The Distribution of Staphylococci in Bioaerosols from Red-Meat Abattoirs

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Contamination of foodstuffs via the air is generally caused by viable airborne contaminants originating from biological sources (bioaerosols) (Lutgring, Linton, Zimmerman, Peugh, & Heber, 1997; Whyte, Collins, McGill, Monahan, & O'Mahony, 2001). Bioaerosols can be liquid or solid, or can be carried on another particle or suspended in a liquid droplet, and may comprise bacterial spores, cells, fungi, fungal spores, antigens, viruses, plant pollens, toxins, fecal material, or a combination of these (Cundith, Kerth, Jones, McCaskey, & Kuhlers, 2002; Rad-more, 1986; Whyte et al., 2001). When all these substances are distributed in the air, they can serve as a feasible route for food contamination and can ultimately affect the health of both food handlers and consumers (Lutgring et al., 1997). Information on the bioaerosol contamination of food-processing plants is, however, very limited, mainly because of lack of proper equipment, lack of expertise to perform bioaerosol surveys, fear of how the outcomes of such studies will affect various companies, or some combination of these factors. As a result, knowledge of the contribution of the airborne micro-biota to the contamination of food products remains limited.

Although indoor air environments are considered to be protective, they become contaminated with various particles that can be hazardous when concentrations exceed recommended maximum limits: 1,000 CFUs/[m.sup.3] for total number of bioaerosol particles, a limit set by the National Institute of Occupational Safety and Health and the American Conference of Governmental Industrial Hygienists (ACGIH), with the culturable count for total bacteria not to exceed 500 CFUs/[m.sup.3] (Cox & Wathes, 1995; Jensen & Schafer, 1998; Kalogerakis et al., 2005).

A number of authors have recognized poor ventilation systems as possible reservoirs that may distribute bioaerosols in meat-processing plants (Cundith et al., 2002; Whyte et al., 2001). In addition, employees may distribute contaminants through clothes, skin, hair, respiratory tract (coughing and sneezing), fecal matter, and poor hygiene (Chambers, 2001; Cundith et al., 2002; Lutgring et al., 1997). Food handlers are the primary sources of indoor bioaerosols in the food industry, according to Nel and co-authors (Nel, Lues, Buys, & Venter, 2004). Furthermore, airborne microorganisms may be of human origin from purulent discharges of an infected finger or eye; from abscesses, facial eruptions, or nasopharyngeal secretions; or from normal skin (Zadoks et al., 2002). Other sources that are indirectly related to bioaerosols are contaminants from waste handling and disposal, fungal or microbial growth niches in the building, and unsanitary practices, including improper maintenance and poor operating and sanitation. In addition, seasonal and weather-related factors such as geographical location are also known to influence bioaerosols within food-processing environments such as abattoirs (Chang, Chung, Huang, & Su, 2001; Cundith et al., 2002; Lutgring et al., 1997; Pastuszka, Kyaw Thaw Paw, Lis, Wlazlo, & Ulfig, 2000; Ren & Frank, 1992).

Some of the pathogenic bacteria most predominantly found in indoor bioaerosols are members of the Staphylococcus genus because of their ubiquitous nature (Wieser & Busse, 2000). This genus occurs naturally on the skin, as well as on the skin glands and mucous membranes of warm-blooded animals (Nagase et al., 2002a; Nagase et al., 2002b; Wieser & Busse, 2000). Staphylococcus aureus bacteria constitute about 10 percent of the nasal cavity bacteria of healthy humans and occur at levels between 0.01 and 0.1 CFUs/[m.sup.3] in the environment (Sheretz, Bassetti, & Bassetti-Wyss, 2001). Because of their ubiquitous occurrence in nature, staphylococci have been isolated from fresh water, meat, milk, cheese, soil, seawater, dust, and the air (Nel, Lues, Buys, & Venter, 2003; Wieser & Busse, 2000). …