiotic indicated for patients undergoing splenectomy and develop fever
Amoxicillin-clavulanate
*Levofloxacin (for penicillin allergy)
Triad frequently found in Trichinellosis
- Eosinophilia
- Myositis
- Periorbital edema
Clinical presentation of HSV retinitis in an HIV positive patient
- Acute retinal necrosis syndrome➡starts keratitis and conjunctivitis with eye pain; followed by rapidly progressive visual loss
- Fundoscopy➡widespread, pale, peripheral lesions and central necrosis of the retina.
*Might be caused by VZV as well.
Clinical presentation of CMV retinitis in HIV positive patient
- Painless
- Fundoscopy➡fluffy or granular retinal lesions near retinal vessels and associated hemorrhages
Cephalosporin that can cover MRSA
Ceftalorine (fifth generation)
Which cephalosporins can cover anaerobes? Side effects of them
- Cefotixin and Cefotetan (Second generation)
- ⬇Prothrombin➡⬆Risk of bleeding; disulfiram-like effect with alcohol
What is the difference between ertapenem and the other carbapenems?
Ertapenem does not cover Pseudomonas
*All carbapenems cover gram-negative bacilli
How do you use the fluoroquinolones to treat diverticulitis and GI infections?
- Ciprofloxacin, gemifloxacin, levofloxacin must be combined + metronidazole; they do not cover anaerobes
- Moxifloxacin (exception) can be used alone; cover anaerobes
Classic side effects of quinolones
- Bone growth abnormalities in children and pregnant women
- Tendonitis and Achilles tendon rupture
When do you order bacterial antigen detection (Latex Agglutination Tests) in suspected bacterial meningitis?
Patient has received antibiotics prior to lumbar puncture➡culture may be falsely negative
*Delay in LP may happen when head CT is indicated before (Ex, confused patients)
Important feature of the CSF in a tuberculous meningitis
Highest protein level
When do you suspect Listeria as the etiology of meningitis? How do you treat it?
- Risk factors for Listeria:
- Elderly
- Neonates
- Steroid use
- AIDS or HIV
- Immunocompromised, include alcoholism
- Pregnant
- Add Ampicillin to the Tx➡Listeria is resistant to all cephalosporins
Most common neurological deficit from untreated bacterial meningitis
Eighth cranial nerve deficit or deafness
Most accurate test for herpes encephalitis
PCR on CSF
Antibiotics that cover anaerobes in oral and GI infections
- Oral: Penicillin (G, VK, ampicillin, amoxicillin), Clindamycin
- Abdominal/GI: Metronidazole, beta-lactam/lactamase inhibitor, carbapenems, 2nd gen cephalosporins
Treatment for ESBL-producing organisms resistant to carbapenems
- Ceftolozane/tazobactam
- Ceftazidime/avibactam
- Polymyxin (Risk for acute renal injury)
Treatment for encephalitis by aciclovir resistant herpes
Foscarnet
During acute hepatitis which test correlates the best with higher mortality?
⬆Prothrombin time➡⬆risk of fulminant hepatic failure and death
What is directly correlated with the amount or quantity of active hepatitis B virus replication?
Hepatitis B e-antigen➡present only when there is ⬆DNA polymerase activity
*e-antigen↔PCR DNA (viral load, is more precise)
Which indicates that active infection of hepatitis B has resolved?
No AgHBs found
Which is the best indication of treatment for chronic hepatitis B?
- e-antigen or DNA polymerase (PCR DNA hepatitis B)➡strongest indicator of acute viral replication➡Degree of infectivity
- e-antigen (qualitative)↔PCR DNA (quantitative, viral load, is more precise)
Best test to determine response to therapy or failure in therapy for chronic hepatitis B or hepatitis C
PCR DNA hepatitis B and PCR RNA hepatitis C
Most common method of transmission of hepatitis B
Perinatal transmission
- e-antigen ➕➡90% children infected at birth
- e-antigen ➖➡10% children infected
Best treatment for Hepatitis C genotype 1, and for any genotype
- Ledipasvir + Sofosbuvir for genotype 1
- Velpatasvir for all genotypes
Goals of chronic hepatitis treatment
- ⬇DNA polymerase to undetectable levels
- Convert patients from e-antigen to antibody e-antigen
Indications to treat hepatitis C
- ⬆PCR-RNA viral load
- Fibrosis on biopsy (even for hepatitis B)
Sensitive and specific tests for syphilis study on CSF
- FTA-ABS nearly 100% sensitive in CSF
- VDRL and PCR specific
Which test may be useful to diagnose both chlamydia and Neisseria gonorrhoeae?
Nucleic acid amplification test (NAAT)
*Gram stain only detects gonorrhea, with chlamydia infection only see PMNs
What is late secondary syphilis or latent infection?
- Asymptomatic stage with ➕ serology
- After chancre and rash of primary and secondary syphilis have resolved
*End or beyond the first year of infection
Treatment of latent or late secondary syphilis
Benzathine Penicillin IM weekly for 3 weeks
Treatment of primary and secondary syphilis
- One dose IM Benzathine Penicillin
- Oral Doxycycline or Tetracycline for 14 days, for penicillin allergy
Treatment of HACEK group of organisms causing endocarditis
Ceftriaxone
Indications for prophylaxis for endocarditis
- Significant cardiac defect:
- Prosthetic valve
- Previous endocarditis
- Cardiac transplant recipient with valvulopathy
- Unrepaired cyanotic heart disease
- Risk of bacteremia:
- Dental work with blood
- Respiratory tract surgery that produces bacteremia
Best initial empiric therapy for endocarditis
Vancomycin + Gentamicin
Risk factors for endocarditis
- Prosthetic valve ⬆⬆Risk
- Regurgitant and stenotic lesions
- Dental procedures
- Surgery of mouth and respiratory tract + severe valvular disorder (prosthetic valve, cyanotic heart disease)
Most common joint, neurological and cardiac manifestations of untreated Lyme disease
- Joint➡Knee arthritis
- Neurological➡7th cranial nerve or Bell palsy (classically bilateral)
- Cardiac➡Transient AV block
Treatment for Lyme disease when rash, joint compromised or 7th cranial nerve palsy
- Doxycycline
- Amoxicillin or Cefuroxime
Treatment for Lyme disease when cardiac or neurologic manifestations other than 7th CN palsy
Intravenous Ceftriaxone
Prophylaxis indications for Lyme disease when tick bite and no symptoms
Single-dose of doxycycline within 72 hours of tick bite:
- Ixodes scapularis clearly identified
- Tick attachment >24 hours
- Engorged nymph-stage tick
- Endemic area
*Tick bite + no symptoms generally do not need prophylaxis; treat if rash shows up
What must you test before start abacavir in an HIV patient? and why?
HLA B5701 mutation➡⬆risk of life-threatening skin reactions (Steven-Johnson syndrome)
Most important adverse effects of Tenofovir
- Renal Tubular Acidosis (RTA)
- Bone demineralization
*Disoproxil version ⬆risk, alafenamide version is absorbed by CD4➡⬇plasma levels➡⬇adverse effects
Treatment for baby from an HIV positive mother
Zidovudine intrapartum (to the pregnant woman) and for 6 wks (to the baby)➡prevent transmission
Antiretroviral to be avoided during pregnancy
Efavirenz
Indication for Pre-exposure prophylaxis (PrEP) for HIV and what drugs do you give?
- High risk sexual and needle-stick practices with potentially HIV-infected contacts
- Emtricitabine-Tenofovir before exposure and one month after the last exposure
Best initial and definitive treatment for Mucormycosis
- Best initial: Amphotericin B
- Surgical emergency➡resect necrotic areas
*Follow up Tx➡Posaconazole or Isavuconazole
Treatment for invasive Aspergillosis
Voriconazole, Isavuconazole, Caspofungin
- DO NOT use Amphotericin B (is inferior)
Tests for invasive Aspergillosis
- Serum Galactomannan assay
- B-D-glucan level
- PCR
*2 of those ➕➡>95% specificity
Treatment for Plasmodium falciparum
Mefloquine or Atovaquone/proguanil
Treatment for Plasmodium non-falciparum
- Chloroquine
- Primaquine (vivax and ovale only)➡eradicate the hypnozoites in the liver
What you should rule out first before start Primaquine?
G6PD deficiency
Treatment for severe malaria
- Artemisinins (Artemether, Artesunate)
- IV Quinine➡⬇Efficacy, ⬆QT prolongation toxicity
Prophylaxis for malaria when traveling to endemic regions with chloroquine resistance
- Atovaquone-proguanil or mefloquine at least 2 weeks before travel and for 4 weeks after returning
- Doxycycline
*Avoid Mefloquine in seizure, psychiatric, and
cardiac conduction disorders
Treatment for Babesiosis
Azithromycin + Atovaquone
Which infectious diseases may show morulae in WBCs? What is the morulae in WBCs?
- Ehrlichiosis (Monocytic) and Anaplasmosis (Granulocytic)
- Obligate intracellular parasites➡form microcolonies in the cytoplasm of WBCs
Best clinical clues that may suggest Legionnaires’ diseases?
- Atypical community-acquired pneumonia
- CSN features➡confusion
- Gastrointestinal features➡abdominal pain, diarrhea, mild hepatitis
- Hotel and cruise ships
- Relative bradycardia (despite ⬆fever)
- Hyponatremia
Best initial test for Legionnaires’ disease?
Urine antigen testing
*Best overall➡Culture
Treatment for cryptococcal meningitis
IV Amphotericin B + Flucytosine for 2 wks, then fluconazole for 8 wks
Which vaccines are contraindicated in HIV patients?
Live vaccines (MMR, VZ) are contraindicated If CD4<200
*If CD4>200 there are no contraindications
Main side effects of Isoniazid, what you should do to avoid one of them?
- Drug-induced hepatitis
- Peripheral neuropathy➡Vitamin B6 (Pyridoxine) to prevent
Diagnosis of Allergic Bronchopulmonary Aspergillosis
- Previous history most commonly of Asthma or Cystic Fibrosis
- Pulmonary infiltrates on CXR, eosinophilia, ➕skin aspergillus antigen test, antibodies to aspergillus on blood, ⬆IgE levels
Life-threatening complication of untreated retropharyngeal abscess and treatment
- Acute necrotizing mediastinitis
- Urgent surgical drainage to prevent spread to the posterior mediastinum➡lethal pleural and pericardial effusions
Frequent history clues in orbital cellulitis that you should look for
- Ocular trauma or surgery
- Sinusitis
Best initial therapy for HIV
Two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) + one integrase inhibitor
Treatment for Histoplasmosis chronic cavitary lesions
Itraconazole for >1 year
Treatment for Histoplasmosis severe acute pulmonary disease or disseminated disease
Liposomal amphotericin B or amphotericin B for 14 days followed by itraconazole for 1 year or longer
How is the geographic distribution of the most common systemic fungal infections in the United States?
- Histoplasmosis➡ Ohio and Mississippi river valleys
- Coccidioidomycosis➡ southwestern
- Blastomycosis➡central and southeastern, particularly the Mississippi and Ohio river valleys
Clues on history and laboratory findings in disseminated infection of Mycobacterium Avium Complex
- AIDS patients with a CD4+ < 50/mm3
- Fever, weakness, and weight loss, night sweats, diarrhea
- Anemia, hypoalbuminemia, ↑alkaline phosphatase, ↑LDH
Treatment and prophylaxis for MAC disseminated infection
- Tx: Clarithromycin + ethambutol, and consider HAART if drug-naïve; Rifabutin is second line. Continue for > 12 months and until CD4+ is > 100/mm3 for > 6 months
- Prophy: Azithromycin for those with a CD4+ < 50/mm3 or AIDS-defining opportunistic infection
Which complications of infectious mononucleosis are indicated to treat with corticosteroids?
- Airway compromise caused by tonsillar enlargement
- Severe thrombocytopenia
- Severe autoimmune hemolytic anemia
Complications of Infective endocarditis
- Embolic strokes
- Metastatic infection (most common cause of splenic abscess)
- Heart failure (valvular insufficiency)
- Glomerulonephritis
Infective endocarditis most common microorganism based on valve status
- Prosthetic valve➡Streptococcus viridans➡mitral valve (mitral regurgitation)>aortic valve (non-IV drug users, dental procedures)
- Normal valve➡Staphylococcus aureus➡tricuspid valve>mitral valve>aortic valve (IV drug users)
Potential complications of infectious mononucleosis
- Splenic rupture
- Acute airway obstruction
- Autoimmune hemolytic anemia and thrombocytopenia
Treatment for foodborne botulism
Equine serum heptavalent botulinum antitoxin (horse derived antitoxin)
Management of recurrent cystitis clearly linked to intercourse
Postcoital antibiotics➡Nitrofurantoin, TMP-SMX
Common etiologies of aseptic meningitis
- Enterovirus➡maculopapular rash
- Herpes simplex virus
- HIV➡maculopapular rash, transient unexplained fever, generalized lymphadenopathy
Second most common cause of primary adrenal insufficiency worldwide
Tuberculous adrenalitis
Which evaluations should be done on patients with any sexually transmitted infections or who ask for screening for STI?
- Neisseria gonorrhoeae (NAAT)
- Chlamydia trachomatis (NAAT)
- HIV (antigen/antibody testing)
- Syphilis (RPR)
- Trichomonas vaginalis (wet mount or NAAT) in 👩
Most common etiology of bacterial conjunctivitis
Staphylococcus aureus
Best treatment for invasive or systemic burn wound infection
- Piperacilin/tazobactam or carbapenem➡Pseudomonas aeruginosa
- Vancomycin➡MRSA
*Systemic or invasive burn infection▶systemic manifestations (confusion, tachycardia)/microbial invasion into unburned tissue on biopsy
Enterobius vermicularis infection clinical presentation
- Pinworm=Oxiuros
- Perianal pruritus at night
- Mature pinworms spread to vagina➡vulvovaginitis
Treatment for pinworm (Enterobius vermicularis) infection
Pyrantel pamoate or Albendazole for patient and all household contacts
Cryptococcal meningitis treatment
- Induction: Liposomal amphotericin B + flucytosine for ≥2 weeks until acute symptoms resolve or CSF becomes sterile
- Consolidation: high-dose oral fluconazole for 8 weeks
- Maintenance: low-dose oral fluconazole indefinitely or until CD4>100/mm3 for >3 months on ART
Strongest indication for meningococcal vaccination
Asplenia➡highest risk of disseminated meningococcal infection
Signs and symptoms of tissue-invasive CMV disease
- Pulmonary➡dyspnea, dry cough, interstitial infiltrates on chest x-ray
- GI➡abdominal pain, diarrhea, hematochezia
- Mild hepatitis➡⬆AST, ALT, AP, Bilirubin
- Pancytopenia
*Pneumonitis+gastroenteritis+hepatitis
Treatment for tissue-invasive CVM disease
- Minimal signs and symptoms➡Oral Valganciclovir
- Severe disease➡IV Ganciclovir
Echocardiography finding of viral myocarditis
Dilated ventricular chambers and diffuse hypokinesis
Empiric treatment for health-associated pneumonia
- Antipseudomonal cephalosporin: Cefepime or ceftazidime
- Antipseudomonal penicillin: Piperacillin/tazobactam
- Carbapenems: Imipenem, meropenem, doripenem
*Macrolides are not acceptable as empiric therapy; Must cover gram-negative bacilli (E. coli or Pseudomonas)
What is severe pneumocystis pneumonia? What you should add to the treatment to decrease mortality?
- PCP with pO2<70 mmHg, A-a gradient>35
- Steroids
Treatment for pneumocystis pneumonia when there is TMP/SMX toxicity
- Clindamycin and primaquine (contraindicated on G6PD)
or - Pentamidine
Most common adverse effect of TMP/SMX
- Rash
2. Bone marrow suppression
Prophylaxis indication and medications for PCP
- AIDS whose CD4<200/μL
- TMP/SMX
- If TMP/SMX toxicity➡Atovaquone or Dapsone (contraindicated in G6PD)
When may you stop the PCP prophylaxis after initiated?
CD4 is maintained above 200/μL for several months (? 6 at least)
Treatment for a positive PPD or IGRA
Latent tuberculosis (Do first chest x-ray to rule out active TB):
- 9 months of Isoniazid (use pyridoxine (B6)
- combination of Isoniazid and Rifapentine for 12 weeks (given once a week)
Disease caused by Burkholderia pseudomallei
Melioidosis
- Facultative intracellular gram-negative bacilli
- Thailand, Malaysia, Singapur, North Australia
- Contaminated soil or water inoculated in subcutaneous tissue
Clinical presentation of Melioidosis
- Pneumonia: could be associated with shock. x-ray: bilateral opacities
- Skin ulcers/abscesses: 25% of cases, purple colored lesions
- Organ abscesses: kidney, prostate, spleen, liver
How do you suspect disseminated gonococcal infection?
*Triad:
- Polyarticular involvement (asymmetric, migratory arthralgias)
- Tenosynovitis
- Petechial rash (vesiculopustular)
OR
*Septic arthritis (purulent monoarthritis)
Associated adverse effects of fluoroquinolones, and in which patients you should avoid them?
- Upregulate cell-matrix metalloproteases➡⬆collagen degradation▶Achilles tendon rupture, retinal detachment, aortic aneurysm rupture
- Avoid in patients with aortic aneurysm or high risk for aortic aneurysm▶Marfan Sx, Ehlers-Danlos Sx, atherosclerotic disease, uncontrolled hypertension
Most likely diagnosis in an adult patient with hyperkalemia, hyponatremia, eosinophilia, hypotension, lightheadedness (adrenal insufficiency), fever, weight loss, from southeast Asia and pulmonary airspace disease with lymphadenopathy.
- Tuberculous adrenalitis due to miliary tuberculosis
- Paraneoplastic syndrome is wrong because they are associated with ectopic ACTH production➡hypercortisolism
*Antituberculous therapy rarely improves function, irreversible destruction
Most common etiology in a patient with a progressive lesion in the scalp (scaly patches with alopecia with lymphadenopathy) for 6 weeks, with no improvement after 7 days of antibiotics.
*Suspect Tinea capitis Dermatophytes: - Trichophyton tonsurans - Epidermophyton floccosum - Microsporum canis - Microsporum gypseum
General empiric antibiotic therapy for immunocompromised patients with bacterial meningitis
Cefepime (Ceftazidime or Meropenem) + Vancomycin + Ampicillin
- Cefepime: Streptococcus, Neisseria, GBS, H. influenzae, Pseudmona
- Vancomycin: cephalosporin-resistant pneumococci
- Ampicillin: Listeria monocytogenes
Prophylaxis for chronic granulomatous disease
TMP-SMX, itraconazole, interferon gamma
Most common microorganisms to cause brain abscess in a immunocompetent patient
- Streptococcus viridans
- Staphylococcus aureus
- Direct spread (eg, otitis media, mastoiditis, sinusitis)
- Hematogenous spread (eg, endocarditis)
