The activity of antibiotics is proportionate to their concentration in the target organ, which is in turn dependent on their blood concentration (at least for antibiotics taken orally or parenterally). The blood concentration is a function of the half-life. The shorter the half-life, the faster the antibiotic is removed and the more rapid the concentration in the blood goes down and consequently in the target organ. If an antibiotic is metabolised and the metabolite has also antibacterial activity, the half-life may be less important. I don't think there are antibiotics that are independent on half-life, although there are antibiotics with reasonably long half-lifes.

I echo Peter, as T1/2 is the intrinsic property of the drug so every drug will have its own half life and antibiotics are no different. Sometimes Biological half lives of drugs are longer than their plasma half life but I do not think that is the case with antibiotics.

Antibiotic that follow Time dependent killing pattern will highly effected by changing the  half life ( duration and frequency ) e.g penicillins While  Antibiotic that follow concentration dependent killing will little be effected by changing half life e.g Levofloxacin

Most of the antibiotics have the t1/2 distribution at about less than 1 hr. However the t1/2 elimination varies with the type of antibiotics. For example antibiotics such as macrolides,  have longer t1/2 elimination and hence they are mostly prescribed once a day.

These answers all ignore the phenomenon of the hit-and-run effect, usually called the post-antibiotic effect, typical of aminoglycosides, whose actions on micro-organisms outlast their presence in the body. Pharmacokinetics alone cannot give a complete answer.

There are two types of antibiotics (1) Those which produce Time dependent killing-Betalactams-thus amoxicillin must be given 3 times a day, (2) Concentration dependent killing-Single dose of aminoglycosides appears to have same effect but less nephrotoxicity. Post antibiotic effect also plays role. So a generalization of biological half life for antibiotics may be too simplification of Pharmacokinetics 

I agree with the above comments. Pharmacologically,  half-life, in general, is more a reflection of the drug's elimination pattern and is not a measure for efficacy. Clinical efficacy may not have any direct correlation with half-life. In as much as it indicates a drug's biological availability, it will have an influence on efficacy.

Half-life helps in formulating dosing frequency; it is particularly important in the case of long half-life drugs which are prone to cumulative toxicity. Half-life also assumes significance when drugs need to be withdrawn on account of severe adverse events/toxicity.

In the case of antimicrobial agents, the most important factor is that adequate concentrations of the drug are to be maintained (MIC values) so as to produce the desired therapeutic efficacy.  Antimicrobial resistance, perhaps takes the second position, followed by the drug's half-life!

I totally agree with the previous answer.

Some antibiotics have activity dependent on their half life and concentration value above the MIC (minimum inhibitory concentration specific for each bacteria and antibiotics), others have activity dependent on the Cmax/MIC. With the second type usually you have some post-antibiotic effect as described by Aronson.

In general half life concerned more with the treatment schedule than with effectiveness of the therapy. 

Choose the antibiotics is principally based on possible causal agents if empirical, or on MIC if the specific bacteria has been determined. Than you could choose the more active antibiotic and adjust dose - frequencies according to the clinical characteristic of the patient. 

There is another aspect which is often ignored. The doubling time of bacteria. For example rifampicin is given one a day or on alternate days for tuberculosis but is given once a month for leprosy and a  single dose of ceftriaxone is curative for gonococci. So consideration of  half life alone would be too simplification

Generally, there is a correlation between plasma levels and antibiotic half life and their efficacy. This applies to all betalactams (penicillin and suchlike) but does not apply to antibiotics that concentrate at the intracellular level, because although the plasma level may be very low, the cytoplasmatic concentration is much higher. A good example of this is azithromycin, which accumulates in the intracellular compartment reaching concentrations many times higher than the plasma levels. All macrolides share this property, and many quinolones as well.