Gergen, Maria F.

Rutala, William A.

Weber, David J.

Infection Control and Hospital Epidemiology

William A. Rutala

Maria F. Gergen

David J. Weber

Crossref

Microbial Contamination on Used Surgical Instruments

Carolina Digital Repository

1068 infection control and hospital epidemiology august 2014, vol. 35, no. 8table 1. Microbes Contaminating Used Surgical Instru-ments and Microbial Load When Submitted to Central Ster-ilization ServicesVariableNo. (%) ofinstruments(n p 50)Colony count, CFU0–10 29 (58)11–100 10 (20)101–1,000 7 (14)11,000 4 (8)MicrobeCoagulase-negative Staphylococcus species 24 (48)a-Streptococcus species 13 (26)Diphtheroids 10 (20)Micrococcus species 10 (20)Bacillus cereus 9 (18)Bacillus species (not cereus) 5 (10)Escherichia coli 5 (10)Enterococcus (vancomycin susceptible) 2 (4)Pseudomonas aeruginosa 2 (4)Streptococcus pneumoniae 2 (4)Enterococcus species (vancomycin resistant) 1 (2)Pantoea species 1 (2)Serratia marcescens 1 (2)Staphylococcus aureus (oxacillin susceptible) 1 (2)note. Instruments were used in a total of 12 operations. Ofthe 50 instruments cultured, 9 (18%) showed no growth. CFU,colony-forming unit.http://www.cdc.gov/nhsn/acute-care-hospital/index.html. Ac-cessed January 20, 2014.5. Anderson DJ, Kirkland KB, Kaye KS, et al. Underresourcedhospital infection control and prevention programs: penny wise,pound foolish? Infect Control Hosp Epidemiol 2007;28:767–773.6. Weber DJ, Brown VM, Sickbert-Bennett EE, Rutala WA. Sus-tained and prolonged reduction in central line–associated blood-stream infections as a result of multiple interventions. InfectControl Hosp Epidemiol 2010;31:875–877.7. Marschall J, Mermel LA, Classen D, et al. Strategies to preventcentral line–associated bloodstream infections in acute care hos-pitals. Infect Control Hosp Epidemiol 2008;29(suppl 1):S22–S30.8. King B, Schulman CI, Pepe A, Pappas P, Varas R, Namias N.Timing of central venous catheter exchange and frequency ofbacteremia in burn patients. J Burn Care Res 2007;28:859–860.9. Sood G, Heath D, Adams K, et al. Survey of central line–as-sociated bloodstream infection prevention practices acrossAmerican Burn Association–certified adult burn units. InfectControl Hosp Epidemiol 2013;34:439–440.10. Harris AD, Pineles L, Belton B et al. Universal glove and gownuse and acquisition of antibiotic-resistant bacteria in the ICU:a randomized trial. JAMA 2013;310:1571–1580.Microbial Contamination on UsedSurgical InstrumentsSurgical instruments are considered critical items becausethey enter sterile body tissues or the vascular system, and ifcontaminated with any microorganism, including bacterialspores, this could result in an infection. Critical items aregenerally sterilized by steam sterilization if heat resistant. Ifheat sensitive, the object may be sterilized with ethylene oxide,hydrogen peroxide gas plasma, or vaporized hydrogen per-oxide. However, these technologies have a lower margin ofsafety than steam sterilization.1 Because the level of microbialcontamination of the object to be sterilized plays a criticalrole in determining the efficacy of the sterilization process,we evaluated the microbial load on used surgical instrumentsbefore cleaning and sterilization.This study was conducted at the University of North Car-olina Health Care, an 810-bed medical center. A variety ofstainless steel surgical instruments were chosen, includingMayo straight scissors, forceps (eg, curved tip, large, andDebakey), rake, scissors (eg, curved), small-prong fork, small-pronged clamps, hemostats, knife handles, retractor, and nee-dle holders. These instruments were all used in our operatingrooms. After use in surgical procedures, the instruments weretransported in peel packs to the hospital epidemiology lab-oratory and aseptically fully immersed in trypticase soy broth(Remel). The broth and instruments were agitated on a shakerat 150 rpm. After 30 minutes of agitation, two 500-mL sampleswere removed and plated onto sheep blood agar (SBA; Re-mel). The remaining broth was filtered through a disposable0.45-mm cellulosic membrane filter unit (MSI Savur). Anycolonies in the 500-mL samples were identified, and the totalnumber on the device was calculated by multiplying by thevolume of fluid. Any colonies on the SBA or filter were enu-merated and identified using standard microbiological tech-niques.Fifty surgical instruments were obtained from 12 opera-tions. Less than 10 colony-forming units (CFUs) per devicewere recovered from 58% of the used instruments (Table 1).Eleven to 100 CFU were recovered from 20% of the usedinstruments, and greater than 100 CFU (median, 207 CFU)were recovered from 14% of the instruments. In 4 cases (8%),greater than 1,000 CFU were recovered from the instruments(ie, Bacillus cereus on forceps; B. cereus3 32.4 # 10 4.4 # 10on a rake; on a pronged clamp (containing41.94 # 10coagulase-negative Staphylococcus, a-3 35.4 # 10 6.6 # 10Streptococcus, Streptococcus pneumoniae, and35.8 # 10Micrococcus species); and on a hemostat3 41.6 # 10 4.98 # 10(containing S. pneumoniae, a-Strepto-3 45.4 # 10 4.4 # 10coccus). The most common contaminating organisms werecoagulase-negative Staphylococcus species, a-Streptococcus,diphtheroids, Micrococcus species, B. cereus, Escherichia coli,and Bacillus species (Table 1).The data revealed that the microbial load on used surgicalinstruments before cleaning was generally low; 58% had 10CFU or less, and 78% had 100 CFU or less. In a study ofcontamination levels on used surgical instruments beforeDownloaded from https://www.cambridge.org/core. 02 Feb 2021 at 19:24:13, subject to the Cambridge Core terms of use.research briefs 1069cleaning, Nystrom reported that 60% of the instruments car-ried less than 10 CFU, 80% carried less than 100 CFU, and90% carried less than 1,000 CFU.2 Whether the operationswere clean, clean-contaminated, contaminated, or dirty didnot significantly affect the microbial load. Pinto et al3 foundthat fewer microorganisms were recovered from instrumentsused in clean surgeries (47%) in comparison with those usedin contaminated (70%) and infected (80%) surgeries. Thesedata are similar to 3 other studies that evaluated the microbialload on surgical instruments after cleaning4 or before andafter cleaning but before sterilization.5,6 Chan-Myers evalu-ated the bioburden associated with rigid lumened instrumentsbefore and after cleaning and found the bioburden associatedwith rigid-lumened devices after clinical use but before clean-ing was relatively low (median, 132 CFU) per device.6The level of microbial contamination on lumened and non-lumened surgical instruments is approximately 3 log10 CFUlower than that of model test systems used for evaluatingsterilization systems.6 That is, it is usually assumed that thelevel of microbial contamination of a medical or surgicaldevice is 106 CFU. Another level of conservatism is that reg-ulatory agencies require the inactivation of spores, which arethe most difficult contamination to inactivate, rather thanvegetative bacteria, which are commonly found on instru-ments.4-6 Regulatory testing for sterilization validation shouldbe robust but also clinically relevant (eg, microbial load andsoil).Decontamination of used surgical instruments is recom-mended for the following 2 reasons: (1) it protects the staffhandling the instruments from acquiring infection in theevent of a percutaneous injury, and (2) it reduces the mi-crobial contamination on instruments as well as protein andsalt before sterilization and thereby enhances the reliabilityof the sterilization process. Protein and salt have been shownto interfere with the sterilization processes, especially low-temperature sterilization processes.1,7 The exact mechanismby which salt and protein protect against microbial inacti-vation is not understood completely, but it likely representsocclusion of microorganisms in crystalline materials and im-pedance of vapor or gas penetration in a microenvironment.7The low microbial load on used surgical instruments beforecleaning likely reflects contact or use of these instruments innormally sterile body sites and fluids. In contrast, publishedstudies on the bioburden associated with instruments usedin nonsterile sites, such as flexible endoscopes (ie, colono-scopes), report much higher levels of microbial contamina-tion ranging from 108 to 1010 CFU (internal channels).8-10This microbial level is due to the very high numbers of bac-teria present in the human colon. Studies that have evaluatedthe effectiveness of washer-disinfectors commonly used todecontaminate surgical instruments (but not flexible endo-scopes) are capable of removing or inactivating 108 CFU,11which far exceeds the level on used instruments.In summary, our data suggest that properly cleaned non-lumen surgical instruments carry a low microbial load ofrelatively nonpathogenic microbes. In the absence of proteinand salt, low-temperature sterilization technologies are likelyto be effective in preventing cross-transmission of infectionvia nonlumened medical and surgical instruments.acknowledgmentsPotential conflicts of interest. W.A.R. reports being a consultant for AdvancedSterilization Products and Clorox. D.J.W. reports being a consultant forJohnson & Johnson and Clorox. All other authors report no conflicts ofinterest relevant to this article. All authors submitted the ICMJE Form forDisclosure of Potential Conflicts of Interest, and the conflicts that the editorsconsider relevant to this article are disclosed here.William A. Rutala, PhD, MPH;1,2Maria F. Gergen, MT(ASCP);1David J. Weber, MD, MPH1,2Affiliations: 1. Department of Hospital Epidemiology, University of NorthCarolina Health Care, Chapel Hill, North Carolina; 2. Division of InfectiousDiseases, University of North Carolina School of Medicine, Chapel Hill,North Carolina.Address correspondence to William A. Rutala, PhD, MPH, 2163 Bioin-formatics, CB 7030 Chapel Hill, NC 27599 (brutala@unch.unc.edu).Received January 17, 2014; accepted March 17, 2014; electronically pub-lished June 20, 2014.Infect Control Hosp Epidemiol 2014;35(8):1068-1070 2014 by The Society for Healthcare Epidemiology of America. All rightsreserved. 0899-823X/2014/3508-0022$15.00. DOI: 10.1086/677153references1. Alfa MJ, DeGagne P, Olson N, Puchalski T. Comparison of ionplasma, vaporized hydrogen peroxide and 100% ethylene oxidesterilizers to the 12/88 ethylene oxide gas sterilizer. Infect ControlHosp Epidemiol 1996;17:92–100.2. Nystrom B. Disinfection of surgical instruments. J Hosp Infect1981;2:363–368.3. Pinto FMG, deSouza RQ, daSilva CB, Mimica LMJ, GrazianoKU. Analysis of the microbial load in instruments used in or-thopedic surgeries. Am J Infect Control 2010;38:229–233.4. Rutala WA, Gergen MF, Jones JF, Weber DJ. Levels of microbialcontamination on surgical instruments. Am J Infect Control1998;26(2):143–145.5. Chu NS, Chan-Myers H, Ghazanfari N, Antonoplos P. Levelsof naturally occurring microorganisms on surgical instrumentsafter clinical use and after washing. Am J Infect Control 1999;27(4):315–319.6. Chan-Myers H, McAlister D, Antonoplos P. Natural bioburdenlevels detected on rigid lumened medical devices before andafter cleaning. Am J Infect Control 1997;25(6):471–476.7. Jacobs P. Cleaning: principles, methods and benefits. In: RutalaWA, ed. Disinfection, Sterilization, and Antisepsis in Healthcare.Champlain, NY: Polyscience, 1998:165–181.8. Chu NS, Favero M. The microbial flora of the gastrointestinaltract and the cleaning of flexible endoscopes. Gastrointest EndoscClin North Am 2000;10(2):233–244.9. Alfa MJ, Degagne P, Olson N. Worst-case soiling levels forDownloaded from https://www.cambridge.org/core. 02 Feb 2021 at 19:24:13, subject to the Cambridge Core terms of use.1070 infection control and hospital epidemiology august 2014, vol. 35, no. 8table 1. Ultraviolet-C Decontamination of Formica Surfaces in Patient Rooms That Were Experimentally Con-taminated with Methicillin-Resistant Staphylococcus aureus (MRSA) and Clostridium difficile Spores with and with-out a Reflective Coating on WallsMRSA C. difficileVariable Without coating With coating Without coating With coatingCycle time, minutes 5 5 10 10Direct surfaces 4.10 (3.88–4.32); 30 4.68 (4.61–4.76); 30 3.35 (3.14–3.55); 30 3.34 (3.10–3.59); 30Indirect surfaces 2.74 (2.53–2.94); 20 4.21 (4.00–4.42); 20 1.80 (1.36–2.24); 20 2.61 (2.24–2.97); 20Overall 3.56 (3.31–3.80); 50 4.50 (4.38–4.61); 50 2.78 (2.48–3.07); 50 3.05 (2.82–3.28); 50note. Data are mean log10 reduction in colony-forming units (95% confidence interval) and no. of samples,unless otherwise indicated. Patient room is 130 square feet (12.077 m2) in area. Confidence intervals were calculatedbased on a Poisson distribution.patient-used flexible endoscopes before and after cleaning. AmJ Infect Control 1999;27(5):392–401.10. Roberts CG. Studies on the bioburden on medical devices andthe importance of cleaning. In: Rutala WA, ed. Disinfection,Sterilization and Antisepsis: Principles and Practices in HealthcareFacilities. Washington, DC: Association for Professionals in In-fection Control and Epidemiology, 2001:63–69.11. Rutala WA, Gergen MF, Weber DJ. Efficacy of a washer-disin-fector in eliminating healthcare-associated pathogens from sur-gical instruments. Infect Control Hosp Epidemiol 2014;35(7):883–885.Room Decontamination Using anUltraviolet-C Device with ShortUltraviolet Exposure TimeDisinfection of noncritical room surfaces and equipment isnormally performed by manually applying a liquid disinfec-tant with a cloth, wipe, or mop. Studies have shown 10%–50% of the surfaces in rooms with patients colonized orinfected with Clostridium difficile, methicillin-resistant Staph-ylococcus aureus (MRSA), and vancomycin-resistant Entero-coccus (VRE) are contaminated with these pathogens, and alack of thoroughness in cleaning contaminated surfaces insuch rooms (mean, 32% of surfaces and objects cleaned) hasbeen linked to a 120% increase in risk of infection to thenext occupant in that room.1,2 These data have led to effortsto improve surface disinfection practices and the developmentof “no-touch” room decontamination units that avoid theproblems associated with manual disinfection.3Room decontamination units that use ultraviolet-C (UV-C, 254 nm) are commercially available and have been shownto effectively decontaminate surfaces in patient rooms.4-8 Thepurpose of this study was to determine whether a fixed cycle-time UV-C device was effective in inactivating the test bacteriain a patient room with and without reflective coating. Tobetter understand the effect of the reflective coating, the UV-C intensity on surfaces of interest were directly measuredusing a UV-C radiometric sensor.We investigated a single, easily transportable UV-C device(V-360, UltraViolet Devices) that incorporates four 64-inchUV-C lamps having a total output of 1,200 W. The device’scycle time was determined by the manufacturer on the basisof the size and configuration of various-sized rooms. Mea-surements were performed in 2 patient rooms as describedpreviously.8Testing was performed as previously reported using C. dif-ficile spores and a clinical isolate of MRSA.8 The room de-contamination times were fixed at 5 minutes for MRSA and10 minutes for C. difficile spores. Following cycle completion,each Formica template was cultured, and after incubation,the colony-forming units of the test organisms on each platewere quantified.Measurements of UV-C irradiance energy (W/cm2) wereperformed using a radiometer (ILT1700 Research Radiometer,International Light Technologies) equipped with a calibrated,National Institute of Standards and Technology–traceableUV-C detector with appropriate filter and diffuser (SED240/NS254/W, International Light Technologies).For disinfection of MRSA with a 5-minute cycle time, weobserved a 3.56-log10 reduction without the reflective coatingand 4.50-log10 reduction with the reflective coating. For dis-infection of C. difficile spores with a 10-minute cycle time,we observed a 2.78-log10 reduction without the reflective coat-ing and 3.05-log10 reduction with the reflective coating (Table1). The most significant improvements when a reflective wallcoating was used were seen on indirect surfaces, where a 1.47-log10 reduction increase was observed for MRSA and a 0.81-log10 reduction increase was observed for C. difficile spores.Measurements of UV-C irradiance were roughly W/31 # 10cm2 for direct surfaces in both rooms. For indirect surfaces,however, the reflective coating increased the UV-C irradiancetenfold from to (Figure 1).6 53.7 # 10 4.5 # 10These results confirm earlier findings that UV-C devicescan effectively disinfect patient rooms. This unit achieved atotal 3.56-log10 reduction (4.10 direct, 2.74 indirect) forMRSA in 5 minutes and a total 2.78-log10 reduction (3.35Downloaded from https://www.cambridge.org/core. 02 Feb 2021 at 19:24:13, subject to the Cambridge Core terms of use.

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