Another is hospital-acquired pneumonia or nosocomial pneumonia which is when a person gets pneumonia when they’re already hospitalized for something else, this type tends to be more serious because sick patients often have a weakened immune system and the microbes in hospitals are often resistant to the common antibiotics, that’s because hospitals bring together the bacteria that are often the most violent, think great offense as well as the most resistant think great defense and these bacteria are able to swap some of the antibiotic resistance genes with each other, a well-known example is methicillin-resistant staphylococcus aureus or mrsa non-resistant staph aureus can cause pneumonia and other infections but it can also be killed by common antibiotics like ampicillin but some on the other hand is resistant to many antibiotics and is therefore harder to treat.

Another category of pneumonia is ventilator-associated pneumonia, which is a subset of hospital-acquired pneumonia but it specifically develops when ill individuals are connected to a ventilator, oftentimes there’s a biofilm which is a mix of bacteria, sugars and proteins that can coat a surface that forms on the endotracheal tube individuals on a ventilator, they can’t cough and are often pretty sick already, so over time microbes can move from the tube directly into the lung and cause a pneumonia. Now in addition to inhaling microbes, there are also other ways to develop pneumonia, think about this, you’re eating some french fries and instead of swallowing one, you accidentally breathe it in…informally we call that going down the wrong pipe, but we could also say that you aspirated that french fry, normally you’d automatically gag and start coughing and work that french fry out of your lungs. These gag reflexes can be compromised though by drug and alcohol abuse, brain injuries or swallowing issues, so in these cases the french fry might stick around in your lower airways, now of course that french fry isn’t sterile and there might be some microbes stuck to it, if those microbes infect the lungs and you get pneumonia, it’s called aspiration pneumonia.

Aspiration pneumonia can also happen with drinks or even gastric contents like after a bout of vomiting aspirated gastric contents can be particularly nasty because stomach acid can cause a chemical irritation in addition to the possible infection. Another way we can characterize pneumonia is by where the infection is in bronchopneumonia, the infection can be throughout the lungs involving the bronchioles as well as the alveoli in atypical or interstitial pneumonia. The infection is mainly just outside the alveoli in the interstitium and in low bar pneumonia, the infection causes complete consolidation of a whole lobe of the lung, meaning that the entire region is filled with fluid, the vast majority of these are caused by the streptococcus pneumoniae. Usually low bar pneumonia happens in stages.

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