Recently, epidemics that have occurred as a result of the transmission of pathogenic microorganisms by
consuming contaminated fresh vegetables have become more frequent. Among the most massive were poisonings by
bacteria originating from spinach in the Unated States of America, from mung beans in Japan, as well as an
epidemic caused by Escherichia coli from pumpkin in Germany. Unfortunately, hemolytic uraemic syndrome
caused by Escherichia coli in Germany affected 3,950 people in 2011, of whom 53 died. Although vegetables do not
represent a natural habitat for bacteria that cause diseases in humans, it is clear that certain groups of human
pathogenic microorganisms can find their ecological niches in plant production systems. Ways of contaminating
plants with these bacteria are poorly understood. It is assumed that fertilization and irrigation with untreated water
are some of the possible ways of transmitting pathogenic bacteria to agricultural crops. The aim of the research was
to indicate the possible presence of potentially pathogenic strains of bacteria on certain vegetable crops (lettuce,
spinach, tomato, paprika, carrot, parsley, red onion) in the northeastern part of Republika Srpska (Bosnia and
Herzegovina). Samples were collected over three months in 10 greenhouses and 10 vegetable gardens in the
Semberija area. Extraction of bacteria from the samples was performed by immersing the macerated plant tissue in
the extraction solution with sterile pepton water. Indirect culture methods on highly selective chromogenic media
were used to isolate Salmonella enterica and Listeria monocytogenes strains. After comparing the obtained isolates
with positive controls, suspicious colonies were isolated and the strains were confirmed by DNA extraction and
AmpliTest PCR method with specific primers. The presence of Salmonella enterica was confirmed on tomato fruits,
bell peppers, lettuce leaves and red onion bulbs, while Listeria monocytogenes was isolated on lettuce and spinach
leaves. The presence of potential pathogens on fresh vegetables, especially those consumed without prior heat
treatment, is alarming. In order to prevent negative consequences, it is necessary to specify the routes of their
transmission as well as to examine their viability in non-specific ecological niches such as agricultural crops. Data
on the viability of bacteria on agricultural crops can be found in the literature for only a small number of strains that
are “most attractive”, such as Escherichia coli strains, while for other pathogens data are very scarce or non-existent.
Data on their infectivity is even harder to find.
