What are the top 10 most powerful antibiotics?

This is a difficult question to answer, because it depends on the infection.

For bacteria sensitive to it, Meropenem is EXTREMELY potent but it won't do anything against MRSA. Likewise, Vancomycin is EXTREMELY potent against MRSA, but doesn't cover any of the gram negative bacteria that Meropenem does. Some bacteria are only sensitive to otherwise outdated or rarely used (due to wide-spread resistance in other bacteria) antibiotics.

However, a very general and vague list might go something like this, though they are in no particular order:

1) Meropenem and other carbapenem antibiotics due to their extremely broad spectrum of activity. Due to potency and current lack of resistance, is often used as a "drug of last resort".

2) Vancomycin due to being very potent against staph infections including MRSA. Often used as a "drug of last resort" so as to keep resistance low.

3) Co-trimoxazole due to being a combination of two already powerful sulfanamide antibiotics.

4) Piperacillin/Tazobactam due to very broad coverage and Tazobactam's ability to neutralize some bacterial resistance.

5) Levofloxacin due to being one of the most powerful antibiotics that works well orally.

6) Linezolid due to being very active against MRSA and being one of the few if not only anti-MRSA drugs available orally. Often used as a "drug of last resort".

7) Cefepime due to being super broad spectrum and working well with other antibiotics in combination therapy.

8) Polymyxin B (Colistin) due to being extremely potent and available in nebulized or IV form. Due to potency and toxicity issues, is often used as a "drug of last resort".

9) Tigecycline due to anti-MRSA use. Is often used as a "drug of last resort" to keep resistance low.

10) Aztreonam due to being a powerful anti-pseudomonal that is available in IV or inhaled form.