I want to help out with the project, and this is something i know about
imipenem (brand name Primaxin) is usually used for broad spectrum coverage of respiratory infections (people on ventilators). It is a bacteriocidal drug, inhibiting cell wall synthesis with high affinity for penicillin binding proteins. It is an inhibitor of beta lactamase.
Kills: (from PDR)
gram+ aerobes: strep,
gram - aerobes: h.flu, e.coli, citrobacter, pseudomonas (one of big uses in hospitals), enterobacter, actinobacter, aeromonas, pasteurella, proteus
gram + anaerobes: peptostrep, clostridium
gram - anaerobes: fusobacterium and bacteroides.
One drawback froma medical standpoint is that the drug is a salt (can cause fluid overload in patients) so this may impact the use in tanks. It is a combination of several substances (long chemical name), not just a single , so it may have possibilities for toxicity in inverts etc, especially as it can affect kidney function. It is highly soluble in water.
I have access to pdr and other references, and if there are any pharmacists out there they may have more insight.
hope this was helpful.