Reference no: EM133247956

1. Scenario

Sandy was age 33 when her baby girl, Kayla, was born prematurely at 32 weeks. A week or so before Kayla was born, Sandy attended a wine and cheese party, and although she only drank tea, she snacked abundantly on crackers, cheese, and several types of sausage and other meats.

Signs and Symptoms

About a day after the party, Sandy had developed a fever of about 100°F, felt nauseated, and had abdominal pain. She went into premature labor two days later. Baby Kayla showed minimal responsiveness on neonatal tests and was in obvious respiratory distress. She was intubated, and samples of blood from both baby and mother, along with the placenta and meconium, were sent to the lab for testing.

Testing

Specimens were plated on several types of culture media that were incubated at body temperature under both aerobic and anaerobic conditions.

Bacterial colonies were noted growing on blood agar plate cultures prepared from all specimens taken from the baby.

A smear was prepared from one of the bacterial colonies and Gram stained.

Describe the appearance of the bacterial cells in terms of Gram-stain reaction, morphology, and arrangement.

2- Peptidoglycan is a polymer constructed from sugar molecules and peptides. Therefore, what elements make up a molecule of peptidoglycan?

3- A wet mount was also prepared by mixing some of the colony with a drop of saline on a slide and putting a coverslip on top. The bacteria were very motile and appeared to be "tumbling" end-over-end as they moved.

Bacterial flagella are constructed from thousands of molecules of a protein called flagellin that assemble into the flagellum. Regions of secondary structure in a flagellin molecule are β sheets. How does secondary structure form from the linear sequence of amino acids in the primary structure of this molecule?

4- Treatment

Baby Kayla was started on high-dose intravenous (IV) ampicillin shortly after birth. Although the mortality associated with neonatal listeriosis is high, rapid antibiotic treatment resulted in significant gains and she was extubated and breathing on her own in a few weeks. Sandy was also treated with ampicillin, because the bacteria had been found in her blood during testing.

Ampicillin is an antibiotic that binds to enzymes called transpeptidases and block the active site. Transpeptidases normally catalyze a chemical reaction that creates peptide bonds between amino acids to crosslink peptidoglycan, which makes the bacterial cell wall rigid and strong.

Given that the antibiotic targets peptidoglycan, what effect does treatment with ampicillin have on Gram-positive bacterial cells? And on Gram-negative bacterial cells?

5- Does ampicillin increase or decrease the reaction rate of the chemical reaction that makes peptidoglycan?

6- Additional Considerations

Listeria is described as being a facultative intracellular bacterium.

How is Listeria different from a bacterium like Chlamydia, which is an obligate intracellular bacterium?

7- How is Listeria different from a bacterium like Staphylococcus aureus, which is an extracellular pathogen?