Is this a reduced relative clause or a cause-effect structure?

I'm a bit confused about how to analyze the following sentence:

The grey arrows indicate entry of DD bacteria, infecting the corium, extending the lesion and possibly producing the further pus which increases the extent of the under-running of the sole.

My question is about the part:

infecting the corium, extending the lesion and possibly producing the further pus...

Do you think this is a reduced relative clause referring to “DD bacteria” (i.e., originally something like "which infect the corium, extend the lesion...")? Or is it a cause-effect chain starting from “entry of DD bacteria” (suggesting that the entry causes infection, lesion extension, and pus production)?

Grammatically it's clearly a participle phrase, but I'm more interested in how we should interpret the logical relationship — who is the real agent of the actions?

The grey arrows indicate entry of DD bacteria, infecting the corium, extending the lesion and possibly producing the further pus which increases the extent of the under-running of the sole.

I would consider the structure of the sentence in light of the visual element that it is describing, the "grey arrows". Apparently it is a kind of diagram showing the progress of an infection caused by "the entry of DD bacteria", each participial phrase representing a stage of the progress as indicated by those arrows.

The three participial clauses are not a single reduced relative clause but a kind of staged process. The arrows are presenting the progress; they are the visual indicators of its stages and the stages explain the three participial clauses in succession. But the bacteria which have entered are what is creating the infection.

This sentence could well be taken from the transcript of a presentation before an audience where the visual is up on screen and the speaker is using a laser pointer to follow the progress. You need to understand the context of this utterance in order to understand (and forgive) its syntax.