Air sampling methods to evaluate microbial contamination in operating theatres: results of a comparative study in an orthopaedics department
Introduction
Air biocontamination and related health effects are an emerging public health problem. Airborne bacteria, fungi and viruses can cause infection in diverse living or working environments. This is particularly relevant in medical facilities where there are susceptible patients and tissues are exposed to the air during surgery. As such, there is a need for various systems to minimize the introduction, generation and retention of particles in these environments.1, 2 In this context, microbiological monitoring of air quality is useful in order to determine the potential exposure of individuals at risk.
The control of air biocontamination was first deemed to be necessary in order to reduce the risk of deep wound infections in prodedures such as hip arthroplasties.3, 4 It is generally accepted that bacterial contamination of the air in operating theatres, predominantly caused by contaminated skin scales shed from the surgical team, is the main factor causing surgical site infection after clean operations.1, 5, 6
Whilst the procedures for microbiological assessment of other environmental matrices are established in European Law (e.g. methods are specified for the identification of microbes from water samples), there are no established regulations for air monitoring other than the international norm ISO 14698. This states that different sampling methods exist and different types of devices are commercially available, each with limitations, thus leaving the choice of system open.7, 8 Microbiological content of the air can be monitored by two principal methods: active and passive monitoring of air flows.8 In active monitoring, a microbiological air sampler physically draws a known volume of air through or over a particle collection device, which can be liquid or solid, and the number of micro-organisms present is given in colony-forming units (cfu)/m3 of air. This system is applicable when the concentration of micro-organisms is not very high, such as in an operating theatre.2, 9, 10 Passive monitoring uses ‘settle plates’ (i.e standard Petri dishes containing culture media) that are exposed to the air for a given time to collect biological particles; these ‘sediment’ out and are subsequently incubated. Results are expressed in cfu/plate/time or cfu/m2/h.11
Several studies have compared the two sampling methods with discordant results; some studies have found significant correlation between the methods,11, 12, 13, 14 while other studies have found no correlation.15, 16 In particular, Friberg et al. proposed an equation that permits the transformation of the number of cfus settling on a plate over 1 h (cfu/plate/h) into air contamination units (cfu/m3).11, 17
One of the most important questions that still needs to be resolved is whether the data from these monitoring systems are actually relevant to what is happening on the operating table. If one of the principal causes of air biocontamination is the surgical team, the results from the general room monitoring systems may underestimate the real risk of exposure to the patient on the surgical table, which may be surrounded by air with a higher level of micro-organisms.
To evaluate this hypothesis, the present study investigated and compared the levels of air contamination measured with active and passive systems, and also evaluated the level of air contamination near the wound using nitrocellulose membranes.18, 19
Section snippets
Methods
This study was undertaken between January 2010 and January 2011 in the operating theatre of the Department of Orthopaedics and Traumatology of the University Hospital ‘Policlinico Consorziale’, Bari, Italy. Microbial sampling was undertaken during 60 total hip arthroplasties, all performed in the same operating theatre (dimensions 8.7 m × 4.3 m, height 3.14 m, total volume 117.467 m3). The operating theatre is equipped with a turbulent ventilation system of four low-level inlets with air forced
Results
The mean bacterial load for the IMA samplings was 2232.9 (SD 859.7) cfu/m2/h (range 786–4246), which was significantly lower than the results obtained with the nitrocellulose membranes [mean 2768.2 (SD 1325.4) cfu/m2/h, range 1153–6344; t = −2.62, P = 0.0049]. A mean value of 123.2 (SD 58.7) cfu/m3 (range 40–288) was measured with the SAS sampler.
A significant correlation was found between the IMA values and the SAS values (r2 = 0.73, P < 0.0001, Figure 2), and both of these were significantly
Discussion
Infections can be debilitating complications of primary hip arthroplasty, and have been cited as the most common cause of implantation failure.23 Many contributing factors have been implicated such as patient factors, surgical technique and postoperative factors,24 but the environment, progress of the operation, clothes worn, etc. are also important. In this context, the microbiological quality of the air in operating theatres is a significant parameter to control surgical infection, and
Conflict of interest statement
None declared.
Funding sources
University of Bari financial support for scientific research.
References (34)
Air, antibiotics and sepsis in replacement joints
J Hosp Infect
(1988)- et al.
Importance of air quality and related factors in the prevention of infection in orthopaedic implant surgery
J Hosp Infect
(1998) - et al.
The importance of airborne bacterial contamination of wounds
J Hosp Infect
(1982) - et al.
Inconsistent correlation between aerobic bacterial surface and air counts in operating rooms with ultra clean laminar air flows: proposal of a new bacteriological standard for surface contamination
J Hosp Infect
(1999) - et al.
Correlation between surface and air counts of particles carrying aerobic bacteria in operating rooms with turbulent ventilation: an experimental study
J Hosp Infect
(1999) - et al.
Lack of influence of body exhaust gowns on aerobic bacterial surface counts in a mixed ventilation operating theatre. A study of 62 hip arthroplasties
J Hosp Infect
(2003) - et al.
A mobile laminar airflow unit to reduce air bacterial contamination at surgical area in a conventionally ventilated operating theatre
J Hosp Infect
(2007) - et al.
The index of microbial air contamination
J Hosp Infect
(2000) - et al.
Air sampling: settle plates or slit samplers?
J Hosp Infect
(2001) - et al.
Coagulase-negative staphylococcal infections
Infect Dis Clin North Am
(2009)
On the mechanism of adsorption of proteins to nitrocellulose in membrane chromatography
J Chromatogr
The performance of SAS-super-180 air sampler and settle plates for assessing viable fungal particles in the air of dry-cured meat production facility
Food Control
Guideline for prevention of surgical site infection, 1999. Hospital Infection Control Practices Advisory Committee
Infect Control Hosp Epidemiol
Guidelines for environmental infection control in health-care facilities
Post operative infection after total hip replacement with special reference to air contamination in the operating room
Clin Orthop
ISO 14698-1. Cleanrooms and associated controlled environments – biocontamination control. Part 1: General principles and methods
Cited by (46)
Experimental study on the generation of aerosol particles and microorganisms from surgical staff in an operating room
2023, Building and EnvironmentIndoor and outdoor aeromicrobiology
2023, AeromicrobiologyDo Ultraviolet Air Disinfection Units Reduce Contamination by Particulates in Total Knee Replacement Procedures?
2022, Journal of ArthroplastyCitation Excerpt :It should also be mentioned that the Curtis et al study used an active particle counter to measure viable airborne contaminates whereas this study used passive settle plates [19]. A consensus has not been established concerning the best method of measuring airborne contaminates in the OR, however passive sampling allows for localized measurements at different locations including within the sterile field [8,10–12]. A second conclusion, arising from simultaneous measurements at five different sites during each procedure, was the extraordinary prevalence of contamination at some sites within the OR which rose to 75% of procedures studied.
Passive bioaerosol samplers: A complementary tool for bioaerosol research. A review
2022, Journal of Aerosol ScienceCitation Excerpt :The Index recommends a common standard to measure bioaerosol presence using Petri dishes in a 1/1/1 scheme (Pasquarella, Pitzurra, & Savino, 2000). This scheme recommends that open Petri dishes be placed 1 m off the ground, 1 m away from walls or other large obstructions, and samples collected for 1 h (Montagna et al., 2019; Napoli et al., 2012; Pasquarella et al., 2000; Pasquarella et al., 2012; Scaltriti et al., 2007; Setlhare, Malebo, Shale, & Lues, 2014). Sample concentrations are reported as CFU/plate or CFU/(m2 or dm2 or cm2)/h.
Microbiological indoor air quality of hospital buildings with different ventilation systems, cleaning frequencies and occupancy levels
2022, Atmospheric Pollution ResearchCitation Excerpt :Thus researchers and healthcare organizations are more concerned about the infectious bioaerosols in indoor air of hospitals. In this perspective several studies have been conducted worldwide assessing microbial flora and its composition in specific hospital sections such as medical wards (Augustowska and Dutkiewicz 2006), lobbies (Park et al., 2013) and operation theaters (OTs) (Scaltriti et al., 2007; Wan et al., 2011; Napoli et al., 2012). However fewer studies have covered multiple hospital facilities, including intensive care unit (ICU), nursery unit and medical laboratory.