Microbial air monitoring in operating theatres: experience at the University Hospital of Parma

doi:10.1016/j.jhin.2012.01.007

Journal of Hospital Infection

Volume 81, Issue 1, May 2012, Pages 50-57

https://doi.org/10.1016/j.jhin.2012.01.007 Get rights and content

Summary

Background

Microbial air monitoring in operating theatres has been a subject of interest and debate. No generally accepted sampling methods and threshold values are available.

Aim

To assess microbial air contamination in empty and working conventionally ventilated operating theatres over a three-year period at the University Hospital of Parma, Italy.

Methods

Air sampling was performed in 29 operating theatres. Both active and passive sampling methods were used to assess bacterial and fungal contamination.

Findings

In empty theatres, median bacterial values of 12 colony-forming units (cfu)/m³ [interquartile range (IQR) 4–32] and 1 index of microbial air contamination (IMA) (IQR 0–3) were recorded. In working theatres, these values increased significantly (P < 0.001) to 80 cfu/m³ (IQR 42–176) and 7 IMA (IQR 4–13). Maximum recorded values were 166 cfu/m³ and 8 IMA for empty theatres, and 798 cfu/m³ and 42 IMA for working theatres. Combining active and passive samplings, fungi were isolated in 39.13% of samples collected in empty theatres and 56.95% of samples collected in working theatres. Over the three-year study period, bacterial contamination decreased in both empty and working theatres, and the percentage of samples devoid of fungi increased. In working theatres, a significant correlation was found between the bacterial contamination values assessed using passive and active sampling methods (P < 0.001).

Conclusion

Microbiological monitoring is a useful tool for assessment of the contamination of operating theatres in order to improve air quality.

Introduction

Surgical site infection (SSI) is a major complication following surgery and is associated with increased morbidity and mortality, as well as increased costs.1, 2, 3, 4 Over the past decades, the role of air as a vehicle of infection has been the subject of much interest and debate.3, 5, 6, 7, 8, 9, 10, 11, 12, 13 Following a study by the Medical Research Council showing a correlation between microbial air contamination and SSI incidence in prosthetic joint surgery,¹¹ ultraclean operating theatres have been recommended for this type of surgery, while conventional theatres supplied by turbulent airflow systems are recommended for other types of surgery.3, 7 Guidelines for the design and ventilation of operating theatres have been published, and threshold values have been proposed for both ultraclean and conventional theatres.14, 15, 16, 17, 18, 19, 20 However, there is no international consensus on tolerable limits of microbial air contamination, and there are no generally accepted methods and frequencies for air sampling. Moreover, the usefulness of microbiological air monitoring methods is controversial.21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46

A monitoring programme for operating theatres based on microbiological air sampling has been implemented at the University Hospital of Parma, involving both empty theatres (during commissioning and after major renovations) and working theatres. The main objectives of this study were: (1) to assess the microbial air contamination in empty and working operating theatres; (2) to propose local threshold limits for microbial air contamination in operating theatres; and (3) to assess any correlation between active and passive sampling methods.

Section snippets

Setting

Microbial monitoring was performed in 29 conventionally ventilated operating theatres, situated in nine different operating suites. In all theatres, air was supplied by a ventilation system designed to provide 15 air changes per hour. The system was equipped with high-efficiency particulate air filters, which can remove particles of >0.3 μm with an efficiency of 99.97%. Air pressure in the operating theatres was 5 Pa higher than in adjacent rooms.

Air sampling

Microbial air sampling was performed over a

Results

Table I shows the descriptive data, expressed in cfu/m³ and IMA, obtained in all empty and working theatres for both bacteria and fungi. In empty theatres, median bacterial values of 12 cfu/m³ and 1 IMA were recorded, while these values increased significantly (P < 0.001) in working theatres to 80 cfu/m³ and 7 IMA. Values for bacterial contamination varied widely, reaching 166 cfu/m³ and 8 IMA in empty theatres, and 798 cfu/m³ and 42 IMA in working theatres. Bacterial contamination decreased

Discussion

Microbial contamination of the surgical site is a necessary precursor of SSI.³ The origin of pathogens can be endogenous (from patient’s skin, mucous membranes or hollow viscera) or exogenous. Airborne micro-organisms can enter surgical wounds via two pathways: they can fall directly into the wound, or they can land on exposed surfaces and subsequently be transferred to the wound.¹³

Although the role of air as a vehicle of SSI-causing micro-organisms is still being debated,3, 5, 6, 7, 8, 9, 10,

Conflict of interest statement

None declared.

Funding sources

None.

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Microbial air monitoring in operating theatres: experience at the University Hospital of Parma

Summary

Background

Aim

Methods

Findings

Conclusion

Introduction

Section snippets

Setting

Air sampling

Results

Discussion

Conflict of interest statement

Funding sources

Surgical site infections, how high are the costs?

J Hosp Infect

Surgical site infection: incidence and impact on utilization and treatment costs

Am J Infect Control

Guidelines for prevention of surgical site infection

Infect Control Hosp Epidemiol

Preventing surgical site infection

Exp Rev Anti Infect Ther

Role of the environment of the operating suite in surgical wound infection

Rev Infec Dis

Operating room ventilation with laminar airflow shows no protective effect on the surgical site infection rate in orthopedic and abdominal surgery

Ann Surg

Guidelines for environmental infection control in health-care facilities

Postoperative infection in total prosthetic replacement arthroplasty of the hip-joint with special reference to the bacterial content of air in the operating room

Br J Surg

Importance of air quality and related factors in the prevention of infection in orthopedic implant surgery

J Hosp Infect

Aerobiology in the operating room – a review

J Hosp Infect

Air, antibiotics and sepsis in replacements joints

J Hosp Infect

Post-operative aspergillosis

Clin Microbiol Infect

The importance of airborne bacterial contamination of wounds

J Hosp Infect

Linee guida per la definizione degli standard di sicurezza e di igiene ambientale dei reparti operatori

Linee Guida sugli Standard di Sicurezza e di Igiene del Lavoro nel Reparto Operatorio

Microbiological commissioning and monitoring of operating theatre suites

J Hosp Infect

Environmental controls in operating theatre

J Hosp Infect

Air sampling in operating theatres

J Hosp Infect

Microbiological sampling

Hospitals

Airborne nosocomial infection; a contemporary perspective

Infect Control Hosp Epidemiol

Eight-year surveillance of environmental fungal contamination in hospital operating rooms and haematological units

J Hosp Infect

Theatre air sampling – ignorance is bliss

J Hosp Infect

Theatre air sampling – once a year is not enough

J Hosp Infect

Environmental control of microbial contamination in the operating room