In general, pneumonia is now a fairly general term for fluid
accumulation in the lungs. There are more specific lung conditions with
a specific kind of fluid that are not called pneumonia.

Most pneumonias do involve some kind of infection, although there are
enough cases where an infectious agent can't be identified that we have
a term for that, aseptic pneumonia.

The terminology is confusing, partially for historical reasons. For
example, there is a "pneumonia vaccine" for humans, but it is actually a
vaccine against a specific organism, Neisseria pneumoniae, also called
"the pneumonococcas".  Before antibiotics, this was one of the very few
infectious diseases for which anything could be done: through a rather
laborious process, the immune type of the substrain in the patient could
be identified, and an antitoxin given.  Pneumonicoccal typing remains a
useful tool in tracking disease outbreaks, but the therapy is completely
obsolete since we have antibiotics.

Infectious pneumonias can be due to bacteria, fungi, or viruses; the
bacterial form is certainly not limited to the pneumonococcus.
Staphylococcal pneumonia, for example, is not that uncommon and is quite
vicious.  Legionnaire's Disease is a pneumonia caused by Legionella
pneumonia, a somewhat specialized bacterium. Fungal pneumonias can occur
in anyone, but is most common in immunosuppressed patients.

With this range of infectious diseases, there's obviously going to be no
one universal antibiotic.  While giving mixtures of antibiotics as a
"shotgun" is not generally advisable, in a "fulminating", imminently
lethal pneumonia, such as Harri had, shotgun therapy is quite
appropriate.  Just as a guess, it might have been a cephalosporin,
gentamicin, and metronidazole, with some changes to allow oral therapy.

In humans, the mixture of the cocktail will vary with the geographic
area. We also differentiate between "community-acquired" and
"hospital-acquired" pneumonias. The latter occur in already-sick
patients, and are especially nasty since they tend to be the ones that
are resistant to most antibiotics.  Shotgun therapy is probably the
usual start to treating hospital-acquired pneumonias.  A good physician
can often make a reasonable guess, based on symptoms, of the first
antibiotic to try for a community-acquired pneumonia.