Airborne microbiota and related environmental parameters associated with a typical dairy farm plant

Abstract

Food processing plants and agricultural environments have a long-standing history of being known to provide a conducive environment for the prevalence and distribution of microorganisms which emanate as a consequence of activities undertaken in such premises. Microorganisms in the aforementioned environments may be found in the atmosphere (airborne), and/or on food contact surfaces. Airborne microorganisms from food handlers and in food products and raw materials (as part of bioaerosols) have in the past been implicated as having a potential to cause adverse health effects (especially in indoor environments) and therefore also to have economic implications. Recently their effect on food safety has received increased interest. The recent international interest in bioaerosols in the food industry has played a role in rapidly providing increased understanding of bioaerosols and their effects in different food processing environments. However, there is still a lack of research on the actual impact of bioaerosols over time in most of the food premises especially in Southern Africa and other developing countries.

The overall purpose of this dissertation was to assess possible microbial contaminants and the role of selected environmental parameters on these microbes at a dairy farm plant in central South Africa. In relation to the purpose of the study, the objectives of this dissertation were to investigate and establish the food handler’s food safety knowledge, attitude, behaviour and practices. The sub-objective was to investigate the prevalence and distribution of microbial contaminants (both airborne and food contact surface populations), and concomitant environmental parameters. The microbe isolates from both investigations (i.e. air samples and food contact surfaces) were identified to strain level using matrix-assisted laser desorption ionization – time of flight mass spectrometry (MALDI-TOF MS). The findings of this study in relation to food handlers’ food safety knowledge, attitude, behaviour and practices indicated a dire need for training of employees as well as improved health and hygiene measures as emphasised by some of the identified strains. The environmental parameters (both indoor and outdoor) were similar, with no relationship established between airborne microbes’ prevalence and environmental parameters. The samples of the airborne microbial populations in both indoor and outdoor environments were similar. Airborne microbial counts at the dairy farm plant over the entire duration of the study ranged between 1.50 x 101cfu.m-3and 1.62 x 102cfu.m-3. Microbial counts on food contact surfaces ranged between 2.50 x 102 cfu.cm-2 and 1.10 x 105 cfu.cm-2 over the entire duration of the study. A wide variety of microorganisms (from air and food contact surfaces) such as the Gram-positive bacteria, Gram-negative bacteria, as well as fungi were present at the dairy farm plant. A number of the isolated genera have previously been associated with agricultural environments whilst others are associated with hospital environments. The positively identified strains were from genera such as Aeromonas, Arthrobacter, Candida, Pseudomonas, Pantoea, Citrobacter, Staphylococcus, Bacillus, Escherichia, Rhodococcus and Rhodotorula, amongst others.

The isolation of microorganisms associated with food spoilage and foodborne disease outbreaks, which are known as indicator organisms such as Escherichia coli, Staphylococcus and Bacillus from both air and surface samples, signified possible faecal contamination and could be attributed to poor health and hygiene practices at the dairy farm plant. Despite the isolation of microorganisms associated with food spoilage and foodborne disease outbreaks, the isolation of microorganisms not usually associated with the food processing industry (usually associated with hospital environments) was an enormous and serious concern which suggested a need for further investigations at dairy farm plants as the implications of these pathogenic microorganisms in food is not known. The isolation of similar microorganisms from both the air samples and surface swabs suggests that airborne microbes have a potential of settling on food contact surfaces, therefore having a potential to contaminate dairy products which are known to be more prone to contamination and which, because of their nutritional status, serve as a good substrate for the growth of microorganisms.