Air Samples

Although touch and building surfaces were monitored over the 18-month test period, the main interest was in the potential reduction of airborne bioburden as a result of total environmental treatment. For the treated wing, commercially available reusable air filters containing impregnated triclosan polypropylene filter fibers were selected. The control wing contained regular pleated-type disposable filters, the same type used throughout the healthcare campus in the majority of its buildings. The reusable air filters on the treated wing were removed, washed and reinstalled every four months. The disposable filters on the untreated wing were replaced every two months. A total of ten locations were selected for air testing on the treated wing with a corresponding ten on the control wing. Additional sampling was taken outdoors, as well as in the main entrance vestibule and waiting area. These were used for additional comparison with values obtained in the wings. The results for the two wings are compared in Table 3 in which the average values are reported at three equally spaced time intervals over the 18-month study period. Three reference values are provided at the bottom of Table 3 that can be used for additional comparison. These values were the average values over the entire test period. The laboratory value was normalized to 1.0 cfu/ft3 and is used in Table 3 as a base comparison. The air quality in the laboratory was considered as one of the best or preferred levels of air quality on the campus.

It is apparent from Table 3 that the treated wing was maintained at a much ‘cleaner’ level than the control wing throughout the test period. Overall, the results indicate a consistent reduction of

total bioburden with time in the treated wing. There was a consistent reduction and stabilization after 12 months. Air quality was remarkably good and remained close to that found in the microbiology lab. In contrast, the bioburden in the untreated wing appeared to increase continuously with time. Although the level of bioburden in the untreated wing at 18 months was only 42% of the value found in the front entrance vestibule, it was 2.4 times higher than the treated wing and continued to increase. Since this was a new building and the level of airborne bioburden could continue to change with age, it is conceivable that the untreated wing could continue to increase in bioburden well above the value reported. In contrast, it is possible that the treated wing could level out, at or about the level found at the end of this study. That level was only 17% of that of the vestibule and only 16% above the laboratory level. The fact that the bioburden in the treated wing continuously decreased with time while that of the untreated wing continuously increased, does indicate that the antimicrobial treatment was very effective in controlling the bioburden.

Table 3. Air Samples (Average cfu/ft3)

Test Interval

Treated Wing

Untreated Wing

Reduction

6 Months

1.36 (48.3)

1.75 (62.1)

22 %

12 months

1.19 (42.0)

2.26 (79.8)

47 %

18 Months

1.16 (40.9)

2.78 (98.1)

58 %

Reference Values: (Microbiology Lab = 1.00 (35.3)) (Vestibule = 6.69 (236.2)) (Outside = 33.37 (1178.0))

Since the total colony count does not differentiate between species of microorganisms, the air samples taken at the end of the study were examined to determine what viable or living fungi and bacteria were present at that time. For the fungi, when compared to the untreated wing, the treated wing contained 63% less bioburden. This was found to be statistically significant at a P-value = 0.0043 using the Mann-Whitney U test of medians. Also, there was no difference in the distribution of predominant genera of viable fungi between the wings. That is, the same percentage distribution of each species was the same in each of the wings even though the absolute numbers of species was less in the treated wing. For bacteria incubated at 350C, the median reduction was only 25% and was found not to be statistically significant. Also, there was a difference in the distribution of the predominant genera on each wing.

Conclusion

To the authors’ knowledge, this study is the first of its kind involving a healthcare setting. The purpose was to see if the total bioburden or level of microorganisms present in a healthcare environment could be reduced through antimicrobial treatment of surfaces and the air. Since the building was new and contained two identical wings, each containing 12500 square feet (1157 m2), it offered the authors a unique opportunity to conduct a controlled ‘real world’ study.

The treatment consisted of using the well known chlorine based antimicrobial agent triclosan, either through the application of existing products or by developing special purpose products. Physical components of the treated wing included permanent and moveable fixtures, medical instruments, furniture, walls, floors, ceilings and air filters. Included were telephones, computers, filing cabinets, sinks, counters, exam tables, doors and hardware etc. Each item in the treated wing had a corresponding control item on the untreated wing that was tested for comparison. A total of 45 items were selected in each wing for testing surface bioburden. There were 10 locations selected for air sampling on each of the two wings.

The results of the 18-month study showed an average of 40% reduction in colony forming units (cfu) for treated surfaces and a 58% reduction of air borne microorganisms. In the case of air sampling, it was interesting to find that the air quality in the treated wing consistently improved, while

that of the untreated wing got progressively worse. The antimicrobial treatment enabled the wing to maintain the level of airborne bioburden to within 16% of that found in the microbiology lab.

Unfortunately, this study cannot be used to determine what effect the triclosan-treated reusable air filters may have had on reducing the airborne bioburden within the treated wing since the triclosan – treated filters were installed at the same time as the other surfaces were treated. Although the authors realized this at the beginning of the study, there was insufficient time and resources to conduct a comparison of the effect of different treatment applications.

During the study period both wings were used for the same type of outpatient care. This was important to the validity of the study, since dissimilar use functions could have affected the test results and negated a direct comparison. Also, since hospital employees conducted all building maintenance and antimicrobial treatment, strict supervision and proper implementation of specific protocols for cleaning and treating was made possible.

The study had to be terminated after the 18-month period, since after one year of occupancy, renovations and functional changes were being scheduled by management. These resulted in the wings being used for very different types of patient care. Also, to reduce operating costs, all maintenance for the building was contracted out and this prevented any further study to be conducted.

What impact this type of environmental treatment could have on the reduction of nosocomial infections in more critical care facilities remains to be seen. The cost of environmental treatment would have to be determined and compared against any reductions in nosocomial infection rates. However, similar treatment approaches could be integrated into infection control activities and studied within a hospital setting. If nothing else, the building and the patient environment could be maintained in a ‘cleaner’ state of preparedness. Additional comparison of personnel absenteeism rates before and after treatment might also prove interesting, in light of the increasing evidence of the effects of ‘sick building syndromes.’

Obviously, as is the case with many studies like the one reported here, more questions can be asked than answers provided. However, the science is here, the products are available, and nosocomial infections are on the increase. Perhaps it is time to consider improving the treatment of the healthcare environment as well as that of the patient.

Dedication

This paper is dedicated to the memory of Robert S. Watterson III, formerly Vice President of Sales, Microban Products Company, Huntersville NC whose dream was to see the construction of cleaner buildings based on the application of ‘anitmicrobial treated building products’. Perhaps the results of this study suggest that dreams can come true.

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