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270. The answer is E. (Chapter 137) Although this patient's gram stain suggests gono-coccal infection, there is a high incidence of concomitant chlamydial infection. Therefore, he should be treated for both gonorrhea and chlamydia. In addition, a serum test for syphilis and counseling regarding testing for human immunodeficiency virus (HIV) are warranted. This patient should also be educated about condom use and advised to have his sexual partners checked for sexually transmitted diseases (STDs). Metronidazole is not routinely administered unless trichomonas is seen on microscopic urinalysis.

271. The answer is B. (Chapter 137) All of the antibiotic regimens listed are recommended by the Centers for Disease Control and Prevention (CDC) guidelines as effective therapies for gonococcal infection except the single dose of azithromycin 2 g orally. The CDC guidelines suggest 2 g spectinomycin intramuscularly as an acceptable alternative therapy. Azithromycin 1 g orally as a single dose is effective against localized chlamy-dial infection such as cervicitis or urethritis or for postexposure prophylaxis but is insufficient to treat pelvic inflammatory disease.

272. The answer is B. (Chapter 137) There are three stages of syphilis. The primary stage usually occurs about 21 days after initial infection and is characterized by a painless chancre on the penis, vulva, or other area of sexual contact. These typical lesions usually resolve within 3 to 6 weeks. The second stage of syphilis occurs 3 to 6 weeks after the end of the primary stage. Stage II includes nonspecific symptoms (headache, sore throat, fever, malaise), diffuse lymphadenopathy, and rash. The rash is usually dull red and papular, first occurring on the trunk and flexor surfaces and then spreading to the palms and soles. The tertiary stage of syphilis may occur years after inital infection and is characterized by cardiovascular and nervous system involvement. Findings can include tabes dorsalis, acute meningitis, dementia, and thoracic aneurysm. HIV-positive patients may have an accelerated course.

273. The answer is C. (Chapter 137) This patient has acute herpes simplex infection, spread by direct contact with mucosal skin or with nonintact skin. Smears of the lesions may stain for intranuclear bodies, but direct culture of the lesions has a greater sensitivity. Most patients (60 to 90 percent) have at least one recurrent outbreak because the virus remains latent after initial infection. Appropriate therapy includes different regimens of acyclovir, famciclovir, or valacyclovir. Dysuria and systemic symptoms such as fever, headache, and myalgias are common, and some patients develop aseptic meningitis.

274. The answer is E. (Chapter 137) The patient's symptoms and examination findings would determine the treatment. All of the antibiotics listed, plus penicillin and ceftriaxone, are considered safe during pregnancy. If the safety of any treatment is in doubt, an obstetrician should be consulted.

275. The answer is D. (Chapter 138) The CDC formulated a case definition of toxic shock syndrome (TSS) in 1980. In addition to the findings of a fever, hypotension, and rash, at least three of the following organ systems must be involved—gastrointestinal: vomiting, profuse diarrhea; musculoskeletal: severe myalgias or twofold increase in CPK; renal: increase in blood urea nitrogen (BUN) and creatinine two times normal level, pyuria without evidence of infection; mucosal inflammation: vaginal, conjunctival, or pharyngeal hyperemia; hepatic involvement: hepatitis (twofold elevation of bilirubin, AST, ALT); hematologic: thrombocytopenia < 100,000 platelets/^L; central nervous system (CNS): disorientation without focal neurologic signs. Although not included in the case definition, involvement of the respiratory system, and development of adult respiratory distress syndrome (ARDS) and refractory hypotension are late manifestations of TSS that represent end-organ damage.

276. The answer is A. (Chapter 138) TSS was initially a disease of young, healthy, menstruating women (50 percent of cases in 1986 and 1987). Changes in tampon composition and a heightened public and professional awareness of the risks of tampon use are credited for a change in epidemiology. At present, men comprise one-third of patients with TSS, and another 25 percent of cases have been associated with postpartum and S. aureus vaginal infections in nonmenstruating women. In addition, TSS has been associated with nasal packing (nasal tampons) and has been reported after influenza and influenza-like illnesses. Staphylococcus aureus and S. pyogenes are associated with TSS and TSLS, respectively. The TSST-1 exotoxin is a significant factor in the development of many TSS symptoms. Sequelae of TSS are numerous and include a high rate of neurologic deficits. Up to 60 percent of patients who do not receive p-lactamase-stable antibiotics have recurrence of the disease, usually within 2 months of the initial episode, but sometimes up to 1 year later. This second episode is usually less severe than the first, but deaths have resulted from recurrences of mild cases.

277. The answer is C. (Chapter 139) PCP is the most common opportunistic infection in AIDS patients, and more than 80 percent of patients acquire PCP at some time during their illness. Common symptoms include nonproductive cough, shortness of breath, and exertional dyspnea. Chest x-ray findings often demonstrate bilateral alveolar infiltrates, but 5 to 10 percent of patients have a negative chest film. PCP is often the presumptive diagnosis in HIV-positive patients with unexplained hypoxia. Initial therapy for PCP is trimethoprim-sulfamethoxazole (TMP-SMX) orally or intravenously; pentamidine iso-thionate is an acceptable alternative. An ABG should be obtained and results used to determine the need for initiation of steroid therapy. Reinfection is common, and prophylactic therapy with TMP-SMX, inhaled pentamidine, or dapsone is recommended.

278. The answer is D. (Chapter 139) Common etiologies of neurologic symptoms in AIDS patients include AIDS dementia, Toxoplasma gondii, and Cryptococcus neoformans. Of these, toxoplasmosis is most likely to cause focal encephalopathy. It may present with headache, fever, focal neurologic deficits, altered mental status, or seizures. Computed tomographic (CT) findings of ring-enhancing lesions are suggestive of toxo-plasmosis; however, lymphoma, fungal infections, and cerebral tuberculosis may present with similar findings. Other infections such as HSV encephalitis, bacterial meningitis, brain abscess, cytomegalovirus (CMV) encephalitis, and neurosyphilis should be considered in the differential diagnosis of neurological symptoms in AIDS patients.

279. The answer is A. (Chapter 139) Drug reactions are common among HIV patients, and all of the medications listed except acyclovir have been associated with rash. In addition to TMP-SMX, clindamycin, ibuprofen, and dapsone, isoniazid, and pentamidine have been shown to cause rash in HIV patients. Acyclovir has been associated with headache and gastrointestinal symptoms including nausea, vomiting, and diarrhea.

280. The answer is E. (Chapter 139) All of the statements regarding CMV retinitis are true except E. Characteristic funduscopic findings of CMV retinitis are fluffy white retinal lesions, often perivascular. Cotton-wool spots are the most common eye finding in

AIDS patients and are thought to be secondary to microvascular lesions unrelated to CMV. These lesions often resolve spontaneously, and no specific therapy is indicated.

281. The answer is C. (Chapter 140) This patient should receive Td because she cannot remember the last time she received tetanus prophylaxis. In addition, she should receive TIG becayse the wounds are more than 6 h old and are contaminated with dirt. Tetanus prophylaxis in the ED is especially important in elderly Americans (>70 years of age), the majority of whom lack adequate immunity to tetanus. Intravenous drug users and immigrants are also at disproportionate risk of contracting tetanus.

282. The answer is B. (Chapter 140) Tetanospasmin, an exotoxin produced by C. tetani, is responsible for the clinical manifestations of tetanus. These manifestations include muscular rigidity, violent muscular contractions, and autonomic nervous system instability. The most common presenting complaint for patients with generalized tetanus is pain and stiffness in the masseter muscle. Tetanospasmin produces these effects by preventing release of 7-aminobutyric acid (GABA) and glycine from presynaptic terminals thus preventing the normal inhibitory control in the CNS. Clostridium tetani remains localized to the site of the injury. The exotoxin tetanospasmin reaches the CNS by retrograde intraneuronal transport from the peripheral nervous system.

283. The answer is D. (Chapter 141) In developing countries, the most common reservoir of rabies virus is the dog. However, in the United States, new human rabies cases are most commonly associated with exposure to wild carnivores. Rabid wildlife species recorded by the CDC in 1988 include skunks, racoons, bats, and foxes. Domestic species found to be rabid include cats, cows, dogs, and other livestock. Rodents (e.g., squirrels, chipmunks, hamsters, rats, and mice) and lagomorphs (e.g., rabbits and hares) are not rabies carriers.

284. The answer is D. (Chapter 141) Rabies prophylaxis should be considered for travelers to areas where rabies is endemic and for people who engage in wildlife trapping, animal handlers, and veterinarians. The regimen for prophylaxis consists of three doses of human diploid cell vaccine (HDCV) 1 mL intramuscularly at days 0, 7, and 21 or 28. In most vaccinated persons, immunity lasts for 2 years. Rabies antibody titers are usually not required after immunization has been completed but should be considered in anyone who is immunocompromised or is taking immunosuppressive drugs. In this case, the patient may be taking chloroquine simultaneously for malaria prophylaxis, and antibody titers may be warranted. Postvaccination titers should be checked 2 to 4 weeks after immunization has been completed. For any exposure that occurs, immediate treatment consists of thoroughly cleaning the wounds with soap, removing devitalized tissue, copious irrigation with sterile saline or water, and avoidance of suturing. Following these postexposure recommendations reduces the subsequent incidence of rabies by about 90 percent.

285. The answer is E. (Chapter 142) In this case, the infecting organism is probably P. vivax because of the geographic location of the patient's exposure. It is more likely that the patient is suffering a relapse than a reexposure. Relapses may occur in patients with P. vivax or P. ovale because chloroquine therapy does not reach exoerythrocytic parasites that remain dormant in the liver. The recommended therapy for uncomplicated, non-chloroquine-resistant P. vivax is chloroquine phosphate 1-g load, 500 mg in 6 h, and then 500 mg/day for 2 days, plus primaquine phosphate 26.3-mg load (15-mg base) per day for 14 days upon completion of chloroquine therapy. Unless primaquine therapy follows chloroquine therapy, relapses of malaria are common. Relapses of malaria also occur in patients who have previously received "successful" therapy.

286. The answer is A. (Chapter 142) The CDC reports that between 1990 and 1994 more than half of all cases of malaria among U.S. citizens were due to P. falciparum and were acquired from travels in Sub-Saharan Africa. There have also been reports of widespread chloroquine-resistant P. falciparum throughout this area. The appropriate chemoprophy-laxis in this case would be mefloquine rather than chloroquine. In addition, travelers should use mosquito netting, wear long-sleeved clothing, stay in well-screened areas between dusk and dawn, and use pyrethrum-containing insect sprays. Spray can be applied to clothes for additional protection, and an insect repellant containing N,N-diethylmetatoluamide (DEET) should be applied to exposed skin. Even with appropriate chemoprophylaxis and personal protection, it is possible to contract malaria.

287. The answer is E. (Chapter 144) The incidence of food-borne illness is staggering, and the increasing availability of imported fruits and vegetables and an increase in international travel has facilitated the transmission of these diseases across continents. Exact prevalence is difficult to determine because most infections are undiagnosed and unre-ported. The use of antacids, H2 blockers, antibiotics affecting indigenous intestinal bacteria, and antiperistaltic agents can all increase susceptibility to developing a food-borne illness. Viral infections are the most common overall cause of diarrheal disease, but travelers' diarrhea is most likely of bacterial etiology.

288. The answer is C. (Chapter 144) Information regarding ill contacts, recent food and water exposure, and host susceptibility are important factors in making a diagnosis of food-borne illness. Most infectious diarrhea is self-limiting, and routine studies for ova and parasites and stool cultures are not cost effective. If symptoms persist for more than 3 or 4 days, especially when accompanied by dehydration or fever, laboratory studies may be indicated. Fecal leukocytes in stool samples suggest a bacterial pathogen, but the absence of fecal leukocytes does not exclude a bacterial etiology; therefore, the test has limited diagnostic efficacy.

289. The answer is A. (Chapter 144) Enterotoxigenic E. coli is the major cause of travelers' diarrhea. Other strains associated with travel include enterohemorrhagic and enteroinvasive E. coli. All of the organisms listed are also travel-related pathogens, mostly seen after international travel by U.S. citizens. Additional etiologies of travelers' diarrhea include Salmonella, Brucella, Cryptosporidium, and hepatitis A.

290. The answer is D. (Chapter 144) The patient's symptoms developed 9 h after the ingestion of the suspected contaminated food. Of the organisms listed, only V. para-haemolyticus has an incubation period of 6 to 24 h. Staphylococcus aureus and Norwalk viruses usually produce symptoms 1 to 6 h after exposure. Enterotoxigenic E. coli produces symptoms 24 to 48 h after exposure, and Campylobacter produces symptoms 2 to 6 days after ingestion of contaminated food. Vibrio poisoning is commonly associated with ingestion of seafood.

291. The answer is B. (Chapter 145) All of the diseases listed except Q fever may be contracted by a tick bite. Rocky Mountain spotted fever is caused by a rickettsial organism, Rickettsia rickettsia. Relapsing fever is caused by a spirochete, Borrelia burgdorferi. Tularemia is caused by a gram-negative nonmotile coccobacillus, Francisella tularemia. The protozoan parasites, Babesia microti and B. equi, cause babesiosis. Q fever is unique in that it is the only rickettsial infection acquired by aerosol inhalation rather than by an arthropod vector. Q fever is common among domesticated farm animals in the United States and is shed in urine, feces, and afterbirth. The rickettsial organism responsible for causing Q fever is Coxiella burnetti.

292. The answer is C. (Chapter 145) Most viral zoonotic pneumonias are caused by influenza. Influenza types A, B, and C infect humans, but only influenza type A is transmitted between vertebrate animals and humans. In addition to migrating waterfowl, horses and marine mammals can serve as reservoirs. There is also evidence for transmission of influenza virus between specific species, such as humans and pigs. Pandemics of human influenza are believed to occur as a combination of antigenic drift of viral surface proteins

(hemagglutinin and neuraminidase) and a zoonotic reservoir for the virus. Influenza pneumonia carries a high mortality rate, especially in patients older than 70 years. Antiviral therapy with amantadine and rimantadine is effective against influenza A but not against types B or C. Annual influenza vaccination is recommended for healthcare workers.

293. The answer is A. (Chapter 146) Gas-forming soft tissue infections are rapidly progressive. The incubation period is short, with symptoms occurring fewer than 3 days after inoculation. Patients frequently describe pain out of proportion to physical findings and a sensation of "heaviness" of the affected part. On examination, the skin is often bronze-colored with brawny edema and crepitance. Bullae and a malodorous serosan-guinous discharge may be seen. Patients are often irritable or confused and have low-grade fevers with tachycardia out of proportion to the fever. Common laboratory findings include leukocytosis, anemia, metabolic acidosis, thrombocytopenia, coagulopathy, myo-globinemia, and myoglobinuria and abnormalities of kidney or liver function tests. Radi-ologic studies may demonstrate gas within soft tissue planes and within the peritoneal or retroperitoneal spaces.

294. The answer is C. (Chapter 146) Cutaneous abscesses represent 1 to 2 percent of all presenting complaints to EDs. Most patients can be treated with incision and drainage of the abscess and discharged from the ED with follow-up in 2 to 3 days. Antibiotic use is controversial. The risk of systemic infection after local incision and drainage appears to be low. In patients with diabetes, alcoholism, or other underlying immunocompromised states, the threshold for antibiotic use should be lower. In addition, patients with signs of systemic disease such as fever, chills, or cellulitis extending beyond the abscess borders should be strongly considered for antibiotic therapy.

295. The answer is C. (Chapter 147) All of the STDs listed except HIV are reportable communicable diseases according to the CDC guidelines. HIV is reportable in the pediatric population (< 13 years old). In patients older than 13 years, HIV disease is not reportable until the disease has progressed to AIDS. The current CDC definition of AIDS requires an HIV-infected adult to have: (1) a CD4 T lymphocyte count of less than 200, (2) a CD4 T lymphocyte count less than 14 percent of total lymphocytes, or (3) any of the following: pulmonary tuberculosis, recurrent pneumonia, invasive cervical cancer, or 23 other clinical conditions that are listed on the World Wide Web at www.cdc.gov/epo/mmwr/mmwr.html.

296. The answer is D. (Chapter 150) Herpes simplex virus 1 is a frequent cause of cranial nerve (CN) VII (Bell's) palsy. All of the signs or symptoms described can be found with a simple peripheral CN VII palsy, except sparing of the forehead musculature on the affected side. Central CN VII lesions spare the forehead musculature because of cross-inervation from the opposite side. However, a peripheral lesion should cause the patient to be unable to wrinkle the brow on the ipsilateral side. If the forehead is spared, additional investigations such as head CT or magnetic resonance imaging are warranted. The differential diagnosis of Bell's palsy includes tumor, stroke, Guillain-Barre syndrome, Lyme disease, and Ramsay Hunt syndrome. In addition, if a Bell's palsy is found with an otitis media, mastoiditis, or parotitis, an ENT specialist should be consulted.

297. The answer is B. (Chapter 150) CMV is a common herpes virus that is present in 40 to 100 percent of adults, depending on geographic location, socioeconomic status, attendance at day care, and sexual behavior. Symptomatic CMV infections usually occur in the advanced stages of HIV disease and can cause significant morbidity. CMV retinitis occurs in more than 10 percent of AIDS patients and may be treated acutely with gan-cyclovir for 2 to 3 weeks, followed by lifetime suppressive therapy. The natural course of CMV retinitis involves progression to blindness, but the disease process may be slowed with the use of gancyclovir. Gancyclovir cannot cure patients of their CMV, and it does not reverse loss of sight that has already occurred. In addition to retinitis, CMV can cause esophagitis, colitis, or adrenalitis in HIV patients.

298. The answer is A. (Chapter 148) The CDC instituted six basic universal precautions, including all of the listed recommendations, except the recommendation regarding puncture-proof gloves. Gloves should be worn routinely when contact with blood or other body fluids is anticipated. However, to date, no acceptable puncture-proof glove is available. Needles should never be recapped, and they should be disposed of in special "sharps" containers. Pregnant healthcare workers should be aware of the risk of perinatal HIV transmission.

299. The answer is C. (Chapter 148) Certain groups of healthcare workers are at greater risk for contracting TB. Factors to consider include contact with a large number of infected patients, exposure to highly infectious patients, increased ventilation rate of the worker, the duration of exposure, and air-exchange rates in the environment. An increased air-exchange rate in the environment allows for greater filtration of air and a reduction in the number of potentially infective particles in the environment. Healthcare workers in the inner city are at greatest risk for contracting TB. OSHA regulations require healthcare workers and visitors who enter rooms of known or suspected TB patients to wear high-efficiency particulate air masks. All healthcare workers are advised to participate in TB screening and prophylaxis programs.

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