Media for sperm preparations are not in contact with cells for very long and are not really culture media. The products are delivered sterile, making antibiotics unnecessary. In fact, the purpose of using a gradient for sperm is to remove the bacteria (among other things). When preparing sperm with the swim-up technique however, the risk of the sample contaminating the preparation is large, and antibiotics might be needed. This is one of the reasons why Nidacon recommends gradients and not swim-up.

Bacterial contamination and sperm recovery after semen preparation by density gradient centrifugation using silane coated silica paticles at different g forces, C.M Nicholson et al, Hum Reprod, (2000),15(4)662-666.

The use of two density gradient centrifugation techniques and the swim-up method to separate spermatozoa with chromatin and nuclear DNA anomalies, D Sakkas et al, Hum Reprod, (2000), 15(5)1112-1116.

Media for cell culture may need antibiotics, to prevent bacterial growth in the culture dishes. 

Which should you choose?

The most common antibiotics used in cell culture today are:

Penicillin, Streptomycin and/or Gentamycin

Penicillin

Shelf-life is very short and degradation begins soon after adding to aqueous medium. The degradation products are cell-toxic. Addition of penicillin just before use is best, not during manufacture, not before delivery and not before storage . . .  just before use. 

Penicillin degradation products inhibit in-vitro granulopoiesis, Neftel KA et al. Br J Haematol, (1983) 54(2):255-60.

Adverse reactions following intravenous pc-g treatment to degradation of the drug in vitro, Neftel et al. Kliniche Wochen Scrhift (1984) 62:25-29

Effects of β-Lactam antibiotics on profilerating eukaryotic cells, Neftel et al, Antimicrobial Agents and Chemotherapy (1987) p 1657-1661.

Streptomycin

Streptomycin is an aminoglycoside which can cause hearing and skeletal damage to the foetus. 

The antibiotic streptomycin assessed in a battery of in-vitro tests for reproductive toxicology, K. Lemiere et al, Toxicology in Vitro (2007) 21:1348-1353.

Aminoglycoside antibiotics mediate context-dependent suppression of termination codons in a mammalian translation system, M Manuvakhova et al, RNA (2000), 6(7):1044-1055, Cambridge University Press.

Gentamycin

Gentamycin is also an aminoglycoside, classified as a teratogen, not recommended for pregnant women. Gentamycin is nephrotoxic to the foetus, so why use it with gametes or zygotes?

An aminoglycoside antibiotic gentamycin induces oxidative stress, reduces antioxidant reserve and impairs spermatogenesis in rats, K Narayana, J. Tox. Sci, (200 , 33(1):85-96.

Conclusions:

If an antibiotic is to be used, the best choice is Penicillin. It is the least toxic if added just prior to use!

//Anna (Research Coordinator)