25. The answer is b. (Braunwald, 15/e, pp 1125-1131.) Influenza A is a potentially lethal disease in the elderly and chronically debilitated patient. In institutional settings such as nursing homes, outbreaks are likely to be particularly severe. Thus prophylaxis is extremely important in this setting. All residents should receive the vaccine unless they have known egg allergy (patients can choose to decline the vaccine). Since protective antibodies to the vaccine will not develop for 2 weeks, amantadine can be used for protection against influenza A during the interim 2-week period. A reduced dose is given to elderly patients. 26. The answer is c. (Braunwald, 15/e, p 896.) In the treatment of hospitalacquired staphylococcal pneumonia, the incidence of methicillin-resistant staph in the local facility will be very important. In most hospitals, methicillin-resistant staph is common enough to require initial therapy with vancomycin. Oxacillin would be the drug of choice only if the incidence of methicillin-resistant staph is very low. Quinolones are often useful in the treatment of community-acquired pneumonia, but they would not be effective against methicillin-resistant staph. 27. The answer is b. (Braunwald, 15/e, p 1479.) The Infectious Disease Society of America’s guidelines on the treatment of community-acquired pneumonia still recommend the use of sputum gram stain and culture. This is particularly important in the era of multi-antibiotic-resistant S. pneumoniae. Sputum culture and sensitivity can direct specific antibiotic therapy for the patient as well as provide epidemiologic information for the community as a whole. A good sputum sample showing many polymorphonuclear leuko- cytes and few squamous epithelial cells can give important clues to etiology. A Gram stain that shows gram-positive lancet-shaped diplococci intracellu- larly is good evidence for pneumococcal infection. Empirical antibiotic ther- apy becomes more difficult in community-acquired pneumonia as more pathogens are recognized and as the pneumococcus develops resistance to penicillin, macrolides, and even quinolones. 28. The answer is b. (Braunwald, 15/e, pp 1031-1034.) Multidrugresistant tuberculosis (TB) has become an increasing problem in several settings, including correctional facilities and health care institutions. Noncompliance or poor compliance with prescribed anti-TB medications is the major factor in the development of multiple drug resistance. When the disease is suspected, patients should be placed in respiratory isolation and sputum should be obtained for AFB stain, culture, and sensitivity. Treatment of high-risk patients, such as this patient, should be supervised, and multidrug resistance should be assumed. Regular screening of inmates and staff for TB is important for preventing the spread of TB within the facility and for early diagnosis of new infections. 29. The answer is b. (Braunwald, 15/e, pp 242, 954.) The outbreak described is similar to those previously attributed to Escherichia coli 0157:H7. Ingestion of and infection with this organism may result in a spectrum of illnesses, including mild diarrhea, hemorrhagic colitis with bloody diarrhea, acute renal failure, and death. Infection has been associated with ingestion of contaminated beef (in particular ground beef ), ingestion of raw milk, and contamination via the fecal-oral route. Cooking ground beef so that it is no longer pink is an effective means of preventing infection, as are hand washing and pasteurization of milk. 30. The answer is b. (Stobo, 23/e, pp 547-551.) Patients may develop fever as a result of infectious or noninfectious diseases. The term fever of unknown origin (FUO) is applied when significant fever persists without a known cause after an adequate evaluation. Several studies have found the leading causes of FUO to include infections, malignancies, collagen vascu- lar diseases, and granulomatous diseases. As the ability to more rapidly diagnose some of these diseases increases, their likelihood of causing undi- agnosed persistent fever lessens. Infections such as intraabdominal abscesses, tuberculosis, hepatobiliary disease, endocarditis (especially if the patient had previously taken antibiotics), and osteomyelitis may cause FUO. In immunocompromised patients, such as those infected with HIV, a number of opportunistic infections or lymphomas may cause fever and escape early diagnosis. Self-limited infections such as influenza should not cause fever that persists for many weeks. Neoplastic diseases such as lymphomas and some solid tumors (e.g., hypernephroma and primary or metastatic disease of the liver) are associated with FUO. A number of col- lagen vascular diseases may cause FUO. Since conditions such as systemic lupus erythematosus are more easily diagnosed today, they are less frequent causes of this syndrome. Adult Still’s disease, however, is often difficult to diagnose. Other causes of FUO include granulomatous diseases (i.e., giant cell arteritis, regional enteritis, sarcoidosis, and granulomatous hepatitis), drug fever, and peripheral pulmonary emboli. Factitious fever is most com- mon among young adults employed in health-related positions. A prior psychiatric history or multiple hospitalizations at other institutions may be clues to this condition. Such patients may induce infections by self- injection of nonsterile material, with resultant multiple abscesses or polymicrobial infections. Alternatively, some patients may manipulate their thermometers. In these cases, a discrepancy between temperature and pulse or between oral temperature and witnessed rectal temperature will be observed. 31. The answer is a. (Mandell, 5/e, pp 917-923.) Although no evidence exists that prophylactic antibiotic therapy prevents endocarditis, prophy- laxis is recommended for all procedures that may generate bacteremias. Following cardiac catheterization, blood cultures obtained from a distal vein are rarely positive. Thus, prophylactic antibiotics are not currently recommended for cardiac catheterization. Bacteremia commonly occurs following other procedures such as periodontal surgery, tonsillectomy, and prostate surgery. 32. The answer is d. (Mandell, 5/e, pp 1811-1819.) Rabies is caused by a bullet-shaped rhabdovirus. In the United States, dogs are seldom rabid. The animals that present the most danger are wild skunks and bats; foxes are also possible carriers. Raccoons are responsible for an increasing num- ber of cases in the mid-Atlantic states. The incubation period ranges from 4 days to many years, but is usually between 20 and 90 days. The incuba- tion period is usually shorter with a bite to the head than with one to an extremity. In humans, only four definite recoveries from established infec- tion have been reported. Nonimmunized animals that have been bitten should be killed and their brains submitted for virus by immunofluores- cent antibody examination. A negative fluorescent test removes the need to treat the bite victim either actively or passively. 33-36. The answers are 33-c, 34-d, 35-e, 36-b. (Gorbach, 2/e, pp 1334-1335, 1387, 1648, 1692.) Parvovirus B19 is the agent responsible for erythema infectiosum, also known as fifth disease. This disease most com- monly affects children between the ages of 5 and 14 years, but it can also occur in adults. The disease is characterized by a slapped-cheek rash, which may follow a prodrome of low-grade fever. A diffuse lacelike rash may also occur. Complications in adults include arthralgias, arthritis, aplastic crisis in patients with chronic hemolytic anemia, spontaneous abortion, and hydrops fetalis. Desquamation of the skin usually occurs during or after recovery from toxic shock syndrome (associated with a toxin produced by S. aureus). Peeling of the skin is also seen in Kawasaki disease, scarlet fever, and some severe drug reactions. Petechial rashes are often seen with potentially life-threatening infections, including meningo- coccemia, gonococcemia, rickettsial disease, infective endocarditis, atypi- cal measles, and disseminated intravascular coagulation (DIC) associated with sepsis. Infectious mononucleosis is the usual manifestation of infec- tion with Epstein-Barr virus. Since it is a viral disease, antibiotic therapy is not indicated. A diffuse maculopapular rash has been observed in over 90% of patients with infectious mononucleosis who are given ampicillin. The rash does not represent an allergic reaction to β-lactam antibiotics. 37-41. The answers are 37-e, 38-d, 39-c, 40-b, 41-a. (Mandell, 5/e, pp 1555, 1776-1780, 1801-1807.) Although salivary adenitis is the most prominent feature of the communicable disease of viral origin, mumps, involvement of the gonads, meninges, and pancreas is not uncommon. Males who develop mumps after puberty have a 20 to 35% chance of developing a painful orchitis. Central nervous system involvement is com- mon but usually mild, with 50% of cases causing an increase in lympho- cytes detectable in the CSF. Myocarditis, thrombocytopenic purpura, and polyarthritis may also occur as complications of this disease. An inflamma- tory change in the pancreas is a potentially serious problem; symptoms consist of abdominal discomfort and a gastroenteritis-like illness. Although a polyneuritis and a transverse myelitis have been described, the most common manifestation of CNS infection with varicella (chickenpox) is acute cerebellar ataxia. While chickenpox is usually a benign illness in chil- dren, other complications such as myocarditis, iritis, nephritis, orchitis, and hepatitis may occur. Pneumonitis occurs more commonly in adults than children. It can be difficult to distinguish between the vesicular lesions of small- pox and chickenpox. Classically, however, a history of rash with vesicles that develop over a few hours would be typical of a chickenpox infection; vesiculation that develops over a period of days is the rule in smallpox. While fever is characteristic of the prodrome of smallpox, it subsides prior to focal eruptions. Lesions of smallpox are typically all at the same stage of development, in contrast to the various stages seen in a patient with chickenpox. Preparations of vesicular fluid under electron microscopy show characteristic brick-shaped particles with poxvirus. A more readily available test, the Tzanck smear, performed by scraping the base of the lesion, should reveal multinucleated giant cells microscopically in a patient with chickenpox. Humoral immunity appears to be very important in the recovery from enteroviral infections. One of the most common complica- tions for patients with sex-linked or acquired agammaglobulinemia is a chronic central nervous system infection with an echovirus. In the absence of the ability to produce antibodies, this virus spreads rapidly and usually produces a fatal illness. The administration of intravenous preparations of gamma globulin intraventricularly has controlled this serious complication of immune deficiency in some patients. It may take from 9 to 11 days after exposure for the first symptoms of measles to develop. Malaise, irritability, and a high fever often associated with conjunctivitis with prominent tearing are common symptoms. This prodromal syndrome may last from 3 days to 1 week before the character- istic rash of measles develops. One or two days before the onset of the rash, characteristic Koplik spots (small, red, irregular lesions with blue-white centers) may be visible on the mucous membranes and occasionally on the conjunctiva. Classically, the measles rash will begin on the forehead and spread downward, and the Koplik spots will rapidly resolve. 42-46. The answers are 42-a, 43-d, 44-b, 45-e, 46-c. (Braunwald, 15/e, pp 1880-1896.) Pneumonia due to P. carinii was among the first rec- ognized manifestations of AIDS. The chest radiograph typically shows a diffuse bilateral interstitial pattern, but other patterns, including a normal radiograph, may occur. Pneumocystis infection may also occur at extrapul- monary sites. Cytomegalovirus (CMV) is a frequent disseminated pathogen that causes retinitis that may lead to blindness. CMV may also cause pneu- monitis, adrenalitis, and hepatitis, as well as colitis with significant diar- rhea. The protozoan Cryptosporidium may cause a chronic diarrhea that leads to malabsorption and wasting. It can be diagnosed by direct examination of the stool with special concentration or staining techniques or both. Salmonella infections have been recognized with increased frequency in patients with HIV. These patients are typically bacteremic and develop bacteremic relapse; they do not usually present with a diarrheal illness. Patients who present with seizures warrant evaluation for toxoplasmosis. CNS lymphoma and certain other infections may also cause seizures. Patients with toxoplasmic encephalitis may also have toxoplasmic chorioretinitis, although CMV remains the most common identified cause of retinitis in patients with AIDS. 47-51. The answers are 47-c, 48-b, 49-e, 50-d, 51-a. (Braunwald, 15/e, pp 936-937, 1050-1052, 1230.) Treatment of gonococcal infections should be guided by the increasing frequency of antibiotic-resistant Neisse- ria gonorrhoeae and high frequency of co-infection with Chlamydia tra- chomatis. Because of the increased frequency of resistance to penicillin and tetracyclines, ceftriaxone is recommended as the treatment of choice. Doxycycline is added to treat chlamydial and other causes of nongonococ- cal urethritis. First episodes of genital herpes may be particularly severe. Oral acyclovir will accelerate the healing but will not reduce the risk of recurrence once the drug is stopped. Trichomoniasis is usually diagnosed by a wet preparation microscopic examination or by culture. Both the patient and sexual partner should be treated with metronidazole. Penicillin remains the drug of choice for treatment of syphilis. The route of adminis- tration and duration of therapy depend on the stage of disease and pres- ence of CNS involvement and may also be influenced by the HIV serostatus of the patient.