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Table 2 Risk assessment for transmission of methicillin-resistant Staphylococcus aureus (MRSA) ( A ) and hepatitis B ( B ) by instruments autoclaved inside the Steriset Container on a gravity cycle

From: A case study of a real-time evaluation of the risk of disease transmission associated with a failure to follow recommended sterilization procedures

(A) MRSA   
Factors contributing to exposure risk Calculated risk Supporting reference or data
MRSA prevalence in hospital inpatient population (15%) 15:100 Infection Control Department data from the involved hospital
Risk of transmission via contaminated instruments 1:1 Assume highest risk
Likelihood that contaminated instrument was used 1:1 Assume highest risk
Efficacy of washer/disinfector 1:100,000 Table 1. Consistent removal of 99.999% or more of inoculated MRSA
Effect of MRSA desiccation 1:10 [5] and authors’ unpublished data
Effect of autoclaving inside the Steriset Container on gravity cycle (270 F for 15 minutes, pressure 28–30 psig) 1:10,000,000 Table 1. Consistent killing of 108 colony-forming units (CFU) of MRSA in liquid suspension (limit of detection <1 log10CFU/mL)
Individual risk ~1 × 10-14 (1 in 100 trillion)  
(B) Hepatitis B virus (HBV)*   
Factors contributing to exposure risk Calculated risk Supporting reference or data
Prevalence of hepatitis B (HBsAg positive) in U.S. population (0.5%) 5:1,000 [1, 5, 6]
Risk of transmission via contaminated instruments 1:1 Assume highest risk
Likelihood that contaminated instrument was used 1:1 Assume highest risk
Efficacy of washer/disinfector (removes 99.999% of vegetative bacteria)** 1:100,000 [1] and Table 1
Effect of HBV desiccation 1:1 [1]
Effect of autoclaving inside the Steriset Container on gravity cycle (270 F for 15 minutes, pressure 28–30 psig) 1:10,000,000 Table 1**
Individual risk ~1 × 10-14 (1 in 100 trillion)  
  1. *The risk of transmission of hepatitis C or HIV would be lower than the risk of transmission of hepatitis B.
  2. **Enveloped viruses have greater susceptibility to disinfectants and heat than vegetative bacteria such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci.