Case Studies Questions and Answers

Case Studies Questions and Answers You are observing a culture plate on which bacteria seem to have grown over the entire plate (even areas that weren't inoculated!). The organism on this plate most likely possesses which of the following structures that allow it to do this? Flagella Bacteria are most active at which phase of growth? Log Which of the following choices depicts correct scientific nomenclature? S. aureus S. aureus S. aureus S. Aureus S. aureus Enterotoxins are: Toxins that produce gastrointestinal symptoms Which of the following situations would most likely allow for an opportunistic pathogen to cause disease? An infant born with severe combined immunodeficiency Match the following terms with the best real world example: Infection: ear infection Healthcare-associated infection: Catherter-associated UTI Colonization: Asymptomatic presence of MRSA in healthy adults axilla Which one of the following microorganisms is NOT a common pathogen in healthcare-associated infections? Chickenpox (Varicella) Which one of the following practices of healthcare workers is most likely to expose a patient to a potential healthcare-associated infection (HAI)? Washing hands only at the beginning and end of a work shift A series of Hepatitis B vaccines is required for most (if not all) healthcare workers. Select the best rationale for this. It protects the healthcare worker from occupational exposure When should gloves be removed? Before lab coat or gown Case study #2 Interpret the Gram stain result shown above. Keep in mind that this is a gram stain of a specimen and the contestant bacteria (pink background) make bacteria look different than in pure culture. Interpret the Gram stain result shown above. Keep in mind that this is a gram stain of a specimen and the contestant bacteria (pink background) make bacteria look different than in pure culture. Gram-positive cocci This organism is catalase and coagulase positive. What organism is causing his infection? S. aureus Resistance of this organism to which antibiotic has been reported for the first tine in the US in 1968 and is monitored in most healthcare institutions today? Methicillin Why is this organism common in these types of infections? It is part of our skin microbiome What is NOT good drug(s) of choice for an empirical antibiotic therapy of uncomplicated skin infection, assuming that the patient was infected with Staphylococcus aureus? Vancomycin plus ceftaroline vancomycin plus ceftaroline are prescribed for patients with MRSA bacteremia. Case Study #3 A 28-year-old male presented to the Emergency Department (ED) with a 1-day history of sore throat and fever. Upon physical examination, there was tonsillar swelling noted without the presence of pus. A throat swab was collected, and a rapid antigen detection test (RADT) for Group A Streptococcus (GAS) was performed in the ED. Results were negative. A throat swab for culture was also collected. The patient was sent home with a diagnosis of presumed viral pharyngitis. The next day the patient returned to the ED with worsening sore throat and difficulty swallowing. Pus was seen on the tonsils. The physician has ordered a throat culture. It came positive for Gram-positive cocci. What is the likely diagnosis for this patient's sore throat? Bacterial pharyngitis For what microorganism is a throat culture usually screened? Streptococcus pyogenes The photograph below shows the result of a throat culture after overnight incubation. A Gram stain was performed and showed gram-positive cocci in chains. What bacterial agent most likely caused this patient's sore throat? Streptococcus pyogenes Base on the picture presented in the Q3, what type of hemolysin does this species produce? Beta hemolysin What is the recommended antibiotic treatment for this patient's infection? Penicillin Case Study #4 An unvaccinated 6-year-old child was taken by his mother to their primary healthcare physician with a 48-hour history of sore throat and fever. The child was prescribed amoxicillin. Three days later, the child was taken to a local hospital ER with a worsening condition after 5 days of general malaise, fever, persistent sore throat, inability to swallow and an increase in neck diameter. The physical examination showed hypertrophic tonsils with easily bleeding pseudo-membranous plaques and necrotic areas. The child was diagnosed as a suspected case of diphtheria, admitted to an isolation ward and treated with penicillin G sodium, piperacillin/tazobactam and vancomycin intravenously. What infectious agent caused the child's disease? C. diphtheriae How long is incubation period for this disease? 2-5 days Which is NOT a characteristic of the bacterium causing disease? spore forming What lab test could the physician order to further confirm infection? ELEK test What additional treatment could the doctor prescribe to this patient? antitoxin treatment Case Study #5 A 15 year-old male was brought to the emergency room by his sister. He gave a 24-hour history of dysuria and noted some "pus-like" drainage in his underwear and on the tip of his penis. He claimed that he had not had any sexual relations. Urine and urethral drainage were collected for testing. His urine appeared clear and his urine culture was negative although urinalysis was positive for leukocyte esterase and multiple white blood cells were seen on microscopic exam of the urine. A gram stain was performed on the urethral drainage. He was given antimicrobial agents and scheduled for a follow-up visit one week later. He did not return. The Gram stain above was performed in the clinic. How would you interpret this Gram stain? White blood cells, Gram-negative diplococci Based on the Gram stain result above, with what organism is the patient infected? N. gonorrhoeae What property allows this organism to infect the urethra? Pili allow the organism to adhere to the urethral wall Why was the urine culture negative if the patient has an infection? This organism is fastidious and requires special conditions. What is the current recommended test for diagnosing this infection? Nucleic Acid Amplification Case Study #6 A 5-year-old child attends a popular day care center in Salt Lake City. The day care administration called the child's mother to come and take him home because he had explosive diarrhea. Because the mother had a new job and could not miss work she took the child to a "drop-in facility" the next day. That facility also called her to retrieve the child. On the third day, the mother repeats the process with yet a third facility. By this time the child is passing loose stools tinged with blood and pus. The mother agrees to take the child to the doctor. The child presents with diarrhea, fever and shows signs of dehydration. IV rehydration was started, and a stool culture was collected. By this time, several children in the first center are showing similar symptoms, and several more children from all three centers fall ill in the following days. Of the following, which are characteristic of the Enterobacterales order? (select all that apply) Ferment glucose Reduce Nitrates Do not produce cytochrome oxidase Which of these common pathogen(s) belong to the Enterobacterales order? Only A and B (Salmonella and Shigella) Which common member of the Enterobacterales is most likely to cause the symptoms seen in this child (and is commonly transmitted in day care centers)? Shigella What common hygiene practice is often missing in small children that leads to the spread of this organism? Hand washing What is the most common reservoir for this organism? Exclusively other humans Case Study #7 A 65 year-old man presents to the hospital with a one week history of malaise, headache, fever, and chills. He is admitted and over the next week his disease progressed with a worsening cough and shortness of breath. His physical exam was benign except for pulmonary compromise. The patient is current on all of their vaccinations and has no recent travel history. A chest radiograph showed multilobar infiltrates. Other significant laboratory findings include an elevated white blood cell count with increased polymorphonuclear neutrophils. Because the patient had a prior history of drug abuse and alcoholism, a toxicology screen and HIV serology were performed. Both were negative. A bronchoscopy was performed, with a bronchoalveolar lavage (BAL) showing many white blood cells, but no organisms. Calcofluor white stains for fungi and direct fluorescent-antibody stain (DFA) for Pneumocystis were also negative. Routine bacterial culture of the BAL was negative. Why was the BAL routine bacterial culture negative? Routine bacterial culture was not sufficient to recover the pathogen Based on the patient's history and condition, what testing should be performed next? BAL culture for Legionella An organism was recovered only on buffered charcoal yeast extract agar. Based on this information, what is the most likely pathogen? L. pneumophila The organism was most likely transmitted by: Inhalation of water droplets What other testing can be performed to detect this organism in a patient? Urinary antigen testing Case study #8 An 18-year-old female presented to an outpatient clinic in Utah with complaints of diarrhea and abdominal discomfort. The patient first noted mild abdominal discomfort and three loose bowel movements per day five days prior to evaluation. Two days prior to evaluation, she noted intermittent, crampy abdominal pain. She denied drinking well water, recent travel, relation of the pain to meals, dysuria, or hematuria. Patient mentioned she had recently gotten a new puppy. On exam, the patient had a fever of 38°C; otherwise, her vital signs were normal. Mild, lower abdominal tenderness was noted. Fecal examination demonstrated a greenish, watery stool with traces of blood. Microscopic exam of the feces showed few white blood cells. What specimen should be used to recover the potential pathogen? Stool Based on the patient's history, which of the following diarrheal agents is the most likely cause of her infection Campylobacter jejuni The Gram Stain of this organism is most likely: Curved, gram negative bacilli Select two other traits that correspond with the most likely pathogen: Transmitted through contaminated food products Most common cause of bacterial gastroenteritis Case Study #9 The health department was notified of 25 people who had developed an infectious skin rash after they had used a hotel pool and hot tub. Analysis of the rash indicated the infection was primarily with hair follicles or in the dermis. Skin infections such as this are common in individuals with extensive exposure to contaminated water. Cultures of the hot tub filter and the pustules grew oxidase-positive thin Gram-negative rods that produced a fruity odor on blood agar and non-lactose fermenting colonies surrounded by a greenish pigment on MacConkey agar. What is the most likely causative agent? Pseudomonas aeruginosa This organism is notorious for also causing which of the following? Infections in burn wounds External otitis Bacterial kertitis Mucoid strains of this organism cause invasive pulmonary disease in which patients: Cystic Fibrosis Of the following options, which are potential reservoirs for this organism in the hospital setting? Select all that apply. Nebulizers Disinfectant solutions Hands of hospital personnel Flowers Case Study #10 A 34-year-old man housed in a prison dormitory presented at the prison hospital with a 2-week history of fever, abdominal pain, and cough. His chest radiograph was normal and no other tests were performed. Three months later, the man was still complaining of a cough and increasing pain in his chest and was evaluated at a community hospital. A repeat chest radiograph showed evidence of multiple pulmonary cavitary lesions. An acid-fast stain was performed on the man's sputum. The photo below is a representation of his acid-fast stain. Thirty-one other inmates housed in the man's dormitory were also infected with the same organism. Which of the following in an example of an acid-fast stain? Kinyoun Stain Interpret the acid-fast stain depicted above Bacteria retains color after acid decolorization Based of the clinical presentation, what is the most likely pathogen causing his infection? Mycobacterium tuberculosis Of the following which is NOT a risk factor for Mycobacterium tuberculosis infections? Living in a small town What antimicrobial agent is not be used to treat the patient? Cefalexin Case Study #11 A 35-year-old woman presented to the oral surgeon with an extremely painful molar tooth and a swollen gum. She reports that the area "tastes bad." She has a fever, and the area is tender to the touch. The surgeon drained the area of several milliliters of foul-smelling pus which was sent to the lab for aerobic and anaerobic culture and Gram stain What is the likely source of the patient's infection? Her own oral microbiota Which of the following represents the expected Gram Stain report? WBCs and a mixture of organisms Which of the following represents the expected culture report? Mixed aerobic and anaerobic organisms What is the usual treatment for this type of infection? Surgical debridement and broad-spectrum antibiotics For what organism may the surgeon be particularly concerned if the infection appeared to be spreading through "sinus tracts"? Actinomyces israelii Case Study #12 A 30-year-old man visited his wife's father-in-law in Simsbury, Connecticut. They took a walk in the woods to observe the fall foliage. Several days after his return to suburban Atlanta he had "flu-like" symptoms. He didn't recall any "bug bites." Examination at the clinic revealed a round rash on his back at the waistline. His travel history and presentation were a sure diagnosis, but blood was sent for serological confirmation. What was the likely causative agent for his rash and other symptoms? Borrelia burdoferi What is the usual vector for this organism? Tick Why was he unlikely to have seen the "bug" that bit him? It was in the nymph stage and very small What is the most common sequela of this infection when left untreated? Arthritis What is the preferred diagnostic method for this disease? Two-step serological testing of blood to detect antibodies to the organisms. Case Study #13 Historically, antibiotics were available in the open markets in under-developed countries due to unscrupulous vendors having illegally acquired them. They were often of a lower dosage than how they were labeled, and were rarely within their expiration date. These questions are meant to have the student ponder the consequence of this history. Ceftriaxone resistance has been observed in E. coli and Klebsiella isolates recovered from several patients in a district hospital. What class of drugs appears to have been compromised? Third Generation cephalosporins What is the feared mechanism of resistance for Third Generation cephalosporins Extended-spectrum beta-lactamase What other resistance acquisition would make these organisms particularly problematic? Carbapenemase production Which of these drugs is NOT in the same class as ceftriaxone? Ceftaroline Which of these drugs would be resistant if the organism acquired the mechanism in #3? Imipenem Case Study #14 A 50-year-old, previously healthy man presents to the emergency department with 2 days of worsening dyspnea. He had fever, cough, and fatigue during the week before presentation. He appears acutely ill. The body temperature is 39.5°C (103°F), heart rate 110 beats per minute, respiratory rate 24 breaths per minute, and blood pressure 130/60 mm Hg. The oxygen saturation is 87% while the patient is breathing ambient air. The white-cell count is 7300 per microliter with lymphopenia. Chest radiography shows patchy bilateral opacities in the lung parenchyma. A reverse-transcriptase-polymerase-chain-reaction assay detects the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acids in a nasopharyngeal swab. What is the name of the disease afflicting the patient? COVID19 SARS-CoV-2 has a DNA genome False The detection technique used in the case study is an example of: Direct detection How is SARS-CoV-2 transmitted? Social gatherings indoors with no face coverings Fomites Respiratory droplets Close and/or prolonged contact with an infected individual Case Study #15 A 31-year-old male injection drug user presents to the emergency department with a chief complaint of shortness of breath. He describes a 1-month history of intermittent fevers and night sweats associated with a nonproductive cough. He has become progressively more short of breath, initially dyspneic only with exertion but now dyspneic at rest. He appears to be in moderate respiratory distress. His vital signs are abnormal, with a temperature of 39°C, heart rate of 112 bpm, respiratory rate of 20/min, and oxygen saturation of 88% on room air. Physical examination is otherwise unremarkable but notable for the absence of abnormal lung sounds. Chest x-ray film reveals a diffuse interstitial infiltrate characteristic of pneumocystis pneumonia, an opportunistic infection. What is the underlying disease most likely responsible for this man's susceptibility to pneumocystis pneumonia? AIDS What is the pathogenesis of the immunosuppression caused by this underlying disease? Decrease in CD4 + T cells What are some of the common clinical manifestations seen during this disease's progression? (mark all that apply) Kaposi Sarcoma Recurrent opportunistic infections Wasting syndrome Which of the following is the most likely predisposing factor leading to this man acquiring his underlying condition? Injection drug use What is the recommended treatment for this man's underlying condition? HAART and antibiotics