Internal Medicine EOR: Infectious Disease (Smarty PANCE)

What is botulism?

Paralytic illness caused by Clostridium botulinum toxin - blocks acetylcholine release at neuromuscular junction causing flaccid paralysis

What are the three main types of botulism?

Foodborne (preformed toxin in contaminated food), infant (spore ingestion), wound (spore contamination of wounds)

What foods are commonly associated with foodborne botulism?

Home-canned foods, smoked/fermented fish, honey (in infants), improperly preserved foods

What is the classic triad of botulism symptoms?

Descending flaccid paralysis, bulbar symptoms (diplopia, dysarthria, dysphagia), absence of fever

What are the characteristic "4 D's" of botulism?

Diplopia, Dysarthria, Dysphagia, Descending paralysis

How is botulism diagnosed?

Clinical diagnosis confirmed by mouse bioassay or detection of toxin in serum/stool/food, EMG shows decreased CMAP amplitude

What is the treatment for botulism?

Botulism antitoxin (equine heptavalent for adults, BabyBIG for infants), supportive care with mechanical ventilation if needed

What is the timeframe for botulism antitoxin effectiveness?

Most effective within 24 hours of symptom onset - does not reverse existing paralysis but halts progression

What is candidiasis?

Fungal infection caused by Candida species (most commonly C. albicans) - can be superficial or invasive/systemic

What are the major risk factors for invasive candidiasis?

Immunosuppression, broad-spectrum antibiotics, central venous catheters, TPN, chemotherapy, prolonged ICU stay

What is oropharyngeal candidiasis (thrush)?

White plaques on oral mucosa/tongue that scrape off leaving erythematous base - common in HIV, inhaled steroids, antibiotics

What are the first-line treatments for oropharyngeal candidiasis?

Clotrimazole troches or nystatin suspension for mild cases; fluconazole 100-200mg daily for moderate-severe

What is esophageal candidiasis and its presentation?

Candida infection of esophagus causing odynophagia, dysphagia, retrosternal pain - AIDS-defining illness if CD4 <100

How is esophageal candidiasis diagnosed and treated?

Diagnosis: endoscopy with biopsy; Treatment: fluconazole 200-400mg daily x 14-21 days (first-line)

What is vulvovaginal candidiasis presentation?

Thick white "cottage cheese" discharge, vulvar pruritus, erythema, dyspareunia - NOT sexually transmitted

What is the treatment for uncomplicated vulvovaginal candidiasis?

Topical azoles (miconazole, clotrimazole) x 1-7 days OR single-dose fluconazole 150mg PO

What defines candidemia and its treatment?

Candida species in blood cultures - treat with echinocandin (micafungin, caspofungin) or fluconazole, remove central lines

What is Chlamydia trachomatis?

Obligate intracellular bacteria causing most common bacterial STI in US - often asymptomatic (70% women, 50% men)

What are the clinical manifestations of chlamydia in women?

Often asymptomatic, mucopurulent cervicitis, urethritis, PID (pelvic inflammatory disease), dysuria, intermenstrual bleeding

What are the clinical manifestations of chlamydia in men?

Urethritis (dysuria, urethral discharge), epididymitis, proctitis, reactive arthritis

What is the gold standard diagnostic test for chlamydia?

Nucleic acid amplification test (NAAT) - can use urine, urethral, cervical, or rectal swabs

What is the first-line treatment for uncomplicated chlamydia?

Doxycycline 100mg PO BID x 7 days (preferred) OR Azithromycin 1g PO single dose

What is lymphogranuloma venereum (LGV)?

Chlamydia trachomatis serovars L1-L3 causing painless genital ulcer → painful inguinal lymphadenopathy → proctocolitis

What are the complications of untreated chlamydia in women?

Pelvic inflammatory disease (PID), ectopic pregnancy, tubal infertility, chronic pelvic pain, Fitz-Hugh-Curtis syndrome

What is Fitz-Hugh-Curtis syndrome?

Perihepatitis associated with PID (chlamydia or gonorrhea) causing right upper quadrant pain - "violin string" adhesions

What is cholera?

Severe diarrheal illness caused by Vibrio cholerae toxin - transmitted via contaminated water/food in endemic areas

What is the characteristic presentation of cholera?

Profuse watery diarrhea ("rice-water stools"), vomiting, rapid dehydration, hypovolemic shock, no fever

What is the mechanism of cholera toxin?

Increases cAMP in intestinal epithelial cells causing massive secretion of water and electrolytes into intestinal lumen

How much fluid can be lost in severe cholera?

Up to 1 liter per hour - can lead to severe dehydration and death within hours if untreated

What is the cornerstone of cholera treatment?

Aggressive fluid repletion - oral rehydration solution (ORS) for mild-moderate, IV fluids for severe cases

What antibiotics shorten cholera duration?

Doxycycline 300mg single dose OR Azithromycin 1g single dose - reduces duration and transmission

What electrolyte abnormalities are common in cholera?

Hypokalemia, metabolic acidosis, hyponatremia from massive fluid and electrolyte losses

What is Cryptococcus neoformans?

Encapsulated yeast causing opportunistic infection - most common fungal CNS infection in AIDS patients

What are the major risk factors for cryptococcal infection?

Advanced HIV/AIDS (CD4 <100), organ transplantation, chronic corticosteroid use, sarcoidosis, cirrhosis

What is the most common presentation of cryptococcosis?

Cryptococcal meningoencephalitis - subacute headache, fever, altered mental status, minimal meningeal signs

How is cryptococcal meningitis diagnosed?

CSF analysis: high opening pressure, lymphocytic pleocytosis, low glucose; Cryptococcal antigen (CrAg) positive; India ink stain

What is the induction therapy for cryptococcal meningitis?

Amphotericin B + flucytosine x 2 weeks (induction phase)

What is the consolidation and maintenance therapy?

Consolidation: fluconazole 400mg daily x 8 weeks; Maintenance: fluconazole 200mg daily x 1 year minimum

Why is serial lumbar puncture important in cryptococcal meningitis?

Elevated CSF opening pressure common - therapeutic LPs reduce intracranial pressure and improve outcomes

What is cryptococcal antigen (CrAg) screening?

Screen all HIV patients with CD4 <100 - if positive, treat preemptively even if asymptomatic to prevent meningitis

What is cytomegalovirus (CMV)?

Herpesvirus (HHV-5) causing latent infection - reactivates with immunosuppression, especially in transplant and AIDS patients

What are the major risk groups for CMV disease?

HIV/AIDS (CD4 <50), solid organ/bone marrow transplant recipients, congenital infection in neonates

What is CMV retinitis presentation?

Floaters, visual field defects, blurred vision - "pizza pie" or "cottage cheese and ketchup" fundoscopic appearance

What is CMV colitis presentation?

Diarrhea (often bloody), abdominal pain, fever, weight loss - seen in transplant recipients and AIDS patients

How is CMV infection diagnosed?

PCR for CMV DNA (quantitative viral load), tissue biopsy showing "owl's eye" inclusion bodies, pp65 antigenemia

What is the first-line treatment for CMV retinitis?

Ganciclovir 5mg/kg IV BID OR valganciclovir 900mg PO BID x 14-21 days (induction), then maintenance therapy

What is congenital CMV and its manifestations?

Most common congenital infection - causes sensorineural hearing loss, microcephaly, intellectual disability, hepatosplenomegaly

What prophylaxis prevents CMV in high-risk transplant patients?

Valganciclovir 900mg daily x 3-6 months post-transplant (donor positive/recipient negative highest risk)

What is diphtheria?

Acute infection caused by toxin-producing Corynebacterium diphtheriae - rare in US due to vaccination

What is the characteristic finding in diphtheria?

Adherent gray pseudomembrane on tonsils/pharynx/nose that bleeds when removal attempted

What are the major complications of diphtheria?

Myocarditis (most common cause of death), neurologic complications (cranial nerve palsies, polyneuropathy), airway obstruction

What is the mechanism of diphtheria toxin?

Inhibits protein synthesis by inactivating elongation factor-2 (EF-2) causing cell death

How is diphtheria diagnosed?

Clinical diagnosis + culture on Loeffler or tellurite media, PCR for toxin gene

What is the treatment for diphtheria?

Diphtheria antitoxin (equine-derived) PLUS antibiotics (penicillin or erythromycin) - antitoxin only neutralizes unbound toxin

What is the "bull neck" appearance?

Massive cervical lymphadenopathy and soft tissue edema seen in severe diphtheria

What vaccination prevents diphtheria?

DTaP (children), Tdap (adolescents/adults) - toxoid vaccine provides immunity, boosters every 10 years

What is Epstein-Barr virus (EBV)?

Herpesvirus (HHV-4) causing infectious mononucleosis - transmitted via saliva ("kissing disease")

What is the classic triad of infectious mononucleosis?

Fever, pharyngitis (with tonsillar exudates), lymphadenopathy (especially posterior cervical)

What are the characteristic laboratory findings in EBV/mono?

Lymphocytosis with >10% atypical lymphocytes, positive heterophile antibody (Monospot test), elevated transaminases

What is the timeframe for heterophile antibody positivity?

Positive in 85-90% of cases by week 2-3 of illness - may be negative early, repeat if high suspicion

What physical exam findings suggest infectious mononucleosis?

Splenomegaly (50%), pharyngeal exudates, palatine petechiae, posterior cervical lymphadenopathy

What rash occurs with amoxicillin use in EBV infection?

Diffuse maculopapular rash in 90-100% of patients - NOT true penicillin allergy, avoid amoxicillin/ampicillin

What are the major complications of EBV?

Splenic rupture (avoid contact sports x 4 weeks), airway obstruction, hemolytic anemia, neurologic complications

What is the treatment for infectious mononucleosis?

Supportive care only - rest, hydration, NSAIDs/acetaminophen; corticosteroids only for severe complications (airway obstruction)

What malignancies are associated with EBV?

Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma, post-transplant lymphoproliferative disorder

What is Neisseria gonorrhoeae?

Gram-negative diplococcus causing gonorrhea - second most common bacterial STI in US (after chlamydia)

What are the clinical manifestations of gonorrhea in men?

Urethritis with purulent discharge, dysuria (symptomatic in 90%), epididymitis, proctitis, pharyngitis

What are the clinical manifestations of gonorrhea in women?

Often asymptomatic (50%), mucopurulent cervicitis, urethritis, PID, Bartholin gland abscess

What is the diagnostic test for gonorrhea?

Nucleic acid amplification test (NAAT) - high sensitivity/specificity, can use urine or swabs (urethral, cervical, rectal, pharyngeal)

What is the current treatment for uncomplicated gonorrhea?

Ceftriaxone 500mg IM single dose (1g if >150kg) - treat presumptively for chlamydia with doxycycline

What is disseminated gonococcal infection (DGI)?

Bacteremic spread causing triad of tenosynovitis, dermatitis (pustular lesions), and migratory polyarthralgia

What is gonococcal ophthalmia neonatorum?

Purulent conjunctivitis in newborns from infected birth canal - prevented with erythromycin eye ointment at birth

What is Fitz-Hugh-Curtis syndrome in gonorrhea?

Perihepatitis from ascending infection causing right upper quadrant pain - "violin string" adhesions between liver and peritoneum

Why is dual therapy important in gonorrhea treatment?

High rates of chlamydia co-infection (40-50%) and emerging antibiotic resistance in gonorrhea

What are HSV-1 vs HSV-2?

HSV-1: primarily orolabial herpes; HSV-2: primarily genital herpes (though either can cause either)

What is the presentation of primary genital herpes?

Multiple painful vesicles/ulcers on genitals, tender inguinal lymphadenopathy, systemic symptoms (fever, myalgia), dysuria

What is the presentation of recurrent genital herpes?

Milder than primary - localized painful vesicles, prodrome (tingling/burning), shorter duration, no systemic symptoms

How is genital herpes diagnosed?

PCR or viral culture from vesicle fluid (best), HSV-specific IgG serology (type-specific), Tzanck smear (multinucleated giant cells)

What is the treatment for primary genital herpes?

Acyclovir 400mg PO TID, valacyclovir 1g PO BID, or famciclovir 250mg PO TID x 7-10 days

What is suppressive therapy for recurrent genital herpes?

Daily antiviral therapy reduces recurrences by 70-80% and transmission risk - valacyclovir 500mg daily or acyclovir 400mg BID

What is HSV encephalitis?

Most common cause of sporadic viral encephalitis - temporal lobe involvement, altered mental status, seizures, fever

How is HSV encephalitis diagnosed and treated?

MRI shows temporal lobe abnormalities, CSF PCR for HSV; Treatment: acyclovir 10mg/kg IV q8h x 14-21 days

What is neonatal herpes and its prevention?

Severe disseminated HSV infection in newborns - prevent with C-section if active lesions at delivery, treat mother with antivirals

What is Histoplasma capsulatum?

Dimorphic fungus endemic to Ohio/Mississippi River valleys - found in soil contaminated with bird/bat droppings

What are the clinical presentations of histoplasmosis?

Acute pulmonary (90% asymptomatic), chronic cavitary pulmonary (mimics TB), disseminated (in immunocompromised)

What is acute pulmonary histoplasmosis presentation?

Flu-like illness with fever, cough, chest pain, headache 1-3 weeks after heavy exposure (cave exploration, construction)

What populations are at risk for disseminated histoplasmosis?

HIV/AIDS (CD4 <150), transplant recipients, chronic corticosteroids, TNF-alpha inhibitors, extremes of age

What are the manifestations of disseminated histoplasmosis?

Fever, weight loss, hepatosplenomegaly, pancytopenia, adrenal insufficiency, mucosal ulcers

How is histoplasmosis diagnosed?

Urine/serum Histoplasma antigen (best for disseminated), fungal culture, tissue biopsy with GMS/PAS stain

What is the treatment for mild acute pulmonary histoplasmosis?

Observation only for mild cases in immunocompetent patients - self-limited in most cases

What is the treatment for severe/disseminated histoplasmosis?

Induction: liposomal amphotericin B x 1-2 weeks; Maintenance: itraconazole 200mg TID x 3 days then BID x 12 months

What chest X-ray findings suggest histoplasmosis?

Diffuse reticulonodular infiltrates, hilar lymphadenopathy, calcified granulomas ("buckshot" calcifications)

What is HIV (Human Immunodeficiency Virus)?

Retrovirus targeting CD4+ T cells causing progressive immunodeficiency leading to AIDS if untreated

What defines AIDS (Acquired Immunodeficiency Syndrome)?

CD4 count <200 cells/mm³ OR presence of AIDS-defining illness (regardless of CD4 count)

What are the stages of acute HIV infection?

Acute retroviral syndrome (2-4 weeks post-exposure) → clinical latency (years) → AIDS (without treatment)

What is acute retroviral syndrome presentation?

Mononucleosis-like illness: fever, pharyngitis, lymphadenopathy, rash, myalgia, headache (2-4 weeks after infection)

What is the best screening test for HIV?

4th generation HIV Ag/Ab combo test - detects p24 antigen and HIV antibodies, positive 2-4 weeks post-infection

What test confirms HIV diagnosis?

HIV-1/HIV-2 differentiation immunoassay followed by HIV RNA (viral load) if discordant results

What are the AIDS-defining illnesses? Use mnemonic PC HELP

Pneumocystis pneumonia, Candida (esophageal), HIV encephalopathy, Lymphoma (CNS), Kaposi sarcoma, Progressive multifocal leukoencephalopathy

When should antiretroviral therapy (ART) be initiated?

Immediately upon diagnosis regardless of CD4 count - early treatment improves outcomes and prevents transmission