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USMLE Step 2 (Fach) / Infectious disease (Lektion)

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• Pneumonia Pathogens:- Typical pneumonia: Streptococcus pneumoniae, Haemophilus influenzae- Atypical pneumonia: Mycoplasma pneumoniae (most common in the ambulatory setting), Chlamydophila pneumoniae, Legionella pneumophila, Coxiella burnetii- Hospital-acquired pneumonia (onset > 48 hours after admission): Gram-negative pathogens (Pseudomonas aeruginosa, Enterobacteriaceae), Staphylococcus aureus, Streptococcus pneumoniae- COPD, smokers: Haemophilus influenzae- Immunocompromised patients: Encapsulated bacteria, Pneumocystis jirovecii, Aspergillus fumigatus, Cytomegalovirus- Newborn infants: Escherichia coli, Group B streptococcus, Streptococcus pneumoniae Clinical features:- Classic: Sudden onset, fever, productive cough (purulent yellow-green sputum or hemoptysis), dyspnea, night sweats, pleuritic chest pain.- Atypical: Gradual onset, dry cough, headaches, myalgias, sore throat, GI symptoms.- Lung examination may show ↓ or bronchial breath sounds, rales, wheezing, dullness to percussion, egophony, and/or tactile fremitus. Diagnostics:- ↑ CRP, ↑ ESR, leukocytosis, ↑ procalcitonin (PCT), ABG to rule out respiratory failure- Blood cultures - Urine: Legionella antigen detection, pneumococcal antigen test - PCR and antibody tests to detect Chlamydia pneumoniae - Imaging: Chest x-ray, CT thorax Criteria for hospitalization: Based on CURB-65 score- Confusion (disorientation, impaired consciousness)- Urea > 7 mmol/L (20 mg/dL)- Respiratory rate ≥ 30/min- Blood pressure: systolic BP ≤ 90 mm Hg or diastolic BP ≤ 60 mm Hg- Age ≥ 65 years Treatment:- General measures: Physical therapy, hydration, pulse oximetry monitoring, oxygen, analgesics- Outpatient treatment: Macrolide OR doxycycline- Outpatient with risk factors: Respiratory fluorochinolone (eg, levofloxacin, moxifloxacin, gemifloxacin)- Non-ICU inpatient: Respiratory fluoroquinolone- ICU patient: Antipneumococcal beta-lactam (ceftriaxone, cefotaxime) + azithromycin- If Pseudomonas is suspected: Antipseudomonal beta-lactam (piperacillin/tazobactam, cefepime, meropenem, or imipenem) + respiratory fluoroquinolone ± an aminoglycoside- If MRSA is suspected: Add vancomycin or linezolid Complications: Pleural effusion, empyema, lung abscess, necrotizing pneumonia, bacteremia
• Tuberculosis Epidemiology:- Countries with the highest incidence: India, Indonesia, China, Nigeria, Pakistan, and South Africa Risk factors:- For active disease (i.e., reactivation): Immunosuppression (HIV/AIDS), alcoholism, preexisting lung disease, diabetes, advancing age, treatment with TNF-α inhibitors.- For TB exposure in the United States: Homelessness and crowded living conditions (e.g., prisons), emigration/travel from developing nations, employment in a health profession, interaction with known TB contacts. Clinical presentation:- Constitutional symptoms: fever, weight loss, night sweats, fatigue, lymphadenopathy- Pulmonary symptoms: dyspnea, productive cough (possibly hemoptysis) lasting > 3 weeks- 80% pulmonary tuberculosis- 20% extrapulmonary tuberculosis (CNS, heart, urogenital and gastrointestinal tracts, skin) Diagnostics:- Chest x-ray:→ Primary TB infection: Cavitation is uncommon, hilar lymphadenopathy, pleural effusions, Ghon complex→ Reactivated disease: upper lobe cavitary lung lesions - Sputum microscopy with acid-fast stain (Ziehl-Neelsen stain)- Culture (gold standard): E.g., Löwenstein-Jensen agar- If latent TB: Interferon-γ release assay (for patients who have received BCG vaccine) or Tuberculin skin test (for children <5 years) Treatment:- Active tuberculosis: 2 months of isoniazid + rifampin + pyrazinamide + ethambutol, then 4 months of isoniazid + rifampin- Latent tuberculosis: Isoniazid monotherapy for 9 months
• Acute pharyngitis Etiology:- Bacterial: Group A streptococci (GAS), Neisseria gonorrhoeae, Corynebacterium diphtheriae, M pneumoniae.- Viral: Rhinovirus, coronavirus, adenovirus, HSV, EBV, CMV, influenza virus, coxsackievirus, acute HIV infection. Clinical presentation:- Typical of streptococcal pharyngitis: Fever, sore throat, pharyngeal erythema, tonsillar exsudate, cervical lymphadenopathy, soft palate petechiae, headache, vomiting, scarlatiniform rash (indicates scarlet fever).- Atypical of streptococcal pharyngitis: Coryza, hoarseness, rhinorrhea, cough, conjunctivitis, anterior stomatitis, ulcerative lesions, GI symptoms. Diagnosis:- Clinical evaluation- Rapid GAS antigen detection- Throat culture. - Centor criteria  Treatment:- If GAS is suspected, begin empiric antibiotic therapy with penicillin ×10 days. - Cephalosporins, amoxicillin, and azithromycin are alternative options. Complications: Acute rheumatic fever, poststreptococcal glomerulonephritis, mastoiditis, sinusitis, otitis media, retropharyngeal or peritonsillar abscess, and, rarely, thrombophlebitis of the jugular vein (Lemierre syndrome) due to Fusobacterium.- Peritonsillar abscess may present with odynophagia, trismus (“lockjaw”), a muffled “hot potato” voice, unilateral tonsillar enlargement, and erythema, with the uvula and soft palate deviated away from the affected side. Culture abscess fluid and localize the abscess via intraoral ultrasound or CT. Treat with antibiotics and surgical drainage.
• Cytomegalovirus - Seroprevalence: 70% of adults in the United States- Transmission: Congenital, sexual intercourse, transfusions, transplants, saliva, urine Clinical presentation:- Heterophile-negative mononucleosis- CMV retinitis: Associated with retinal detachment (“pizza pie” retinopathy); presents with floaters and visual field changes (CD4+ < 50/mm3).- CMV esophagitis and/or CMV colitis: odynophagia, abdominal pain, bloody diarrhea: Endoscopic examination of the GI tract typically shows linear ulcers.- CMV pneumonitis: Presents with cough, fever, and sparse sputum production; associated with a high mortality rate. Much more common in patients with hematologic malignancies and transplant patients than in those with AIDS.- CNS involvement: Can include polyradiculopathy, transverse myelitis, and subacute encephalitis (CD4+ < 50/mm3; periventricular calcifications). Diagnostics:- CBC: relative lymphocytosis with > 10% atypical lymphocytes- Blood smear: large atypical lymphocytes with intranuclear inclusion bodies that have an owl-eye appearance- Monospot (heterophile antibody) test: negative- Serological tests- Serum PCR- Indirect immunofluorescence assay: pp-65 CMV antigens Treatment:- In immunocompetent patients: None- In immunosuppressed patients→ CMV retinitis: valganciclovir→ CMV esophagitis/colitis: valganciclovir; if severe ganciclovir or foscarnet→ CMV pneumonia: IV ganciclovir/foscarnet and IV immunoglobulin (IVIG) therapy→ CMV encephalitis: IV ganciclovir and IV foscarnet
• Mycobacterium avium complex Most frequent opportunistic bacterial infection in AIDS patients.- Occurs usually only if CD4 count < 50/μL. Clinical presentation:- Night sweats, fever, weight loss- Lymphadenopathy- Abdominal pains, diarrhea- Anemia, leukocytosis Diagnostics:- Obtain mycobacterial blood cultures (in 2-3 weeks).- Labs show anemia, hypoalbuminemia, and ↑ serum alkaline phosphatase and LDH.- Biopsy of bone marrow, intestine, or liver reveals foamy macrophages with acid-fast bacilli. Typical granulomas may be absent in immunocompromised patients. Therapy:- Macrolide (clarithromycin or azithromycin) plus ethambutol- Rifabutin may be added in some cases- Continue for > 12 months and until CD4+ is > 100/mm3 for > 6 months. Prophylaxis: azithromycin, clarithromycin, or, in select cases, rifabutin
• Brain abscess Pathogens:- Viridans streptococci (∼50% of cases), often secondary to sinusitis- Staphylococcus aureus (10-15% of cases)- Coagulase-negative staphylococci (∼10% of cases)- Obligate anaerobes (eg, Bacteroides species; 15-40% of cases)- Gram-negative aerobic bacteria (e.g., Enterobacteria, Pseudomonas species; 15–30% of cases)- Parasites (eg, neurocysticercosis in patients from Latin America, Sub-Saharan Africa, and Asia)- In immunocompromised states: Toxoplasma, Aspergillus, Candida, Mucormycosis (also known as Zygomycosis), Cryptococcus - Direct spread: Due to paranasal sinusitis (10%), otitis media or mastoiditis (33%), or dental infection (2%).- Direct inoculation: Affects patients with a history of head trauma or neurosurgical procedures.- Hematogenous spread (25%): Often shows a middle cerebral artery distribution with multiple abscesses that are poorly encapsulated and located at the gray-white junction. Clinical presentation:- Dull persistent headache - Symptoms of raised intracranial pressure (e.g., vomiting, papilledema, altered mental status)- Focal neurological deficits- Fever- Generalized or focal seizures (∼30% of cases) Diagnostics:- CT/MRI: intraparenchymal lesions with a central hypodense (necrotic) area and peripheral ring enhancement- Biopsy (and drainage): microscopic examination and culture Differential: Brain metastases, tuberculomas, neurocysticercosis, subacute hemorrhage and/or infarction Treatment:- Early surgical drainage and biopsy of the abscess- Antibiotic therapy for 6-8 weeks (usually IV)→ Initial empirical therapy (eg, third-generation cephalosporin + metronidazole ± vancomycin) → If brain abscess < 2.5 cm, history of symptoms < 1 week, and no signs of ICP → antibiotic therapy without surgical drainage may be attempted→ In all other cases → begin immediately after abscess biopsy/drainage- Intracranial pressure management- Seizure prophylaxis (e.g., anticonvulsants)
• Meningitis Risk factors:- Otitis media, sinusitis- CSF leak after head trauma or neurosurgery- Immunocompromise (e.g., AIDS, asplenia, alcoholism, chronic illness, sickle cell anemia)- Maternal group B Streptococcus infection during birth- Crowded living conditions (e.g., college dormitories, military barracks) Pathogens:- < 1 month: Group B Streptococcus (most common), Escherichia coli, Listeria monocytogenes- Children (6 months-6 years): Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae - Teens/Adults (6-60 years): Neisseria meningitidis (most common in teens), Streptococcus pneumoniae, Enteroviruses, Herpes simplex virus (HSV-2)- Elderly (>60 years): Streptococcus pneumoniae (most common), gram-negative bacilli, Listeria monocytogenes- Immunocompromised patients: Listeria monocytogenes, gram-negative bacilli, Streptococcus pneumoniae, Cryptococcus spp., CMV, VZV, HSV, JC virus, Mycobacterium tuberculosis, toxoplasma gondii Clinical presentation:- Classic triad of meningitis: fever, headache, and neck stiffness (nuchal rigidity)- Altered mental status- Photophobia- Nausea, vomiting- Malaise- Seizures- If due to N. meningitidis: myalgia and possibly petechial rash; Waterhouse-Friderichsen syndrome Diagnostics:- Signs of meningeal irritation: Kernig sign and Brudzinski sign- Blood cultures before antibiotic therapy is started- Lumbar puncture unless CNS mass effect is suspected (e.g., in case of focal neurological deficits, papilledema, altered mental status, or seizures) Treatment (empiric):< 1 month: ampicillin + cefotaxime + aminoglycoside (eg, gentamicin)> 1 month to < 50 years: vancomycin + third-generation cephalosporin (eg, cefotaxime or ceftriaxone)> 50 years: vancomycin + ampicillin + third-generation cephalosporin (eg, cefotaxime or ceftriaxone) Postexposure chemoprophylaxis:- Indicated in cases of meningitis caused by H. influenzae, N. meningitidis, or S. pneumoniae- Indicated for all individuals exposed to the index case- Drugs of choice: rifampin, ciprofloxacin, or ceftriaxone Complications:- Most common: sensorineural hearing loss (transient or permanent)- Focal neurological deficits - Seizures - Cognitive impairment - Spasticity or paresis- Cerebral edema and elevated ICP- Waterhouse-Friderichsen syndrome
• Encephalitis Etiology:- HSV and arboviruses (most common)- Rare: CMV, toxoplasmosis, West Nile virus, VZV, Borrelia, Rickettsia, Legionella, enterovirus, Mycoplasma, and cerebral malaria. - Children and the elderly are the most vulnerable. Clinical presentation:- Altered consciousness, headache, fever, and seizures. - Lethargy, confusion, coma, and focal neurologic deficits (cranial nerve deficits, accentuated DTRs) may also be present. Differential: Brain abscess, malignancy, toxic-metabolic encephalopathy, subdural hematoma, and subarachnoid hemorrhage. Diagnostics: - CSF: lymphocytic pleocytosis and moderately ↑ protein. - Obtain a LP for cell count, glucose, protein, culture for bacteria, fungi, and mycobacteria, Gram stain (bacteria), acid-fast stain (mycobacteria), India ink stain (Cryptococcus). - Order a PCR for HSV, CMV, EBV, VZV, and enterovirus. Obtain West Nile IgM serologies. Consider a wet preparation (free-living amebae) and a Giemsa stain (trypanosomes) if the history is suggestive.- CT or MRI may demonstrate characteristic temporal lobe signal abnormalities in HSV encephalitis. Treatment:- HSV encephalitis: Requires immediate IV acyclovir.- CMV encephalitis: Treat with IV ganciclovir ± foscarnet.- Give doxycycline for suspected Rocky Mountain spotted fever or ehrlichiosis. - Treat Lyme encephalitis with ceftriaxone.
• Fever of unknown origin A temperature of >38.3°C (> 100.9°F) of at least 3 weeks’ duration that remains undiagnosed following 3 outpatient visits or 3 days of hospitalization. Differential:- Infectious: TB, endocarditis (eg, HACEK organisms), occult abscess (abdominal, prostatic), osteomyelitis, catheter infections, sinusitis. In HIV patients, consider MAC, histoplasmosis, or CMV.- Neoplastic: Lymphomas, leukemias, hepatic and renal cell carcinomas.- Autoimmune: Still disease, SLE, cryoglobulinemia, polyarteritis nodosa, connective tissue disease, granulomatous disease (including sarcoidosis).- Miscellaneous: Pulmonary emboli/DVT, IBD, alcoholic hepatitis, drug fever, familial Mediterranean fever, factitious fever.- Idiopathic (10–15%). Diagnostics:- Confirm the presence of fever, and take a detailed history, including family, social, sexual, occupational, dietary, exposures (pets/animals), and travel.- Labs: Obtain a CBC with differential, ESR, serum protein electrophoresis, multiple blood cultures, sputum Gram stain and culture, UA and culture, and PPD. Specific tests (ANA, RF, CK, viral cultures, viral serolo- gies/antigen tests) can be obtained if an infectious or autoimmune etiology is suspected.- Imaging: Obtain a CXR. CT of the chest, abdomen, and pelvis should be done early in the workup of a true FUO. Invasive testing (marrow/liver biopsy) is generally low yield. Laparoscopy and colonoscopy are higher yield as second-line tests (after CT). Treatment: Stop unnecessary medications. Patients with FUO and a completely ⊝ workup have a good prognosis, with fevers resolving over months to years.
• Lung abscess A localized collection of pus and necrotic tissue within lung parenchyma caused by microbial infection. Risk factors:- Aspiration due to reduced level of consciousness, dysphagia- Bronchial obstruction: lung cancer, foreign body aspiration, bronchial stenosis- Immunocompromised state Pathogens:- Most commonly: mixed infections caused by anaerobic bacteria (e.g., Peptostreptococcus, Prevotella, Bacteroides, Fusobacterium spp.)- Less commonly: monomicrobial lung abscess caused by S. aureus, Klebsiella pneumoniae, Streptococcus pyogenes, Streptococcus anginosus Clinical findings:- Indolent presentation with symptoms that evolve over weeks to months- Fever- Cough with production of foul-smelling sputum- Anorexia, weight loss- Night sweats- Hemoptysis Diagnosis:- Gram stain, culture, and sensitivity of expectorated sputum- Radiologic imaging (x-ray or CT): irregular rounded cavity with an air-fluid level in lung region on aspiration that is dependent on body position Treatment:- Antibiotics that covers anaerobes (e.g., clindamycin, ampicillin-sulbactam, carbapenems)- If medical therapy fails, percutaneous catheter drainage or surgical resection may be considered.
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• Influenza Epidemiology:- Seasonal pattern: Fall and winter Clinical features:- Incubation period: a few hours to several days- Sudden onset of high fever, chills, headache, muscle/joint aches, fatigue, and malaise- Patients often develop acute bronchitis with a cough that is usually dry but may produce small amounts of clear or blood-tinged sputum.- Hypotension and bradycardia are common (especially among women and older patients) Diagnostics:- Normal or slightly elevated inflammatory markers; relative lymphocytosis- Rapid antigen test: Used for early diagnosis- Serological testing (e.g., via complement fixation): Used to diagnose an infection after it has resolved - Infection is likely if serum antibody titers increase 4-fold within 1-2 weeks after acute illness Treatment:- Supportive: Rehydration, antipyretics and analgesia (e.g., acetaminophen), antitussives (e.g., dextromethorphan)- Neuraminidase inhibitors: if can be administered within first 48 hours→ Inhalative zanamivir→ Oral oseltamivir→ IV Peramivir
• Urinary tract infection Pathogens:- Escherichia coli: in ∼ 80% of UTIs- Proteus mirabilis: urease-producing → causes alkaline urine with an ammonia smell- Klebsiella pneumoniae- Enterobacter species- Others: Staphylococcus saprophyticus, Enterococci (e.g. Enterococcus faecalis), Ureaplasma urealyticum- Adenoviruses can cause hemorrhagic cystitis in children and immunocompromised patients. Predisposing factors:- Female sex- Sexual intercourse- Catheter-associated- Host-dependent factors: Structural/functional abnormalities of the urinary tract (e.g., BPH, vesicoureteral reflux, neurogenic bladder, calculi or stones), pregnancy, diabetes mellitus, immunocompromise, uncircumcised males, chronic constipation in toddlers Clinical features:- Dysuria, frequency, urgency- Suprapubic pain- Gross hematuria may be present Diagnostics:- Dipstick urine- Urinalysis with microscopy: Pyuria (≥ 5-10 WBC/hpf), bacteriuria- Urine culture: ≥ 105 CFU/mL→ Indications: Complicated UTI, age ≥ 65 years, recent use of antibiotics- Diagnostic imaging: In complicated cystitis, suspicion of structural abnormalities→ Ultrasound, cystoscopy, CT, intravenous pyelogram Treatment:- Uncomplicated cystitis: TMP-SMX (3 days) OR Nitrofurantoin (5 days) OR Fosfomycin (single dose). Do not give nitrofurantoin/fosfomycin if pyelonephritis is suspected.- Complicated cystitis: Fluoroquinolones (e.g., ciprofloxacin, levofloxacin)→ Treatment is extended to 7 days→ Do not use nitrofurantoin/fosfomycin because they do not reach prostate- Pregnant women with cystitis: Ampicillin, amoxicillin, or oral cephalosporins for 7 to 10 days.
• Pyelonephritis Pathogens:- Escherichia coli (∼ 75-90% of cases) - Pseudomonas aeruginosa- Klebsiella pneumoniae- Proteus mirabilis- Gram-positive bacteria (e.g., Enterococcus faecalis, Staphylococcus aureus) Risk factors:- Female gender- Pregnancy- Urinary tract obstruction: Foreign bodies (e.g., catheters or other urologic instrumentation); anatomical abnormalities (e.g., benign prostatic hyperplasia, vesicoureteral reflux, nephrolithiasis, ureteral strictures)- Cystitis- Recent administration of antibiotics (possible antibiotic resistance)- Immunosuppression (e.g., HIV, diabetes)- Acute kidney injury Clinical features:- High fever, chills- Flank pain, costovertebral angle tenderness (usually unilateral, may be bilateral)- Dysuria as well as other symptoms of cystitis (e.g., frequency, urgency)- Weakness, nausea, vomiting  Diagnostics:- Urinalysis: Pyuria, leukocyturia, WBC casts, bacteriuria, microhematuria- Blood: ↑ Inflammatory markers, normal or ↑ renal function parameters- Urine culture and blood culture- CT imaging indicated if: No response to therapy within 72 hours; Complicated pyelonephritis (e.g., obstruction, sepsis); History of nephrolithiasis Treatment:- Uncomplicated pyelonephritis: Oral fluoroquinolones (e.g., ciprofloxacin for 7 days)- Complicated pyelonephritis: IV fluoroquinolones (e.g., ciprofloxacin) for 10-14 days- Pyelonephritis in pregnancy: Hospitalization + IV third-generation cephalosporins (e.g., ceftriaxone)
• Human immunodeficiency virus (HIV) Acute HIV infection:- Also referred to as acute retroviral syndrome (ARS) or described as a mononucleosis-like syndrome. - Fever, fatigue, myalgia and arthralgia, headache- Generalized nontender lymphadenopathy- Generalized rash- Gastrointestinal symptoms (nausea, diarrhea, weight loss)- Oropharyngeal symptoms (sore throat, ulcerations, painful swallowing) Clinical latency and non-AIDS defining conditions:- Chronic subfebrile temperatures- Persistent generalized lymphadenopathy- Localized opportunistic infections (e.g., oral candidiasis , vaginal infections)- Oral hairy leukoplakia (lesions located mainly on the lateral borders of the tongue) - Chronic diarrhea (> 1 month)- Skin manifestations (e.g. molluscum contagiosum, warts, exacerbations of psoriasis, shingles) AIDS-defining conditions Diagnostics:- Screening tests→ Combination antigen/antibody tests: detect both HIV antigen (p24) and anti-HIV antibodies→ Antibody-only test: ELISA- Confirmatory tests→ HIV-1/HIV-2 antibody differentiation immunoassay→ Western blot- Detection of viral RNA: For neonates, indeterminate results- Post-treatment monitoring→ Viral RNA load: indicator of ART response→ CD4 count and CD4/8 ratio Treatment:- 3 NRTI (e.g., zidovudine, lamivudine, abacavir)- 2 NRTI (e.g., lamivudine + abacavir) AND→ 1 NNRTI (e.g., efavirenz) OR→ 1 Protease inhibitor (e.g., lopinavir) OR→ 1 Integrase inhibitor (e.g., raltegravir)
• Syphilis Epidemiology:- Sex: M > F (10:1)- Peak incidence: 20-29 years Etiology:- Pathogen: Treponema pallidum- Transmissibility: 30% in active disease (stadium I/II)! Clinical features:1. Primary syphilis- Primary lesion (chancre)- Resolves spontaneously within 3-6 weeks, typically without scarring- Regional (usually inguinal) nontender lymphadenopathy2. Secondary syphilis- Begins approx. 8-12 weeks after primary infection; typically lasts 2-6 weeks- Constitutional symptoms: Generalized nontender lymphadenopathy, fever, fatigue, myalgia, headache- Polymorphic rash: Typically nonpruritic macular or papular rash; disseminated; involves trunk and extremities, also the palms and soles- Condylomata lata- Patchy alopecia (moth-eaten alopecia)3. Latent: No clinical symptoms, despite seropositivity4. Tertiary syphilis- Gumma- Cardiovascular syphilis: aortitis, aortic aneurysm, syphilitic mesaortitis- Neurosyphilis: Meningitis, Argyll Robertson pupil, Tabes dorsalis Diagnostics:1. Screening with nontreponemal tests→ Rapid Plasma Reagin (RPR): generally the test of choice→ VDRL→ Possible negative result in early infection2. Confirmatory test with treponemal tests→ Treponema pallidum particle agglutination (TPPA)→ Fluorescent treponemal antibody absorption test (FTA-ABS)→ Greater sensitivity in early infection; positive even after treatment- Direct detection→ Darkfield microscopy, may be combined with immunofluorescence → Polymerase chain reaction (PCR) Treatment:- First-line therapy: benzathine penicillin G- Primary, secondary, or early latent: IM, single dose is sufficient- Late latent, tertiary, or date of transmission unknown: weekly IM injections over a 3-week course- Neurosyphilis: IV for 10-14 days
• Chancroid Chancroid (also known as soft chancre) is a highly contagious STI caused by Haemophilus ducreyi. Clinical features:- Very painful genital ulcers- The primary lesions are erythematous papules that become pustular and erode into ulcers.- Deep, small (∼ 10-20 mm in diameter), well-demarcated lesions with a grayish necrotic base- Unilateral painful inguinal lymphadenopathy that appears 1-2 weeks after ulcer Diagnostics: Clinical- Gram-stain: gram-negative rods in ulcer exudate (swab sample) suggestive of Haemophilus ducreyi infection- Dark field examination for Treponema pallidum and HSV PCR to rule out primary syphilis and genital herpes, respectively- Culture: confirms diagnosis (not always conducted) Treatment: Single dose oral azithromycin or IM ceftriaxone
• Lymphogranuloma venerum A sexually transmitted disease caused by C. trachomatis. Clinical features:- Painless ulcer at the site of inoculation that may go unnoticed. - A few weeks later, tender inguinal lymphadenopathy (usually unilateral) and constitutional symptoms develop.- If untreated, proctocolitis may develop with perianal fissures and rectal stricture; obstruction of lymphatics may lead to elephantiasis of genitals. Diagnostics:- Serologic tests (complement fixation, immunofluorescence) Treatment: Doxycycline (oral for 21 days)
• Cellulitis A deeper skin infection involving dermis and subcutaneous tissue. Pathogen:- Staphylococcus aureus → causes purulent cellulitis- Streptococcus pyogenes (group A Streptococcus) → causes nonpurulent cellulitis- Pasteurella multocida (secondary to dog and cat bites) Risk factors:- Diabetes mellitus- Immunodeficiency (e.g., alcoholism, HIV infection) - Chronic lymphedema - Circulatory disorders: arteriovenous insufficiency, chronic edema, stasis - Obesity- Local skin defects (e.g., tinea pedis) Clinical features:- Erythematous skin lesion with poorly defined margins- Pasty consistency of the affected region- Lymphadenitis- Systemic symptoms: fever, chills, confusion- Possibly purulent exudate Diagnostics: Clinical - Laboratory findings: leukocytosis, ↑ CRP, ↑ ESR- Wound and blood culture: identify pathogen; rule out bacteremia- Ultrasonography: rule out occult abscess- MRI: distinguish cellulitis from osteomyelitis Treatment: - Elevation of the affected limbs- Mild infection: Oral antibiotics (e.g. penicillin V, cephalosporin, dicloxacillin, clindamycin- Moderate infection: IV penicillin (e.g., oxacillin, nafcillin) or a cephalosporin (e.g., cefazolin, ceftriaxone)- Continue IV antibiotics until signs of infection improve. Follow up with oral antibiotics for 2 weeks.- If purulent → surgical debridement + add vancomycin Complications:- Necrotizing fasciitis- Recurrent cellulitis in 20-50% of cases- In orbital cellulitis: blindness, cavernous sinus thrombosis, intracranial abscess
• Erysipela Superficial skin infection involving the upper dermis, with lymphangitis and lymphadenitis. Pathogen: group A Streptococcus (Streptococcus pyogenes)- The most common portal of entry for the pathogen is through a small skin lesion (e.g., interdigital tinea pedis)! Clinical features:- Location: lower limbs (80% of cases), face - Sudden onset; tender, sharply demarcated skin lesion, with erythema, edema, and warmth- Lymphangitis: Red streaks radiating from the skin lesion, extending along the course of the lymphatic vessels, and lymphadenitis (swollen, tender regional lymph nodes) may be present.- Systemic symptoms: fever, chills, nausea, headaches, muscle and joint pain Diagnosis:- Primarily a clinical diagnosis- Inspect skin for lesions as potential portals of entry- Lab: Leukocytosis, ↑ CRP, ↑ ESR Treatment:- Uncomplicated: IM or oral penicillin or erythromycin- Otherwise treat as cellulitis Complications:- Recurrent erysipelas- Thrombophlebitis- Abscess- Cellulitis- Necrotizing fasciitis- Lymphedema
• Necrotizing fasciitis Rapidly progressive infection resulting in extensive necrosis of deep tissue (subcutaneous tissue, fascia, and muscle) and systemic infection that can develop into a life-threatening condition within hours. Pathogen: Group A Streptococcus; frequently mixed infection (with aerobic and anaerobic gram-negative bacteria)- Gas gangrene is a type of necrotizing fasciitis caused by Clostridium perfringens  Clinical features:- Rapidly progressive with fast spread - Crepitus- Pain out of proportion with the physical exam- Blue-Grey discoloration of the skin, bullae formation, loss of sensation in the affected area - Systemic symptoms: fever, chills, acute illness- Fournier's gangrene: necrotizing fasciitis of the external genitals Diagnosis:- Laboratory analysis: leukocytosis, ↑ CRP, ↑ ESR, elevated CK levels, hyperglycemia, ketoacidosis- X-ray: subcutaneous accumulation of air Treatment: - Monitoring in an intensive care unit- Immediate extensive surgical debridement with tissue culture and histopathology (confirmatory test)- Broad-spectrum parenteral antimicrobial therapy Complications:- Sepsis (urosepsis in Fournier's gangrene) - Disseminated intravascular coagulation- Organ dysfunction (e.g., acute kidney injury)- Severe necrosis requiring amputation of limb
• Osteomyelitis Pathogens:- Staphylococcus aureus: Children and adults- Staphylococcus epidermidis: Diabetic patients with foot ulcers and pressure ulcers; Patients with prosthetics- Streptococci: Diabetic patients with foot ulcers and pressure ulcers; Neonates and infants- Pseudomonas aeruginosa: IV drug users; Plantar puncture wounds (especially if wearing rubber-soled footwear)- Salmonella: Sickle cell anemia patients- Klebsiella: Patients with UTIs or a history of UT instrumentation- Fungal pathogens: Immunocompromised patients; IV drug users- Mycobacterium tuberculosis Acute osteomyelitis- Onset: usually gradual, over several days- Chief complaint: pain at the site of infection, possibly related to movement- Possible localized findings: point tenderness, swelling, redness, warmth- Possible systemic findings: malaise, fever, chills- Infants: long bone metaphysis, joints- Adults: vertebral involvement is most common Chronic osteomyelitis- Onset: usually following a prior episode of osteomyelitis; may last for months- Chief complaint: recurrent pain- Swelling, redness- Local sinus tract formation, perhaps draining pus Diagnostics:- Initial work-up includes blood cultures, inflammatory markers, and x-ray imaging.- MRI (most sensitive): Cortical destruction, bone marrow inflammation, soft tissue involvement- Bone biopsy (confirmatory test) Treatment: IV antibiotics for extended periods (4 to 6 weeks)- Empiric therapy: Antipseudomonal cephalosporins (ceftazidime, cefepime) OR antipseudomonal fluoroquinolones (ciprofloxacin, levofloxacin) + IV Vancomycin  - Follow with ESR and CRP weekly
• Fever of unknown origin Definition:- Fever >38.3°C (101°F)- Continuing “on several occasions” for at least 3 weeks- No diagnosis over this time period despite 1 week of inpatient workup / 3 outpatient visits Etiology:- Infection – most common cause→ TB and other mycobacterial infection→ Occult abscesses (e.g., hepatic, retroperitoneal) → UTI/complicated UTI→ Endocarditis→ Sinusitis→ HIV→ Infectious mononucleosis and other viruses→ Malaria and other parasitic infections- Occult neoplasms – second most common cause→ Lymphoma (especially Hodgkin lymphoma)→ Leukemia- Collagen vascular disease → SLE→ Still disease→ Polyarteritis nodosa (PAN) →  Temporal arteritis→ Polymyalgia rheumatica- Granulomatous disease (e.g., sarcoidosis, Crohn disease)- Drug fevers (e.g., sulfonamides, penicillin, quinidine, barbiturates)- Pulmonary embolism- Hemolytic anemia- Familial Mediterranean fever - Gout- Subacute thyroiditis- Factitious illnesses
• Neutropenic fever Neutropenic patient with fever and a neutrophil count ≤ 500/μL (severe risk of bacterial infection). Etiology:- Often chemotherapy-induced. - Bacterial infections, aspergillosis, candidiasis, herpes virus Diagnostics:- CXR- Panculture (blood, urine, sputum, line tips, wound)- CBC- Complete metabolic panel Treatment:- Place the patient on reverse isolation precautions (positive-pressure room, masks, and strict handwashing for those entering the patient’s room).- Broad-spectrum antibiotics must be administered without delay to avoid sepsis and life-threatening complications.- Use an anti-pseudomonal ß-lactam drug (cefepime, meropenem, or piperacillin-tazobactam) - If fever persists beyond 4 to 5 days despite broad-spectrum antibacterial therapy, give antifungal agents, such as IV amphotericin B. Consider G-CSF.
• Sepsis - Definition Sepsis: acute and life-threatening organ dysfunction due to abnormal host response to infection.- Organ dysfunction = an acute change in total SOFA score ≥ 2 points- Infection = may be confirmed (via culture) or suspected Septic shock: 1. Sepsis + 2. Significant circulatory, metabolic, and cellular abnormalities +3. Requiring vasopressor therapy to maintain a mean blood pressure of ≥ 65 mmHg and presence of increased lactate levels > 2 mmol/L (18 mg/dL)  Quick SOFA criteria (qSOFA): to predict mortality in adult patients with suspected infection outside of the ICU (e.g., ward, emergency unit, or prior to hospitalization). Positive if ≥ 2 of the following are present:- Mental status change- Respiratory rate: ≥ 22 breaths per minute- Systolic BP: ≤ 100 mmHg→ If positive, assess SOFA score SOFA score = Sequential Organ Failure Assessment Score- Based on six different scores, one each for the respiratory, cardiovascular, hepatic, coagulation, renal and neurological systems.
• Lyme disease PathogenIn the US: - Borrelia burgdorferi, an anaerobic, facultative intracellular spirochete bacteria Vector: mainly Ixodes scapularis (deer or black-legged tick) in the northeastern and upper midwestern US Stage I (early localized Lyme disease):- Symptoms develop within 7-14 days after a tick bite.- Erythema chronicum migrans (EM)→ Occurs in 80% of infected individuals→ Self-limiting (typically subsides within 3-4 weeks)- Flu‑like symptoms Stage II (early disseminated disease)- Symptoms develop 3-10 weeks after a tick bite- Migratory arthralgia that can progress to Lyme arthritis- Cranial nerve palsies: Most commonly peripheral facial nerve palsy- Nocturnal radicular pain, paresthesia, and paresis- Meningitis- Polyneuropathy (mononeuritis multiplex, asymmetrical)- Lyme carditis: Risk of cardiac arrhythmias (e.g., AV Block) and rarely myopericarditis- Ocular manifestations: including conjunctivitis, retinal vasculitis, optic neuropathy, and uveitis Stage III (late Lyme disease):- Symptoms develop months to years after the initial infection- Chronic Lyme arthritis (10% of cases) - Late neuroborreliosis Diagnostics: Two‑step serological testing1. Initial test: enzyme‑linked immunosorbent assay (ELISA)2. Confirmatory test: Western blot- Cerebrospinal fluid testing Treatment:- No neurological manifestations: Doxycycline OR Amoxicillin (if < 8 years) OR Cefuroxime - Neurological manifestations/cardiac arrhythmias: intravenous ceftriaxone
• Ehrlichosis Pathogen: Ehrlichia chaffeensis, Ehrlichia ewingii (intracellular, gram-negative bacteria) Epidemiology: southeastern and south central US, mid-Atlantic States Reservoir: white tail deer Route of transmission: bite of the lone star tick (Amblyomma americanum) → infection of monocytes and macrophages Clinical infection (incubation period of 1–2 weeks):- Flu-like illness: High fever, headaches, malaise, myalgias, chills- Similar to RMSF, but usually without a rash (“spotless” RMSF)- Possibly neurologic symptoms (confusion, stiff neck, clonus)- May cause renal failure and GI bleeding Diagnosis:- Leukopenia, thrombocytopenia- Elevated liver enzymes & LDH- Wright-Giemsa stain of blood smear: detection of morulae inside the infected monocytes- Serology via IFA: IgG Ehrlichia titer- PCR Treatment: Empiric doxycycline while awaiting confirmatory testing
• Giardiasis Epidemiology:- Giardia lamblia is widespread throughout the world and affects ∼ 200 million people per year worldwide.- In the US, Giardiasis is the most common intestinal disease caused by parasites. Transmission- Waterborne: from drinking of recreational water (e.g., lakes, rivers, ponds, swimming pools)- Fecal-oral (e.g., through food handlers, people in daycare and nurseries): Giardia cysts are passed into the environment from the feces of infected people and animals. Clinical features:- 3-25 days after ingestion of cysts → diarrhea consisting of soft, voluminous, frothy, and greasy stools (stools tend to float; no blood!)- Excessive gas, abdominal pain, and cramps- Fatigue, nausea/vomiting, anorexia- Chronic: Malabsorption (eg, lactose intolerance), profound weight loss, vitamin deficiencies Diagnostics: - Stool analysis: microscopic confirmation of cysts or trophozoites- Immunoassay: detection of Giardia lamblia antigens in stool Treatment: Metronidazole (3x/day for 5 days)
• Legionella pneumonia Epidemiology:- Contaminated water: Hospital, travel (cruise, hotel)- High-risk patients: Elderly, patients with chronic diseases, immunocompromised individuals, smokers Clinical features:- Fever > 38.8 °C- Relative bradycardia- Gastrointestinal (diarrhea, vomiting, cramps)- Neurological abnormalities, especially confusion, agitation and stupor- Pulmonary symptoms delayed Diagnostics:- Hyponatremia- Chest x-ray: Patchy unilobular or interstitial infiltrates- Sputum gram stain: PMN, no/few organisms- Urine Legionella antigen Treatment:- Drug of choice: fluoroquinolones (preferably levofloxacin, alternatively moxifloxacin) for 7-10 days- Second-line treatment: macrolides (e.g., erythromycin or azithromycin) for 3 weeks
• Cat scratch disease Etiology:- Bartonella henselae, fastidious gram-negative bacilli- Can be transmitted by cat scratch/bite Clinical features:- General: malaise, loss of appetite, fever- Papule at scratch/bite site develops approx. 4-6 days after exposure (in > 50% of cases)- Regional lymphadenopathy 1-3 weeks following exposure- ± Fever of unknown origin (≥ 14 days) Diagnostics:- Usually clinical- ± Serology (Indirect fluorescence assay (IFA) testing and ELISA)- Histological study: Warthin-Starry staining Treatment:- Generally self-limiting- Azithromycin
• Vaccines for adults with HIV HAV: - Chronic liver disease (including HBV & HCV)- Men who have sex with men- IV drug users HBV: All patients without documented immunity to HBV HPV: All patients age 11-26 Influenza: Annually for all patients (inactivated formulation) Meningococcus: All patients Pneumococcus:- PCV13 once- PPSV23 8 weeks later, 5 years later & at age 65 Tdap:- Tdap once (repeat with each pregnancy in women)- Td every 10 years Live vaccines (eg, MMR, zoster, varicella) are contraindicated if CD4+ cell count <200/mm3.
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• Vibrio vulnificus Epidemiology:- Gram-negative, free-living in marine environments- Ingestion (oysters) or wound infection- ↑ Risk in those with liver disease (cirrhosis, hepatitis) Clinical features:- Rapidly progressive (often < 12 hours)- Septicemia – septic shock, bullous lesions- Cellulitis – hemorrhagic bullae, necrotizing fasciitis Diagnostics:- Blood and wound cultures Treatment:- Empiric in those with likely illness as highly fatal- Intravenous ceftriaxone + doxycycline
• Disseminated histoplasmosis Epidemiology:- Midwest & central United States (Ohio & Mississippi River Valleys)- Soil contaminated by bird or bat droppings- ↑ Dose exposure or immunocompromised (eg, AIDS) Clinical features:- Systemic: Fevers, chills, malaise- Weight loss & cachexia- Pulmonary: Cough, dyspnea- Mucocutaneous lesions: Papules, nodules- The presence of ulcerative oral lesions is specific for histoplasmosis- Reticuloendothelial: HSM, LAD Diagnosis:- Lab findings: Pancytopenia, transaminitis, ↑ LDH & ferritin- Chest x-ray: reticulonodular or interstitial infiltrate - Urine/serum Histoplasma antigen (polysaccharid antigen test)- Serology- Culture (takes 4-6 weeks) Treatment: - Amphotericin B (moderate-severe disease)- Itraconazole (mild disease/maintenance)
• Hookworm infections Pathogen: - Human hookworms: Ancylostoma duodenale, Necator americanus- Zoonotic hookworms: Dog (Ancylostoma caninum) or cat (Ancylostoma braziliense) Mode of transmission: Percutaneous penetration of larvae (primarily via barefoot contact with contaminated sand or soil) Clincal features:- Cutaneous entry: pruritus, erythema, maculopapular rash, occasionally serpiginous marks- In zoonotic hookworm infections: cutaneous larva migrans- Respiratory tract: dry coughing, wheezing- Intestine: abdominal pain, weight loss, nausea, vomiting, diarrhea- Anemia Diagnosis:- CBC: eosinophilia and microcytic anemia- Confirmatory test: stool examination for eggs or worms Treatment: - Human hookworms: Bendazoles, pyrantel pamoate- Cutaneous larva migrans: Bendazoles, ivermectin
• Tetanus prophylaxis ≥ 3 tetanoid toxoid doses:- No TIG- Clean or minor wound: Tetanus vaccine if last dose ≥ 10 years ago- Dirty or severe wound: Tetanus vaccine if last dose ≥ 5 years ago Unimmunized, uncertain, or < 3 tetanus toxoid doses:- Clean or minor wound: Tetanus vaccine, no TIG- Dirty or severe wound: Tetanus vaccine + TIG
• Disseminated gonococcal infection Clinical features:- Purulent monoarthritis &/OR - Triad of tenosynovitis, dermatitis (erythematous papules & pustules), asymmetric migratory polyarthralgias Diagnosis:- Blood cultures (may be negative)- Synovial fluid analysis: inflammatory effusion with neutrophil predominance; Gram stain & culture or NAAT- Culture or NAAT of urethra, cervix, pharynx, rectum Treatment:- Intravenous ceftriaxone, switch to oral (cefixime) when clinically improved- Empiric azithromycin OR doxycycline for concomitant chlamydial infection- Joint drainage for purulent arthritis
• Actinomycosis Pathogen: Anaerobic, gram ⊕, form branching filaments. Not acid fast (unlike Nocardia). Risk factors:- Dental infections & trauma (extraction)- Immunosuppression, diabetes mellitus, malnutrition Cervicofacial actinomycosis:- Slowly progressive, nonpainful, indurated mass in the neck/face; most commonly in the mandible region- Sinus tracts with sulfur granules- Fever/lymphadenopathy are common Diagnosis:- Fine needle aspiration- Culture > 14 days Treatment:- Penicillin 2-6 months- Alternatives (in the event of penicillin allergy): doxycycline, clindamycin- Surgery (severe disease)
• Staphylococcal toxic shock syndrome Risks:- Tampon use- Nasal packing- Surgical/postpartum would infection Pathogenesis: Staphylococcus aureus exotoxin release acting as superantigens Clinical features:- Fever > 38.9 °C- Hypotension- Diffuse macular rash involving palms & soles- Desquamation 1-3 weeks after disease onset- Vomiting, diarrhea- Altered mentation without focal neurologic signs Treatment:- Supportive therapy (fluid replacement)- Removal of foreign body (eg, tampon)- Antibiotic therapy (eg, clindamycin + vancomycin)
• Mucormycosis Etiology: Mucorales, most commonly Rhizopus Risk factors:- Diabetes mellitus (ketoacidosis)- Immunosuppression: Hematologic malignancy, solid organ or stem cell transplant- Iron overload Clinical features:- Acute/aggressive- Fever, nasal congestion, purulent nasal discharge, headache, sinus pain- Necrotic invasion of palate, orbit, brain  Diagnosis:- Sinus endoscopy with biopsy & culture- Biopsy: broad, nonseptate hyphae, with right-angle branching on microscopy Treatment:- Surgical debridement- Liposomal amphotericin B- Elimination of risk factors (eg, ↑ glucose, acidosis)
• Echinococcosis Pathogens:- Echinococcus granulosus: causes cystic echinococcosis- Echinococcus multilocularis: causes alveolar echinococcosis Transmission:- From the fur of definitive hosts (eg, dogs or cats)- Contaminated dirt (eg, dog feces) Cystic echinococcosis:- Single hepatic cyst (hydatid cyst) with daughter cysts- Hepatomegaly → RUQ pain- Lung involvement in 25% of cases Diagnostics:- ELISA- Cysts: Eggshell calcifications Treatment: Albendazole
• Chikungunya fever Epidemiology:- Tropical/subtropical parts of Central/South America, Africa & Asia- Vector: Aedes mosquito (also transmits dengue & Zika) Clinical features:- Incubation period: 3-7 days- High fevers & severe polyarthralgias (almost always present)- Headache, myalgias, conjunctivitis, maculopapular rash- Lymphopenia, thrombocytopenia, transaminitis Treatment:- Supportive care (initial symptoms usually resolve in 7-10 days)- Chronic arthralgias/arthrits occurs in >50% (may require methotrexate)
• Necrotizing (malignant) otitis externa Risk factors:- Elderly (age > 60)- Diabetes mellitus- Aural irrigation (cerumen removal) Microbiology: Pseudomonas Clinical features:- Severe, unremitting ear pain (worse at night & with chewing)- Deficits of lower cranial nerves (eg, facial, vagus, accessory)- Granulation tissue in the external auditory canal- Elevated ESR Diagnostics:- CT scan to identify bone destruction- MRI to identify intracranial extension (e.g., venous sinus thrombosis, cranial abscess)- Gallium-67 scan in order to monitor response to treatment- Biopsy: distinguishes malignant otitis externa from a tumor and helps optimize treatment Treatment:- IV ciprofloxacin- ± Surgical debridement
• Pertussis Etiology:- Pathogen: Bordetella pertussis is a gram‑negative, obligate aerobic coccobacillus- Transmission: airborne droplet (through coughing); direct contact with oral or nasal secretions Clinical features:- Catarrhal stage (∼ 1–2 weeks)- Paroxysmal stage (∼ 2–6 weeks)→Intense paroxysmal coughing (often occurring at night)→ Followed by a deep and loud inhalation or high-pitched “whooping” sound→ Accompanied by tongue protrusion, gagging, and struggling for breath→ Followed by the expulsion of phlegm or posttussive vomiting (risk of dehydration)- Convalescent stage (weeks to months) Diagnostics:- Blood count: lymphocyte-predominant leukocytosis (50,000-60,000/μL) that corresponds with disease severity - Pathogen detection (to confirm the diagnosis): Culture (gold standard) or PCR: samples from deep nasopharyngeal aspiration or posterior nasopharyngeal swabAs B. pertussis only grows on respiratory epithelium, blood cultures are always negative! Treatment: Macrolides- Age < 1 month: Azithromycin x 5 days- Age ≥ 1 month: Azithromycin x 5 days OR clarithromycin x 7 days OR erythromycin x 14 days Prophylaxis: recommended for all close contacts despite vaccination status. Macrolides are also the preferred antibiotics for prophylaxis.
• Causes of esophagitis in HIV Candida albicans:- White plaques- Oral thrush Herpes simplex virus:- Herpetic vesicles & round/ovoid ulcers- Concurrent perioral/oral HSV- Superficial Cytomegalovirus:- Deep, linear ulcers- Distal esophagus Viral esophagitis is more likely in patients who have:- Severe odynophagia (pain with swallowing)- No dysphagia (difficulty swallowing)- No thrush
• Ecthyma gangrenosum An ulcerative lesion extending into the dermis that develops in the setting of bacteremia. Pathogen: Pseudomonas aeruginosa Pathophysiology:- Classically develops in patients with P aeruginosa bacteremia who are immunocompromised- Bacteria invade vasculature, causing septic vasculitis and cutaneous necrosis- Virulence factors: Exotoxin A, elastase, phopholipase C, pyocyanin Clinical features:- Rapid progression (within 12-18 hours) of painless red macules → induration, development of pustules, vesicles, and/or bullae → crusted ulcers- Can involve skin or mucous membranes Treatment: Antipseudonomal penicillin
• Bacterial endocarditis prophylaxis High-risk cardiac conditions:- Prosthetic heart valve- Previous infective endocarditis- Structural valve abnormality in transplanted heart- Certain congenital heart disease Indicated procedures & appropriate coverage:- Gingival manipulation or respiratory tract infection→ Viridans group Streptococcus coverage (eg, amoxicillin)- GU or GI tract procedure in setting of active infection→ Enterococcus coverage (eg, ampicillin)- Surgery on infected skin or muscle→ Staphylococcus coverage (eg, vancomycin)- Surgical placement of prosthetic cardiac material→ Staphylococcus coverage (eg, vancomycin)
• Acute rheumatic fever Epidemiology:- Peak incidence: age 5-15- Twice as common in girls Clinical features:Major:- Joints (migratory arthritis)- Carditis- Nodules (subcutaneous)- Erythema marginatum- Syndeham choreaMinor:- Fever- Arthralgias- Elevated ESR/CRP- Prolonged PR interval Late sequelae: Mitral stenosis/regurgitation Prevention: Penicillin for group A streptococcal pharyngitis
• Preseptal vs orbital cellulitis Preseptal cellulitis- Eyelid erythema & swelling- Chemosis- Treatment: Oral antibiotics Orbital cellulitis:- Symptoms of preseptal cellulitis + Pain with EOM, proptosis &/or ophthalmoplegia with diplopia- Reduced vision- Treatment: Intravenous antibiotics ± surgery
• Trichinellosis Epidemiology & life cycle:- Ingestion of undercooked meat (usually pork)- More endemic in Mexico, China, Thailand, parts of central Europe & Argentina- Gastric acid releases larvae that invade small intestine & develop into worms- Female worms release larvae (up to 4 weeks later) that migrate & encyst in striated muscle Intestinal stage (within 1 week of ingestion)- Can be asymptomatic or include abdominal pain, nausea, vomiting & diarrhea Muscle stage (up to 4 weeks after ingestion)- Myositis- Fever, subungual splinter hemorrhages- Periorbital edema- Eosinophilia (usually > 20 %) with possible elevated CK & leukocytosis Treatment: Bendazoles
• Syphilis treatment Primary: Penicillin G (IM) x 1 dose- Alternate: Doxycycline x 14 days Secondary: Penicillin G (IM) x 1 dose- Alternate: Doxycycline x 14 days Latent (asymptomatic): Penicillin G (IM) x 3 doses- Alternate: Doxycycline x 28 days Tertiary (eg, CV, gummas): Penicillin G (IV) x 14 days- Alternate: Ceftriaxone x 14 days
• Bacillary angiomatosis Epidemiology:- Bartonella henselae/quintana- Cat exposure or homelessness (lice)- Severe immunocompromise: Advanced HIV (CD4 < 100/mm3) Manifestations:- Vascular cutaneous lesions: Papular, nodular, peduncular; bleed easily- Systemic symptoms: Fever, night sweats, fatigue- Organ involvement rarely: Liver, bone, CNS Diagnosis:- Lesional biopsy: → Vascular proliferation→ The Warthin-Starry stain is used to visualize bacilli.→ Neutrophilic infiltrate Treatment: - Doxycycline or erythromycin- Antiretroviral therapy

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