[Identification of aerobic and facultatively anaerobic sporulating bacteria isolated during the primary milk collection].
Aerobic and/or facultatively anaerobic sporulating Gram-positive bacteria of the genus Bacillus influence nutritive and sensory properties of pasteurized milk by their proteolytic and lipolytic activity. Since particularly raw milk is a source of pasteurized milk contamination by spore-producing bacteria, our investigations were focused on identification of bacilli from operations of milk agricultural primary production. The species B. licheniformis and B. cereus (Crielly et al., 1994) are the most frequently isolated ones in the process of milk production. While B. licheniformis as well as B. subtilis and B. pumilus are mesophilic species, B. cereus is rather psychrotrophic, and as to their health impacts they cause diseases from foods (Griffiths, 1990; Christiansson, 1992; Becker et al., 1994). Sixty-six strains were isolated and identified from operations of milk agricultural primary production (Tab. I). B. licheniformis occurrence (58 strains) was most frequent in the set of samples, followed by B. subtilis (5 strains), B. pumilus (one strain) and B. cereus (one strain), i.e. these are species classified to morphological group I (oval, cell-nonswelling spores). Only one strain Paenibacillus amylolyticus (formerly Bacillus amylolyticus) was isolated from morphological group II (oval, cell-swelling spores). Species representation of isolated strains is in agreement with literacy data (Phillips and Griffiths, 1986; Sutherland and Murdock, 1994; Crielly et al., 1994;). Our results did not confirm the seasonal occurrence (winter-summer) of mesophilic and psychrotrophic bacilli species as reported in literature (McKinnon and Pettipher, 1983; Sutherland and Murdock, 1994; Crielly et al., 1994). Biochemical and physiological characteristics of 66 isolates (Tab. I) are in agreement with literary data (Gordon et al., 1973; Parry et al., 1983; Priest et al., Ash et al., 1993). Strong proteolytic, amylolytic or lipolytic activities of the tested strains could influence the nutritive value of milk as a raw material. Taking into account the dominant representation of bacilli of morphological group I in raw and pasteurized milk (Sutherland and Murdock, 1994; Crielly et al., 1994) their review with basic phenotypic characteristics is shown in Tab. II. As follows from our results mesophilic species from so called "B. subtilis group" (96.9%) were isolated from agricultural primary production of milk most frequently. This is the reason why in addition to B. cereus it is also necessary to identify these species: seven tests shown in Tab III are recommended for their rapid differentiation.
Pácová
Z
Z
Czech Collection of Microorganisms, Faculty of Science, Masaryk University, Brno, Czech Republic.
Vyhnálková
Lukásová
J
J
Holec
J
J
D000818:Animals; D001419:Bacteria / Q000302:isolation & purification*; D002417:Cattle; D003612:Dairying; D005516:Food Microbiology; D008892:Milk / Q000382:microbiology*