Hospital aerobic monitoring using the Air Guardian accelerated settle plate sampling device.

Ben Charnock; Microbiologist, Karen Ryan; Head Microbiologist, Medipure Ltd Chester UK

December 2003

Introduction

 The air carries a quarter of all infections; therefore aerobic monitoring within hospitals and other medical environments should be considered a crucial part of any infection control strategy. In order to establish the type of organisms present and in what numbers, it is necessary to carry out aerobic monitoring using effective, reproducible equipment capable of sampling air of numerous sites which could be causing infection.

There are currently many aerobic sampling devices on the market e.g. Casselaâ Slit Sampler, Biotestâ Air Sampler, Rodacâ Contact Plates and settle plates to name a few.

Many devices require an operator to work in the vicinity of the device while it is running. Some equipment can be expensive, therefore only selected sites can be sampled and a true picture of the problem cannot be established.

The Air Guardian is a portable unit that works by passing  air across an agar plate where microbes in the air are deposited.  Overall, the sampling device works on the basis of an accelerated settle plate.   Each unit has a fifteen to thirty minute time delay after it is activated, allowing sufficient time for the test personnel to leave the sample site, therefore preventing biological contamination of the sample site by the test person, thus avoiding false readings.  The sampler samples 3 cubic metres of air every 30 minutes and can be set for 30 minutes, 60 minutes, 90 minutes and 120 minutes. Other models exist which  will sample for up to one shift [ 8 hrs]  After sampling for the set time, sampling stops automatically. 

By using multiple units [ even 10 at one time] very meaningful data can be gathered on a chosen site.

Sampling locations.

The Air Guardian can be placed wherever aerobic sampling is required. For sampling inside small cavities such as ventilation pipe work and ducting the Dip Slide Air Guardian can be inserted.  They are self contained and operate of rechargeable batteries.

Infection Control.  

The Air Guardian is very compact sampling within a short time and can be used to sample air at many locations within a hospital department. It has the potential of picking up infection-causing organisms such as MRSA, TB and Legionella (selective media and organism identification procedures must be followed). 

Case History  :-   Aerobic monitoring of a HSDU unit.

The Air Guardian has been successfully used to aerobically monitor the air of locations within HSDU and SSD departments. The device can be used anywhere and further studies will be carried out at other locations within a hospital or any other medical environment. An example of the type of data collected using the device can be found in Tables 1 and 2.  

Air Guardians were set up at various sites of a HSDU clean room instrument packing area and autoclave room. Each unit was sprayed with 70 % Isopropyl alcohol and wiped dry prior to placing a Tryptone Soya agar plate inside each unit. After a fifteen-minute time delay, sampling was carried out for 30 minutes with 3 cubic metres of air being sampled. All agar plates were incubated at 35⁰C for 48 hours with all colonies counted and expressed as microbes per cubic metre. The experiment was repeated at 2-week intervals to build up a trend analysis of the air quality. 

Table 1.  Aerobic monitoring using the Air Guardian: HSDU Clean room packing area.  

Table 2. Aerobic monitoring using the Air Guardian: HSDU Autoclave room.

Conclusions.

On comparison of data obtained from two locations within a HSDU unit, fewer microbes were found in the clean room compared with higher numbers in the autoclave room.

It is interesting to note in the HSDU quoted above  that an improved cleaning regime was introduced after the first visit and improvements can be seen to have taken place by the second  and third visits. These areas were clean but were  capable of being cleaner by taking simple hygiene actions.

This technique in conjunction with swabbing is the best way to monitor this kind of work environment.

Gowning and covering of heads and feet were problem areas . This monitoring lead the infection control function to demand adherence to the rules which were in place but not being strictly followed..

Procedures followed by personnel for working inside the clean room were tightened and   all personnel wore  gowns , head protection, changed foot wear and wash hands prior to entering the room. This indicates that the measures of infection control in place are working effectively, however, should there be a  further lapse in procedures this would be observed by higher counts obtained using the Air Guardian. The monitoring function in this case a private company  [ Medipure Ltd]  sat on the infection control steering committee. This has been identified by all the health professionals involved  as a bonus, acting as a catalyst and a facilitator in tackling the problems.  Recommendations were made at committee and actions policed by the appropriate function.

It is appreciated that the value of this  data is  to build up trend analysis of the overall air quality within this particular hospital unit and any subsequent hospital environments that are sampled using the Air Guardian device.  This can be a daunting task . Medipure offers free training on how to use and interpret results as well as set up the logistics of taking the samples  to any private or NHS facility.

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Typical HSDU Cleanroom Floor Plan

Air Guardian

Technical papers