New and Emerging Foodborne Pathogens ◾ 417
non-Shiga toxin producing Escherichia coli, Helicobacter pylori, Aeromonas species (Chapter 29),
nematode Gnathostoma, bovine spongiform encephalopathy (BSE) (Chapter 29), and Nipah virus,
some of which are discussed briefly.
Cronobacter sakazaki 12–14
Cronobacter sakazakii (formerly Enterobacter sakazakii) is considered an emerging opportunistic
pathogen that primarily infects infants, but now it has been implicated to cause disease in adults.
Cro. sakazaki is a gram-negative, facultative anaerobic, nonsporulating, motile rod-shaped bacterium and is the member of the Enterobacteriaceae family. Six species of Cronobacter have been
identified. Cro. sakazaki produces a yellow pigmented colony on a tryptic soy agar (TSA) plate and
can grow at a temperature range of 6°C–45°C with an optimum temperature of 37°C–43°C. In
general, these organisms are thermotolerant and can adapt well to osmotic desiccation stress. They
can survive in infant cereal with an A W range of 0.30–0.83 for up to 12 months. Cronobacter has
been associated with a number of outbreaks involving powdered infant formula (PIF). Cronobacter
spp. has also been isolated from varieties of foods, including rice, bread, milk, cheese, dried foods,
spices, tea, meats, water, and vegetables. These organisms are also found in food factories, including a powdered infant formula production facility and livestock facilities.
The pathogenesis of Cro. sakazaki is not fully understood; however, the bacterium is known to
translocate from the gastrointestinal tract to the blood where it multiplies in large numbers and
then crosses the blood brain barrier to reach to cerebrospinal fluid. In infants, it causes bacteremia,
necrotizing enterocolitis, neonatal meningitis, and memingoencephalitis. The mortality rate in
infants is 50%–80%. Recently, it has been shown that adults, especially the immunocompromised
adults and the elderly are susceptible to this infection, showing clinical symptoms of pneumonia,
sepsis, foot ulcers, wound infections, and osteomyelitis. For isolation of this pathogen, FDA and
ISO methods are used that involve preenrichment and/or selective enrichment before plating on
TSA or chromogenic media. Yellow-pigmented colonies are further confirmed by biochemical
testing and by PCR methods. Various control strategies have been proposed that include, strict
hygienic practices during PIF production, monitoring of the processing environments, raw materials, and final product testing. Thermal treatment, including rehydration of PIF with water at 70°C
or higher, can reduce counts by 4 logs. In addition, irradiation, bacteriophages, bacteriocins, and
plant phenolics have been proposed for inactivation of Cronobacter spp. in foods.
Clostridium difficile 15,16
Clostridium difficile is a gram-positive, rod-shaped, spore-forming obligate anaerobe. It is traditionally considered a nosocomial, hospital-acquired human pathogen and is responsible for antibiotic
associated diarrhea (AAD). It was first reported in 1978 by John Bartlett and his colleagues. Since
2003, Clo. difficile infection (CDI) cases have risen dramatically and caused numerous fatalities in
both North America and Europe. In 2007, there were 3875 deaths reported in the United States.
Clo. difficile colonizes human and animal intestines and has been isolated from many domestic and
wild animals: pigs, calves, poultry, horses, donkeys, dogs, cats, seals, snakes, rabbits, and ostrich.
This organism has been isolated primarily from ground meats (pork, beef, and poultry) at a prevalence rate of 3%–12% or higher. It has been also isolated less frequently from raw vegetables
(cucumber, onions, radishes, carrots, mushrooms, and ready-to-eat salads) and milk. The ubiquitous nature of this organism (resulting from spore formation), fecal contamination of the soil, and
its presence in food processing and the packaging environment are thought to be responsible for
non-Shiga toxin producing Escherichia coli, Helicobacter pylori, Aeromonas species (Chapter 29),
nematode Gnathostoma, bovine spongiform encephalopathy (BSE) (Chapter 29), and Nipah virus,
some of which are discussed briefly.
Cronobacter sakazaki 12–14
Cronobacter sakazakii (formerly Enterobacter sakazakii) is considered an emerging opportunistic
pathogen that primarily infects infants, but now it has been implicated to cause disease in adults.
Cro. sakazaki is a gram-negative, facultative anaerobic, nonsporulating, motile rod-shaped bacterium and is the member of the Enterobacteriaceae family. Six species of Cronobacter have been
identified. Cro. sakazaki produces a yellow pigmented colony on a tryptic soy agar (TSA) plate and
can grow at a temperature range of 6°C–45°C with an optimum temperature of 37°C–43°C. In
general, these organisms are thermotolerant and can adapt well to osmotic desiccation stress. They
can survive in infant cereal with an A W range of 0.30–0.83 for up to 12 months. Cronobacter has
been associated with a number of outbreaks involving powdered infant formula (PIF). Cronobacter
spp. has also been isolated from varieties of foods, including rice, bread, milk, cheese, dried foods,
spices, tea, meats, water, and vegetables. These organisms are also found in food factories, including a powdered infant formula production facility and livestock facilities.
The pathogenesis of Cro. sakazaki is not fully understood; however, the bacterium is known to
translocate from the gastrointestinal tract to the blood where it multiplies in large numbers and
then crosses the blood brain barrier to reach to cerebrospinal fluid. In infants, it causes bacteremia,
necrotizing enterocolitis, neonatal meningitis, and memingoencephalitis. The mortality rate in
infants is 50%–80%. Recently, it has been shown that adults, especially the immunocompromised
adults and the elderly are susceptible to this infection, showing clinical symptoms of pneumonia,
sepsis, foot ulcers, wound infections, and osteomyelitis. For isolation of this pathogen, FDA and
ISO methods are used that involve preenrichment and/or selective enrichment before plating on
TSA or chromogenic media. Yellow-pigmented colonies are further confirmed by biochemical
testing and by PCR methods. Various control strategies have been proposed that include, strict
hygienic practices during PIF production, monitoring of the processing environments, raw materials, and final product testing. Thermal treatment, including rehydration of PIF with water at 70°C
or higher, can reduce counts by 4 logs. In addition, irradiation, bacteriophages, bacteriocins, and
plant phenolics have been proposed for inactivation of Cronobacter spp. in foods.
Clostridium difficile 15,16
Clostridium difficile is a gram-positive, rod-shaped, spore-forming obligate anaerobe. It is traditionally considered a nosocomial, hospital-acquired human pathogen and is responsible for antibiotic
associated diarrhea (AAD). It was first reported in 1978 by John Bartlett and his colleagues. Since
2003, Clo. difficile infection (CDI) cases have risen dramatically and caused numerous fatalities in
both North America and Europe. In 2007, there were 3875 deaths reported in the United States.
Clo. difficile colonizes human and animal intestines and has been isolated from many domestic and
wild animals: pigs, calves, poultry, horses, donkeys, dogs, cats, seals, snakes, rabbits, and ostrich.
This organism has been isolated primarily from ground meats (pork, beef, and poultry) at a prevalence rate of 3%–12% or higher. It has been also isolated less frequently from raw vegetables
(cucumber, onions, radishes, carrots, mushrooms, and ready-to-eat salads) and milk. The ubiquitous nature of this organism (resulting from spore formation), fecal contamination of the soil, and
its presence in food processing and the packaging environment are thought to be responsible for