Staphylococcus aureus: This bacterium is a common cause of infections in patients with ear tubes, and its gram-positive cocci appearance can sometimes be mistaken for bacilli, especially if the bacteria are in chains or the technician is inexperienced. However, given the context, it's more likely that the description aims towards a bacillus form, but S. aureus is so prevalent it remains a top consideration.

Corynebacterium species: These are gram-positive bacilli that can be found in various parts of the human body, including the ear. They are known to cause infections, especially in compromised sites like those with ear tubes.
Bacillus species: While less common, Bacillus species can cause infections and are gram-positive bacilli. Their presence in ear drainage, especially in a patient with ear tubes, makes them a plausible cause.

Diphtheria (Corynebacterium diphtheriae): Although rare in areas with good vaccination coverage, diphtheria is a serious and potentially deadly infection caused by a gram-positive bacillus. The presence of ear tubes and drainage could be a site for this infection, especially if the patient has not been vaccinated or has been exposed to someone with the infection.
Actinomycosis (Actinomyces species): These gram-positive bacilli can cause chronic infections and are known to form abscesses and drain tracts. While less common, they can be found in the ear and could be a cause of chronic infection in a patient with ear tubes.

Nocardia species: These are gram-positive, partially acid-fast bacilli that can cause a variety of infections, including those of the ear. However, they are more commonly associated with pulmonary or cutaneous infections.
Listeria monocytogenes: Although more commonly associated with severe infections in immunocompromised individuals, Listeria can cause infections in otherwise healthy individuals, including ear infections. However, its presence in ear drainage would be uncommon.