Final answer:
Acute glomerular nephritis is most often caused by ‘Streptococcus pyogenes,’ due to the immune complexes formed between the bacteria's antigens and the body's antibodies.
Step-by-step explanation:
The organism that causes acute glomerular nephritis is Streptococcus pyogenes (b). This bacterium, which is also responsible for throat and skin infections, does not directly infect the kidney glomeruli. However, the immune complexes formed in the blood between Streptococcus pyogenes antigens and antibodies can lodge in the capillary endothelial cell junctions of the glomeruli, causing significant inflammation and damage in a process known as glomerulonephritis.