Clinical Diagnosis Quiz

Infectious Disease Overview

• Infectious diseases are conditions caused by pathogens like bacteria, viruses, fungi, or parasites.
• Nosocomial infections, also referred to as hospital-acquired infections, are infections that occur in patients during their stay in a healthcare facility, such as a hospital or nursing home..
• Infectious disease presentations vary but are typically characterized by signs, symptoms, workup, and treatment.
• Prevention measures include vaccination and hygiene practices.

Objectives of Presentation

• List and describe common nosocomial infections, including their presentation, natural history, treatment, and prevention.
• Describe symptoms, signs, workup, and treatment for various infectious diseases.

Specific Infectious Diseases (Bacterial)

• Bacterial Diseases:

  • Acute rheumatic fever
  • Bartonella
  • Botulism
  • Campylobacter jejuni
  • Chlamydia
  • Cholera
  • Diphtheria
  • Gonococcal infections
  • MRSA (Methicillin-resistant Staphylococcus aureus)
  • Salmonellosis
  • Shigellosis
  • Tetanus

• Mycobacterial Diseases:

  • Atypical mycobacterial disease

• Spirochetal Diseases:

  • Lyme disease
  • Rocky Mountain spotted fever
  • Syphilis

Case Studies

• Case 1: 21-year-old female presenting with double vision, difficulty swallowing, urinary retention, and abdominal pain. Her partner reports she is otherwise healthy and has been canning green beans.
• Case 2: 32-year-old woman experiencing fever, a lesion behind her knee, and a "poppy seed" sized blood blister following scratching.
• Case 3: 45-year-old male with a painless lesion on his genitals present for three weeks.
• Case 4: 6-year-old male experiencing intermittent fever, fatigue, migratory joint pain, weight loss, systolic murmur with a thrill in mitral area radiating to axilla; left knee mildly swollen and warm, and painless nodules over ankles and elbows.
• Case 5: 13-year-old female presenting with multiple episodes of watery diarrhea resembling rice water and severe dehydration in Syria.

Bacterial Classification

• Gram-positive bacteria: Have a thick cell wall, appearing purple in Gram stain. Examples include Staphylococcus, Streptococcus, and Enterococcus.

• Gram-negative bacteria: Have a thin cell wall, appearing pink in Gram stain. Examples include E. coli, Pseudomonas, Haemophilus influenzae, and Proteus.

• Aerobic bacteria: Require oxygen for growth. Examples include Bacillus, species of Mycobacterium and species of Pseudomonas.

• Anaerobic bacteria: Do not require oxygen for growth. Examples include species of Clostridium.

• Facultative anaerobes: Can grow with or without oxygen.

Mycoplasma, Rickettsia and Chlamydia

• Mycoplasma: Small organism, frequently causing atypical pneumonia and tuberculosis.
• Rickettsia: Obligate intracellular bacteria, often transmitted by ticks or fleas. Major examples include Rickettsia rickettsii (Rocky Mountain Spotted Fever).
• Chlamydia: Intracellular bacteria, frequently implicated in sexually transmitted diseases (STDs) like Chlamydia trachomatis.

Antibiotic Mechanisms of Action (MOA)

• Antibiotics target various bacterial processes like cell wall synthesis, folic acid metabolism, protein synthesis, and cytoplasmic membrane structure.

Types of Antibiotics

• Several different classes of antibiotics function by inhibiting bacterial processes. Examples include ß-Lactams, Aminoglycosides, Glycopeptides, Ansamycins, Quinolones, and Streptogramins.

Mycobacterium Marinum

• Pathophysiology: Causes nodular lymphangitis.
• Exposure Risks: Fresh and saltwater exposure, often with fish handlers or swimmers in lakes or oceans.
• Signs and Symptoms: Primary lesions (2-8-week incubation) of erythematous papules evolving into nodules spreading up the lymph chain which may ulcerate or form abscesses.
• Diagnosis: Organisms detected with microscope and culture of biopsied tissue specimens. PPD test can be used.
• Treatment: Warm compresses to lesions and antibiotics like Clarithromycin and Rifampin for 2-3 months.

Mycobacterium Avium Complex (MAC)

• Epidemiology: Commonly found in environments, but transmission occurs mostly when CD4 count is <50. Often a significant infection in patients with AIDS.
• Signs and Symptoms: Fever, fatigue, night sweats, wasting, gastrointestinal upset, unilateral firm fluctuant lymphadenitis.
• Management/Diagnosis: Laboratory testing for diagnosis, including blood cultures and lymph node biopsies; pulmonary symptoms would lead to chest x-rays and sputum analysis. Treatment includes prophylaxis for individuals with HIV and CD4 count <50 with Azithromycin and management with Clarithromycin + rifampin + ethambutol for a year.

Rocky Mountain Spotted Fever

• Etiology: Caused by Rickettsia rickettsii.
• Epidemiology: 6,000 cases annually in the U.S., mostly fatal.
• Where does it occur: 60% of cases primarily in North Carolina, Oklahoma, Arkansas, Tennessee, and Missouri.
• Pathophysiology: Tick bite transmission (within 2 hours). Spread through the circulatory system and lymphatic system; infects endothelial cells and smooth muscle cells.
• Signs and Symptoms: Fever, flu-like illness, headache, erythematous/macular rash that transforms into petechiae, nausea/vomiting/abdominal pain.
• Diagnosis: Clinical findings, biopsy if needed. Lab results often include thrombocytopenia.
• Treatment: Empiric treatment (within 5 days) with doxycycline 100mg PO/IV BID for 7 days, continuing treatment for 3 days after defervescence.

Lyme Disease

• Etiology: Caused by Borrelia burgdorferi, spread by Ixodes scapularis ticks (“deer ticks”).
• Epidemiology: High case numbers, especially in the Eastern and Midwestern US.
• Pathophysiology: Tick bite transmission is the route. Early symptoms often start with a skin lesion.
• Signs and Symptoms: Early localized presentation may feature an erythema migrans skin rash (sometimes described as bulls-eye appearance). Early disseminated symptoms may include neurologic symptoms like Bell’s palsy and carditis. Late Lyme can include arthritis, often in the knee joint.
• Diagnosis: Clinical findings along with a skin lesion. ELISA and Western Blot tests may need to be run.
• Treatment: Doxycycline is the primary oral treatment. If severe or with associated meningitis or cardiac complications, alternative parenteral options are available

Syphilis (Treponema Pallidum)

• Etiology: Caused by Treponema pallidum, transmitted through mucous membrane or broken skin contact.
• Epidemiology: Resurgence in prevalence since HIV epidemic. Over 207,000 confirmed US cases in 2022.
• Signs and Symptoms: Primary: a painless ulcer (chancre). Secondary: maculopapular skin rash, lymphadenopathy. Latent: Asymptomatic period. Tertiary: Cardiac, neurologic, eye/skin complications.
• Diagnosis: Darkfield microscopy, nontreponemal tests (VDRL), and treponemal tests (TP-PA).
• Treatment: Benzathine penicillin G IM for a single dose.

Other Reportable Diseases

• Diphtheria:-Etiology: Corynebacterium diphtheriae-Signs/Symptoms: Sore throat, dysphagia, low-grade fever, malaise, tachycardia, gray-white pseudomembrane on pharynx, "bullneck." -Diagnosis: Throat culture, nasal swab looking for Corynebacterium organisms.

• Bartonella:-Etiology: Gram-negative rod, obligate anaerobe. -Associated illness: Cat-scratch disease, trench fever.

• Campylobacter Enteritis:-Etiology: Campylobacter jejuni

  • Signs/Symptoms: Inflammatory diarrhea, cramping periumbilical pain. -Diagnosis: Stool culture, testing for gram negative, comma-shaped bacteria or PCR.

• Cholera:-Etiology: Vibrio cholerae-Signs/Symptoms: Copious watery diarrhea, "rice water" stools, dehydration. -Diagnosis: Stool culture for gram-negative, comma-shaped bacteria or PCR.

• Clostridiodes Difficile:-Etiology: Clostridiodes difficile-Associated conditions: Antibiotic-associated diarrhea, colitis. -Risk factors: Older patients, immunocompromised, recent antibiotic use. -Signs/Symptoms: Diarrhea, abdominal pain, fever, (frequent stools with blood or pus). Can become severe with toxic megacolon.

• Acute Rheumatic Fever:Pathophysiology: Autoimmune reaction subsequent to untreated strep pharyngeal infection.

• Clinical features: Arthritis, carditis, subcutaneous nodules, erythema marginitum, Sydenham's chorea (late finding, 8 months after initial infection).

• Treatment: Aspirin, corticosteroids, treatment for underlying strep infection (penicillin).

• Other diseases listed in the slides were presented in a summary format. A more detailed analysis should include symptoms, treatment, risk factors, diagnosis, etc.

Test your medical knowledge with this clinical diagnosis quiz that presents various patient cases across different age groups and symptoms. Evaluate your ability to diagnose conditions based on provided medical scenarios and concepts, including infectious diseases and microbiology.