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A patient undergoing emergency surgery for trauma receives 20 blood transfusions during the operation. Four weeks later, she develops a syndrome resembling infectious mononucleosis. Which of the following is the most likely causative organism?
CMV is probably transmitted in the leukocyte component of transfusions. The syndromes include fever and lymphocytosis. Screening donors for this virus reduces the incidence of transmission.
A 32-year-old woman acutely develops high fever, hypotension, and rash. This is followed by vomiting, diarrhea, confusion, and abdominal pain. In the hospital, evidence of multiorgan failure develops. Desquamation of the skin occurs 1 week after the acute illness. On further history, the illness started 3 days after the onset of menstruation. Which of the following is the most likely diagnosis?
TSS is most characteristically seen in females using vaginal tampons and is secondary to staphylococcal enterotoxins called TSS toxin 1 (TSST-1). Abrupt onset is characteristic. The clinical criteria for diagnosis include high fever, a diffuse rash that desquamates on the palms and soles over the subsequent 1–2 weeks, hypotension, and involvement in three or more organ systems. This involvement can include GI dysfunction (vomiting and diarrhea), renal insufficiency, hepatic insufficiency, thrombocytopenia, myalgias with elevated creatine kinase (CK) levels, and delirium. Staphylococcal scaled skin syndrome most often affects newborns and children. It results in localized or quite extensive fluid-filled blisters that easily rupture to expose denuded skin. It is caused by an exfoliative toxin.
An 18-year-old man develops fever, neck stiffness, and headache. On examination, his blood pressure is 105/80 mm Hg, pulse 100/min, temperature 38.7C, and neck flexion is very painful. The ears, throat, and sinuses are normal; there are no focal neurologic signs, and the remaining examination is normal. His is the second case of meningitis in his university dormitory building. Which of the following is the most likely causative organism?
In epidemics, N. meningitidis is usually the cause, generally serotype A (sub-Saharan Africa) or C (North America). Serotype B is more common in sporadic outbreaks.
A 45-year-old woman is undergoing chemotherapy for breast cancer. She presents 10 days after her last chemotherapy with fever (temperature >38.5C), but no other symptoms except a sore throat and mouth. On examination, she looks well, there is oral mucositis, ears are normal, lungs are clear, and the central line site is clean. The CXR, urinalysis, and biochemistry are normal. Her WBC is 800/mL and the absolute neutrophil count is low (<500). Which of the following is the most appropriate next step in management?
Several antibiotic combinations could be used and may vary with the indigenous organisms. Aminoglycoside and cephalosporin are commonly used in combination. The antibiotic combination must cover both Gram-positive and Gram-negative organisms. Antifungal or viral agents are not empirically started unless there is an appropriate clinical fungal or viral infection. In some centers, empiric antifungal agents are started if the patient remains febrile on antibiotics after 5 days. Observation alone is not an option, since these individuals usually have some form of bacteremia causing the fever.
An elderly bedridden patient in the hospital develops cough, fever, and shortness of breath. On examination, the JVP is 4 cm, heart sounds are normal, and there are crackles on inspiration in the right lower lobe. A CXR reveals a new right lower lobe infiltrate and his WBC is 15,000/mL. He was admitted to the hospital 7 days ago for the treatment of congestive heart failure. Which of the following is the most likely diagnosis?
Hospital-acquired pneumonia is defined as pneumonia occurring >48 hours after admission and not incubating at the time of admission. It is caused by S. aureus, Gram-negative bacilli, or Streptococcus pneumoniae. Mixed aerobic and anaerobic infections are also common. Pulmonary embolism is always a consideration in the diagnosis based on clinical probability. The elevated WBC makes atelectasis unlikely and the normal JVP rules out congestive heart failure.
A 74-year-old man residing in a nursing home develops symptoms of high fever, diarrhea, chest pain, and nonproductive cough. His temperature is 40C, blood pressure 120/80 mm Hg, respiration 24/min, and oxygen saturation 90%. He has bibasilar crackles, normal heart sounds, and a soft nontender abdomen. His CXR reveals bilateral lower lobe infiltrates. He is not able to provide any sputum, and the urine is positive for legionella antigen. Which of the following is the most appropriate antibiotic choice?
Legionnaires’ disease is transmitted via infectious aerosols and may cause severe disease characterized by dry cough and fevers. Mild infections and asymptomatic seroconversion also occur. Natural reservoirs for the organisms include streams, hot springs, and stagnant lakes. Amplifiers are man-made water supplies that favor growth of legionellae. Common amplifiers are hot water systems and heat exchange units. Treatment of choice is either a newer generation macrolide-like azithromycin, or a respiratory quinolone-like levofloxacin or moxifloxacin. Erythromycin is also an option but the newer macrolides are better tolerated. Tetracyclines or TMP/SMX are second line options, and the cephalosporins are not effective for legionella.
A businesswoman needs to make frequent trips to South America, but every time she is there, she develops traveler’s diarrhea, which requires her to change her business schedule. To prevent future episodes during business trips, she is inquiring about prophylaxis methods. Which of the following is the most helpful advice for her?
Prophylactic antibiotics can prevent enteric bacterial infections, but at the cost of drug side effects (rash, Clostridium difficile colitis) and the possibility of developing an infection with a drug-resistant organism. Most experts recommend against taking daily prophylaxis unless the consequences of traveler’s diarrhea outweigh the risks of the side effects. Such individuals include patients with inflammatory bowel disease (IBD), or immunocompromised states like transplant recipients. Bismuth subsalicylate at a dosage of two tablets (525 mg) four times a day is safe and effective for up to 3 weeks, but can be difficult to take because of the large quantity required. It is also only 60% effective in preventing symptoms. Improving food and drink selection and appropriate caution are the best advice, and medications are only indicated if moderate or severe symptoms develop, including taking loperamide for severe diarrhea.
The dental condition illustrated in Fig. is usually associated with a congenital infectious disease. The teeth are characterized by centrally notched, widely spaced, peg-shaped upper central incisors and molars that have poorly developed cusps. Which of the following is the most likely diagnosis?
Figure illustrates Hutchinson’s teeth, which is a manifestation of late congenital syphilis. This may be associated with cardiovascular and neurologic manifestations as well as “saddle nose” and “saber shins.”
A 53-year-old man with alcoholic cirrhosis presents with increasing jaundice and abdominal discomfort. He reports no fevers or chills. On examination, his blood pressure is 100/60 mm Hg, pulse 100/min, temperature 38.1C. He has a distended abdomen, peripheral edema, and shifting dullness. The abdomen is tender and bowel sounds are present. A diagnostic paracentesis is performed; the total cell count is 940/mL with polymorphonuclear neutrophils (PMNs) equal to 550/mL, Gram stain is negative, and cultures are pending. Which of the following is the most likely diagnosis?
The findings of SBP can be subtle and not as dramatic as that of secondary peritonitis (when bacteria contaminate the peritoneum). As many as 80% of patients with SBP will present with fever. Preexisting ascites is almost always present, but only 10% of cirrhotics at most will develop SBP. The microbiology is characteristically that of a single organism (E. coli most commonly). Polymicrobial infection should suggest the possibility of peritonitis secondary to a perforation. More than 300 PMNs/L of ascitic fluid is said to be diagnostic.
A 20-year-old woman presents with headache, anorexia, chilly sensations, pain, and drawing sensations in both sides of her jaw. She has also noticed discomfort in both lower abdominal quadrants. Physical examination reveals bilateral enlarged parotid glands that are doughy, elastic, and slightly tender; with a reddened orifice of Stensen’s duct. Her abdomen is soft with bilateral lower quadrant abdominal tenderness, a temperature of 38.5°C, and a pulse rate of 92/min. Laboratory data show hemoglobin 13 g/dL; hematocrit 40%; WBC 9000/mL, with 35% segmented neutrophils, 7% monocytes, and 58% lymphocytes. Which of the following is the most likely diagnosis?
Mumps is an acute, communicable infection with localized swelling of one or more salivary glands. At times, gonads, meninges, pancreas, and other organs can be involved. Up to 25% of infections are inapparent clinically. The virus is transmitted in saliva but is also found in urine, and this might be another source of transmission.
Which of the following statements concerning Lyme disease is correct?
Lyme disease is caused by the spirochete B. burgdorferi, a fastidious microaerophilic bacterium. It is a tick-transmitted disease but is not caused by the tick. The incubation period is 3–32 days and is associated, initially, with minimal immune response. Perhaps as many as 25% of patients lack the characteristic skin lesion.
An 18-year-old woman visits her physician because of 3 weeks of malaise, 2 weeks of fever, and a sore throat. Physical examination shows pharyngeal infection with enlarged tonsils and a patchy, white exudate; enlarged, palpable anterior and posterior cervical, axillary, and inguinal lymph nodes; tenderness in the right upper quadrant; and minimal splenomegaly. Laboratory data show hemoglobin 14 g/dL; hematocrit 42%; platelets 380,000/mL; WBC 8500/mL, with 35% segmented neutrophils, 1% eosinophils, and 64% lymphocytes, of which 36% were atypical. Which of the following is the most likely diagnosis?
Infectious mononucleosis is an acute, selflimited infection of the lymphatic system by the EBV. Typical infectious mononucleosis has an incubation period of 4–8 weeks. The prodrome includes malaise, anorexia, and chills, and then the classic symptoms of pharyngitis, fever, and lymphadenopathy develop. Headache is also common.
A 19-year-old woman was traveling in a rural area of South America. She returned 3 weeks ago and, over the past few days, has gradually developed lower abdominal pain and diarrhea. Now the symptoms are much worse with 10 stools a day consisting mostly of mucus and blood. She is afebrile, the abdomen is tender in left lower quadrant, and the remaining examination is normal. Her stool is mostly comprised of blood and mucus. Which of the following is the most likely causative organism?
An 18-year-old man develops fever, neck stiffness, and headache. On examination, his blood pressure is 110/80 mm Hg, pulse 100/min, temperature 38.7C, and neck flexion is very painful. The ears, throat, and sinuses are normal; there are no focal neurologic signs; and the remaining examination is normal. There are no reported similar cases in the community. Which of the following is the most likely causative organism?
In adults (age >15 years), S. pneumoniae is the single most common organism, accounting for one-third to one-half of all cases. This pneumococcal predominance is even more pronounced in sporadic cases.
A 21-year-old man presents with symptoms of headache, fever, chills, and discomfort in both sides of his jaw. He has also noticed discomfort in his testes, but no dysuria or urethral discharge. Physical examination reveals bilateral enlargement of the parotid glands, as well as bilateral testicular enlargement and tenderness on palpation. His temperature is 38.5°C pulse rate of 92/min, and the remaining examination is normal. Laboratory data show hemoglobin 15 g/dL; hematocrit 40%; WBC 12000/mL, with 30% segmented neutrophils, 8% monocytes, and 62% lymphocytes. Which of the following statements concerning this disease is true?
Orchitis occurs in about 20% of males, but is usually unilateral, thus sterility is rare. The disease is caused by a paramyxovirus and one infection confers lifelong immunity. The incubation period is 14–18 days. Serum amylase is elevated in most cases of mumps because of parotitis, not pancreatitis. Other complications include thyroiditis, myocarditis, and polyarthritis.
A 43-year-old businesswoman is developing a new enterprise in Mexico. On her most recent trip, she developed diffuse watery diarrhea with severe cramps 1 week after arriving. The illness resolved after about 2 days with no further complications. Which of the following is the most likely causative organism?
The most common cause of traveler’s diarrhea worldwide is toxigenic E. coli. In North Africa and Southeast Asia, Campylobacter infections predominate. Other causative organisms include Salmonella, Shigella, rotavirus, and the Norwalk agent. The most common parasite causing traveler’s diarrhea is Giardia lamblia.
A 22-year-old man is an avid spelunker (cave explorer) and has recently been exploring several caves. A routine CXR taken for a new job reveals hilar adenopathy and two patches of pneumonitis. His physical examination is completely normal. Careful questioning reveals he has just gotten over a “cold” with mild fever, cough, and malaise. Which of the following is the most likely diagnosis?
Histoplasma capsulatum is a dimorphic fungus with worldwide distribution. In the United States, it is particularly common in Southeastern, mid-Atlantic, and Central states. It is frequently found in soil enriched by droppings of certain birds and bats. Caves are common sites of infection. Most infections are asymptomatic or mild and require no therapy. Acute disseminated infection usually occurs in patients with HIV infection or other immunocompromised states, but chronic dissemination can occur in immunocompetent patients. Findings may include hepatosplenomegaly, lymphadenopathy, anemia, and Addison’s disease. Mediastinal fibrosis can result in superior vena cava compression. Fibrosis can also involve the pulmonary arteries, esophagus, and pulmonary veins. Only rare nonviable organisms are found on pathologic examination in such cases. The prognosis is generally poor.
A previously well 28-year-old female has developed gradual onset of fever and malaise over 2–3 weeks. She also complains of arthralgias and myalgias. Repeated measurement of her temperature reveals a low grade fever between 38C and 39C. Physical examination reveals an oval retinal hemorrhage with a clear, pale center; a pansystolic cardiac murmur heard best at the apex; and small, tender nodules on her fingertips. Which of the following is the most likely causative organism?
This woman likely has native valve endocarditis, probably in the setting of a previous valvular abnormality. Streptococci cause over half the cases of native valve endocarditis in nonintravenous drug abusers. Of these, 75% are viridans streptococci. Streptococcus bovis is the most common nonviridans streptococcus causing endocarditis and is usually found in the older population (60 years), particularly if bowel lesions are present. Staphylococcal endocarditis is the next most common type, but it is usually associated with a more acute presentation. Enterococci cause about 6% of cases in native valve endocarditis, but fungi are rare causes.
A 55-year-old man is receiving chemotherapy for colon cancer. His last dose was 2 weeks ago, and he now has symptoms of fevers and chills but no other localizing symptoms. His examination is normal except that he is pale. Investigations reveal that he is neutropenic (absolute neutrophil count <500/mL), and his CXR is normal.
Cytotoxic chemotherapy frequently results in neutropenia and subsequently Gram-negative bacillary infection. Pseudomonas, Staphylococcus, Candida, and Aspergillus infections are also common.
An 18-year-old man of European decent with selective immunoglobulin A (IgA) deficiency presents with another respiratory tract infection. He has had two episodes of pneumonia in the past year requiring antibiotic therapy. He now has symptoms of fever, cough, and sputum production. His CXR reveals a right lower lobe infiltrate.
Selective immunoglobulin A (IgA) deficiency predisposes to G. lamblia infection, hepatitis virus, and S. pneumoniae. H. influenzae infection occurs, but this is not as characteristic as Giardia.
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