Sample size guideline

SMT LABS continuously aspire to deliver your test results as soon as possible. To avoid unnecessary delays, please abide by the following instructions:


It is very important that we receive the completed Sample Submission Form (attached), with clear written testing instructions and your supporting purchase order. These documents have to accompany your samples, when delivered to our laboratories in order to avoid any unnecessary delays. It is also a mandatory SANAS (ISO 17025) requirement that we receive clear and explicit instructions from all clients as well as supporting documents.  We strive to register all samples on the day of receipt, however this may not always be possible if samples are received after 15:00.

Sample sizes:

Our test methods require a specific quantity of the sample to be tested. If we do not receive a sufficient quantity of the sample, we unfortunately cannot conduct the tests required.  See our SMT-R-94 Sample Size Guideline

For more important information to register a client profile and submit samples go to New clients

We thank you in advance for your assistance in this regard.

Test today, improve tomorrow!

Black Friday 10% discount

10% off all samples received and collected on Friday.

Contact your Key Account Manager to arrange your samples to be picked-up.

Rozanne 083 411 0935
Carol 066 312 0313
Vernette 082 092 3383
Samantha 082 836 2017
Office 051 880 0102

This is the ideal opportunity to send in a few extra samples to make sure that your products are not contaminated with Salmonella.

4 Anjou Street

Test today, improve tomorrow!

SMT LABS comments on the Salmonella outbreak in KZN

Quick facts

  • Contrary to popular belief, Salmonella is not only associated with chicken and fish.
  • Although contaminated foods are usually from animal origin, such as poultry, pork, raw milk and eggs, other foodstuffs (e.g. vegetables and fruit juices) may also be contaminated.
  • One would think that the shell of an egg is the perfect barrier to ensure that Salmonella does not enter the egg, however in some cases infected chickens produce eggs that contain Salmonella even before the shell is formed.
  • Interestingly, some outbreaks have previously been traced back to contaminants in spices!
  • Contamination of foodstuffs does not necessarily occur due to contact with animal feces or contaminated water, but can also originate from infected individuals that do not wash their hands after using the bathroom and then handles the foodstuffs in production and/or packing facilities.


Why is Salmonella dangerous?

Salmonella causes salmonellosis and in some cases typhoid fever (only caused by certain strains of Salmonella). Common symptoms of salmonellosis are headaches, fever, diarrhea, nausea, vomiting, abdominal pain and cramps. These symptoms may appear as early as 12 – 96 hours after infection. With the correct treatment, salmonellosis may be resolved within 5 – 7 days. It can however cause more serious infections in infants, the elderly and individuals with a compromised immune system.

Top Tips

1. In the warmer months of summer, Salmonella flourishes and special care should be taken to keep the cold chain of your raw materials and final products in order to avoid increased numbers of bacteria.

2. SMT LABS can help you with regular testing of your products to ensure outbreaks are prevented fast and effectively.

3. SMT LABS can test various matrices to identify the source of contamination in your facility, including surface swabs, hand swabs, boot swabs, rectum swabs, fluff, animal feed, water and food products.

4. SMT LABS turnaround time for Salmonella testing is 3-5 days.

5. Prevention is better than cure – test today, improve tomorrow!

Bioaerosols in the Food and Beverage Industry

This month we are featuring an exert from the book: Ideas and Applications Toward Sample Preparation for Food and Beverage Analysis. 

This chapter was written by Shirleen M. Theisinger (MD SMT LABS) and Olga de Smidt (Lecturer at CUT). It was also published by:  World’s largest Science, Technology & Medicine, Open Access book publisher

Bioaerosols in the Food and Beverage Industry

Bioaerosol monitoring is a rapidly emerging area of industrial hygiene. Microbial roles in atmospheric processes are thought to be species specific and potentially depend on cell viability. Accumulating evidence suggests that exposure to bioaerosols may cause adverse health effects, including disease. Studies of bioaerosols have primarily focused on chemical composition and biological composition, and the negative effects thereof on ecosystems and human health have largely gone unnoticed. This gap can be attributed to international standards on acceptable maximum bioaerosol loads not being uniform and the lack of uniform standardized methods for collection and analysis of bacterial and fungal bioaerosols. In this chapter, bioaerosol composition, relevance of bioaerosols to the food processing facility, sampling and detection approaches, and complications were discussed.

Airborne particles and bioaerosols are easily transported, transferred and displaced from one environment to the other. Complex mixtures of bioaerosols such as fungi, allergens, and bacteria along with nonbiological particles (e.g., dust, smoke, particles generated by cooking, organic, and inorganic gases) are contained in indoor environments [34]. The bioaerosols and their components could pose an environmental hazard when presented in high concentrations in indoor environments, resulting in spoilage/contamination of food products or occupational health risks [35].

3.1. Food product–related risk: spoilage or contamination

Before spoilage becomes obvious, microbes have begun the process of breaking down food molecules for their own metabolic needs, resulting in a variety of sensory cues such as off-colors,off-odors, softening of fruits and slime. Firstly, the sugars are easily digested carbohydrates, then plant pectins are degraded, and proteins are attacked and produce volatile compounds with characteristic smells such as amines, ammonia, and sulfides. Early detection of spoilage would be advantageous in reducing food loss because there may be interventions that could halt or delay deterioration. Several methods for determining concentrations of spoilage microbes or volatile compounds produced by spoilage microbes have been devised. Many of these methods are considered insufficient as they are time consuming and/or do not give constant, reliable results and are labor intensive [31].

Food can also be contaminated by the presence of harmful chemicals and microbes which can cause illness when consumed. For this reason, traceability and source determination of contamination remain a relevant topic in food preservation research [36]. Bioaerosols implicated in respiratory-associated hazards have received much attention, but the potential of foodassociated microbes and food-borne pathogens in bioaerosols to cause food spoilage needs to be clarified. Evidence exists that pathogenic microbes are found in the air, and that these microbes are present in certain products. However, traceable evidence of bioaerosols as the causative agent of spoilage or contamination of food products is not readily available.

3.2. Food handler-related risk: occupational health

Exposure to higher risks of biological hazards is characteristic to certain industries such as health care, agriculture, fishery, some food industries, construction, and mining. Workers employed in these industries have higher prevalence of respiratory diseases and airway inflammation [37]. It is difficult to conduct a comprehensive evaluation of personal bioaerosol exposure in occupational or indoor environments [38], owed to the complex composition of bioaerosols, and the lack of standardized sampling/analysis methods [37]. Without appropriate personal exposure assessment and standardized sampling/analysis methods, establishing dose relationships and relevant exposure guidelines are difficult.

Exposure to bioaerosols in the occupational environment is associated with a wide range of health effects including infectious diseases, acute toxic effects, allergies, and cancer. These possibilities have been studied for the last 20 years; several cases of pulmonary cancers were reported in workers exposed to aflatoxins via respiratory route [39, 40]. In Denmark, an increase in the risk of liver cancer has been reported for workers exposed to aflatoxins in concerns processing livestock feed [41]. Larsson and coworkers [42] have also shown that asymptomatic dairy farmers exposed to airborne mold dust may have signs of immunostimulation and inflammation in their alveolar space. Farmers exposed to mold dust may exhibit signs of alveolitis [42], and severe toxic irritative reactions can occur after a single inhalation of high levels of spores [43]. Studies have suggested that inhalation exposure to mold spores
is another cause of organic dust toxic syndrome [44]. Occupational biohazards of biological origin are grouped into (1) occupational diseases of the respiratory tract and skin caused by allergenic/and or toxic agents forming bioaerosols, and (2) agents causing zoonoses and other infectious diseases spread through various exposure vectors [45].

The following questions summarize important aspects to address when planning a bioaerosol monitoring approach and can be used as guidelines.

Why sample? 

Formulate the objectives for sampling clearly. It is important to establish whether sampling bioaerosols is necessitated by baseline monitoring for compliance or to confront an existing quality (product) and/or safety (food handler health) problem for which bioaerosols as causative agent need to be ruled out.

Where to sample? 

The notion of sampling before doing a critical assessment of the facility is a current shortcoming. This approach can even be misleading because it produces information that is difficult to interpret, might create unnecessary concern, and may lead almost inevitably to the sampling having to be repeated professionally/by external consultants. Foci for the assessment should include environmental factors, factory design/layout, equipment, product type, and food handlers (health, shifts/placement, skills level, training, behavior) [76]. Certain
environmental factors such as temperature, airflow, and relative humidity can be associated with bioaerosol levels [104]. Heating, air-conditioning, or ventilating systems may provoke fluctuations in temperature and relative humidity. Detectable bacterial and fungal levels can also be affected by these factors, since they require specific environmental conditions to grow and propagate. Sampling sites to consider include areas with negative air pressure, raw material area where a lot of dust is generated, under air vents, areas where water spraying or misting can occur, active floor drains and areas with higher worker activity or other movement.

Which bioaerosol component to measure? 

Information from the evaluation/investigation should be able to establish which bioaerosol component is of interest: viable microbial components (culture dependent) or nonviable but still bioactive (culture independent) component. Although culture-dependent methods are by far the most widely used procedures for assessing the microbiological content of bioaerosols (Table 1); it is now widely accepted that such methods significantly underestimate the total quantity of microbes present. Plate count media describe the well-known problem that only a small fraction (10%) of airborne microbes forms colonies on a typical culture media, thus leading to a significant underestimation of the actual viable airborne bioaerosol concentration. The vast remaining number of airborne microbes can be described as viable but nonculturable, indicating very low metabolic activity or resting dormant state. Dead airborne bacteria or fungi debris or toxins retain their allergenic or toxic properties and are therefore also relevant to any occupational health assessment.

Which air sampler to use?

Impingement sampling devices (Table 5) can be used to detect both viable and nonviable bioaerosol components. Either viable or nonviable components can be assessed using impaction (Table 4) or filtration (Table 6), respectively. Choosing a sampling device will also depend on availability, level of expertise and funding.

How often and when to sample? 

In a new program for compliance monitoring, it is advisable to start with more frequent data collection as this will allow for baseline establishment.  When the data are available to show that the bioaerosols in a system/area are stable enough, the number of data collection points can be reduced. Microbial results can differ depending on the activity in a specific area. Sampling times should include both “dynamic” and “static” conditions monitoring.

New Amies Gel Swab facts

Switch to excellence, switch swabs

One of our core values is EXCELLENCE.  

To maintain excellence, we are always looking for ways to serve our clients better and to ensure we deliver the best possible service.  With that comes change.  We urge you to change with us and to stay the best in your industry.  We are introducing a new swab and will not be using the dry cotton tip swab any more.  To make the change easy peasy, you are welcome to send all your unused cotton tip swabs back to us with your next samples and we will replace them free of charge.

Please contact your Key Account Manager or SMT LABS to assist you with arrangements. Our new office number is 051 880 0102.

The question on your mind must be, WHY?

The new swab contains AMIES media that ensures the safe arrival of any organisms that might be present on the swab, right to our doorstep!
Let’s talk a little bit of science behind the AMIES media!

AMIES media contains:

  • potassium
  • calcium and
  • magnesium salts

The above aid in maintaining osmotic equilibrium by controlling the permeability of bacterial cells, while a phosphate buffer maintains the pH of the medium.

AMIES media provides a favourable environment for bacteria, which in turn keeps the cells viable during transportation and ensures accurate results.

Click the link for instructions on how to use the new Amies gel swab. Amies swabs – instructions

Thank you for your continued use of SMT LABS’ services and we hope to hear from you soon.

Kind regards, 

Shirleen Theisinger
MD and Lab Quality Manager 

SMT LABS Official: Listeria protocol and notification

At SMT LABS we provide fast and efficient service and testing for the detection of Listeria monocytogenes in food and swabs.  Products include: Meat and meat products, Poultry and poultry products, Spice, Egg and egg products, Vegetables and fruits, Dairy and dairy products, Grain and grain products.

1. Listeria species

The genus Listeria contains six species, namely L. grayi, L. innocua, L. ivanovii, L. seeligeri, L. welshimeri and L. monocytogenes. Although L. ivanovii and L. monocytogenes can cause illness in mice and other animals, it is only L. monocytogenes that is associated with human Listeriosis. If any of the other strains (non-pathogenic to humans) are detected in a product or facility, it indicates that the environment and nutritional conditions are favourable for the growth of the pathogenic strain, L. monocytogenes and that precautions should be taken.

2. Types of Testing

There are two tests that can be performed to determine if a product contains Listeria monocytogenes.
The first is detection, which is a qualitative test that provides a positive/negative answer for the absence/presence of Listeria monocytogenes in 25g of product. For this test the sample is incubated overnight in an enrichment broth to enable multiplication of the bacteria for further isolation tests. The detection test is more sensitive and can detect lower numbers of the organism as compared to enumeration.

The second test is enumeration (count) and is a quantitative test to determine the number of bacteria present in 1g of product. For this test a representative sample is evaluated, however bacteria are only detected at levels higher than 10 CFUs/g. Enumeration can be performed in certain cases where the specification is < 100 CFUs/g of Listeria monocytogenes.



  1. Three different types of swabs

We also now have three different swabs available for the equipment and environmental swabs for Listeria monocytogenes.