Comparative effects of washing solution and the survival of <i>Staphylococcus aureus</i> on tomatoes

Abstract

Various types of fruits and vegetables are often eaten raw or consumed after minimum processing in which this has been connected to an increase in outbreaks of fresh produce associated with food borne diseases in the recent times. In order to determine the micro-flora, survival of Staphylococcus aureus on ripe and unripe tomatoes and to also asses the efficiency of some washing solutions, 100 tomatoes, both ripe and unripe were randomly bought from different selling points in Sagamu Markets, Ogun State Nigeria. Surface swabs of the tomatoes were cultured on both nutrient broth, and selenite F broth. The sample from nutrient broth was then sub cultured on Blood Agar, Mannitol Salt Agar, and MacConkey Agar, (MSA), Potato Dextrose Agar (SDA), while the one on Selenite F Broth was cultured on Salmonella Shigella Agar (SSA). Density of Staphylococcus aureus ATCC 25923 after pre-inoculation on ripe and unripe tomatoes, and after the application of washing solutions on tomatoes, was determined by surface spread count. The prevalence of any of the isolated micro-flora could not be significantly linked with either ripe or unripe tomatoes (0>0.05).Mean residual counts (log CFU/g) of bacteria was significantly higher in ripe tomatoes (3.52 ±2.40) than unripe tomatoes (2.30 ±1.96) after pre inoculation with Staphylococcus aureus (t =2.75, P< 0.05). Among the washing solution, hypochlorite was observed to be twice more efficient than hydrogen peroxide and thrice efficient than saline solution. In conclusion, Staphylococcal colonization of tomatoes skin is significantly reduced in unripe tomatoes. And also, hypochlorite solutions are better than hydrogen peroxide and saline in Staphylococcal decontamination from tomatoes.

Key words: washing solution, Staphylococcus aureus, tomatoes