A sleuth story Patricia Cornwall would appreciate

Microbes, a Pharmacy Clean Room, Waste Bins, ATP, and a keen-eyed pharmacist

Recently I was part of a trio who presented an intriguing case-study of a microbiological contamination issue in a pharmacy clean room – it took months to solve, and ATP proved an excellent tool.

Tyler Weaver, Josh Guinter (Children’s Hospital of Philadelphia) and I delivered our paper entitled “Resolving microbial contamination of reusable waste bins in a pharmacy clean-room” at the Sept Association for the Healthcare Environment (AHE) conference in Pittsburg PA.

We are soon to publish – in meantime click here to view our PowerPoint presentation.

The story in a nutshell…

  Within a hospital, a Pharmacy Clean Room (PCR) is where sterile medications are prepared for patients – it is an “inner sanctum” with restricted access and is regularly tested for microbes to ensure all surfaces are scrupulously decontaminated to an ISO Standard – at a level higher than operating rooms.

A recent failure in a PCR resulted in 753 patients being infected with 64 deaths across 20 USA states.

The problem

  • PCR work-surfaces are required to be regularly tested for microbes. Two tests in PCR exceeded allowable level – triggering immediate action
  • Surfaces and ducts were scrupulously cleaned – but tests failed a second time. Several weeks of investigations proceeded
  • Then a keen-eyed pharmacist noticed a gown-tie moving as it hung from a waste bin in the PCR
  • Tie-movement meant air-flow; airflow meant bugs could waft in air – perhaps bin was source?
  • The reusable bins were tested, found to have very high microbial counts, and bin-vendor A was asked to remedy

The remedy

  • Microbe tests are expensive, so bins were ATP-tested as surrogate (ATP detects microbes and other living cells)
  • Bin-vendor A could not reduce ATP count to target-level  of <250 Relative Light Units (RLU) – aver of highest counts was 14,844 RLU
  • Second vendor (Vendor B) supplied bins for testing – all passed – aver of highest counts was 103 RLU – hospital changed to Vendor B for PCR.
  • No further PCR work-surface tests failed.

The explanation

  • Vendor A supplied bins “nested”. Entrapped moisture in bottom bin enabled microbial growth
  • When pushed into bin, discarded gowns created “piston effect” liberating microbial aerosol which wafted onto PCR work-surface
  • Vendor B wash process had higher level of bin decontamination. Bins supplied individually, not nested.
  • In 4 years: bins have exceeded ATP threshold of 250 RLU occasionally, and none since Aug 2015; no failures in PCR work-surface microbe tests have occurred.

Take Home Messages

  • Vendors of reusable bins have differing wash, drying  and delivery processes. Ask for details of processes and ATP-test (particularly if for PCR use).
  • ATP testing using a threshold of 250 RLU is a useful adjunct for checking QA of external waste bins used in PCR

Which patient clipboard is more sanitary – wood or plastic?

In this week’s APIC Listserve, Kim Roberts posed a great Q…Which clipboard is more sanitary – wood or plastic/metal?
All answers received to date state that plastic/metal clipboards would be more hygienic than wood as the latter was porous and could not be as easily decontaminated as non-porous plastic/metal.
In this specific case I agree. Wooden clipboards are commonly made of compressed wood fibre and are usually quite porous.
The above conclusion is reasonable, but not evidence-based.
In fact the literature supports a contrary view – that wood is better.
In 1992 Kass et al found that Californian households using wooden chopping boards suffered Salmonella food poisoning at half the state average, and those using plastic boards were twice the state average.
Independent of Kass et al, in 1994 Ak, Cliver and Kaspar at Univ Wisconsin-Madison challenged wooden and plastic boards with pathogens and found they disappeared in a short time from wooden boards but persisted on plastic boards, Furthermore they found nicks in plastic boards were harder to disinfect.
Cliver, now at UC Davis, commented on both studies and concluded in 2005 that, “…wooden cutting boards are not a hazard to human health, but plastic cutting boards may be.”
But I suspect the results with dense-wood chopping boards do not apply to porous fibre clipboards.

So keep writing on plastic and chopping on wood.

Publications (since 2003 – click link)


  • Grimmond T. Sharps Injuries – why aren’t we at zero? Webber Teleclass June 17, 2020. https://webbertraining.com/schedulep1.php?command=viewClass&ID=1485. Author copy (non-audio)Available.


  • McPherson B, Sharip M, Grimmond T. 2019. The impact on life cycle carbon footprint of converting from disposable to reusable sharps containers in a large US hospital geographically distant from manufacturing and processing facilities. PeerJ 2019;7:e6204. doi.org/10.7717/peerj.6204
  • Grimmond T, Good L. EXPO-S.T.O.P. 2016 and 2017 blood exposure surveys: An alarming rise. Am J Infect Control 2019 Dec;47(12):1465-1470. doi: 10.1016/j.ajic.2019.07.004.  Author copy available.
  • Grimmond T. UK safety-engineered device use: changes since the 2013 sharps regulations. Occupational Medicine 2019;69:352–358. doi:10.1093/OCCMED/kqz087. Author copy available.
  • Grimmond T, Good L. EXPO-S.T.O.P. 2016-17 Report. J Assoc Occup Hlth Prof, Winter 2019;39(1):9-11. Author copy available.


  • Grimmond T, Neelakanta A, Miller M, Saiyed A, Gill P, Jennifer Cadnum J, Olmsted R, Donskey C, Pate K, Miller K. A microbiological study to investigate the carriage and transmission potential of Clostridium difficile spores on single-use and reusable sharps containers. Am J Infect Control. 2018;46:1154-9. doi.org/10.1016/j.ajic.2018.04.206. Author copy available.
  • Good L, Grimmond T. Burnson J, et al. Exposure Injury Reduction Strategies: Results that Protect Lives. J Assoc Occ Hlth Prof. Fall,2018;38(4):10-13. (Copy courtesy AOHP).
  • Grimmond T. Safety Engineered Device Usage and Activation in Six Western U.S. Hospitals. J Assoc Occup Hlth Prof 2018;38(4):14-8. Author copy available.


  • Grimmond T, Good L. Exposure Survey of Trends in Occupational Practice (EXPO-S.T.O.P.) 2015: A national survey of sharps injuries and mucocutaneous blood exposures among health care workers in US hospitals.  Am J Infect Control 2017;45(11):1218–1223. doi.org/10.1016/j.ajic.2017.05.023. Author copy available.
  • Good L, Grimmond T. Proven Strategies to Prevent Bloodborne Pathogen Exposure in EXPO-S.T.O.P. Hospitals. J Assoc Occup Hlth Prof 2017:36(1);1-5. (Copy courtesy AOHP).


  • Brown C, Dally M, Grimmond T, Good L. Exposure Study of Occupational Practice (EXPO-S.T.O.P.): An update of a national survey of sharps injuries and mucocutaneous blood exposures among HCW in US hospitals. J Assoc Occup Hlth 2016;36(1):37-42. Author copy available.
  • Grimmond T. Sharps Injury Prevention: Challenges and Effective Strategies. Webber Teleclass June 29, 2016. Mp3 avail https://webbertraining.com/recordingslibraryc4.php.  Author copy (non-audio) available.


  • Grimmond T, Good L. EXPO-S.T.O.P. 2012: Year two of a national survey of sharps injuries and mucocutaneous blood exposures among healthcare workers in USA hospitals. J Assoc Occup Hlth Prof 2015;35(2):52-57. Author copy available.


  • Grimmond T, Naisoro W. Sharps injury reduction: A 6-year, 3-phase study comparing use of a small patient-room sharps disposal container with a larger engineered container. J Infect Prev 2014;15 (5):170-174. https://doi.org/10.1177/1757177414543088. Author copy available.
  • Grimmond T. Frequency of use and activation of safety-engineered sharps devices: a sharps container audit in five Australian capital cities. Healthcare infection 2014;19(3):95-100. http://dx.doi.org/10.1071/HI14009. Author copy available.
  • Grimmond T. The Effect of Temperature, Needle Gauge and Wall Thickness on the Force Required for Needles to Puncture Sharps Containers. J Clin Engin 2014;39(2):71-5. Author copy available.
  • Grimmond T. Use and activation of safety engineered sharps devices in a sample of 5 Florida healthcare facilities. J Assoc Occup Hlth Prof 2014;34(1):13-15. Author copy available.
  • De Sousa F, Martin D, Grimmond T. The impact of a liner-less reusable clinical waste bin system on costs, waste volumes and infection risk in an Australian acute-care hospital. Healthcare Infection, 2014, 19, 76–80. http://dx.doi.org/10.1071/HI13048. Author copy available.


  • Grimmond T, Good L. EXPO-S.T.O.P.: A national survey and estimate of sharps injuries and mucocutaneous blood exposures among healthcare workers in USA. J Assoc Occup Hlth Prof 2013;33(4):31-36. Author copy available.
  • Grimmond T. Using reusable containers for hospital waste – is there an infection risk? South Afr J Epidemiol Infect 2013;28(4):197-201.


  • Grimmond T, Reiner S. Impact on Carbon Footprint: An LCA of Disposable vs Reusable Sharps Containers in a Large US Hospital. Waste Management & Research 2012;30:639-642. Author copy available.


  • Grimmond T. Conducting Research – It’s Your Everyday Work. J Assoc Occup Hlth Prof Spring 2010;30(2):12-14. Author copy available.
  • Grimmond T. Trends in Sharps Injury Prevention. Webber Teleclass, Feb 2010. MP3 avail https://webbertraining.com/recordingslibraryc4.php.  Author copy (n0n-audio) available.
  • Grimmond T, Bylund S, Anglea C, at al. Sharps injury reduction using a sharps container with enhanced engineering: A 28 hospital non-randomized intervention and cohort study. Am J Infect Control 2010;38:799-805. Author copy available.


  • Grimmond T, Rings T, Taylor C, Creech R, R. Kampen R, W. Kable W, et al. Sharps Injury Reduction Using Sharpsmart – A Reusable Sharps Management System. J Hosp Infect 2003;54(3):232-238. Author copy available.