22
Modern Food Microbiology
Brevibacillus (Bre • vi • ba • cil’lus). Previously classified as Bacillus spp. as noted above, these
organisms occur in soil and water, and are common on plants, and in air, and dust. At least nine species
are recognized.
Brochothrix (bro • cho • thr’ix; Gr. brochos, loop; thrix, thread). These Gram-positive nonsporeforming rods are closely related to the genera Lactobacillus and Listeria,
40 and some of the common
features are discussed in Chapter 25. Although they are not true coryneforms, they bear resemblance
to this group. Typically, exponential-phase cells are rods, and older cells are coccoids, a feature typical
of coryneforms. Their separate taxonomic status has been reaffirmed by rRNA data, although only
two species are recognized: B. thermosphacta and B. campestris. They share some features with the
genus Microbacterium. They are common on processed meats and on fresh and processed meats that
are stored in gas-impermeable packages at refrigerator temperatures. In contrast to B. thermosphacta,
B. campestris is rhamnose and hippurate positive.
44 The mol% G + C content of DNA is 36. They do
not grow at 37
◦ C.
Burkholderia (Burkholder • ia). Gram-negative rods that occur on plants (especially certain flowers),
in raw milk, and cause vegetable spoilage. In a study of raw cow’s milk in Northern Ireland, 14 out of
26 (54%) samples contained B. cepacia.
34 They are significant pathogens in cystic fibrosis patients.
They were formerly classified in the genus Pseudomonas.
Campylobacter (cam • py’ • lo • bac • ter; Gr. campylo, curved). Although most often pronounced
“camp’lo • bac • ter,” the technically correct pronunciation should be noted. These Gram-negative, spirally curved rods were formerly classified as vibrios. They are microaerophilic to anaerobic. The genus
has been restructured since 1984. The once C. nitrofigilis and C. cryaerophila have been transferred to
the new genus Arcobacter; the once C. cinnaedi and C. fenneliae are now in the genus Helicobacter;
and the once Wolinella carva and W. recta are now C. curvus and C. rectus.
45 The mol% G + C content
of DNA is 30–35. For more information, see reference 32 and Chapter 28.
Carnobacterium (car • no • bac • terium; L. carnis, of flesh-meat bacteria). This genus of Grampositive, catalase-negative rods was formed to accommodate some organisms previously classified as
lactobacilli. They are phylogenetically closer to the enterococci and vagococci than the lactobacilli.
6,12
They are heterofermentative, and most grow at 0
◦ C and none at 45
◦ C. Gas is produced from glucose
by some species, and the mol% G + C for the genus is 33.0–37.2. They differ from the lactobacilli
in being unable to grow on acetate medium and in their synthesis of oleic acid. They are found on
vacuum-packaged meats and related products, as well as on fish and poultry meats.
11,23,48
Citrobacter (cit • ro • bac’ter). These enteric bacteria are slow lactose-fermenting, Gram-negative rods
that typically produce yellow colonies on plate count agar. All members can use citrate as the sole
carbon source. C. freundii is the most prevalent species in foods, and it and the other species are not
uncommon on vegetables and fresh meats. The mol% G + C content of DNA is 50–52.
Clostridium (clos • tri’di • um; Gr. closter, a spindle). These anaerobic spore-forming rods are widely
distributed in nature, as are their aerobic counterparts, the bacilli. The genus contains many species,
some of which cause disease in humans (see Chapter 24 for C. perfringens food poisoning and
botulism). Mesotrophic, psychrotrophic, and thermophilic species/strains exist; their importance in
the thermal canning of foods is discussed in Chapter 17. A reorganization of the genus created the
following five new genera: Caloramater, Filifactor, Moorella, Oxobacter, and Oxalophagus.
8 The
Modern Food Microbiology
Brevibacillus (Bre • vi • ba • cil’lus). Previously classified as Bacillus spp. as noted above, these
organisms occur in soil and water, and are common on plants, and in air, and dust. At least nine species
are recognized.
Brochothrix (bro • cho • thr’ix; Gr. brochos, loop; thrix, thread). These Gram-positive nonsporeforming rods are closely related to the genera Lactobacillus and Listeria,
40 and some of the common
features are discussed in Chapter 25. Although they are not true coryneforms, they bear resemblance
to this group. Typically, exponential-phase cells are rods, and older cells are coccoids, a feature typical
of coryneforms. Their separate taxonomic status has been reaffirmed by rRNA data, although only
two species are recognized: B. thermosphacta and B. campestris. They share some features with the
genus Microbacterium. They are common on processed meats and on fresh and processed meats that
are stored in gas-impermeable packages at refrigerator temperatures. In contrast to B. thermosphacta,
B. campestris is rhamnose and hippurate positive.
44 The mol% G + C content of DNA is 36. They do
not grow at 37
◦ C.
Burkholderia (Burkholder • ia). Gram-negative rods that occur on plants (especially certain flowers),
in raw milk, and cause vegetable spoilage. In a study of raw cow’s milk in Northern Ireland, 14 out of
26 (54%) samples contained B. cepacia.
34 They are significant pathogens in cystic fibrosis patients.
They were formerly classified in the genus Pseudomonas.
Campylobacter (cam • py’ • lo • bac • ter; Gr. campylo, curved). Although most often pronounced
“camp’lo • bac • ter,” the technically correct pronunciation should be noted. These Gram-negative, spirally curved rods were formerly classified as vibrios. They are microaerophilic to anaerobic. The genus
has been restructured since 1984. The once C. nitrofigilis and C. cryaerophila have been transferred to
the new genus Arcobacter; the once C. cinnaedi and C. fenneliae are now in the genus Helicobacter;
and the once Wolinella carva and W. recta are now C. curvus and C. rectus.
45 The mol% G + C content
of DNA is 30–35. For more information, see reference 32 and Chapter 28.
Carnobacterium (car • no • bac • terium; L. carnis, of flesh-meat bacteria). This genus of Grampositive, catalase-negative rods was formed to accommodate some organisms previously classified as
lactobacilli. They are phylogenetically closer to the enterococci and vagococci than the lactobacilli.
6,12
They are heterofermentative, and most grow at 0
◦ C and none at 45
◦ C. Gas is produced from glucose
by some species, and the mol% G + C for the genus is 33.0–37.2. They differ from the lactobacilli
in being unable to grow on acetate medium and in their synthesis of oleic acid. They are found on
vacuum-packaged meats and related products, as well as on fish and poultry meats.
11,23,48
Citrobacter (cit • ro • bac’ter). These enteric bacteria are slow lactose-fermenting, Gram-negative rods
that typically produce yellow colonies on plate count agar. All members can use citrate as the sole
carbon source. C. freundii is the most prevalent species in foods, and it and the other species are not
uncommon on vegetables and fresh meats. The mol% G + C content of DNA is 50–52.
Clostridium (clos • tri’di • um; Gr. closter, a spindle). These anaerobic spore-forming rods are widely
distributed in nature, as are their aerobic counterparts, the bacilli. The genus contains many species,
some of which cause disease in humans (see Chapter 24 for C. perfringens food poisoning and
botulism). Mesotrophic, psychrotrophic, and thermophilic species/strains exist; their importance in
the thermal canning of foods is discussed in Chapter 17. A reorganization of the genus created the
following five new genera: Caloramater, Filifactor, Moorella, Oxobacter, and Oxalophagus.
8 The