Is deliberately seeding hospital rooms with Bacillus spores a good idea? No, I don’t think so either!

A fascinating Italian/Belgian multicentre study introduces us to the idea of “biocontrol” for problematic surface contamination. They test using “live” cleaning products that deliberately seed hospital surfaces with Bacillus species spores in an attempt to reduce the ecological space for pathogenic microbes through a “competitive exclusion” approach. Ridiculous as it sounds, there’s some logic to this idea. We’re just beginning to understand the potential of complementing a depleted microbiome in human health, so perhaps the same theory goes for the “environmentome”?

The study design is on the one hand impressive and ambitious, with more than 20,000 surfaces samples collected from the three hospitals. However, it is also messy and confusing, with different intervention and sampling protocols in the three hospitals. In particular, it’s a real shame that areas were not randomized to receive the “live” vs. conventional cleaning agents. It seems clear that this was not a carefully planned multicentre study using a standardized protocol – it reads more like three separate studies shoe-horned together.

That said, the results are impressive. Areas treated with the “live” cleaning agents were significantly less likely to be contaminated with coliforms, S. aureus, Candida albicans, with a more moderate impact on C. difficile. However, it’s difficult to determine the scale of the reduction since the relative rather than actual load reductions are reported.

A neat sub-experiment at one of the hospitals is perhaps the most convincing part of the study, where conventional and “live” cleaning agents were alternated (Figure). You can clearly see that the microbial load tracked downwards when the “live” agent was used, and rebounded when the conventional agent was reinstated.

vandini bacillus sporesFigure: Bacterial load of coliforms (black circles) and S. aureus (white circles). Black arrow = beginning of the “live” cleaning agent; black dotted arrow = conventional cleaning agent.

Notwithstanding the impressive reductions, this approach is ringing some alarm bells:

  • Do we really know what we’re doing by deliberately seeding the hospital environment with bacterial spores? Almost all microbes can be pathogenic to immuno-compromised patients. Plus, whilst you know what you’re putting down, you don’t know what it will become when exposed to the selective pressure of hospitals. The authors did take a look at this, using antibiotic susceptibility testing and a PCR assay to show that Bacillus species identified from the original cleaning agents and from hospitals surfaces during study did not differ in their carriage of antibiotic resistance genes. However, this is only scratching the surface of a complex risk.
  • Where do all the pathogens go? Having an environment that is full of Bacillus spores does not make a scrap of difference to the amount of pathogens that are shed into the environment. So, either the Bacillus spores somehow reduce the amount of time that these pathogens survive on surfaces, or offer them a more complex hiding place. I suspect the latter is more likely.
  • Related to this, recent work has identified established biofilms on dry hospital surfaces with important implications. Won’t a daily dose of Bacillus spores only serve to promote the buildup of this biofilm?
  • The authors proffer some potential reasons for the lower bacterial counts, including competition for nutrients and quorum sensing to destabilize biofilms. I think these are very unlikely, because they rely on the Bacillus spores germinating on the surfaces. I suspect that the spores remain firmly as spores, and the reductions are explained by occlusion and competition for space.
  • Ethics can be a pain, but it’s there for a reason – to prevent our patients from unnecessary harm. The outcome of their ethical submission was surprising: “The two Ethics Committees stated that a formal authorization was not necessary because the probiotic products would not be directly administered to patients but exploited for cleaning of hospital surfaces only.” Applying a soup of Bacillus species spores to a patient’s room is pretty much the same thing as applying the soup directly to their skin. Personally, I’d like to choose whether or not I’m admitted to a room deliberately seeded with Bacillus spores!
  • The authors insist on calling the “live” cleaning agents ‘probiotics’, which seems misplaced. To me, ‘xxx-biotics’ implies something that is administered to a patient.

The use of “live” cleaning agents provides an interesting alternative approach to antimicrobial surfaces, or chemicals with residual biocidal activity. However, I am not sure I accept the authors stark choice as their final conclusion: When it comes down to risk management, one has to decide whether a patient should stay in an environment dominated by food grade microorganisms or in an environment harboring an elevated level of increasingly resistant pathogens.’ Personally, I’d prefer to be cared for in an environment with minimal levels of bacterial contamination, and free from contamination with pathogens. Is that too much to ask?

Article citation: Vandini et al. Hard Surface Biocontrol in Hospitals Using Microbial-Based Cleaning Products. PLoS One 2014;9:e108598.


8 thoughts on “Is deliberately seeding hospital rooms with Bacillus spores a good idea? No, I don’t think so either!

  1. Dear John,
    You right, this is the way italian research is so exciting nowdays. But few years ago the experts of Infection Control & Epidemiology in Rome had to cry the death of 4 or 5 newborns affected by Necrotizing Enterocolitis acquired in their incubators
    Season greetings.


  2. I totally agree – this is not a good option for the reasons as you have discussed. But I am really curious about what the mechanism of action could be at dry surfaces. Is it a matter of changing surface tension or another physical mechanism?
    I don’t believe so… I would expect that the “mechanism” is either that you will not pick up pathogens from the layer beneath the layer of Bacillus using contact plates or that the high amount of Bacillus inhibit other organisms on the culture plates.

    Taking into account the poor study design, the questionable statistics, lack of proper controls, method of sampling and the small and insignificant effects it is difficult to draw any conclusions about the effect. Also, the safety is a major question and I hope hospitals are not tempted to use the method.


  3. This rings a bell with me. We were rather concerned about a year or so ago to come across a new “probiotic cleaner” being marketed for the domestic environment, which is being endorsed by a well known UK TV presenter who hosts a show called “How clean is you home”. I did see some support data which came from the same lab in Belgium and shows that the probiotic cleaner contains Bacillus strains

    If you go to – you will find what the TV presenter says which includes:

    “There’s a houseful coming for Christmas, including toddlers and oldies. How do you keep on top of the dirt and germs?
    First, chuck out that antibacterial spray – most bacteria in our homes are good for us and protect our health; you don’t want to kill them off and encourage the growth of superbugs. Much better to use Aggie’s Probiotic cleaners which are 100 per cent natural and inhibit the growth of harmful bacteria for up to eight days! They also smell fantastic and give the most amazing shine. Available from selected branches of Sainsbury’s and Lakeland from £2.99”

    If you want to see more go to


  4. Use of bacteria for control of pathogens in health care facilities is probably not a good idea . I just attended a meeting on infection control in hospitals in which three cases of infection were reported in immuno-compromised persons that were acquired from people in the same facility using probiotics. Bacillus species are know to case infection in immune-compromised persons and should probably never be considered being used in a hospital environment.


  5. Certainly makes me uncomfortable at first, will have to read more about this? Bacillus must be the topic this week, as I just shared a discussion regarding their presence on x-ray aprons/lead wearables in the Operating Room and their respective cfu load (confirmed over 1 Million CFUs). 20+ years in the OR and I continue to learn something each day. Thanks for sharing regarding this study, had never heard of such a thing. The battle against infections continues!


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