Spoilage potential of a novel group of bacteria isolated from dairy products

Abstract

Cold-tolerant bacteria, also known as psychrotrophic bacteria, are notorious contaminants of milk in the refrigerated dairy food chain. These organisms, especially the pseudomonads, may produce heat-resistant enzymes that are responsible for the breakdown of proteins and lipids in milk and dairy products. Such reactions result in a variety of defects in the raw or unprocessed milk that may affect the suitability of such milk for further processing. The enzymes produced may cause defects in long-life dairy products such as cheese, butter and long-life milk. In the present study, a range of 18 yellow pigmented psychrotrophic bacteria, collectively known as flavobacteria, were isolated from local dairy products. One aim of this study was to identify these bacteria to species level using molecular techniques. A second aim was to determine the spoilage potential of these organisms based on profiles generated by the BIOLOG system (that may relate to hydrolytic enzymes produced). Of the 18 isolates, 14 belonged to the genus Chryseobacterium while 4 were identified as Empedobacter isolates. The most active spoilage organisms in this group were shown to be C. bovis, C. shigense and E. brevis. These findings illustrate that enzymatically catalysed defects in dairy products should not be attributed solely to acknowledged psychrotrophic bacteria such as the pseudomonads, but that flavobacterial species may also be actively involved.

The Opportunistic Pathogen Chryseobacterium balustinum WLT: Pathogenicity and Antibiotic Resistance

“…However, severe antibiotic resistance makes them hard to control, especially in immunocompromised patients or stressed animals, and this has been the case for C. balustinum. The first isolation was reported in halibut and was recognized as a food spoilage bacterium rather than a pathogenic bacterium since it was isolated from the fin of the fish [5,6,30]. In this study, we observed the mortality of farmed rainbow trout and verified that it originated from the infection by C. balustinum designated as WLT.…”

“…Chryseobacterium balustinum was first isolated from halibut that was unfit for sale because of discoloration and the softening of skin and muscle tissue [5]. Until recently, the bacterium was considered as a dairy and seafood food spoilage organism [5,6]. Similar to Flavobacterium spp., some strains of Chryseobacterium spp.…”

Bacterial levels and diversity in kitchen sponges and dishwashing brushes used by consumers

“…These bacteria have low nutrient requirements, grow fast at a wide temperature range and may form biofilms (Møretrø & Langsrud, 2017). Chryseobacterium has been found in salmon and small‐scale cheese production environments and in raw foods (de Beer et al, 2005; Møretrø et al, 2016; Schirmer et al, 2013; Tsôeu et al, 2016). Enhydrobacter is not frequently found in food processing environments, but was reported to dominate in Norwegian kitchen sinks in a previous study (Moen et al, 2016).…”

Co-occurrence of antibiotic and metal resistance in long-term sewage sludge-amended soils: influence of application rates and pedo-climatic conditions

“…Published research studies on Chryseobacterium indoltheticum pathogenicity and antibiotic resistance are extremely scarce. Tsôeu et al (2016) reported that among 14 Chryseobacterium species isolated from dairy products, two C. indoltheticum isolates were identified and showed a certain potential to cause spoilage defects in dairy products because they were able to utilize a wide range of compounds in the BIOLOG system. In their investigation on multidrug resistance in Chryseobacterium, Michel et al (2005) reported that most Chryseobacterium sp.…”