Microorganisms able to grow or survive at cold temperatures: A hidden danger on board ships

 Martin Walker, Port Health Officer, Suffolk Coastal Port Health Authority, Felixstowe, England

For this month’s article, I am grateful to Dr. Maria Gambuzza of the Ufficio di Sanita Marittima di Messina who has submitted this very timely piece.

Key message:

• There are several types of foodborne pathogenic microorganisms able to multiply at low temperatures.
• On board cruise ships there is an increased risk for food contamination from these “psychrophilic microorganisms”, due to very large amounts of foods stored in the cold storage rooms.
• There are some simple rules to prevent or limit these bacteria from growing and spreading inside the cold storage rooms.

The microorganisms live in every part of the biosphere, and some of them are even capable of growing at low temperatures, including those below the freezing point. These microorganisms live in the sea or in high mountains, but unfortunately also in the refrigerators, where they may spoil or, as pathogens, contaminate foods. Therefore, although storing foods in the refrigerator is the best way to keep them safe from bacterial contamination, there are also types of bacteria that can grow in cold temperature as well as inside the refrigerators.

The typical changes of the modern era leading to increased reliance on low temperature storage of food, has resulted in a change of the spectrum of foodborne diseases, with increased risk of infections caused by so-called “emerging food-borne pathogens”, including the bacterial strains Listeria monocytogenes, Yersinia enterocolitica, Aeromonas spp., Plesiomonas shigelloides, Pseudomonas spp., and moulds such as Penicillium and Cladosporium spp (1),(2).


Example of pathogens able to survive in refrigerated foods”

In the last columns of the right the “survival” and “optimum growth” temperatures are indicated.

• Make sure fridges are set at ≤5°C (SHIPSAN Manual reference 3.4.40 and 3.4.19)
• Ensure that all food is packaged, covered and stored properly (SHIPSAN Manual reference 3.4.10)
• Avoid leaving the fridge doors or the cold storage rooms open for longer than necessary (SHIPSAN Manual Reference 3.4.17)
• Keep raw foods covered and separated from cooked foods (SHIPSAN Manual reference 3.4.10)
• Clean and sanitize regularly using antibacterial such as bleach cleaners (3.3.18)
• Check for discoloration or molds in foods and immediately dispose them(SHIPSAN Manual Reference 3.4.21). Molds are often signs of bacterial growth. 
• Allow frozen food to thaw in one of the following ways (SHIPSAN Manual reference 3.4.33); 
  • under refrigeration at a temperature of ≤5°C (41°F) ;
    
  • by completely submerging food in cold running potable water at a temperature not above 21°C (70°F) for a period not exceeding 4 hours;
  • as part of cooking process (but only when thawing is taken into consideration in determining cooking time and following any directions on the food packaging);
  • by using a microwave (attention is to be given to ensure a proper thawing cycle – controlled time or temperature).

SHIPSAN recommends a thawing temperature of 5°C (41°F) or below as best practice however some EU countries require that frozen foods are thawed in a temperature of <8°C (46°F).

Erratum 25/10/2017: The sentence “…with increased risk of infections caused by so-called “emerging food-borne pathogens”, including the bacterial strains Listeria monocytogenes, Yersinia enterocolitica, Aeromonas spp., Plesiomonas shigelloides, Pseudomonas spp., and moulds such as Penicillium and Cladosporium spp (1),(2)" was changed to“with increased risk of infections caused by so-called “emerging food-borne pathogens”, including the bacterial strains Listeria monocytogenes, Yersinia enterocolitica, Aeromonas spp., Plesiomonas shigelloides, Pseudomonas spp., and toxigenic effects caused by mycotoxins produced by moulds such as Penicillium and Cladosporium spp (1),(2)"


REFERENCES

1. Jackson V, Blair IS, McDowell DA, et al. The incidence of significant foodborne pathogens in domestic refrigerators. Food Control 2007; 18: 346-51.
2. Behravesh CB, Williams IT, Tauxe RV. Emergin foodborne pathogens and problems: expanding prevention efforts before slaughter or harvest. In: Institute of Medicine (US). Improving Food Safety Through a One Health Approach: Workshop Summary. Washington (DC): National Academies Press (US); 2012. A14. Available from: http://www.ncbi.nlm.nih.gov/books/NBK114501/
3. Haddad N, Burns CM, Bolla JM et al. Long-term survival of Campylobacter jejuni at low temperatures is dependent on polynucleotide phosphorilase activity. Appl Environ Microbiol 2009; 75: 7310-18.
4. Rossvoll E, Ronning HT, Granum PE et al. Toxin production and growth of pathogens subjected to temperature fluctuations simulating consumer handing of cold cuts. Int J Food Microbiol 2014; doi.: 10.1016.
5. Ingham SC. Growth of Aeromonas hydrophila and Plesiomonas shigelloides on cooked crayfish tails during cold storage under air, vacuum and a modified temperature. J Food Prot 1990; 53: 665-67.
6. De Jonghe V, Coorevits A, Van Hoorde K. Influence of storage conditions on the growth of Pseudomonas species in refrigerated raw milk. Appl Environ Microbiol 2011; 77: 460-70.
7. Sautour M, Dantigny P, et al. A temperature-type model for describing the relationship between fungal growth and water activity. 2001; 67: 63-69. 
8.  EU SHIPSAN TRAINET Project partnership, European manual for hygiene standards and communicable diseases surveillance on passenger ships, (2011)