Why is it more difficult to grow poliomyelitis viruses than to grow bacilli that cause diphtheria?

Growing poliomyelitis viruses is more challenging than culturing the bacilli that cause diphtheria primarily due to their differing natures; polioviruses are obligate intracellular pathogens that require living host cells for replication, whereas diphtheria bacilli (Corynebacterium diphtheriae) can grow on artificial media. Additionally, polioviruses need specific cell lines for propagation, which can be more complex and require stringent conditions, while diphtheria bacilli can thrive in standard laboratory environments. This dependence on living cells makes the cultivation of polioviruses more labor-intensive and technically demanding.