Pneumocystis Pneumonia (PCP) – Opportunistic Infections

00:00 Lastly we will consider pneumocystosis caused by pneumocystis jiroveci. This used to be called pneumocystis carinii and it was one of the first indications that the AIDS epidemic was starting. In the early 1980s, there was a cluster of cases of what's called PCP pneumonia, pneumocystis pneumonia in gay men in California and this was never seen in such numbers. It was a very rare disease, only seen in severely immunocompromised people. The presence of this infection, of PCP in these men was an early clue that something was going on and that led to the discovery of the virus causing AIDS. So PCP pneumonia was one of the first measures used to say, is there AIDS in this community? This fungus is inhaled from the environment, but we actually do not know the precise source, so we know that Aspergillus for example is everywhere, we know that Candida is part of your normal flora, we really do not know where pneumocystis comes from. We do think that we acquire infection at a young age, perhaps as children we inhale these, the organism simply remain in the lung for a long time, our immune system takes care of them and it's only when our immune function decreases, is it a problem. So for example, if you develop AIDS, then pneumocystis starts to replicate and causes pneumonia. So it's probably already there at the onset, you don't acquire it when you get AIDS. These organisms are rarely found outside the lung, so this is a lung disease and that is indicated by the name pneumocystis pneumonia.

01:53 How do we diagnose it? You can take samples, clinical specimens, sputum samples from the lung and then you can stain them with silver, you can stain them with antibodies, directed against the antigen of the fungus, or you can do polymerase chain reaction on bronchoalveolar lavage, or a biopsy that you have taken to discover the nucleic acid of the organism. And once confirmed you can treat it with trimethoprim sulfamethoxazole. A different drug than we've used for all of the other fungal infections.

02:29 So let's take a look at the summary of some of these drugs that are used to treat these opportunistic fungal infections. Let's zoom in on the top part of this chart. You can see that Candida, Cryptococcus and Aspergillus can all be treated with amphotericin B. Candida can also be treated with nystatin, that's a topical form of treatment for candid intertriginous Candida, whereas the amphotericin B is an intravenous application for systemic infection and then we can go lower down into this chart and see the treatments for Aspergillus, itraconazole.

03:08 Candida and Cryptococcus we can use fluconazole and Candida and Aspergillus; voriconazole.

03:15 In the class of Echinocandins, we can use caspofungin, intravenously to treat systemic Candida infections. And a pyrimadine inhibitor flucytosine is an oral drug to treat both Cryptococcus and Candida.