Whooping Cough

Faiz Jiwani

Whooping Cough Assignment

What is a Gram-negative organism? How does the structure of a Gram-negative organism contribute to its virulence?

A gram-negative organism has an outer membrane covering a thin layer of peptidoglycan on the outside. The outer membrane prevents the initial stain from penetrating. When this type of organism is rinsed with alcohol, it easily removes crystal violet. After gram staining it appears pink because of the alcohol. The structure of this gram-negative bacteria includes a thick lipid bilayer on the outside, which is selectively permeable (not everything can pass through), and one of those things is the gram stain.

Why is it difficult to grow Bordetella pertussis in a laboratory?

It’s hard to grow BP in the lab because this organism is very complicated. It grows best at 35-37 degrees Celsius. It requires specialized media because it is inhibited by a variety of substances such as fatty acids, heavy metals, sulfides and peroxides. Growth is inhibited by the organism’s own waste products so media containing activated charcoal, ion-exchanging resins or high concentrations of blood are often used to neutralize these inhibitory substances. This organism will usually not grown on MacConkey agar or Chocolate agar. Bordet-Gengou agar (BGA) is often used because it contains potato starch to mop up inhibitory toxins, and is peptone-free. It also contains glycerol as a stabilizer and often an antibiotic (methicillin) to suppress many gram-positive organisms. BP is a relatively slow-growing organism with shiny and smooth colonies visible after 3-6 days of incubation.

Discuss and evaluate the methods used to identify Bordetella pertussis.

There are many ways to identify Bordetella pertussis. Gathering a culture and diagnosing it is one of the most common methods. Culture is best done from nasopharyngeal specimens collected during the first 2 weeks of cough when viable bacteria are still present. Polymerase Chain...