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Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008

Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008 [PDF - 948 KB]

Table 10. Factors affecting the efficacy of sterilization.

Factors Effect
Cleaning1 Failure to adequately clean instrument results in higher bioburden, protein load, and salt concentration. These will decrease sterilization efficacy.
Bioburden1 The natural bioburden of used surgical devices is 100 to 103 organisms (primarily vegetative bacteria), which is substantially below the 105-106 spores used with biological indicators.
Pathogen type Spore-forming organisms are most resistant to sterilization and are the test organisms required for FDA clearance. However, the contaminating microflora on used surgical instruments consists mainly of vegetative bacteria.
Protein1 Residual protein decreases efficacy of sterilization. However, cleaning appears to rapidly remove protein load.
Salt1 Residual salt decreases efficacy of sterilization more than does protein load. However, cleaning appears to rapidly remove salt load.
Biofilm accumulation1 Biofilm accumulation reduces efficacy of sterilization by impairing exposure of the sterilant to the microbial cell.
Lumen length Increasing lumen length impairs sterilant penetration. May require forced flow through lumen to achieve sterilization.
Lumen diameter Decreasing lumen diameter impairs sterilant penetration. May require forced flow through lumen to achieve sterilization.
Restricted flow Sterilant must come into contact with microorganisms. Device designs that prevent or inhibit this contact (e.g., sharp bends, blind lumens) will decrease sterilization efficacy.
Device design and construction Materials used in construction may affect compatibility with different sterilization processes and affect sterilization efficacy. Design issues (e.g., screws, hinges) will also affect sterilization efficacy.

Modified from Alfa and Rutala. 851

1 Factor only relevant for reused surgical/medical devices


Table 11. Comparative evaluation of the microbicidal activity of low-temperature sterilization technology.

    Carriers Sterilized by Various Low-Temperature Sterilization Technologies
Challenge ETO 12/88 100% ETO HCFC-ETO HPGP 100 HPGP 100S PA Reference
No salt or serum1 100% 100% 96% 100% ND ND Alfa 721
10% serum and 0.65% salt2 97% 60% 95% 37% ND ND Alfa 721
Lumen (125 cm long x 3 mm wide) without serum or salt1 ND 96% 96% ND ND ND Alfa 721
Lumen (125 cm long x 3 mm wide) with 10% serum and 0.65% salt2 44% 40% 49% 35% ND 100%1 Alfa 721
Lumen (40 cm long x 3 mm wide)3 ND ND 100% 95% 100% 8% Rutala 856
Lumen (40 cm long x 2 mm wide)3 ND ND 100% 93% 100% ND Rutala 856
Lumen (40 cm long x 1 mm wide)3 ND ND 100% 26% 100% ND Rutala 856
Lumen (40 cm long x 3 mm wide)4 ND ND 100% 100% 100% ND Rutala 856

Modified from Rutala. 825

Abbreviations: ETO=ethylene oxide; HCFC=hydrochlorofluorocarbon; ND=no data; HPGP=hydrogen peroxide gas plasma; PA=peracetic acid.

1Test organisms included Enterococcus faecalis, Mycobacterium chelonae, and Bacillus atrophaeus spores.

2Test organisms included E. faecalis, P. aeruginosa, E. coli, M. chelonae, B. atrophaeus spores, G. stearothermophilus spores, and B. circulans spores.

3Test organism was G. stearothermophilus spores . The lumen test units had a removable 5 cm center piece (1.2 cm diameter) of stainless steel sealed to the narrower steel tubing by hard rubber septums.

4Test organism was G. stearothermophilus spores. The lumen test unit was a straight stainless steel tube.


Table 12. Suggested protocol for management of positive biological indicator in a steam sterilizer.


  1. Take the sterilizer out of service. Notify area supervisor and infection control department.
  2. Objects, other than implantable objects, do not need to be recalled because of a single positive spore test unless the sterilizer or the sterilization procedure is defective. As soon as possible, repeat biological indicator test in three consecutive sterilizer cycles. If additional spore tests remain positive, the items should be considered nonsterile, and supplies processed since the last acceptable (negative) biological indicator should be recalled. The items from the suspect load(s) should be recalled and reprocessed.
  3. Check to ensure the sterilizer was used correctly (e.g., verify correct time and temperature setting). If not, repeat using appropriate settings and recall and reprocess all inadequately processed items.
  4. Check with hospital maintenance for irregularities (e.g., electrical) or changes in the hospital steam supply (i.e., from standard ≥97% steam, <3% moisture). Any abnormalities should be reported to the person who performs sterilizer maintenance (e.g., medical engineering, sterilizer manufacturer).
  5. Check to ensure the correct biological indicator was used and appropriately interpreted. If not, repeat using appropriate settings. If steps 1 through 5 resolve the problem
  6. If all three repeat biological indicators from three consecutive sterilizer cycles (step 2 above) are negative, put the sterilizer back in service. If one or both biological indicators are positive, do one or more of the following until problem is resolved.
  7. A. Request an inspection of the equipment by sterilizer maintenance personnel.
    B. Have hospital maintenance inspect the steam supply lines.
    C. Discuss the abnormalities with the sterilizer manufacturer.
    D. Repeat the biological indicator using a different manufacturer's indicator.

If step 7 does not resolve the problem
Close sterilizer down until the manufacturer can assure that it is operating properly. Retest at that time with biological indicators in three consecutive sterilizer cycles.


Modified from Bryce. 839

Disclosure of Financial Interests and Relationships (2000- July 2004)

William A. Rutala: Honoraria from Advanced Sterilization Products, Kimberly-Clark; consultation with Advanced Sterilization Products, Aesculap, Clorox, 3M, SC Johnson, Intelligent Biocides, Metrex; and an educational grant from Consumer Specialty Products Association, Kimberly-Clark.

David J. Weber: Honoraria from Consumer Specialty Products Association; consultation with Clorox; and educational grant from Consumer Specialty Products Association.

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