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1. what antibiotic what antibiotic was the most effective against S. aureus ?

2. what antibiotic was the most effective against E. Coli?

3. What other factors, beside effectiveness are considered before prescribing an antibiotic to a person ?

4. If the laboratory isolates S. aureaus from five patients on the same day, is it necessary to test the antimicrobial susceptibility of each isolate? Why

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Jamar Ferry
Jamar FerryLv2
28 Sep 2019
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Related questions

Case Study #1: A Common Opportunistic Infection

Ben, a seven-year-old second grader, quickly finished his homework after school so he could play outside with his friend form next door. Since Ben had started coughing the day before, his mother insisted he wear his jacket. At bedtime, Ben was exhausted from his busy day. When kissing his forehead goodnight, Ben’s mother noted that he felt a little warm. To help Ben sleep more comfortably since he was likely getting a cold, his mother gave him a dose of pediatric Tyenol, “Poor Ben,” she thought. “Three weeks ago he had the flu and now a cold is starting. He could really use a break.”

In the morning, Ben didn’t come to the breakfast table when called. His mother found Ben still in bed, barely responsive, and extremely feverish. She immediately drove him to the walk-in clinic in their neighborhood. Ben’s oral temperature was 40.8C (105.4F). IV fluids were started and an ambulance transported Ben to the nearest hospital.

In the hospital emergency room, Ben presented with the following viral signs: temperature = 41.9C (107.4F), pulse = 162 bpm, pulse ox = 90%, respirations = 24/minutes and labored, BP = 62/54 mmHg. Ben was completely unresponsive. His physical exam was remarkable for rales or “crackles” heard over both right and left lower lung fields. Bilateral chest radiographs were ordered and revealed infiltrates in the lower lobes of both lungs.

Preliminary lab results yielded a white blood cell count of 16,200 cells/mm^3 and a differential count with 74% neutrophils, including 18% bands. Respiratory acidosis was indicated by an arterial blood pH of 7.2. These results were immediately called from Ben’s local hospital to his new facility and broad-spectrum IV antibiotic therapy was initiated.

9. Approximately 6 hours later, the clinical microbiologist examined the BAP and chocolate agar plates. What morphological features did she likely observe on the plates? Why were these two media types selected for culturing?

10. What results would you predict from the following tests?

Optochin

Catalase

Bacitracin

Bile solubility

Quellung reaction

11. What is the significance of the following laboratory results?

The WBC

High neutrophil count with elevated bands

Respiratory acidosis

Automated identification and sensitivity testing were initiated and the presumptive microbe identification called to the other facility to aid in treatment. Ben’s attending physician was relieved to find that the CSF was sterile, as she had just initiated prophylactic antibiotic treatment of Ben’s caregivers. Unfortunately, she reported that Ben’s condition had continued to decline and he has been pronounced dead earlier that hour. She requested that identification/sensitivity data be forwarded upon completion so Ben’s record could be finalized.

12. Why was Ben’s physician relieved that the CSF was sterile? What possible infection was she considering?

13. Assuming Ben was receiving broad-spectrum IV antibiotic therapy that was effective against his infection, what reasons can you give to explain his rapid deterioration and eventual death when receiving an appropriate empiric therapy?

Within 6 hours, the Virek analyzer confirmed the identity of this microbe and indicated its sensitivity to penicillin, cephalosporins, and fluoroquinolones. While Ben’s attending physician was pleased that her staff had not been exposed to a resistant microbe, she was frustrated to have lost a young patient to one so sensitive to standard antibiotics.

14. Were there any predisposing factors that put Ben at greater risk for this infection?

1. The pH for the water in the MSA recipe is expected to be from 7.2-7.6. If the pH was too low, what could you expect to see? Select one:

a. The entire plate would be yellow

b. Nothing abnormal

c. The agar would crack at pH 6.5

d. E. coli would turn purple

2. Which of the following would the MSA medium NOT be considered: Select one:

a. Complex medium

b. Chemically defined medium

c. Differential medium

d. Selective medium

3. If you took a swab from a patient and cultured it on a MSA plate, which of the following could be identified by just using this test? Select one:

a. Staphylococcus epidermidis

b. Escherichia coli

c. Staphylococcus aureus

d. Micrococcus luteus

4. If you streaked the 3 organisms in this lab on a PEA plate and after incubating for 2 days at 37 degrees Celcius nothing grew (but they did grow on a NA plate made at the same time and grown in the same conditions), which of the following is the most likely cause for this result? Select one:

a. The agar was toxic.

b. The beef extract was bad.

c. The temperature was too low.

d. Too much phenylethyl alcohol was used

. e. The temperature was too high.

5. Why is the NA plate inoculated in addition to the Columbia CNA with 5% sheep blood agar plate? Select one:

a. Used to compare growth on non-selective medium

b. Used as second selective medium

c. Used to promote hemolysis

d. Used because it is easier to see

e. Used as a practice plate

Part I – The PA
It had nally arrived! e day Margo had been waiting for—retirement day. And given that the temperature had hovered around 40 degrees the last week of March in Ohio, retirement along with the move to the warm south couldn’t come soon enough. Most of Margo’s belongings had been boxed up and sent on to Florida the previous week, but a few remaining items, including her wide screen TV, would be transported in the car.
Week of April 7th
The drive to Bradenton, Florida, went smoothly. After spending three days on the road, Margo arrived at the condo retirement community. It had all the luxuries one could imagine, including a spa-like pool area, a nail salon providing manis and pedis, a beauty shop, yoga studio, nutritionist, and therapeutic massage service. But before any of those amenities could be enjoyed, final moving efforts had to be undertaken. Although family had o ered to help with the move, Margo wanted to do this solo, and felt there was nothing she couldn’t lift or move herself—so she spent the rest of the afternoon rearranging and positioning the furniture, rugs, stereo, and computer equipment.
Week of April 14th
As she surveyed her new place the following week, Margo felt satisfied that her decision to move to Florida had been the right one and that her new condo suited her perfectly. One final move of the television away from the window and closer to her replace would be her last task. Unfortunately, while positioning the large at screen, she caught her right index finger on the plastic trim, resulting in a painful cut that bled a little more than expected. But after washing the wound with soap and water, things seemed to be under control and the warm sun and balmy 80 degree temperatures made her think it was time for a swim. After the swim, a nice massage would prevent any aches and pains that might result from overdoing the furniture moving, and a manicure to repair the damage the manual labor had done to her nails would be the perfect end to the day.
Week of April 28th
Margo had been enjoying Florida-living for two weeks now. The only down side was the fact that the area where she had cut her ngertip was painful, swollen, appeared red, and felt warm to the touch. If the pain didn’t go away soon, Margo was going to have to have her finger looked at by a physician. Then, in the middle of the next night, the throb- bing became unbearable and she knew it was time to head to the doctor. Unfortunately, she hadn’t had the time to
find a personal physician in the area and so her only option was to go to the urgent care facility not far from her condo.
May 3rd
At the urgent care center, a physician’s assistant (PA) asked Margo a variety of personal health questions and carried out his clinical assessment, noting the following details:
Age: 65
BP 134/80
Weight 120 lbs., Height 5 ́5 ̋
HR 59
Respiration rate 18
O2 sat. 99
Type 2 diabetes (diagnosed 3 years prior)
Following careful cleaning and examination of Margo’s wound, the PA prescribed an antibiotic called Bactrim DS (trimethoprim/sulfamethoxazole-double strength) in a tablet form to be taken by mouth two times a day for 10 days. The patient information sheet that Margo received from the clinic identified her diagnosis as cellulitis, which was curious because the person who had examined her had not mentioned that particular word. Margo dutifully followed prescribing instructions, taking her medication as suggested, but after five days the wound continued to swell, her pain had increased, and moving her finger had become dificult.
Part II – The ARNP
May 8th
The next day, Margo went to another urgent care facility where she hoped she would nd some relief. John, an Advanced Registered Nurse Practitioner (ARNP), took her history and performed his clinical assessment, noting a normal body temperature and normal-size lymph nodes. While examining the injured finger, he observed significant
swelling, mild erythemia, and a small wound with minimal clear exudate. Other than the index finger, the rest of Margo’s hand appeared normal. Upon completing his examination, John cleaned the wound, numbed the area, and injected a medication called Depo-Medrol into Margo’s finger. Afterwards, he talked to Margo about wound infections, including the redness and swelling she had been dealing with. John told Margo to clean her wound three times a day with soap and water and then to dry it thoroughly. He gave her a prescription for the antibiotic Keflex to be taken two times a day for 10 days. He also gave her a visit summary/discharge instruction paper that identified the clinical impression/diagnosis as “cellulitis/foreign body/fungi.” John further instructed Margo to return in 72 hours if her symptoms did not improve.
Once home, Margo closely read the written information she had been given and noted that the document mentioned she had been taking the drug Septra since May 3rd without improvement. Also, her medical services/charge sheet noted “foreign body removal” as a procedure carried out, yet she had no memory of such a procedure. Although at the end
of her clinical visit Margo had signed the paper acknowledging her treatment, she was now more confused than ever regarding the cause of her wound and the course of her treatment.
Questions
1. What is the function of Depo-Medrol? Speculate on the reasoning/consequences of its use in this particular case. 2. What pathogens are targeted by Ke ex (the newest prescription)?
3. What types (genus/species) of fungal pathogens typically cause wound infections?
4. If a fungal pathogen was implicated, would Ke ex eliminate that particular infectious agent?
5. Why did Margo’s recent documents mention she was taking Septra rather than Bactrim as her earliest (May 3rd) documents listed?

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