Ectoparasites and vector-borne diseases US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Ectoparasites and vector-borne diseases. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Ectoparasites and vector-borne diseases US Medical PG Question 1: A 34-year-old man comes to the physician because of progressive swelling of the left lower leg for 4 months. One year ago, he had an episode of intermittent fever and tender lymphadenopathy that occurred shortly after he returned from a trip to India and resolved spontaneously. Physical examination shows 4+ nonpitting edema of the left lower leg. His leukocyte count is 8,000/mm3 with 25% eosinophils. A blood smear obtained at night confirms the diagnosis. Treatment with diethylcarbamazine is initiated. Which of the following is the most likely route of transmission of the causal pathogen?
- A. Penetration of the skin by hookworms in feces
- B. Penetration of the skin by cercariae from contaminated fresh water
- C. Deposition of larvae into the skin by a female black fly
- D. Ingestion of encysted larvae in undercooked pork
- E. Deposition of thread-like larvae into the skin by a female mosquito (Correct Answer)
Ectoparasites and vector-borne diseases Explanation: ***Deposition of thread-like larvae into the skin by a female mosquito***
- The symptoms described, including progressive **nonpitting edema** (lymphedema), a history of **fever** and **lymphadenopathy** after travel to an endemic area (India), and significant **eosinophilia**, are classic for **lymphatic filariasis**.
- Lymphatic filariasis, caused by filarial worms like *Wuchereria bancrofti* or *Brugia malayi*, is transmitted by **mosquitoes** that deposit infectious larvae onto the skin during a blood meal.
*Penetration of the skin by hookworms in feces*
- This describes the transmission of **hookworm infection**, which causes **iron deficiency anemia** and gastrointestinal symptoms, not lymphedema or high eosinophilia with nocturnal microfilaremia.
- While hookworms can cause eosinophilia, the clinical presentation of chronic lymphedema and the need for a nocturnal blood smear point away from hookworm infection.
*Penetration of the skin by cercariae from contaminated fresh water*
- This is the transmission method for **schistosomiasis**, which can cause symptoms depending on the species and affected organs, such as **urinary tract disease**, **hepatic fibrosis**, or **intestinal inflammation**.
- Schistosomiasis does not typically present with the progressive lymphedema and episodic lymphadenitis characteristic of filariasis.
*Deposition of larvae into the skin by a female black fly*
- This describes the transmission of **onchocerciasis** (river blindness), caused by *Onchocerca volvulus*.
- Onchocerciasis primarily causes skin disease (intense **pruritus**, dermatitis) and **ocular lesions** leading to blindness, not extensive lymphedema of the limbs.
*Ingestion of encysted larvae in undercooked pork*
- This is the route of transmission for **trichinellosis**, caused by *Trichinella spiralis*.
- Trichinellosis involves **muscle pain**, fever, and periorbital edema, but not chronic lymphedema of the extremities or the specific nocturnal periodicity for diagnosis.
Ectoparasites and vector-borne diseases US Medical PG Question 2: A 45-year-old man presents to the physician with complaints of fever with rigors, headache, malaise, muscle pains, nausea, vomiting, and decreased appetite for the past 3 days. He informs the physician that he had been backpacking on the Appalachian Trail in the woods of Georgia in the month of June, 2 weeks ago, and had been bitten by a tick there. His temperature is 39.0°C (102.3°F), pulse is 94/min, respirations are 18/min, and blood pressure is 126/82 mm Hg. His physical exam does not reveal any significant abnormality except for mild splenomegaly. Laboratory studies show:
Total white blood cell count 3,700/mm3 (3.7 x 109/L)
Differential count
Neutrophils 85%
Lymphocytes 12%
Monocytes 2%
Eosinophils 1%
Basophils 0%
Platelet count 88,000/mm3 (95 x 109/L)
Serum alanine aminotransferase 140 IU/L
Serum aspartate aminotransferase 80 IU/L
Microscopic examination of a peripheral blood smear stained with Wright-Giemsa stain shows the presence of morulae in the cytoplasm of leukocytes. In addition to drugs for symptomatic relief, what is the most appropriate initial step in the treatment of this patient?
- A. Doxycycline (Correct Answer)
- B. Ceftriaxone
- C. Rifampin
- D. Ciprofloxacin
- E. Daptomycin
Ectoparasites and vector-borne diseases Explanation: ***Doxycycline***
- The patient's presentation with **fever, myalgia, headache, thrombocytopenia, leukopenia, elevated liver enzymes**, a history of **tick bite** in an endemic area (Appalachian Trail, Georgia), and the presence of **morulae in leukocytes** strongly indicates **ehrlichiosis** or **anaplasmosis**.
- **Doxycycline** is the **first-line treatment** for all rickettsial diseases, including ehrlichiosis and anaplasmosis, regardless of age or pregnancy status, due to its effectiveness in preventing severe complications.
*Ceftriaxone*
- While effective against many bacterial infections, **ceftriaxone** is **not effective** against intracellular bacteria like *Ehrlichia* or *Anaplasma*.
- It is typically used for conditions like Lyme disease (later stages), meningitis, or community-acquired pneumonia, which do not match the complete clinical picture here.
*Rifampin*
- **Rifampin** is sometimes used for treatment of ehrlichiosis in patients who **cannot tolerate doxycycline**, but it is **not the first-line agent**.
- Its primary uses are for tuberculosis and prophylaxis of meningococcal disease, making it an inappropriate initial choice given the classic presentation.
*Ciprofloxacin*
- **Ciprofloxacin** is a fluoroquinolone antibiotic primarily used for urinary tract infections, respiratory infections, and some gastrointestinal infections.
- It has **no significant activity** against species of *Ehrlichia* or *Anaplasma* and is therefore not indicated for this condition.
*Daptomycin*
- **Daptomycin** is a lipopeptide antibiotic used for treating **Gram-positive bacterial infections**, especially those resistant to other antibiotics (e.g., MRSA).
- It is **ineffective** against the intracellular Gram-negative bacteria causing ehrlichiosis or anaplasmosis.
Ectoparasites and vector-borne diseases US Medical PG Question 3: A 33-year-old man presents to the emergency department with a fever and fatigue. He states that he has not felt well since he returned from a hiking trip in Alabama. He is generally healthy and has no other medical conditions. His temperature is 101°F (38.3°C), blood pressure is 127/85 mmHg, pulse is 108/min, respirations are 14/min, and oxygen saturation is 99% on room air. Physical exam including a full dermatologic inspection is unremarkable. Laboratory studies are ordered as seen below.
Hemoglobin: 13 g/dL
Hematocrit: 39%
Leukocyte count: 2,200/mm^3 with normal differential
Platelet count: 77,000/mm^3
Serum:
Na+: 139 mEq/L
Cl-: 100 mEq/L
K+: 4.3 mEq/L
HCO3-: 24 mEq/L
BUN: 19 mg/dL
Glucose: 98 mg/dL
Creatinine: 1.3 mg/dL
Ca2+: 10.2 mg/dL
AST: 92 U/L
ALT: 100 U/L
Which of the following is the most likely diagnosis?
- A. Lyme disease
- B. Babesiosis
- C. Influenza
- D. Ehrlichiosis (Correct Answer)
- E. Rocky Mountain spotted fever
Ectoparasites and vector-borne diseases Explanation: ***Ehrlichiosis***
- This patient's symptoms (fever, fatigue), recent travel to an **endemic area** (Alabama), **leukopenia** (WBC 2,200/mm^3), **thrombocytopenia** (platelet 77,000/mm^3), and **elevated liver enzymes** (AST 92, ALT 100) are highly characteristic of ehrlichiosis, a **tick-borne disease**.
- The absence of a rash helps differentiate it from some other tick-borne illnesses.
*Lyme disease*
- While Lyme disease is also tick-borne, it typically presents with an **erythema migrans rash**, which is absent in this case.
- Lyme disease is less commonly associated with the **pronounced leukopenia** and **thrombocytopenia** seen here.
*Rocky Mountain spotted fever*
- Rocky Mountain Spotted Fever (RMSF) is characterized by a **maculopapular rash** that often starts on the ankles and wrists and spreads centrally, involving the palms and soles. This rash is absent in the patient.
- While RMSF can cause thrombocytopenia and elevated liver enzymes, the **lack of rash is a key differentiator**.
*Babesiosis*
- Babesiosis is a tick-borne parasitic infection that causes **hemolytic anemia**, which is not clearly indicated by the patient's hemoglobin and hematocrit, and typically results in severe fatigue and sometimes splenomegaly.
- This condition is often seen in immunocompromised individuals or those without a spleen, and the labs here are more consistent with ehrlichiosis than babesiosis.
*Influenza*
- Influenza presents with fever, fatigue, myalgia, and respiratory symptoms, but it does not cause **thrombocytopenia**, **leukopenia**, or **elevated liver enzymes** to the extent seen in this patient.
- The symptoms are more indicative of a **tick-borne illness** given the travel history and specific lab abnormalities.
Ectoparasites and vector-borne diseases US Medical PG Question 4: A 32-year-old woman presents to your office with abdominal pain and bloating over the last month. She also complains of intermittent, copious, non-bloody diarrhea over the same time. Last month, she had a cough that has since improved but has not completely resolved. She has no sick contacts and has not left the country recently. She denies any myalgias, itching, or rashes. Physical and laboratory evaluations are unremarkable. Examination of her stool reveals the causative organism. This organism is most likely transmitted to the human host through which of the following routes?
- A. Insect bite
- B. Penetration of skin (Correct Answer)
- C. Sexual contact
- D. Inhalation
- E. Animal bite
Ectoparasites and vector-borne diseases Explanation: ***Penetration of skin***
- The symptoms of **abdominal pain**, **bloating**, **intermittent copious non-bloody diarrhea**, and a recent **cough** are highly suggestive of a **hookworm infection**.
- Hookworm larvae (filariform larvae) primarily penetrate the skin, usually through bare feet, as their mode of entry into the human host.
*Insect bite*
- Although some parasitic infections are transmitted by insect bites (e.g., malaria, Chagas disease), hookworms are not transmitted this way.
- **Insect-borne diseases** typically present with different clinical manifestations or geographical associations.
*Sexual contact*
- **Sexually transmitted infections** involve direct contact of mucous membranes or body fluids during sexual activity.
- Hookworm infection transmission through sexual contact is not a recognized route.
*Inhalation*
- **Inhalation** is a route of transmission for respiratory pathogens (e.g., influenza, tuberculosis) or certain fungal infections, but not for hookworms.
- While hookworm larvae migrate through the lungs, the initial infection pathway is not via inhalation.
*Animal bite*
- **Animal bites** transmit diseases like rabies or certain bacterial infections, but not parasitic hookworms.
- Hookworm infection does not result from direct contact with an animal's saliva or puncture wound.
Ectoparasites and vector-borne diseases US Medical PG Question 5: A 42-year-old man presents to a free dermatology clinic, complaining of itchy skin over the past several days. He has no insurance and lives in a homeless shelter. The patient has no significant medical history. Physical evaluation reveals 2 mm erythematous papules and vesicles on his back and groin, with linear excoriation marks. Careful observation of his hands reveals serpiginous, grayish, threadlike elevations in the superficial epidermis, ranging from 3–9 mm in length in the webbing between several digits. What should be the suggested treatment in this case?
- A. No medication should be administered, only proper hygiene.
- B. Antiviral medication
- C. Permethrin (Correct Answer)
- D. Antifungal medication
- E. Broad-spectrum antibiotic
Ectoparasites and vector-borne diseases Explanation: ***Permethrin***
- This patient's symptoms, including intense itching, erythematous papules and vesicles, linear excoriations, and especially the **serpiginous, grayish, threadlike elevations (burrows)** in the web spaces of the fingers, are classic signs of **scabies**.
- **Permethrin cream** (5%) is the first-line treatment for scabies due to its high efficacy and safety profile, targeting the *Sarcoptes scabiei* mite.
*No medication should be administered, only proper hygiene.*
- While good hygiene is important for overall health, it is **insufficient** to eradicate a parasitic infestation like scabies.
- Scabies requires **specific pharmacologic intervention** to kill the mites and eggs, as they are not simply washed away.
*Antiviral medication*
- **Antiviral medications** are used to treat viral infections (e.g., herpes, varicella), which do not present with the characteristic burrows or respond to antiviral agents.
- The patient's symptoms are indicative of a **parasitic infestation**, not a viral one.
*Antifungal medication*
- **Antifungal medications** are indicated for fungal infections (e.g., ringworm, candidiasis), which typically present with a different morphology (e.g., annular lesions with raised borders) and lack the classic burrows seen in scabies.
- The clinical presentation points away from a fungal etiology.
*Broad-spectrum antibiotic*
- **Broad-spectrum antibiotics** treat bacterial infections. While secondary bacterial infections can occur due to scratching in scabies, the primary issue here is the mite infestation itself, which antibiotics do not address.
- Treating the primary scabies infestation is crucial to stop the itching and prevent further secondary infections.
Ectoparasites and vector-borne diseases US Medical PG Question 6: A 20-year-old man comes to the physician because of a 3-day history of fever, myalgia, and swelling in his left groin after a recent camping trip in northern California. He appears acutely ill. Physical examination shows tender, left-sided inguinal lymphadenopathy and an enlarged, tender lymph node in the right axilla that is draining bloody necrotic material. Microscopic examination of a lymph node aspirate shows gram-negative coccobacilli with bipolar staining and a safety-pin appearance. This patient's condition is most likely caused by an organism with which of the following reservoirs?
- A. Squirrels (Correct Answer)
- B. Deer
- C. Bats
- D. Dogs
- E. Birds
Ectoparasites and vector-borne diseases Explanation: ***Squirrels***
- The clinical presentation of **fever**, **myalgia**, **tender lymphadenopathy (buboes)**, especially with **bloody necrotic material drainage**, in a patient with recent outdoor exposure in **northern California**, is highly suggestive of **bubonic plague**.
- Microscopic examination revealing **gram-negative coccobacilli with bipolar staining** and a **safety-pin appearance** is **pathognomonic for *Yersinia pestis***, the causative agent of plague.
- The primary reservoir for *Y. pestis* is **wild rodents**, particularly **ground squirrels, prairie dogs, and rock squirrels** in the western United States, including California.
- Transmission occurs via flea bites from infected rodents, or through direct contact with infected animals.
*Deer*
- **Deer** are not reservoirs for *Yersinia pestis*.
- Deer serve as reservoirs for **Lyme disease** (*Borrelia burgdorferi*) transmitted by *Ixodes* ticks, which presents with erythema migrans, not buboes with bipolar-staining bacteria.
- Deer may also harbor ticks that transmit other diseases (ehrlichiosis, anaplasmosis), but none match this clinical picture.
*Bats*
- **Bats** are not associated with *Yersinia pestis* infection.
- Bats are reservoirs for **rabies virus** and **Histoplasma capsulatum** (histoplasmosis from bat guano in caves).
- Neither presents with the characteristic bubonic lymphadenopathy and gram-negative coccobacilli with bipolar staining seen here.
*Dogs*
- **Dogs** are not primary reservoirs for plague, though they can become infected and rarely transmit to humans.
- Dogs are reservoirs for **rabies**, **leptospirosis**, and **Capnocytophaga** infections.
- These do not match the clinical presentation of buboes and the pathognomonic microscopic findings of *Y. pestis*.
*Birds*
- **Birds** are not reservoirs for *Yersinia pestis*.
- Birds can harbor **Chlamydophila psittaci** (causing psittacosis/atypical pneumonia) and **Cryptococcus neoformans** (in pigeon droppings).
- These present with respiratory symptoms, not bubonic lymphadenopathy with bipolar-staining bacteria.
Ectoparasites and vector-borne diseases US Medical PG Question 7: A 24-year-old female comes to the physician because of flu-like symptoms and a new rash for 2 days. She denies contacts with sick individuals or recent travel abroad, but recently went camping in Vermont. Vital signs are within normal limits. Examination of the lateral right thigh shows a circular red ring with central clearing. Which of the following is the natural reservoir of the pathogen responsible for this patient's symptoms?
- A. Rat
- B. Rabbit
- C. Tick
- D. Mouse (Correct Answer)
- E. Flea
Ectoparasites and vector-borne diseases Explanation: ***Mouse***
- The patient's symptoms, including **flu-like illness** and a **circular red rash with central clearing** (erythema migrans) after camping in Vermont, are classic for **Lyme disease**.
- The causative agent, *Borrelia burgdorferi*, is primarily maintained in **white-footed mice** (genus *Peromyscus*) in its natural reservoir during its larval and nymphal stages.
*Rat*
- While **rats** can carry and transmit various diseases, they are not the primary natural reservoir for *Borrelia burgdorferi*, the pathogen responsible for Lyme disease.
- Diseases associated with rats often include **leptospirosis** and **plague**, which present with different clinical pictures.
*Rabbit*
- **Rabbits** are known reservoirs for diseases like **tularemia** (*Francisella tularensis*), which can cause fever, skin lesions, and lymphadenopathy, but typically not the characteristic **erythema migrans** rash.
- They are not a significant natural reservoir for *Borrelia burgdorferi*.
*Tick*
- The **tick** (specifically *Ixodes scapularis* or **deer tick**) is the **vector** that transmits *Borrelia burgdorferi* to humans, not the natural reservoir.
- The tick acquires the bacteria from infected animal hosts such as mice and deer.
*Flea*
- **Fleas** are vectors for diseases such as **bubonic plague** (*Yersinia pestis*) and **endemic typhus** (*Rickettsia typhi*), which do not manifest with erythema migrans.
- They are not involved in the transmission or natural history of **Lyme disease**.
Ectoparasites and vector-borne diseases US Medical PG Question 8: A 29-year-old man comes to the physician because of a 3-day history of a swollen right knee. Over the past several weeks, he has had similar episodes affecting the right knee and sometimes also the left elbow, in which the swelling lasted an average of 5 days. He has a history of a rash that subsided 2 months ago. He lives in Connecticut with his wife and works as a landscaper. His temperature is 37.8°C (100°F), pulse is 90/min, respirations are 12/min, and blood pressure is 110/75 mm Hg. Physical examination shows a tender and warm right knee; range of motion is limited by pain. The remainder of the examination shows no abnormalities. His hematocrit is 44%, leukocyte count is 10,300/mm3, and platelet count is 145,000/mm3. Serum electrolyte concentrations are within normal limits. Arthrocentesis is performed and the synovial fluid is cloudy. Gram stain is negative. Analysis of the synovial fluid shows a leukocyte count of 70,000/mm3 and 80% neutrophils. Serologic testing confirms the diagnosis. Which of the following is the most likely cause?
- A. Rheumatoid arthritis
- B. Neisseria gonorrhoeae
- C. Borrelia burgdorferi (Correct Answer)
- D. Campylobacter jejuni
- E. Osteoarthritis
Ectoparasites and vector-borne diseases Explanation: ***Borrelia burgdorferi***
- The patient's **migratory polyarthritis** (affecting knee and elbow intermittently), history of a **rash** (consistent with erythema migrans), and residence in an **endemic area** (Connecticut) strongly suggest **Lyme disease**.
- **Synovial fluid analysis** showing high leukocyte count with neutrophilic predominance is typical of inflammatory arthritis, including Lyme arthritis, and **serologic testing** will confirm the presence of *Borrelia burgdorferi* antibodies.
*Rheumatoid arthritis*
- While rheumatoid arthritis causes inflammatory polyarthritis, it typically presents with **symmetrical joint involvement**, morning stiffness, and often involves smaller joints first, which is not described.
- The presence of a preceding **rash** and resolution within weeks is not characteristic of rheumatoid arthritis.
*Neisseria gonorrhoeae*
- **Disseminated gonococcal infection** can cause migratory polyarthralgia or septic arthritis, but it is typically associated with a history of recent unprotected sexual activity and often with tenosynovitis or dermatitis (pustular or vesicular lesions).
- While gram stain is negative in this case, gonococcal arthritis usually has a more rapid onset and systemic symptoms.
*Campylobacter jejuni*
- *Campylobacter jejuni* is a common cause of **reactive arthritis**, which can cause inflammatory joint pain after a gastrointestinal infection.
- However, reactive arthritis typically involves the **lower extremities** and has a specific pattern of oligoarthritis, often with enthesitis or dactylitis, and the preceding rash and geographical factors do not fit.
*Osteoarthritis*
- Osteoarthritis is a **degenerative joint disease** characterized by pain that worsens with activity and improves with rest, and typically affects older individuals.
- It does not present with a preceding **rash**, migratory inflammatory episodes, or a highly inflammatory synovial fluid (high leukocyte count with neutrophilic predominance).
Ectoparasites and vector-borne diseases US Medical PG Question 9: A 32-year-old man is brought to the physician by his wife for a 3-day history of fever, headaches, and myalgias. He returned from a camping trip in Oklahoma 10 days ago. He works as a computer salesman. His temperature is 38.1°C (100.6°F). Neurologic examination shows a sustained clonus of the right ankle following sudden passive dorsiflexion. He is disoriented to place and time but recognizes his wife. Laboratory studies show a leukocyte count of 1,700/mm3 and a platelet count of 46,000/mm3. A peripheral blood smear shows monocytes with intracytoplasmic morulae. Which of the following is the most likely causal organism?
- A. Coxiella burnetii
- B. Rickettsia rickettsii
- C. Anaplasma phagocytophilum
- D. Borrelia burgdorferi
- E. Ehrlichia chaffeensis (Correct Answer)
Ectoparasites and vector-borne diseases Explanation: ***Correct: Ehrlichia chaffeensis***
- The presence of **intracytoplasmic morulae** in **monocytes** is a pathognomonic sign for *Ehrlichia chaffeensis* infection, which causes **human monocytic ehrlichiosis**.
- The patient's symptoms of **fever, headache, myalgias, thrombocytopenia, leukopenia**, and the history of a **camping trip** in an endemic area (Oklahoma) are highly consistent with ehrlichiosis.
*Incorrect: Coxiella burnetii*
- This bacterium causes **Q fever**, characterized by fever, headache, and atypical pneumonia, but it does **not cause intracytoplasmic morulae** in monocytes or frequently lead to the degree of leukopenia and thrombocytopenia seen here.
- While it can be acquired from environments, the **microscopic findings** rule it out in this specific case.
*Incorrect: Rickettsia rickettsii*
- This organism causes **Rocky Mountain spotted fever**, which presents with fever, headache, myalgias, and a characteristic **rash** that is usually present on the palms and soles, none of which are mentioned here.
- It does not form **intracytoplasmic morulae** in monocytes.
*Incorrect: Anaplasma phagocytophilum*
- This bacterium causes **human granulocytic anaplasmosis**, which is clinically similar to ehrlichiosis but forms **morulae in granulocytes** (neutrophils), not monocytes.
- The peripheral blood smear specifically identifies morulae in **monocytes**, directing towards *Ehrlichia*.
*Incorrect: Borrelia burgdorferi*
- This spirochete causes **Lyme disease**, characterized by an **expanding erythematous rash (erythema migrans)**, fever, and musculoskeletal symptoms, but it does not cause leukopenia or thrombocytopenia.
- It does not produce **morulae** in any blood cells.
Ectoparasites and vector-borne diseases US Medical PG Question 10: A 45-year-old male presents to his primary care physician complaining of drainage from his left great toe. He has had an ulcer on his left great toe for over eight months. He noticed increasing drainage from the ulcer over the past week. His past medical history is notable for diabetes mellitus on insulin complicated by peripheral neuropathy and retinopathy. His most recent hemoglobin A1c was 9.4%. He has a 25 pack-year smoking history. He has multiple sexual partners and does not use condoms. His temperature is 100.8°F (38.2°C), blood pressure is 150/70 mmHg, pulse is 100/min, and respirations are 18/min. Physical examination reveals a 1 cm ulcer on the plantar aspect of the left great toe surrounded by an edematous and erythematous ring. Exposed bone can be palpated with a probe. There are multiple small cuts and bruises on both feet. A bone biopsy reveals abundant gram-negative rods that do not ferment lactose. The pathogen most likely responsible for this patient’s current condition is also strongly associated with which of the following conditions?
- A. Otitis externa (Correct Answer)
- B. Waterhouse-Friedrichsen syndrome
- C. Gastroenteritis
- D. Toxic shock syndrome
- E. Rheumatic fever
Ectoparasites and vector-borne diseases Explanation: ***Otitis externa***
- The patient's presentation with a chronic **diabetic foot ulcer** with exposed bone and **gram-negative, non-lactose fermenting rods** on bone biopsy indicates **osteomyelitis** caused by ***Pseudomonas aeruginosa***.
- ***Pseudomonas aeruginosa*** is strongly associated with **otitis externa** (swimmer's ear), particularly **malignant otitis externa** in diabetic and immunocompromised patients.
- This is a classic association tested on USMLE: *Pseudomonas* causes both diabetic foot osteomyelitis and otitis externa.
*Waterhouse-Friedrichsen syndrome*
- This syndrome involves adrenal hemorrhage and fulminant sepsis, classically caused by ***Neisseria meningitidis***.
- Not associated with *Pseudomonas aeruginosa*.
*Gastroenteritis*
- Primarily caused by enteric pathogens such as *Salmonella*, *Shigella*, *Campylobacter*, *E. coli*, or viral agents.
- *Pseudomonas aeruginosa* is not a typical cause of gastroenteritis.
*Toxic shock syndrome*
- Caused by exotoxins from ***Staphylococcus aureus*** (TSST-1) or **Group A Streptococcus** (pyrogenic exotoxins).
- Not associated with *Pseudomonas aeruginosa*.
*Rheumatic fever*
- A delayed autoimmune complication of **Group A Streptococcal pharyngitis**.
- Not related to *Pseudomonas* infections or diabetic foot ulcers.
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