Whilst I would agree with Stephan that you may introduce problems, you do raise an important point. The most common cause of contamination is usually from high copy amplified target generated previously. With bacteria and fungi you have an additional issue that many of these organisms are already present in the environment /air eg aspergillus. These organisms are not an issue for most individuals but are a serious problem for immunosuppressed transplantation patients and detecting infection early (low level) is critical. There is, however, a real possibility of generating false positives if you are not using filtered air. If you have a room with filtered air that would be ideal. Mask up.

On general points :You really need 3 sets of pipettes - one for only dealing out PCR reagent, one for only aliquotting low copy pre-PCR sample target, one set for dealing with high copy amplified target if you are running out gels. The processes should be carried out in different locations / dedicated rooms / work spaces, separate lab coats etc. Always use filter tips, UV irradiate pipettes before / after use and where possible following MIQUE guidelines

www.ncbi.nlm.nih.gov/pubmed/1924661 . Never bring high copy amplified targets near your primary source material. The same applies to segregation of your PCR reagents in dedicated freezers. I often use water for injection as a source of sterile water in the PCR mixes where necessary. vials can then be discarded after use.

Most laminar flow hoods come with germicidal UV irradiation sources which can reduce sources of PCR amplifiable contamination. They may be of limited use for spore / conidia elimination though.To eliminate cross contamination from previously amplified target, consider using dUNG or adding artic shrimp DNAse in a pre-PCR step, spray surfaces with DNA-away.

Ian Teo

In my opinion, without flow is better. The flow will create some aerosol that will contaminate all the place and not only the hood.

Whilst I would agree with Stephan that you may introduce problems, you do raise an important point. The most common cause of contamination is usually from high copy amplified target generated previously. With bacteria and fungi you have an additional issue that many of these organisms are already present in the environment /air eg aspergillus. These organisms are not an issue for most individuals but are a serious problem for immunosuppressed transplantation patients and detecting infection early (low level) is critical. There is, however, a real possibility of generating false positives if you are not using filtered air. If you have a room with filtered air that would be ideal. Mask up.

On general points :You really need 3 sets of pipettes - one for only dealing out PCR reagent, one for only aliquotting low copy pre-PCR sample target, one set for dealing with high copy amplified target if you are running out gels. The processes should be carried out in different locations / dedicated rooms / work spaces, separate lab coats etc. Always use filter tips, UV irradiate pipettes before / after use and where possible following MIQUE guidelines

www.ncbi.nlm.nih.gov/pubmed/1924661 . Never bring high copy amplified targets near your primary source material. The same applies to segregation of your PCR reagents in dedicated freezers. I often use water for injection as a source of sterile water in the PCR mixes where necessary. vials can then be discarded after use.

Most laminar flow hoods come with germicidal UV irradiation sources which can reduce sources of PCR amplifiable contamination. They may be of limited use for spore / conidia elimination though.To eliminate cross contamination from previously amplified target, consider using dUNG or adding artic shrimp DNAse in a pre-PCR step, spray surfaces with DNA-away.

Ian Teo