Can a sterile, sealed container of saline become infected?

[Alfred001]

I was watching the below video on cleaning contact lenses, which have to be sterile when you put them in your eyes or you risk an eye infection. The video says take your lenses out, put them in this container of hydrogen peroxide and seal them up. You leave them in there for 6 hours and the hydrogen peroxide gets converted to saline and then they say the lenses can stay in there for 7 days.

I'm wondering, what if the lenses were to be left there indefinitely? How could they get infected if everything in the container had been killed by the hydrogen peroxide? Is there any chance they could get infected if left in there for a month and if so how, where would the life come from?

Again, the container is completely sealed.

 

Edited June 15, 2019 by Alfred001

[StringJunky]

How can hydrogen peroxide be converted to saline when there's no saline components in the molecule?  They are separate products . Concerning  period of effectiveness: the peroxide is probably constantly decomposing to the point that, after 7 days, it''s no longer considered useful as a disinfectant. It is not an inherently stable molecule, which makes sense when you think that if it was stable it would not be reactive for killing pathogens. Saline works by creating a diffusion gradient such that water is sucked out of any micro-organisms present. The solution uses a two-pronged approach to keeping the lenses sterile.

Edited June 15, 2019 by StringJunky

[John Cuthber]

I'm fairly sure that the saline used in storing contact lenses is 0.9% NaCl and is isotonic with blood (and tears) so it causes less irritation when you put the lenses back in.

It's not, in any way, intrinsically bactericidal. However it's likely to have some bactericide added to keep it sterile.

My guess is  that the stuff being sold is a solution of salt in a mixture of water and hydrogen peroxide.
Once the peroxide decomposes you are left with saline.

4 hours ago, Alfred001 said:

Is there any chance they could get infected if left in there for a month and if so how, where would the life come from?

It's also possible that some spore-forming microbes would survive long enough for the peroxide to decay, and then start growing.

 

Ask your optician.

 

 

 

 

 

[CharonY]

On 6/15/2019 at 5:29 AM, John Cuthber said:

I'm fairly sure that the saline used in storing contact lenses is 0.9% NaCl and is isotonic with blood (and tears) so it causes less irritation when you put the lenses back in.

It's not, in any way, intrinsically bactericidal. However it's likely to have some bactericide added to keep it sterile.

My guess is  that the stuff being sold is a solution of salt in a mixture of water and hydrogen peroxide.
Once the peroxide decomposes you are left with saline.

It's also possible that some spore-forming microbes would survive long enough for the peroxide to decay, and then start growing.

 

Ask your optician.

 

 

 

 

 

IIRC there were basically antibacterial composition (which were also termed preservative-containing solutions) and hydrogen peroxide based solutions, which are sold as one or two-step systems. In the former a catalyst is included which allows faster and controlled degradation of the peroxide. One thing to add regarding contamination is that sterilization can be incomplete in a number of cases. The most common one, I imagine, is the formation of biofilms on lenses, which are quite more resilient to hydrogen peroxide (and other stressors). If kept in saline for long enough, they provide the reservoir for renewed bacterial growth.