Purpose
Gram staining differentiates bacteria by their cell walls’ chemical and physical properties. It is usually the first step in bacterial identification in the laboratory and a valuable diagnostic tool. You recently learned about Gram Stains in Chapters 3 and 4. This activity will show how this technique can be applied in the clinical setting. This assignment meets the requirements of the General Education and Biology STEM Pathways assessment programs.
Learning Outcome
Students will apply the scientific method when analyzing laboratory results and medical information.
Task
Read the case study below.
Copy/paste and answer the following:
Write an evidence-based conclusion regarding the causative agent of Isabella’s disease.
Your answer should include supporting evidence from the case study stain and the descriptions of the possible pathogens.
State one remaining question about staining, microscopy techniques, or bacterial structures.
Evaluation Criteria
Submissions will be graded according to a 9-point rubric; however, the rubric does not reflect the total number of points of the assignment. To view the rubric, click on the three vertical dots in the upper right-hand corner of the page.
Case Study
Isabella is a 24-year-old nursing student. She works full-time in the local emergency department. Earlier in the week, she began to feel tired and run down. She had a severe headache, fever, and her neck felt stiff. At work, there had recently been an increase in influenza cases, so she initially thought she might be getting sick with the flu. She decided to take a few days off to rest and took acetaminophen (Tylenol) for the pain. The symptoms persisted and worsened over the next few days. Her roommate convinced her to go to the emergency room for medical attention.
Alex, the physician’s assistant that Isabella frequently works with, observed that Isabella was running a high fever, had a visibly stiff neck, and complained of a headache. These are common signs and symptoms of meningitis, an infection of the membranes around the brain. They quickly ordered a lumbar puncture (spinal tap) to analyze cerebrospinal fluid (CSF). In the laboratory, a thin smear of CSF was prepared and Gram-stained. Many white blood cells (WBCs) were observed in the specimen. Smaller microbial cells (indicated by the arrows) were also observed [Figure 1].
picture: https://commons.wikimedia.org/w/index.php?curid=76563138
Below are descriptions of some possible pathogens:
Chlamydia trachomatis- C. trachomatis is a gram-negative coccus commonly infecting the genital tract. Symptoms include abnormal discharge and a burning sensation when urinating. It most commonly occurs in individuals under the age of 25. It is the most common bacterial cause of sexually transmitted diseases.
Echoviruses- Diseases caused by echoviruses range from minor febrile illness to meningitis and encephalitis (brain inflammation). They are small, nonenveloped viruses with a genome composed of RNA. Echoviruses are transmitted through the fecal-oral route.
Haemophilus influenzae- H. influenzae is a Gram-negative bacillus. It may cause pneumonia, bloodstream infections, meningitis, epiglottitis (swelling of the throat), cellulitis (skin infections) or infections arthritis (inflammation of the joint). Diseases caused by H. influenzae mostly occur in children younger than 5 years old and adults 65 years or older.
Influenza viruses- influenza is a common illness with seasonal variation. It is caused by one of several enveloped RNA viruses. In rare cases influenza infection can result in meningitis. Individuals with weakened immune systems or young children are at the highest risk for this complication.
Neisseria meningitidis- N. meningitidis is a Gram-negative coccus associated with meningitis and septicemia (blood infection). Diseases caused by N. meningitidis are associated with high mortality. The disease spreads through close contact with infected individuals. It most commonly affects infants and adolescents.
Streptococcus pneumoniae- S. pneumoniae is a Gram-positive coccus that may cause pneumonia, bronchitis, bloodstream, and meningitis. It often resides in the respiratory tract, sinuses and nasal cavity of asymptomatic carriers. It is spread through direct person-to-person contact via respiratory droplets. It most commonly affects children and the elderly
