A 5-year-old girl is brought to your office with a complaint of sore throat, headache, and fever for the past 3 days. Her temperature is 39 degrees Celsius and her examination is notable for pharyngeal erythema, palatal petechiae, and bilateral anterior cervical lymphadenopathy. You obtain a rapid antigen detection test for group A Streptococcus, which is positive. This is her third episode of streptococcal pharyngitis in the last 2 months. Of the following, the MOST appropriate treatment for this patient is:

An 18-year-old young woman presents to your office with a 4-day history of left ear pain and swelling. She reports no recent trauma or insect bites to the ear, but did have a new piercing along the upper pinna about 1 week ago. Her past medical history is significant only for seasonal allergies. Physical examination shows an uncomfortable young woman complaining of 8 out of 10 pain in her left ear and left lateral neck. Vital signs show a temperature of 37 degrees Celsius, respiratory rate of 18 breaths/min, heart rate of 95 beats/min, and blood pressure of 125/65 mm Hg. Her left ear is impressively swollen, hot, erythematous, and tender along the helix; there is fluctuance with an earring embedded in the swelling. Left postauricular swelling is also seen. There is no lymphadenopathy and she has full range of motion in her neck. The left tympanic membrane and external auditory canal appeared normal. Laboratory data are as follows: WBC 10.4, lymphocytes 30%, neutrophils 66%, monocytes 1%, hemoglobin 13 g/dL, hematocrit 40%, platelet 369K. When the earring is removed, about 3 mL of pus is expressed. The pus is sent for culture and Gram stain (see picture). Of the following, the BEST choice for initial therapy is:

A 6-year-old previously healthy fully immunized boy is brought to your office by his mother. He has had a cough and runny nose for 1 week and developed fever yesterday. Today, the boy is complaining of neck pain, resists turning his head to the side, is refusing to eat, and will only take small sips of water. On physical examination, the boy is tired appearing with a temperature of 40.3 degrees Celsius, heart rate of 130 beats/min, respiratory rate of 45 breaths/min, and oxygen saturation of 98% by pulse oximetry. His lung fields are clear with good aeration. He has tender anterior cervical lymphadenopathy, torticollis, and his posterior oropharynx appears erythematous. The remainder of his physical examination is within normal limits. Of the following, the test MOST likely to confirm this boy's diagnosis is:

A 5-year-old girl presents to your clinic for evaluation of fever for 7 days. She recently returned from Pakistan where she travelled with her parents to visit family. She did not receive pre-travel vaccinations. Vital signs show a temperature of 38.7 degrees Celsius, respiratory rate of 30 breaths/min, heart rate of 120 beats/min, and blood pressure of 105/65 mm Hg. On physical examination, she has abdominal tenderness and hepatosplenomegaly. Laboratory data are: WBC 17K, segmented neutrophils 80%, lymphocytes 20%, hemoglobin 9.2 g/dL, platelet count 87K, AST 230, ALT 250. Of the following, the test that is MOST likely to establish the diagnosis in this child is:

A 10-year-old boy with spina bifida is brought to his pediatrician for evaluation of cloudy urine. He has a history of neurogenic bladder requiring catheterization. He has had multiple urinary tract infections in the past. Vital signs show a temperature of 38.1 degrees Celsius, respiratory rate of 20 breaths/min, heart rate of 88 beats/min, and blood pressure of 110/60 mm Hg. On physical examination, he has no motor function of his lower extremities. Laboratory data show: urinalysis with 3+ leukocytes and nitrite negative, urine Gram stain with gram-positive cocci in pairs and chains. Of the following, the BEST therapy for this infection is:

You are asked to evaluate a male neonate delivered earlier today to a 23-year-old woman who recently emigrated from Africa. The baby is full term, based on the mother's history, but appears very small. The mother did not receive regular prenatal care and has no documentation of any prenatal tests. She reports no major medical issues during her pregnancy other than a few minor viral illnesses. She reports only 2 sexual partners in her life and denies any unusual vaginal discharge or genitourinary symptoms. Physical examination of the neonate shows a small slightly jaundiced infant with a birth weight of 2600 g and length of 46 cm. Head circumference is 32.5 cm. Lung fields are clear. A 3/6 systolic murmur is heard at the left sternal border, with transmission into the lung fields. The murmur extends past S2, and no ejection click is appreciated. The liver can be palpated 2 cm below the right costal margin, and the spleen is palpable 2.5 cm below the left costal margin. A diffuse dark erythematous maculopapular rash is present on the torso. An ophthalmology consult has been requested for absent red reflexes bilaterally. Laboratory data include: WBC 6.9K, lymphocytes 50%, neutrophils 45%, monocytes 5%, hemoglobin 17 g/dL, hematocrit 51%, platelet count 77 K, ALT 93, AST 69. Head ultrasonography is shown. Of the following, the MOST likely pathogen to be causing these findings in this neonate is:

You are called to see a postpartum 24-year-old woman in labor and delivery. She emigrated from El Salvador 1 year ago, and was found to be HIV-positive during her prenatal care here in the United States. She just delivered a 3000 g full term female newborn and has a 3-year-old son who was born in El Salvador and emigrated with her. The 3-year-old boy is stated to be very small for his age and is frequently sick, but has only been seen once in the emergency department during the past year. She is requesting HIV testing for both of her children. Of the following, the BEST recommendations to evaluate these two children are:

An 8-month-old female infant presents to the office with a 2-day history of fever, irritability, crying, vomiting, and blood-streaked diarrhea. She was a full term infant and has no significant past medical history. The parents report no recent travel other than to visit the maternal aunt for Thanksgiving 12 days ago. The aunt had prepared chitterlings (hog intestines), but the infant did not eat any and only took formula and boiled rice the aunt had made specifically for her. No one at dinner reported any subsequent illnesses. After returning home, she developed fever, was diagnosed with otitis media, and started on a course of amoxicillin, which is nearing completion. Her immunizations are up to date. Physical exam shows an irritable crying female infant with a temperature of 39 degrees Celsius, heart rate of 120 beats/min, and respiratory rate of 30 breaths/min. Her anterior fontanelle is slightly sunken and her lips and mucosa are dry. She is making tears. Her lungs are clear to auscultation bilaterally and her heart sounds are normal. Her abdomen is soft with no guarding or rebound tenderness. There is a large amount of urine as well as blood-tinged diarrhea in her diaper. The baby is admitted to the local hospital for intravenous hydration and continued on amoxicillin. A routine stool culture is sent. She improves and is discharged after 48 hours. Three days later, the infant returns to your office and appears stable and well-hydrated. Her stool culture is noted to be negative for Salmonella, Shigella, and Campylobacter species. The mother reports that the patient is improving, but that the vomiting, fever, and bloody diarrhea are still present. Of the following, the MOST likely infectious etiology for this infant is:

An 18-year-old young woman presents to the pediatric clinic for evaluation of a rash. She was initially ill with upper respiratory symptoms, and then 5 days later, developed pruritic lesions over her extremities. Vital signs show a temperature of 37.9 degrees Celsius, respiratory rate of 18 breaths/min, heart rate of 90 beats/min, and blood pressure of 105/65 mm Hg. On physical examination, she is uncomfortable, but nontoxic in appearance. There is a rash concentrated on her hands and legs as pictured. Of the following, the MOST likely etiology for the illness is:

A 4-year-old girl is brought to your office for cold symptoms for the past 10 days. Her chief complaint is a mild sore throat, malaise, and fever to 38.3 degrees Celsius. The parents were not concerned because her symptoms were improving, but today the girl is complaining of chest pain and is refusing to eat or play. The pain is in the center of her chest and is worsened with deep breaths. She has no recent travel, and the only ill contact was a family friend from Eastern Europe who visited 2 weeks ago and had an upper respiratory infection. The girl has no significant past medical history, but she has an older sibling with autism and has not received vaccinations. Physical examination shows a female child in mild-moderate distress with a temperature of 38 degrees Celsius, heart rate of 150 beats/min, respiratory rate of 30 breaths/min, and blood pressure of 80/50 mm Hg. Her examination is significant for 2+ tonsils bilaterally with a thick gray exudate, shotty bilateral cervical adenopathy, intercostal retractions with occasional rales, distant S1 and S2 with an S3 gallop. Her extremities are warm with 2+ pulses bilaterally. The electrocardiogram shows first degree A-V block with QTc prolongation and nonspecific ST-T wave changes. Of the following, the BEST explanation for this clinical presentation is:

A 13-year-old adolescent girl and her 4-year-old brother are brought to your office because of diarrhea that has lasted over 2 weeks. The diarrhea is watery, brown, with no obvious blood, and occurs over 10 times daily. Both children have mild abdominal discomfort, but have been able to go to school. Neither child reports fever, chills, nausea, or vomiting. The children have 2 additional siblings, 11 and 7 years of age, respectively, who have no symptoms. There is no significant past medical or family history for any of the children or parents. The family was on vacation 1 month ago and spent most of the time in the resort's swimming pool. The family ate at several different restaurants. The mother reports the groundskeeper was meticulous about checking and maintaining the pool's chlorine concentration daily. Physical examination shows a female adolescent and young boy with normal vital signs and no abnormal findings on physical examination. Of the following, the MOST likely pathogen responsible for the symptoms in these children is:

A 20-month-old girl is brought to your office with complaints of fever and right ear pain. On physical examination, her temperature is 38.5 degrees Celsius. The right ear shows a bright red tympanic membrane, which is bulging with a purulent effusion. The left ear is normal. You note that this is her fourth episode of otitis media in the last 7 months. Her last ear infection was 3 weeks ago and she was treated with amoxicillin. Of the following, the BEST approach for management of this patient is to initiate a: