ATYPICAL PNEUMONIA

There are three major types:

1. Legionella pneumophilia – discovered in the late 70’s because of an outbreak. Most commonly live in freshwater amoebas. This is a disease caused by technology, more specifically by cooling systems based on circulating water. The water with the amoebas is pushed into a room and starts accumulating. Patients inhale a critical mass. The bacteria don’t know what to do so they go into what looks like an amoeba to them alveolar macrophages. They grow until the cell bursts and another cell is infected.

The person might not have any symptoms at all. Legionnaire’s disease develops if there is a predisposing factor like age, heavy smoking, cardiac transplant, dose bacteria, or low immunity. Mortality is 15-60% when untreated. Pontiac Fever is a mild form of the disease it’s flu like with a dry nonproductive cough. Today you might see this disease from hotels with that type of cooling system.

2. Mycoplasma pneumoniae – a species with no cell wall, so if someone comes in, never treat him or her with penicillin or anything that acts on the cell wall. The bacterium is pleotrophic and adheres to cells via P1 adhesin. The bacteria don’t make toxin, rather the bacteria depleting the cells of cholesterol cause the disease. It can cause a mild self-limiting bronchitis or pneumonia mainly in teenagers and young adults. It resembles viral pneumonia.

Diagnosis can be made easily using cold agglutination – make the bacteria cold and it clumps, as you raise the temperature it stops clumping.

3. Chlamydia pneumoniae – no peptidoglycan but the cell wall does have cross-linked peptides. It resembles a virus because it needs host ATP. The elementary body (EB) binds to cells and multiplies. Then the bacteria go into the cells and turn into reticular bodies (RB). These multiply and burst out to infect again. They can be killed with antibiotics. The disease is similar to the one above, but the bacteria don’t cold agglutinate. The exclusive host is humans. Chlamydia psittaci are from parrots and can infect humans. This pneumonia is most common in adults.

Category: Medicine Notes , Microbiology Notes