Indicator Organisms

The “total viable count on surface” measures the number of colony-forming units (cfu) per a defined surface area (e.g., 1 cm²). This is typically assessed using total plate count agar, with colonies counted after 48 hours of incubation at 30–35°C. It serves as an indicator of hygiene in food production, revealing potential microbial loads and contamination sources. The “aerobic mesophilic count” represents the number of cfu that develop on a plate count medium under mesophilic conditions (approximately 30–37°C) over a set incubation period, providing insight into the microbial status of production environments and overall sanitation levels.

Coliform bacteria are indicators of fecal contamination and are often used to monitor water quality. Their detection on surfaces in the production environment or in solid foods signals that hygienic conditions need improvement. Coliform bacteria, which include genera from the Enterobacteriaceae family, share biochemical characteristics such as positive lactose fermentation and negative oxidase reaction. They can be identified using nutrient media with chromogenic substrates for their enzyme β-galactosidase (e.g., X-GAL).

Enterobacteriaceae are gram-negative, rod-shaped bacteria typically 1-5 µm in length. They are facultative anaerobes, mostly motile, but some genera are non-motile. Enterobacteriaceae are oxidase-negative and can be distinguished from similar genera by this trait. These bacteria are normal components of the gut flora in humans and animals and are also widely spread in the environment (e.g., soil, water). Some genera, such as Cedecea, Citrobacter, Enterobacter, Escherichia, Hafnia, Klebsiella, Kluyvera, Morganella, Proteus, Rahnella, Salmonella, Serratia, Shigella, and Yersinia, are pathogenic and can cause serious diseases.

Enterococci are gram-positive organisms that belong to the intestinal bacteria, alongside the gram-negative Enterobacteriaceae. They may appear as contaminants in various fermented foods, indicating poor sanitary conditions during production and processing. However, Enterococci are also used as starter cultures in fermentation processes, contributing to the development of organoleptic properties in fermented foods. In water, Enterococci serve as indicators of faecal contamination, appearing only if introduced by human or animal feces.

Yeasts and molds can contaminate foods, leading to quick spoilage. Molds, in particular, can produce toxic or allergenic substances, posing significant health risks. These organisms can spread rapidly through dust and aerosols, consistently contaminating production surfaces. Therefore, they should be included in hygiene monitoring sampling plans.

Yeasts are facultative anaerobic, unicellular fungi that ferment sugar to CO2 and H2O, or to alcohol and CO2 under anaerobic conditions. These properties are commercially exploited in brewing, wine, and baking industries, with Saccharomyces cerevisiae being the most common industrial strain. Candida species are significant in food spoilage, residing on human and animal mucosa.

The term “mold” commonly refers to the visible part of fungi present on the surface of contaminated food. Beneath the surface, fungi form mycelium, which cannot be seen with the naked eye. Specific molds and yeasts are used industrially, such as in cheese production. However, harmful mold genera can produce toxins (mycotoxins) and have allergenic potential due to their spore formation. Besides food spoilage, molds are also a concern in buildings infested by mold.