Effectiveness of vinegar in reducing/eliminating multidrug resistant Enterobacteriaceae inoculated into the fresh leafy vegetable Eruca vesicaria

Nowadays, the emergence of multidrug-resistant strains of bacteria has become a serious 
threat to public health worldwide. Therefore, the purpose of this work was to study the impact of 
vinegar on reducing/removing of multidrug-resistant (MDR) Enterobacteriaceae from artificially 
contaminated fresh leafy vegetables. Nine strains of MDR Enterobacteriaceae were under 
investigation which previously isolated and identified from ready-to-eat food samples. Rocket plant 
samples were dipped in different concentrations (0, 5, 10, 15 and 30%) prepared from vinegar (5% 
acetic acid) at four-time intervals (0, 10, 20 and 30 min.). The earlier treatments were inoculated 
with the target organisms at rate of ≈ 4.5 log CFU/ml. The results showed that, the pH values of the 
tested vinegar treatments were in the range 2.15 to 2.55. Divergences in the behavior among tested 
MDR Enterobacteriaceae species and even among strains within the same species were clearly 
observed. Enterobacter cloacae 1 was the most resistant strain, it resisted vinegar concentrations 
up to 15%. Dipping rocket leaves at 30% vinegar showed dramatic reduction in the 
Enterobacteriaceae populations. A steep decline in the populations of Enterobacter cloacae 1, 
Enterobacter ludwigii, Klebsiella pneumoniae and Proteus sp. was noticed after only 10 minutes. 
However, Enterobacter cloacae 2, Enterobacter sp., Hafnia alvei 1 and 2 decreased gradually to 
become undetectable after 20 or 30 min. Although Citrobacter sedlakii showed sharp reduction 
after 30 minutes, few cells (0.12 %) survived dipping in vinegar up to 30%. This is the first report 
demonstrating the efficacy sanitation against MDR Enterobacteriaceae.