Cronobacter sakazakii in foods and factors affecting its survival, growth, and inactivation

https://doi.org/10.1016/j.ijfoodmicro.2009.02.029Get rights and content

Abstract

Cronobacter sakazakii has been isolated from a wide range of environmental sources and from several foods of animal and plant origin. While infections caused by C. sakazakii have predominantly involved neonates and infants, its presence on or in foods other than powdered infant formula raises concern about the safety risks these foods pose to immunocompromised consumers. We have done a series of studies to better understand the survival and growth characteristics of C. sakazakii in infant formula, infant cereal, fresh-cut produce, and juices made from fresh produce. Over a 12-month storage period, the pathogen survived better in dried formula and cereal at low aw (0.25–0.30) than at high aw (0.69–0.82) and at 4 °C compared to 30 °C. C. sakazakii grows in formulas and cereals reconstituted with water or milk and held at 12–30 °C. The composition of formulas or cereals does not markedly affect the rate of growth. C. sakazakii grows well on fresh-cut apple, cantaloupe, watermelon, cabbage, carrot, cucumber, lettuce, and tomato at 25 °C and in some types of produce at 12 °C. Treatment of fresh fruits and vegetables with sanitizers such as chlorine, chlorine dioxide, and a peroxyacetic acid-based solution causes reductions of 1.6–5.4 log CFU/apple, tomato, and lettuce. Cells of C. sakazakii in biofilms formed on stainless steel and enteral feeding tubes or dried on the surface of stainless steel have increased resistance to disinfectants. Death of cells in biofilms is affected by atmospheric relative humidity. These studies have contributed to a better understanding of the behavior of C. sakazakii in and on foods and on food-contact surfaces, thereby enabling the development of more effective strategies and interventions for its control.

Introduction

Neonatal infections believed to have been caused by Cronobacter sakazakii, formerly Enterobacter sakazakii (Iversen et al., 2008), were first reported by Urmenyi and Franklin (1961). Numerous cases have been subsequently described. A book (Farber and Forsythe, 2008) and several reviews (Nazarowec-White and Farber, 1997a, Lai, 2001, Iversen and Forsythe, 2003, Lehner and Stephan, 2004, Gurtler et al., 2005, Bowen and Branden, 2006, Drudy et al., 2006, Mullane et al., 2006, Friedemann, 2007) have summarized information on taxonomy, biochemical characteristics, epidemiology, pathogenicity, clinical etiology, and survival and inactivation characteristics of C. sakazakii in foods and the environment.

Reconstituted powdered infant formula and powdered milk have been the most common vehicles implicated in neonatal C. sakazakii infections. Other unidentified sources of the pathogen were involved in cases of infections in infants, children, and immunocompromised adults having underlying medical conditions (Jimenez and Gimenez, 1982, Pribyl et al., 1985, Hawkins et al., 1991, Emery and Weymouth, 1997, Dennison and Morris, 2002). C. sakazakii infections in these age groups raise concerns about the survival and growth characteristics of the pathogen in foods other than powdered and reconstituted infant formula and milk. C. sakazakii has been isolated from a wide range of foods and beverages (Table 1), thereby posing some level of safety risk to the consumer. Information about how the behavior of C. sakazakii on these foods is affected by conditions to which they are exposed would be meaningful when developing strategies and interventions for its control.

Summarized here is a series of experiments conducted in our laboratories. No attempt is made to review the numerous excellent studies reported internationally. The text evolved from a presentation at an International Meeting on Cronobacter (E. sakazakii) in Dublin, Ireland, 22–23 January 2009 at which we were invited to give an overview of our Cronobacter research. Objectives of our work were to better define the survival and growth characteristics of C. sakazakii upon exposure to environments and conditions mimicking those imposed by processes and practices followed in commercial channels and in food storage and preparation areas in hospitals, day-care centers, and the home.

Section snippets

Recovery of stressed cells

Several differential and selective media have been developed for detecting or enumerating C. sakazakii in clinical, food, and environmental samples (Hsing-Chen and Wu, 1992, Iversen et al., 2004b Leuschner et al., 2004a, Leuschner et al., 2004b, Oh and Kang, 2004). While these media are promising for recovering the pathogen from various sources, their suitabilities for supporting repair of stressed or injured cells and colony development by these cells were not compared. C. sakazakii is known

Survival in powdered infant formula

Differences in composition of infant formulas, coupled with differences in aw and storage temperature, are likely to affect the survival of C. sakazakii in powdered infant formula and other foods. The pathogen is known to survive for at least two years in powdered infant formula at low aw (Edelson-Mammel et al., 2005, Barron and Forsythe, 2007). We undertook a study to determine the effects of aw and storage temperature on the survival characteristics of the pathogen in four commercially

Survival in dry infant cereals

Milled, reconstituted cereals are common weaning foods for infants at the age of 4–6 months. The immune systems in these infants is not fully developed. We and others have described conditions affecting the survival of C. sakazakii in powdered and reconstituted infant formula but not dry or reconstituted infant cereal. Recognizing that other foodborne pathogens, e.g., enterohemorrhagic Escherichia coli O157:H7 (Deng et al., 1998) and toxigenic Bacillus cereus (Jaquette and Beuchat, 1998), can

Attachment and formation of biofilm

Attachment of bacteria and fungi to surfaces may be followed by the production of exopolysaccharide and biofilm formation (Kumar and Anand, 1998). C. sakazakii has been reported to be able to attach to abiotic materials such as silicon, latex, polycarbonate, stainless steel, glass, and polyvinyl chloride and form biofilms (Iversen et al., 2004b, Lehner et al., 2005, Grimm et al., 2008). We examined conditions affecting attachment of and biofilm formation by C. sakazakii on stainless steel and

Survival and growth on produce and in unpasteurized juice

Among the ready-to-eat foods from which C. sakazakii has been isolated are lettuce (Soriano et al., 2001), seed sprouts (Kim et al., 2009), and other vegetables (Geiges et al., 1990, Ottaviani et al., 1992, Leclercq et al., 2002, Weiss et al., 2005). The incidence of foodborne diseases associated with consumption of fresh produce has increased in recent years. The ability of C. sakazakii to grow at temperatures as low as 5.5 °C (Nazarowec-White and Farber, 1997b) raises concern about its

Conclusions

C. sakazakii can be found in a wide range of foods and beverages, many of which are not subjected to treatments or processes that will inactivate the pathogen. Its ability to survive and grow in these products raises concern about safety risks not only to neonates and infants but also to older immunocompromised consumers. The suitability of infant cereals and some types of fresh fruits and vegetables to support luxuriant growth of C. sakazakii is of particular concern. The ability of the

Acknowledgments

Studies involving infant formula and cereal were supported, in part, by a grant from the International Life Sciences Institute – North America (ILSI N.A.). Studies on fresh produce were supported by a grant from the United States Department of Agriculture (USDA). The opinions expressed herein are those of the authors and do not necessarily represent the views of ILSI N.A. or USDA.

References (113)

  • GurtlerJ.B. et al.

    Growth of Enterobacter sakazakii in reconstituted infant formula as affected by composition and temperature

    Journal of Food Protection

    (2007)
  • GurtlerJ.B. et al.

    Inhibition of growth of Enterobacter sakazakii in reconstituted infant formula by the lactoperoxidase system

    Journal of Food Protection

    (2007)
  • GurtlerJ.B. et al.

    Survival of Enterobacter sakazakii in powdered infant formula as affected by composition, water activity, and temperature

    Journal of Food Protection

    (2007)
  • GurtlerJ.B. et al.

    Enterobacter sakazakii: a coliform of increased concern to infant health

    International Journal of Food Microbiology

    (2005)
  • IversenC. et al.

    Risk profile of Enterobacter sakazakii, an emergent pathogen associated with infant milk formula

    Trends in Food Science and Technology

    (2003)
  • IversenC. et al.

    Isolation of Enterobacter sakazakii and other Enterobacteriaceae from powdered infant formula milk and related products

    Food Microbiology

    (2004)
  • IversenC. et al.

    A selective differential medium for Enterobacter sakazakii, a preliminary study

    International Journal of Food Microbiology

    (2004)
  • JaquetteC.B. et al.

    Survival and growth of psychrotrophic Bacillus cereus in dry and reconstituted infant rice cereal

    Journal of Food Protection

    (1998)
  • JimenezE.B. et al.

    Septic shock due to Enterobacter sakazakii

    Clinical Microbiology Newsletter

    (1982)
  • KimH. et al.

    Survival and growth of Enterobacter sakazakii on fresh-cut fruits and vegetables and in unpasteurized juices as affected by storage temperature

    Journal of Food Protection

    (2005)
  • KimH. et al.

    Survival of Enterobacter sakazakii on fresh produce as affected by temperature, and effectiveness of sanitizers for its elimination

    International Journal of Food Microbiology

    (2006)
  • KimH. et al.

    Fate of Enterobacter sakazakii attached to or in biofilms on stainless steel upon exposure to various temperatures or relative humidities

    Journal of Food Protection

    (2008)
  • KimK. et al.

    Prevalence and genetic diversity of Enterobacter sakazakii in ingredients and of infant foods

    International Journal of Food Microbiology

    (2008)
  • KimH. et al.

    Microbiological examination of vegetable seed sprouts in Korea

    Journal of Food Protection

    (2009)
  • KimuraB. et al.

    Evaluation of TaqMan PCR assay for detecting Salmonella in raw meat and shrimp

    Journal of Food Protection

    (1999)
  • KumarC.G. et al.

    Significance of microbial biofilms in the food industry: a review

    International Journal of Food Microbiology

    (1998)
  • LehnerA. et al.

    Biofilm formation, extra-cellular polysaccharide production, and cell-to-cell signaling in various Enterobacter sakazakii strains: aspects promoting environmental persistence

    Journal of Food Protection

    (2005)
  • LenatiR.F. et al.

    Growth and survival of Enterobacter sakazakii in human breast milk with and without fortifiers as compared to powdered infant formula

    International Journal of Food Microbiology

    (2008)
  • LinL.-C. et al.

    Survival and growth of Enterobacter sakazakii in infant cereal as affected by composition, reconstitution liquid, and storage temperature

    Journal of Food Protection

    (2007)
  • LinL.-C. et al.

    Survival of Enterobacter sakazakii in infant cereal as affected by composition, water activity, and temperature

    Food Microbiology

    (2007)
  • MahT.F. et al.

    Mechanisms of biofilm resistance to antimicrobial agents

    Trends in Microbiology

    (2001)
  • MusgroveM.T. et al.

    Identification of Enterobacteriaceae from washed and unwashed commercial shell eggs

    Journal of Food Protection

    (2004)
  • NassereddinR.A. et al.

    Microbiological quality of sous and tamarind, traditional drinks consumed in Jordan

    Journal of Food Protection

    (2005)
  • Nazarowec-WhiteM. et al.

    Enterobacter sakazakii: a review

    International Journal of Food Microbiology

    (1997)
  • Nazarowec-WhiteM. et al.

    Incidence, survival, and growth of Enterobacter sakazakii in infant formula

    Journal of Food Protection

    (1997)
  • PribylC. et al.

    Azteonam in the treatment of serious infections

    American Journal of Medicine

    (1985)
  • RobertsonL.F. et al.

    Microbiological analysis of seed sprouts in Norway

    International Journal of Food Microbiology

    (2002)
  • Al-DughanA.M. et al.

    Surface contamination of camel carcasses

  • BalebonaC.M. et al.

    Modified most-probably-number technique for the specific determination of Escherichia coli from environmental samples using a fluorogenic method

    Journal of Microbiological Methods

    (1990)
  • BanksJ.G. et al.

    Preservation by the lactoperoxidase system (LP-S) of a contaminated infant formula

    Letters in Applied Microbiology

    (1985)
  • Bar-OzB. et al.

    Enterobacter sakazakii infection in the newborn

    Acta Pediatrics

    (2001)
  • BeuchatL.R.

    Use of sanitizers in raw fruit and vegetable processing

  • BowenA.B. et al.

    Invasive Enterobacter sakazakii disease in infants

    Emerging Infectious Diseases

    (2006)
  • BreeuwerP. et al.

    Desiccation and heat tolerance of Enterobacter sakazakii

    Journal of Applied Microbiology

    (2003)
  • BulgarelliM.A. et al.

    Microbiological quality of cowpea paste used to prepare Nigerian akara

    Journal of Food Science

    (1988)
  • CabassiC.S. et al.

    Bacteriologic findings in ostrich (Struthio camelus) eggs from farms with reproductive failures

    Avian Diseases

    (2004)
  • CastanoA. et al.

    Counts, behavior and species of Enterobacteriaceae during manufacture of dry-cured lacon, a Spanish traditional meat product

    Alimentaria

    (2001)
  • Chaves-LopezC. et al.

    Characterization of Enterobacteriaceae isolated from an artisanal Italian ewe's cheese (Pecorino Abruzzese)

    Journal of Applied Microbiology

    (2006)
  • ChoiS.H. et al.

    Gram-negative bacteria selective medium to detect post-pasteurization contamination of market milk by using dye reduction test

    Korean Journal of Dairy Science

    (1999)
  • CottynB. et al.

    Bacterial populations associated with rice seed in the tropical environment

    Phytopathology

    (2001)
  • Cited by (146)

    View all citing articles on Scopus
    View full text