BACTARIAL
48-year-old female is hospitalized for pneumonia that was unresponsive to initial therapy on an outpatient basis. Laboratory studies significant for MRSA with a minimum inhibitory concentration (MIC) for vancomycin of 1.5 mg/L in both sputum cultures. Blood cultures show no growth. Which of the following would be an appropriate initial treatment option for this case of MRSA?
A. Daptomycin
B. Vancomycin
C. Daptomycin plus linezolid
D. Vancomycin with daptomycin plus gentamicin plus rifampin.
Correct Answer: B.
In the hospital setting, if laboratory studies reveal a vancomycin MIC ≥2, then another initial treatment agent should be considered. Vancomycin would still be the preferred agent in this case, as the MIC was <2. The duration of therapy in cases of pneumonia is generally seven days.
IV acyclovir is the first-line therapy for which of the following presentations of neonatal herpes?
A. Disseminated herpes simplex virus (HSV) infection
B. Skin, eyes, and mouth HSV infection
C. Herpes encephalitis
D. All of the above
E. A and C only
Correct Answer: D. All of the above
Because both the disseminated variant and the CNS disease variant of neonatal herpes virus infection can initially present with only cutaneous or mucosal skin lesions, intravenous acyclovir is indicated as the first-line therapy.
Up to 60% of patients who will eventually develop HSV encephalitis (a characteristic of CNS disease) will present with similar cutaneous findings to patients with neonatal HSV infection confined to the skin and mucous membranes.
According to clinical trials performed on immune reconstitution inflammatory syndrome (IRIS) in HIV patients, which of the following subtypes of patients were found to benefit the most from corticosteroid therapy?
A. Pneumocystis jiroveci-related IRIS
B. Mycobacterium tuberculosis-related paradoxical IRIS
C. Mycobacterium avium complex-related IRIS
D. Cryptococcus neoformans-related IRIS
Correct Answer: B.
Paradoxical IRIS presents with the worsening of tuberculosis symptoms after a period of improvement and is due to the reactivation of the patient’s immune system as a result of antituberculosis treatment or the initiation of antiretroviral therapy. According to clinical trials, the initiation of corticosteroids in this scenario has resulted in the improvement of these symptoms, in addition to a decreased length of hospital stay.
A 45-year-old male exterminator presents with a 1-week history of headaches, nonproductive coughing, and conjunctival suffusion. The patient has a history of a rat bite he received 8 days prior. Which of the following bacterial infections is most likely in this patient?
A. Salmonella species
B. Streptobacillus moniliformis
C. Leptospirosis
D. Pasteurella multocida
Correct Answer: C.
Leptospirosis is commonly associated with exposure to rats through contaminated urine as well as direct contact through rat bites. Finding of leptospirosis is conjunctival injection, headaches, a non-productive cough, and diarrhea.
A 41-year-old woman is evaluated for a 3-week history of fever, dyspnea on exertion, and dry cough. These symptoms have persisted despite an initial empiric course of amoxicillin; additionally, levofloxacin was initiated 4 days ago without improvement. She works as a landscaper, and she relocated to Arizona from the Midwest approximately 3 months ago.
On physical examination, temperature is 38.8 °C (101.8 °F), pulse rate is 113/min, and respiration rate is 17/min. On lung examination, crackles are heard in the left upper chest.
Blood and sputum cultures are negative.
Chest radiograph demonstrates an infiltrate in the left upper lobe and hilar lymphadenopathy.
Option A. Coccidioides serology
Option B. Legionella sputum culture
Option C. Pneumococcal urinary antigen
Option D. Pneumocystis polymerase chain reaction on respiratory sample
Answer : A
Coccidioides is a dimorphic fungus endemic to desert regions of the Western United States. Infection is usually acquired by inhalation of aerosolized arthroconidia;
The most common clinical presentation is pneumonia with symptoms of cough, fever, and chest pain, and is often difficult to distinguish from bacterial community-acquired pneumonia. Serologic testing for Coccidioides antibodies is recommended for initial evaluation;
Which of the following management is appropriate for preventative prophylaxis in non-HIV-infected patients with HIV-infected partners?
A. Pre-exposure prophylaxis (PrEP) should be continued until the partner’s genital secretions have undetectable HIV viral load levels.
B. PrEP is contraindicated in patients with osteoporosis.
C. After a potential exposure, the HIV-negative patient should continue therapy with PrEP for 3 months.
D. PrEP should be continued indefinitely if there is a suspicion that the infected partner is not taking combination antiretroviral therapy in a continuous manner.
ANSWER: D
EXPLANATION: In HIV-uninfected patients with HIV-infected partners who are at risk for the development of viremic failure due to medication non-compliance, PrEP should be continued indefinitely or until the partner’s serum viral load is undetectable for at least 6th months.
A 76-year-old female is transported from the nursing home to the ED complaining of persistent, non-bloody, watery diarrhea. The patient has a history of recurrent UTI and finished a course of levofloxacin about six days ago. On physical examination, her temperature is 39.4°Celsius, heart rate is 111 bpm, respiratory rate is 17/min, and blood pressure is 70/43 mm Hg, moderate tenderness on abdominal exam, without rebound or guarding. After receiving IV fluids in the ED, the patient's BP improves, but she becomes hypotensive after another 3 liters of NS. Labs are remarkable for a white blood cell (WBC) count of 25,000 cells/uL and a creatinine level of 2.6 mg/dL. Urinalysis only positive for leukocytes. Urine and stool cultures are pending. An abdominal CT reveals generalized bowel wall edema of the colon, no ileus, and no free air or other evidence of perforation. She is admitted for further management. What is the best treatment to initiate based on these findings?
A. Vancomycin 125 mg PO 4 times per day
B. Fidaxomicin 200 mg PO 2 times per day
C. Vancomycin 500 mg PO 4 times per day + metronidazole 500 mg intravenously every 8 hours
D. Fecal microbiota transplantation
Correct Answer: C.
Per the most recent Infectious Diseases Society of America (IDSA) guidelines, two main factors should be considered when beginning treatment for CDI: peak WBC and peak serum creatinine. These values determine whether an initial episode is non-severe, severe, or fulminant, which has treatment implications. This patient has a WBC >15,000 cells/uL, elevated creatinine, presents with shock and colitis on imaging. There is no ileus or toxic megacolon. This is considered a fulminant initial episode without ileus, and the recommended regimen for patients with fulminant colitis without ileus is oral vancomycin plus parenteral metronidazole. In the setting of ileus, fecal microbiota transplantation (FMT) administered via enema is the recommended treatment.
A 62-year-old female presents with complaints of watery diarrhea for the past 8 days. The patient lives on a pig farm. Due to her daily exposure, you decide to order a microscopic examination of a stool specimen to rule out any ova and parasites. Which of the following is the most prevalent organism found in a microscopic examination of stool specimens for ova and parasites?
A. Giardia lamblia
B. Cryptosporidium parvum
C. Blastocystis hominis
D. Entameba histolytica
ANSWER:C
Blastocystis hominis, commonly referred to simply as blastocystis species, is the most common organism found while performing microscopic examinations of stool specimens in search of ova and parasites. Although these organisms are a frequent incidental finding in asymptomatic patients, in cases such as this when the patient is presenting with a diarrheal illness lasting more than a week, it is appropriate to initiate therapy with metronidazole.
A 49-year-old man is evaluated before initiating antiretroviral therapy. He has newly diagnosed HIV infection. Medical history is also notable for coronary artery disease, hypertension, and chronic kidney disease. Medications are atorvastatin, aspirin, and lisinopril.
Labs: Cr: 1.5. eGFR: 56
CD4 cell count is 250/µL and HIV viral load is 53,841 copies/mL.
Which of the following is the most appropriate regimen for this patient?
Option A. Abacavir, dolutegravir, and lamivudine
Option B. Bictegravir, emtricitabine, and tenofovir alafenamide
Option C. Dolutegravir, lamivudine, and tenofovir disoproxil fumarate
Option D. Emtricitabine and tenofovir alafenamide
ANSWER: B
Guidelines for HIV antiretroviral therapy (ART) generally include use of two or three drugs from two different classes, preferably including an integrase strand transfer inhibitor. Comorbid conditions and drug-drug interactions should be considered when selecting a regimen. Bictegravir, emtricitabine, and TAF is a first-line recommended initial regimen that is appropriate in this patient with chronic kidney disease. TAF is converted to the active drug tenofovir intracellularly and achieves lower plasma concentrations, resulting in less bone and kidney toxicity.
Before a potential lung transplant in patients with cystic fibrosis, which of the following organisms is associated with the highest mortality rate?
a.Pseudomonas aeruginosa
b.Burkholderia cepacia complex
c. Burkholderia multivorans
d. Burkholderia cenocepacia
Correct answer: d. Burkholderia cenocepacia
EXPLANATIONS:
Burkholderia cenocepacia has the greatest increase in mortality rates in cystic fibrosis. The presence of this organism is an absolute contraindication to lung transplant procedures in these patients.
Which of the following immunosuppressive drugs potentiates the effects of maraviroc?
A. Sirolimus
B. Cyclosporine
C. Mycophenolate
D. Tacrolimus
Correct Answer: A. Sirolimus
Sirolimus has an additional effect of decreasing lymphocyte expression of the CCR5 receptor, thereby potentiating the effects of drugs such as maraviroc that act through the antagonism of CCR5.
Even with this interesting benefit, Sirolimus continues to be associated with an increased rate of allograft rejection in renal transplant patient infected with HIV and should be avoided in this population if possible
Of the choices listed, which describes the pharmacokinetics of trimethoprim/sulfamethoxazole (TMP/SMX)?
A. SMX is more lipid-soluble and has an increased volume of distribution in comparison to TMP.
B. In acidic urine, the renal clearance of SMX occurs at a higher rate.
C. Inhibition of sodium channels in the distal nephron gives rise to toxicities from TMP.
D. Levels of both TMP and SMX are affected by a lack of efficient liver function.
Correct Answer: C.
Inhibition of sodium channels in the distal nephron gives rise to toxicities from TMP. TMP may cause the competitive inhibition of Na channels located in the distal nephron, which decreases the ability of the kidney to excrete potassium effectively.
Which of the following mutations in the HIV viral enzyme integrase confers the highest level of drug resistance to integrase inhibitors?
A. N155H
B. E92Q
C. Q148H/R/K
D. R263K
Correct Answer: C. Q148H/R/K
HIV viral integrase mutations at Q148H/R/K signifies an advanced resistance level and are present in patients with ongoing virologic failure, in the course of therapy with raltegravir.
Mutations at Q148H/R/K are associated with an increase in resistance to dolutegravir in situations in which the patient has accumulated additional mutations.