Sterile swabs can be used to test the level of microbial contamination on various surfaces such as air conditioning units, kitchen equipment, hospital wards, spas or any other place. The samples can be analysed for total viable counts (usually referred to as colony forming units) or specific indicator organisms for food spoilage or sewage contamination.

How To Collect Swab Samples

Wear gloves

Select a sampling area of about 10 cm X 10 cm (or 20 cm x 20 cm)

Break the seal round the tube containing the swab

Remove the swab from the tube and rub and roll it firmly several times across the sampling area.

Return the swab into the tube and label the sample

Send the sample to the laboratory for analysis.

If one is sampling a dry surface, it is recommended that a wet or moistened swab is used. The swab test method has proved a popular testing method with flood damage insurance claims, where there may be sewage contamination.

Significance Of Airborne Bacteria In Indoor Environments

Indoor Bacteria have not received as much publicity as the mould. Are indoor bacteria of health significance?

Read more below....

Bacteria are found virtually in every environment including the hot springs, deep-sea hydrothermal vents, glaciers, swamps, and mines! Some heat-loving bacteria (hyperthermophiles) thrive best above 176 °F (80 °C) whereas the psychrophiles (cold-loving) can survive far below 0 °C.

In indoor environments bacteria are present in air and on surfaces. High levels of bacteria concentration indoors is an indication of high occupancy rate, poor ventilation, or poor building maintenance. Similar to mould, some bacteria are associated with water-damaged building materials.

Significance Of Airborne Bacteria

While bacteria do not receive as much publicity as mould when it comes to indoor air quality, they are a health hazard. Some are serious human pathogens and others especially the gram negative bacteria produce toxic compounds (endotoxins) from the outer membrane of their cell wall. Endotoxins may have a role in sick building syndrome.

Indoor airborne bacteria can loosely be categorized into bacterial pathogens and environmental bacteria associated with water-damaged building materials. Bacterial pathogens are capable of causing severe diseases in humans if inhaled, ingested or if they come into contact with the skin. The most important airborne bacterial infections in indoor environments are tuberculosis, nosocomial pneumonia, and legionellosis. These infections are primarily acquired through inhalation of the causative agents.

Environmental bacteria generally associated with mouldy building materials include Acinetobacter, Bacillus, Flavobacterium, Nocardia, Streptomyces, and Thermomonospora. Also associated with water-damaged material are the filamentous bacteria, the Actinomycetes. Some airborne bacteria such as Staphylococcus spp and Micrococcus spp are dispersed into the air from human skin, oral and nasal surfaces, and hair. These bacteria are associated with nosocomial infections in health care facilities.

Sampling For Airborne Bacteria

The commonly used sampling method for airborne bacteria is the impaction of air onto agar media using volumetric samplers such as Andersen, SAS, or RCS. Samples can also be collected by impingement into liquid media. However, for routine air quality monitoring agar based sampling is recommended. Trypticase soy agar (TSA) media is usually used when sampling for bacteria. It is important to select a medium suitable for growth of the target organism, for example when sampling for some specific bacteria such as Legionella. Sampling time depends on the sampler used but generally not more than 10 minutes. Shorter times are recommended in heavily contaminated areas. Samples are kept cool and shipped for overnight delivery to the laboratory for incubation and identification of the dominant species.

References

1. Chin, S. Yang, Patricia A. Heinsohn (Editors). Sampling and analysis of indoor microorganisms. 2007. John Wiley & Sons, Inc.(ISBN-13:978-0-471-73093-4
2. Flannigan, B., R.A. Samson, and J.D. Miller (Editors). Microorganisms in home and indoor work environments: diversity, health impacts, investigation and control. 2001. London, UK: Taylor & Francis (ISBN: 0-415-26800-1).
3. Wanner, H-U, AP Verhoeff, A Colombi, B Flannigan, S Gravesen, A Mouilleseux, A Nevalainen, J Papadakis, and K Seidel. 1993. Biological Particles in Indoor Environments. Indoor Air Quality and Its Impact On Man. Brussels: Commission of the European Communities. Report No. 12.
   

For more information on indoor bacteria, please visit http://www.moldbacteria.com/ or call 905-290-9101.

Cladosporium cladosporioides is a common household mould found growing on damp walls in the bedroom, living room, bathrooms, around tubs, shower stalls, or window frames and ceilings. It may appear as dark brown or black scattered colonies or patches. Cladosporium cladosporioides is a common cause of mould allergy. But, not everybody is allergic to this mould! So, if you see this mould growing in your house and you or your family members are not feeling sick, do not panic. Just have the mould cleaned up.

The causes of sick building syndrome (SBS) are still not well understood. SBS has always been associated with poor ventilation in airtight energy efficiency buildings and biological and chemical pollutants. In the April issue of Occupational and Environmental Medicine, Dr. Stafford and colleagues suggest that job related factors could be a major contributor to sick building syndrome.

Collecting mold and bacteria samples from air is very easy. The first thing to decide is the kind of results you want and for what purpose. This will help you to decide on the sampling equipment and the media to use. For example, if sampling for a specific bacterium or fungus, you would want to use a sampling agar media that is suitable for the growth of the target organism. The efficiency of the air sampling pumps for the collection of the target organism has also to be considered.

Sampling equipment can be expensive. However, for a company that does not collect air samples every other week, renting the equipment is a better option. Sampling media can be obtained directly from the manufacturers or their resale agents. For companies collecting only a few samples in a month, sampling media can be obtained from a good mold testing laboratory.

A colony of bacteria or yeast refers to a mass of individual cells of same organism, growing together. For moulds, a colony is a group of hyphae (filaments) of the same mould growing together. What are colony forming units then? A colony forming unit refers to an individual colony. It is used as a measure of the number of microorganisms present in or on surface of a sample. Colony forming units may be reported as CFU per unit weight, CFU per unit area, or CFU per unit volume depending on the type of sample tested. To determine the number of colony forming units, a sample is prepared and spread or poured uniformly on a surface of an agar plate and then incubated at some suitable temperature for a number of days. The colonies that form are counted. CFU is not a measure for individual cells or spores as a colony may be formed from a single or a mass of cells or spores.