1. Review article:
OT surveillance: Air sampling or Conventional swabbing?!
ABSTRACT
Surgical site infections (SSIs) are the second to third most common site of health care
associated infections. These complications of surgical procedures cause considerable
morbidity, if these occur deep at the site of the procedure, can carry mortality as high as
77 %[1]. There is considerable evidence available to indicate that the surgical site infections are
a significant health risk to hospital patients. Sources of infection may be either endogenous
(from the patient himself) or exogenous from the theatre environment. A large body of
information is available which indicates that prevention of post operative infection is
dependent on several factors including effective theatre design, sterilisation and disinfection
procedures, good surgical technique, bacterial contamination of theatre air, discipline which
includes restricting the movement of staff[2]. Many of debates are extended over on this topic
including the frequency of microbiological surveillance for operation theatres.
Key words: Air sampling, three bucket system, slit sampler, colony forming units
INTRODUCTION & SITUATION ANALYSIS
Even today most of the surgeons are worrying about the OT associated infections with
anaerobes like clostridium tetani in most of the instances. Infections with Cl. tetani are
associated with very bad surgical procedures which includes the over jealous manipulations of
the tissues of surgical site and leaving the dead tissue in the surgical site at the end of the
procedure and also heavy dust in the operation theatre environment. Surveillance for clostridial
spores is an age old concept of OT surveillance and lost its importance with the available and
applicable OT sterilization and disinfection awareness programmes and practices.
Routine testing for clostridial spores is not mandatory except during certain situations like
new constructions or structural alterations are made to the theatre. But pyogenic infections
mostly with S.aureus and S.epidermidis are possible even with technically qualitative surgical
procedures[3]. Healthy carriers have been found to shed staphylococci which is responsible for
inevitable airborne contamination. While there is evidence to indicate that most outbreaks are
caused by heavy dispersers[4], every attempt should be made to minimize airborne transmission
within operating theatres. Studies in a number of operating theatres have suggested that there is
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2. a general relationship between total air count and risk of infection. Counts in the range of
700-1800/m 3 were related to significant risk of infection and when they were under 180/m 3 the
risk was slight[6].
So prevention of airborne microbial contamination will prevent the surgical site infections.
To achieve this basic strategy we should follow the certain guidelines. Which would include,
proper and continuing education to staff to prevent shedding of microbes and restrict the
unnecessary movements of OT staff within and outside the OT environment.
MEASURES TO REDUCE MICROBIAL LOAD IN OT:
Fumigation alone cannot sterilize or make the OT environment safe. Failure to provide
adequate operation theatre ventilation is associated with risk of postoperative infections.
Theatre ventilation has been found to be a critical factor in prosthetic and joint surgery[6].
While maintaining the proper ventilation ,we have to be careful about the microbial load in the
OT environment .Filtration of OT air by fitting the HEPA filters are mandatory to fulfill the
above criteria. Since the operation theater environments are the dynamic, good equipment and
arrangements are only not safe since it becomes unsafe because of human activities. Culture
swabs from unnecessary surfaces of OT environment (roof, upper parts of wall) may causes
confusion during the interpretation of the results[4]. Dust should be removed with cloth wetted
with clean water Chemical and disinfectants should not be used as habit.. Chemical agents or
disinfectants or detergents should be used when OT floor and surfaces are contaminated with
blood and body fluids.Swabbing the surfaces with suitable commercially available disinfectant
Bacillocid (Mixture of dihydroxy formaldehyde, glutaraldehyde and bezalkonium chloride) by
using the three bucket system will remove the majority of the microbes.
• 1st Bucket with water: Dirty mop is rinsed
• 2nd Bucket with fresh water for rinsing: Mop rinsed again in this water
• 3rdBucket with suitable disinfectant: Mop is immersed in the solution and floor
should be mopped liberally. Wash the used mop with disinfectant after use and dry.
STANDARD GUIDELINES AND PLANNING FOR AIR SAMPLING:
There are no nationally agreed standards for any country or place regarding when to
undertake microbiological sampling in the operating theatre and on the interpretation of
sampling results[5]. However, there is sufficient evidence to support the undertaking of
microbiological air sampling in the operation theatre as part of the vigilance & safety of an
operating theatre, after any major structural replacements (not including High Efficiency
Particulate (HEPA) filter changes and as deemed necessary by the hospital infection control
committee. Health care workers should follow certain guidelines before air sampling. Prior to
air sampling, obtain the suitable air sampling equipment from a laboratory, establish laboratory
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3. time-lines for sample collection, processing and provision of results and should not ignore to
consult the hospital microbiologist or infection control unit.
HOW TO DO THE AIR SAMPLING?.
Bacterial counts in operation theaters are influenced by the number of individuals present,
ventilation and air flow methods. Air sampling should be done after the all new or replacement
work has completed. The ventilation system should run continuously for 24 hours before
sampling and the theatre surfaces and fixed equipment, ducting and air diffuser plates have to
be cleaned.
Settle plate method by using blood agar is being practiced in basic hospitals to detect all
kinds of bacteria in hospital air. Settle plate method with blood agar where the plates have to
keep at 2 ½ feet height on the four corners of room and results are obtained based on the mean
colony number on the all culture plates after a prescribed time. Because of recent advances in
certain surgical procedures and bacterial counts settle plate method is replaced with Slit
sampler and Air centrifuge equipment through which we can calculate the safe levels of
colony counts. There are several different types of air samplers available and the
manufacturer’s instructions for use must be followed. If affordable, the preferred method is to
use a sampler with timer and remote control.
RECOMMENDED METHOD FOR AIR SAMPLING [6]:
1. A single sample should be collected from each operating theatre.
2. The air sampler should be checked for cleanliness before use by following the
manufacturer’s instructions.
3. The theatre being sampled should have been left vacant for a minimum of 15
minutes, preferably one hour. To avoid false-positive results the theatre doors
must be kept closed prior to and during the sampling period .
4. Staff should wear theatre attire and a surgical mask, with proper hands wash
and surgical gloves.
5. Place the agar strips or plate into the sampler under aseptic precautions and
set up the equipment.
6. The air sampler should be placed in the middle of the theatre table at the height
of 2.5 feet and to be secured on a trolley.
7. The air sampler should then be switched on either by remote control or manually,
before leaving the room.
8. The sampling equipment will determine the volume of air sampled. Sampling
volume needs to be more than 0.25 m3 (250 L) and optimally around 1m3 (1000 L).
9. Once sampling is completed, remove the test strips/agar plate aseptically and
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4. label it clearly and send it the processing environment.
RESULTS AND INTERPRETATION:
Culture plates should be incubated under optimum conditions in the microbiology
laboratory. Early culture reports hardly available until after 24 hours of incubation. Aerobic
cultures on non-selective medium (preferably Blood agar) should not exceed 35 colony –
forming units of bacteria and fungi per cubic meter of air for a conventional theatre and 1cfu
for an ultra clean theatre to perform joint replacement and cardiac surgeries[1]. These counts
are not rigid standards and are intended as a guideline only. Even though the swabs are taken
for OT surveillance to isolate and identify the clostridial spores, air sampling is must to
measure the safer load of microbes. In some of the hospitals OT sampling is done by swabbing
and plating on the blood agar and results are being announced after 24-48 hours of aerobic
incubation. By the above mentioned method quantitative estimation of the microbial load is not
possible. Literature which is supporting for this kind of practice is not available from various
sources. Moreover, this type of cultures on non-selective medium will create unnecessary
confusion while detecting OT sterilization status and which should be abandoned.
REFERENCES:
1. Davis N., Curry A, Gambhir AK, Panigrahi H, Walker CR, Wilkins EG, Worsley MA
and Kay PR Intraoperative bacterial contamination in operations for joint replacement. J
Bone Joint Surg Br 1999; 81-B:886-9.
2.Colquun J, Partridge L. Computational Fluid Dynamics Applications in Hospital
Ventilation Design. The Austrilian Hospital Engineer 2003 ; 26 (1) 35-40.
3.Guidelines to standards for operating rooms. located at. http://www.health.wa.gov.
4.Geeta Mehta. Microbiological surveillance of operation theatre – 2005.
http://www.orthoteers.org.
5.Dharan S, Pittet D. Environmental controls in operating theatres. J Hosp infect 2002;
51(2) 79-84.
6.Department of Health, Western Australia . Private Hospital Guidelines, 3rd edition.
1998. http://www.health.wa.gov.
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