Food contaminated with Staphylococcus aureus

Staphylococcus aureus a Gram-positive bacterium produces enterotoxins, which are causative agents foodborne intoxication. Almost any food (except acid product) is suitable for the growth of Staphylococcus aureus, but certain foods have been most often the cause of staphylococcal poisoning.

Consumption of foods contaminated with staphylococcus aureus enterotoxins results in the onset of acute gastroenteritis within 2-6 h.

The food types most frequently involved in this disease are ham and ham products, bakery goods with egg custard filling, chicken products and especially chicken salad, potato salad and cheddar cheese. Others are shrimps, low acid foods stored and served between 5 ° C and 55 ° C.

The reason why ham products are frequently involved is that in their preparation they may contaminated with Staphylococcus aureus, and since this product contains 2-3% salt, other bacteria might grow and inhibit the growth of staphylococci are themselves inhibited by the salt.

Also people handle ham and its products are apt to believe that such foods are not perishable. However, ham and ham product are perishable and should always be held at 4.4 ° C or below.

It is generally understood and accepted that Staphylococcus aureus as a food intoxicant presents a risk only when the growth to high numbers occurs.

Since Staphylococcus aureus cannot grow at temperature below 7 ° C and that multiplication of Staphylococcus aureus in raw products is inhibited or slowed down by competing accompanying microflora, those high numbers are normally not reached under the condition of maintained cold chain.

To reduce Staphylococcus aureus food poisoning, the amount of manual handling should be minimizes. Slicers should be dismantled when cleaned and sanitized. Ham should be sliced when it its cold. Rapid cooking should be permitted by storing food in small, loosely covered containers.
Food contaminated with Staphylococcus aureus

Temperature effects on pathogenic microorganisms

Temperature is a key parameter in bio-control of vegetable foods, since it has a direct influence in microbial growth.

When considering the relationship of temperature to microbial life, two things must be considered: the holding temperature of the micro-organism and the length of time for which microorganisms are exposed to that temperature.

Most pathogenic microorganisms prefer temperature below 42 °C because they normally live at the body temperatures of man and animal or the air temperature experienced by plants. Some types of micro-organisms prefer either extremely cold or hot environments.

Cold temperatures often significantly slow the growth of microorganisms, which is the reason refrigeration is used to control bacterial growth.

In natural environments where micro-organisms are commonly subject to rapid changes in temperature, it is perks not surprising that they have evolved protection mechanisms.

E. coli, for example, synthesize cold shock proteins in response to a temperature down shift.

Researchers reported that, under certain conditions moderately cold storage temperature (-2 to -4 °C) resulted greatly in greater destruction of bacteria than storage at -20 C.

When cells are frozen rapidly, both intra- and extracellular fluid are freezes. Slow freezing, however, causes an intra and extracellular osmotic gradient, which can result in cellular disruption.

High temperatures usually kill most microorganisms. Steam sterilization and boiling water are two common techniques used to kill pathogenic microorganisms.
Temperature effects on pathogenic microorganisms