Question

Nester etal.

MICROBIOLOGY: A Human Perspective

Case Study – Chapter 21 Respiratory System Infectious

A 65-year-old Hispanic man presented to his family physician with a fever (38.7 °C), a productive pink-colored cough, and chest pain which had persisted over 5 days. He had tested positive for TB when he was younger; however, he had never shown signs or symptoms of tuberculosis since then. He had taken no recent medications. He was a smoker and occasionally drank alcohol. He described to his doctor that before he developed the cough with chest pain, he suddenly developed chills and a sore throat with a fever. A rapid test for influenza was negative. He was prescribed acetaminophen, however the fever persisted, and the man returned to his family physician the next day. Blood tests were done which showed that his white blood cell (WBC) count was elevated (>15,000 U/L) along with other tests that indicated inflammation. Although an oral cephalosporin was prescribed, his fever did not improve, and he was subsequently admitted to the hospital.

On admission, laboratory tests showed a high WBC count among other tests that showed inflammation. Rapid antigen tests for influenza and mycoplasma were negative. A sputum was also collected for culture for general and acid-fast bacilli. He was initially diagnosed with bronchopneumonia. Intravenous administration of levofloxacin (LVFX, 600 mg/day) and ampicillin/sulbactam (ABPC/SBT, 7 g/day) was started.

On the second day after admission, the patient’s temperature began to subside. The sputum smear was negative for acid-fast bacilli; however, catalase negative, alpha-hemolytic, Gram-positive diplococci were detected in the blood cultures and sputum cultures. Other biochemical tests showed susceptibility to Taxo-P, bile solubility test positive, bile esculin negative, and NaCl negative.

1. What is the diagnosis of this patient?
   1. Sepsis due to bacterial infection
   2. Bacterial bronchopneumonia and bacteremia
   3. Upper respiratory bacterial infection
   4. Generalized viral infection
2. What agent do you think is causing this problem?
   1. Streptococcus pyogenes
   2. Staphylococcus agalactiae
   3. Streptococcus pneumoniae
   4. Mycobacterium tuberculosis
3. Which of the following is NOT a characteristic of both Streptococcus pyogenes and Streptococcus pneumoniae?
   1. They may cause respiratory diseases.
   2. They may have capsules.
   3. They are catalase negative.
   4. They are both diplococci.
4. Which group of antibiotics is most appropriate when treating this type of infection?
   1. Those that target cell wall synthesis such as penicillins and protein synthesis such as erythromycin are effective if given early in the illness.
   2. Those that target Mycobacterium tuberculosis such as isoniazid.
   3. Those that target cell membrane integrity such as the polymyxins.
   4. Any of the above would be ideal.
5. This type of respiratory infection usually ___.
   1. targets older adults and can be prevented through a pneumococcal vaccine that is available.
   2. targets young adults and can be prevented through a RSV vaccine that is available.
   3. targets older adults and can be prevented through a shingles vaccine that is currently available.
   4. targets children and can be prevented through proper hygiene practices such as handwashing.

Answer 1

Answer to Q1

According to the given data the patient is suffering from upper respiratory bacterial infection. Because his blood sample is negative for TB, Influenza virus and Mycoplasma sp.

Answer to Q2

Streptococcus pneumonia is the causative agent. His blood sample is Mycobacterium sp. negative. The rest of the bacteria given i.e. S.pyrogens and S. agalactiae causes fever and UTI or gastrointestinal problems.

Answer to Q3

The statement “They may cause respiratory diseases” is not correct because S.pyrogen is reported to cause rheumatic fever, rheumatic heart disease, and scarlet fever.

Answer to Q4

“Those that target cell wall synthesis such as penicillins and protein synthesis such as erythromycin are effective if given early in the illness” this is correct as S. pneumonia is a Gram-positive bacteria there is no cell membrane. We can use a cell wall and protein synthesis inhibitor to inhibit the growth of the pathogen. Isoniazid will not be used as it inhibits acid-fast bacilli like M.tuberculosis.

Answer to Q5

This type of infection “targets older adults and can be prevented through a pneumococcal vaccine that is available”. It is reported that S. pneumonia majorly affects older people greater than 60-65 years and as they say that “Prevention is considered to be better than a cure” , vaccination is available which is capable of treating the disease.