PPLO stands for Pleuropneumonia-Like Organism and it means: Mycoplasma.
Pleuropneumonia means pneumonia complicated with pleurisy.
Mycoplasma means any of a group of small typically parasitic bacteria that lack cell walls and sometimes cause diseases.
(I hope this helps in anyway possible. Sorry if it's not in 100 words, I couldn't get to that number. But maybe you can put more words into the sentences and make them longer. But I do really hope this has helped you!)