426. The answer is d. (Tintinalli, 5/e, pp 943-946.) The patient has gono-coccal urethritis (gram stain is a sensitive and specific method of making the diagnosis) and concomitant Chlamydia trachomatis infection. Patients require treatment for the gonococcal infection (usually ceftriaxone intramuscularly) and doxycycline or a macrolide for eradication of the chla-mydial infection. Gonococcal resistance to penicillin and tetracycline (but not to ceftriaxone) has developed. Patients with lymphogranuloma venereum (Chlamydia trachomatis) present with inguinal buboes. Patients with chancroid (Haemophilus ducreyi) present with a painful genital ulcer. Primary syphilis is characterized by a painless chancre that appears 21 days after exposure and disappears in 3-6 wk.
427. The answer is c. (Fauci, 14/e, p 1032.) The Jarisch-Herxheimer reaction is a dramatic flulike reaction that occurs within 2 h of syphilis treatment. It may occur in patients with primary, secondary, or early latent syphilis and is thought to be secondary to the massive destruction of spiro-chetes and the formation of inflammatory mediators (tumor necrosis factor). The VDRL (RPR) is a nonspecific screening test for syphilis and reverts to negative with treatment. The FTA-ABS is a sensitive and specific diagnostic test and will remain positive for life. The rash of Rocky Mountain spotted fever begins in the palms and soles and spreads centrally; the disease may be confirmed by the Weil-Felix test.
428. The answer is d. (Fauci, 14/e, pp 919, 1776.) Patients deficient in complement components C
5, C6, C7, C8, C9 are susceptible to gonococ-cemia and meningococcemia infections due to an inability to mount a bactericidal response to these organisms.
429. The answer is b. (Fauci, 14/e, pp 1089-1091.) The patient's symptomatology is most consistent with mononucleosis. A "monospot" test (IgM or heterophile test) must be ordered to confirm the diagnosis of EBV mononucleosis syndrome. If the heterophile test is negative, the most likely etiology of the mononucleosis is CMV. Atypical lymphocytes may be seen transiently in EBV CMV, toxoplasmosis, drug reactions, viral hepatitis, rubella, mumps, and rubeola. Mononucleosis is transmitted through saliva.
430. The answer is d. (Tintinalli, 5/e, p 1054.) Organisms of the female genital tract may be acquired during passage through the birth canal and may cause meningitis in neonates. These organisms include Listeria monocytogenes, group B ^-hemolytic streptococci, and gram-negative rods such as Escherichia coli. Neonates may develop infections outside the birth canal, namely Salmonella, S. aureus, Proteus, and Pseudomonas, from contact with contaminated persons or articles after birth. The TORCHES organisms (Toxoplasmosis, Rubella, Cytomegalovirus, HErpes simplex, Syphilis) and HIV (human immunodeficiency syndrome) are other intrauterine-acquired infections.
431. The answer is d. (Mehta, p 67. Fauci, 14/e, pp 1060, 1933, 1946.) Disseminated gonococcal infection is the leading cause of bacterial arthritis in young adults. This disease often starts as an early tenosynovitis-dermatitis syndrome, which is often followed by a septic arthritis. Tenosyn-ovitis is most commonly seen over the dorsum of the hand, wrist, ankle, or knee. de Quervain's synovitis is a chronic inflammation of the common sheath of the abductor pollicis longus and extensor pollicis brevis tendons due to repetitive use and causes marked pain and tenderness in the region of the anatomic snuffbox. In Reiter syndrome, patients develop an inflammatory arthritis after an episode of urethritis, dysentery, or cervicitis. It is more common in males than females and HLA-B27 is present in more than 60% of patients. Other findings in Reiter syndrome include conjunctivitis, circinate balanitis (superficial ulcer on the glans penis) and keratoderma blennorrhagicum (papules on the soles of the feet). Patients with Still's disease present with a salmon rash, symmetrical joint involvement, and hepatosplenomegaly.
432. The answer is d. (Fauci, 14/e, p 926.) Specific gram-negative organisms are slow-growing (fastidious) and require carbon dioxide for growth. Blood cultures may take 30 days to become positive. These organisms are often referred to as the HACEK organisms (Haemophilus parainfluenza, Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae).
433. The answer is b. (Fitzpatrick, 3/e, pp 730, 740, 748, 752, 853.) The occupational history and cutaneous skin findings are consistent with sporotrichosis. The mycotic organism Sporothrix schenckii is found in the soil. The lesion begins as a painless nodule that eventually becomes fixed and necrotic. After a few weeks, multiple nodules develop along the lymphatic channels, causing a chronic nodular lymphangitis. Blastomycosis is endemic in the southeastern United States and may be found in agricultural workers but is characterized by pulmonary symptoms. Skin lesions are usually ulcerated, hyperkeratotic, and verrucous. Histoplasmosis is transmitted through bird and bat droppings and is endemic in the Ohio and Mississippi River Valleys of the United States. Agricultural workers and others involved in outdoor activities, including cave explorers, are at risk for outbreaks. An acute pulmonary infection typically precedes the skin lesions. Coccidioidomycosis is caused by a soil saprophyte endemic to the arid San Joaquin Valley of the United States (Arizona, California, and western Texas). Patients present with respiratory symptoms and skin lesions such as erythema nodosum.
434. The answer is d. (Fauci, 14/e, pp 827-830.) Necrotizing fasciitis is a painful and rapidly spreading infection of the fascia of muscle. It often begins at the site of nonpenetrating minor trauma and is usually due to Streptococcus pyogenes, although infections may be polymicrobial. Toxicity is severe and patients require immediate surgical exploration to deep fascia and muscle and subsequent debridement. Necrotizing fasciitis that leaks into the peritoneum is called Fournier's gangrene. Cellulitis is an acute inflammatory condition of the skin that causes erythema, pain, and localized swelling. Erysipelas is a painful superficial cellulitis of the face. Cellulitis is well demarcated from normal skin. Folliculitis is typically due to Staphylococcus aureus; patients present with pustules of the hair follicles. Crepitus (crackling of the skin due to small air bubbles of air moving through the tissues) may be felt in necrotizing fasciitis due to the presence of gas-producing organisms (Clostridium perfringens).
435. The answer is a. (Fauci, 14/e, pp 1182-1185.) Chloroquine-resistant malaria is an increasing problem because Plasmodium vivax and falciparum malaria may be multidrug resistant. Because of the increasing spread and intensity of plasmodium resistance, the Centers for Disease Control and Prevention recommends a weekly dose of mefloquine for all travelers. Chemoprophylaxis is never entirely reliable, and malaria must always be considered in the differential diagnosis of fever in patients who have traveled to endemic areas. Trypanosomiasis, caused by the protozoan Trypanosoma cruzi, is a parasite found only in the Americas. Patients present with the Romana sign (unilateral and painless edema of the periocular tissues) and cardiomyopathy (Chagas disease). Patients with toxo-plasmosis who are immunocompetent are generally asymptomatic and have self-limiting disease.
436. The answer is d. (Fauci, 14/e, p 573.) For unknown reasons, patients with S. bovis bacteremia have a high incidence of colon carcinoma (and perhaps upper gastrointestinal malignancies as well) and require colonoscopy.
437. The answer is c. (Sapira, p 143. Seidel, 4/e, p 232.) The more tender the node, the more likely it is to be due to inflammation. Cancerous nodes are usually nontender. The harder and more discrete the node, the more likely it is to be malignant. Arteries pulsate, not nodes. A left supraclavicu-lar node, since it is located at the end of the thoracic duct, is a clue to gastrointestinal or thoracic malignancy. A sentinel node or Virchow node is a firm supraclavicular node. A Sister Joseph node is a palpable paraumbilical node seen in patients with intrabdominal or pelvic malignancies.
438. The answer is d. (Fauci, 14/e, pp 1177-1179.) E. histolytica is the third most common cause of death by parasites worldwide after schistoso-miasis and malaria. Endemic areas include Mexico, India, Central America, South America, tropical Asia, and Africa. Patients may present with fever, right upper quadrant pain, and stools that are FOBT positive. There is no eosinophilia but alkaline phosphatase is often elevated. Abdominal radiographs (CT scan or MRI) typically show the abscesses.
439. The answer is d. (Fauci, 14/e, pp 780, 2423. Seidel, 4/e, p 790.) The patient is demonstrating signs of meningeal irritation. She has nuchal rigidity, a positive Brudzinski sign (involuntary flexion of the hips and knees when flexing the neck), and a positive Kernig sign (flexing the hip and knee when the patient is supine, then straightening out the leg, causes resistance and back pain). Other signs of meningitis include headache, photophobia, seizures, and altered mental status. Patients with meningitis
(<1%) rarely have papilledema secondary to increased intracranial pressure. Risk factors for meningitis include sinusitis, ear infection, and sick contacts. Fever of unknown origin (FUO) is defined as a fever of >101°F for 3 wk that remains undiagnosed after 1 wk of aggressive investigation.
440. The answer is b. (Fauci, 14/e, pp 835-839, 967.) Dogs are responsible for 80% of animal bites; organisms include P. multocida, Eikenella corrodens, and Capnocytophaga canimorsus (formerly called DF-2). Aero-monas hydrophila is the organism seen in bite wounds from alligators and other aquatic animals. Rabies is an acute viral disease of the central nervous system and is transmitted by infected dogs, cats, skunks, foxes, raccoons, mongooses, wolves, and bats. Pseudomonas aeruginosa may cause a variety of skin lesions, such as "hot tub folliculitis" and ecthyma gangrenosum. Vibrio parahemolyticus is an organism found in undercooked shellfish; patients present with diarrhea.
441. The answer is d. (Fauci, 14/e, pp 798-801.) The incubation period for both S. aureus and B. cereus is 1-2 h after eating. B. cereus toxicity is often due to eating fried (the toxin is heat-stable) or uncooked rice. S. aureus toxicity is usually due to eating ham, poultry, potato or egg salad, mayonnaise, or cream pastries. All the other organisms require an incubation period of >16 h. V. cholera toxicity is due to eating shellfish and causes an inflammatory (presence of fecal leukocytes) diarrhea. V. parahemolyticus toxicity is due to eating mollusks and crustaceans and causes dysentery (production of cytotoxins, bacterial invasion, and destruction of intestinal mucosal cells). Salmonella toxicity is due to eating beef, poultry, eggs, or dairy products and causes a watery diarrhea. Shigella causes dysentery and can be present in potato or egg salad, lettuce, or raw vegetables.
442. The answer is c. (Fauci, 14/e, p 797.) Pathogens that may cause an inflammatory diarrhea and produce fecal leukocytes include Shigella, Salmonella, Campylobacter jejuni, Yersinia enterocolitica, Clostridium dificile, Vibrio parahemolyticus, enterohemorrhagic E. coli, and enteroinvasive E. coli.
443. The answer is c. (Fauci, 14/e, p 1182.) The geographic distribution of glucose-6-phosphate dehydrogenase (G6PD) deficiency, sickle cell disease, sickle cell trait, and thalassemia resembles that of malaria, and having one of these disorders affords protection against P. falciparum.
444. The answer is a. (Fauci, 14/e, pp 798, 1023.) The most likely pathogen responsible for the symptoms is ciquatera poison, which is found in the Caribbean, Hawaii, and Florida and is associated with consumption of carnivorous reef fish such as grouper or barracuda. Scromboid poisoning is associated with consumption of tuna, mackerel, and dolphin; patients present with flushing, headache, dizziness, palpitations, nausea, diarrhea, and vomiting (due to histidine release). Traveler's diarrhea is predominantly due to enterotoxigenic E. coli; patients develop the symptoms within 3-5 days of arriving in a tropical area. Pseudomembranous colitis is a nosocomial infection due to Clostridium dificile; patients often have a previous history of antibiotic use. Mycobacterium marinum is an organism of swimming pools and fish tanks that produces a pustule or nodule at the site of minor trauma.
445. The answer is e. (Fauci, 14/e, p 941.) H. pylori is associated with gastritis, duodenal ulcer, gastric ulcer, non-Hodgkin's gastric lymphoma, adenocarcinoma of the stomach, and mucosa-associated tissue lymphomas (MALT).
446. The answer is b. (Fauci, 14/e, pp 824, 955, 1960.) Osteomyelitis is usually a polymicrobial infection, but S. aureus is the pathogen in over 50% of all cases. Patients with sickle cell disease are at risk of developing Salmonella osteomyelitis (>50% of all cases). Pott's disease is spinal tuberculosis; it usually involves the upper thoracic vertebral bodies.
447-450. The answers are 447-b, 448-d, 449-e, 450-g. (Fauci, 14/e, pp 902, 1063, 1179, 1206, 1225.) Trichinosis is caused by the ingestion of infected pork products. Patients present with abdominal pain, diarrhea, a maculopapular rash, periorbital edema, myositis (especially of the extraoc-ular muscles), eosinophilia, and myocarditis. Acanthamoeba castellanii is associated with contact lens usage. Brucellosis is transmitted through infected milk or raw meat or inhaled during contact with animals (i.e., by slaughterhouse workers, veterinarians, and farmers). Patients present with fever, chills, ophthalmoplegia, joint pain, skin rash, lymphadenopathy, hepatosplenomegaly, cardiac murmur, endocarditis, and meningitis. Cys-ticercosis is associated with the pork tapeworm (Taenia solium); patients commonly present with neurologic manifestations, such as seizures and signs of increased intracranial pressure. CT scan of the head often shows the calcified, multiple lesions of varying size common in neurocysticerco-sis. Giardia lamblia may be asymptomatic or may cause severe diarrhea and malabsorption. Transmission is usually waterborne (i.e., camping sites, sewers, reservoirs) since the cysts survive both cold water and routine chlo-rination. Chlamydia psittaci is associated with bird exposure; patients present with fever, cough, chest pain, dyspnea, pleural effusion, pleural rub, pericardial effusion, and pneumonia. Patients with C. tetani present with an infected wound, muscle spasms, and increased muscle tone especially of the masseter muscles (lockjaw).
450-451. The answers are 451-b, 452-a. (Fauci, 14/e, pp 1153, 1200.) Patients with HIV may develop cryptococcal meningitis. Patients present with headache, irritability, confusion, ataxia, blurred vision, papilledema, and cranial nerve palsies. Fever and neck stiffness are rare. India ink smear of the spinal fluid will demonstrate the encapsulated yeast. Lesions of toxo-plasmosis are usually multiple and ring-enhancing (lymphomas in HIV patients may also be multiple and ring-enhancing, so this description is not pathognomonic for toxoplasmosis). PML is a progressive disorder due to JC virus. The disorder is one of demyelination; patients present with visual deficits, mental impairment, and motor deficits. CT scan or MRI may show the hypodense, nonenhancing white matter lesions. Patients with HIV dementia present with apathy, hyperreflexia, clumsiness, weakness, ataxia, and loss of memory.
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