Operation Theatre (OT) swab aerobic culture test

This test is performed as a surveillance procedure to control surgical infections (infections caused after surgery) due to the micro-organisms present in the OT. The test provides data on the type and count of the microbes in the OT and ascertains if there is a need for disinfection. 

Nosocomial infections are a considerable cause of morbidity and mortality in the world. Surgical site infections are the most common cause of nosocomial infections, second only to urinary tract infections. The infection can be acquired from many different sources such as the air, surface or various articles in the OT.

The occurrence of a post-operative infection depends on different factors as follows:

• Bacterial contamination of the OT air
• Effective sterilisation procedures in the OT
• OT design
• Surgical technique
• OT discipline
• Prophylactic use of antibiotics

Post-operative infections due to the contamination from micro-organisms in the OT can have serious and long-lasting effects on the person and their families. Infections can lead to:

• Extended hospital stays
• Increased resistance to anti-microbial medicines
• Long-term disability
• Additional financial burden on healthcare systems
• Death

Therefore, environmental and instrument sterilisation of the OT requires monitoring.

The OT should be disinfected and sterilised before the swabs are taken.

Sterile swabs are used for sample collection. The swabs are soaked in nutrient broth.

At a bare minimum, swabs from the following sites are required:

• Upper surface of the OT table
• Lower glass surface of the OT lights
• Any two walls from a location above the OT table height
• Floor: two samples, one on either side of the OT table
• Surface of the trolleys used to carry sterile instruments
• Anaesthesia machine (swab the area where medications are placed during use)
• Air conditioner outlet 

Once the swabs are collected, the OT is closed for the day and no one is allowed to enter.

The swabs are labelled and sent immediately to the laboratory for processing.

On the second and third day, fresh swabs are collected from the same surfaces and sent to the lab for analysis.

Normal results:

No growth of any micro-organisms or sparse growth of harmless micro-organisms (that are found on the human skin) in any of the cultures is considered normal. It indicates that the OT can now be used.

Abnormal results:

If there is any growth of aerobic bacteria in the culture, it means that the OT cannot be used and needs to be cleaned and disinfected again. Once the cleaning and disinfection procedure is complete, the test should be repeated.

Some commonly found bacteria that can potentially cause infections are:

• Bacillus spp.
• Staphylococcus aureus
• Coagulase-negative Staphylococcus
• Enterococcus spp.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.