Prevalence of plant beneficial and human pathogenic bacteria isolated from salad vegetables in India

Abstract

BackgroundThe study aimed at enumerating, identifying and categorizing the endophytic cultivable bacterial community in selected salad vegetables (carrot, cucumber, tomato and onion). Vegetable samples were collected from markets of two vegetable hot spot growing areas, during two different crop harvest seasons. Crude and diluted vegetable extracts were plated and the population of endophytic bacteria was assessed based on morphologically distinguishable colonies. The bacterial isolates were identified by growth in selective media, biochemical tests and 16S rRNA gene sequencing.ResultsThe endophytic population was found to be comparably higher in cucumber and tomato in both of the sampling locations, whereas lower in carrot and onion. Bacterial isolates belonged to 5 classes covering 46 distinct species belonging to 19 genera. Human opportunistic pathogens were predominant in carrot and onion, whereas plant beneficial bacteria dominated in cucumber and tomato. Out of the 104 isolates, 16.25% are human pathogens and 26.5% are human opportunistic pathogens.ConclusionsExistence of a high population of plant beneficial bacteria was found to have suppressed the population of plant and human pathogens. There is a greater potential to study the native endophytic plant beneficial bacteria for developing them as biocontrol agents against human pathogens that are harboured by plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-017-0974-x) contains supplementary material, which is available to authorized users.

Transmission of pathogens within the commonly consumed vegetables: Bangladesh perspective

“…Other major plant generated toxins may include phytohaemagglutinin, for red Kidney beans, solanines, for tomato and potato, and for oxalates (spinach and rhubarb) (20)(21)(22). Although washing can be applied to remove these contaminant, in order to further ensure the complete removal of the toxins, the regulatory o bodies like the Center for Disease Control and Prevention (CDC), US Food and Drug Administration (FDA), World Health Organization (WHO) and Center for Science in the Public Interest (CSPI) need to instill the relevant monitoring programs which may include the dietary studies focused to maintain safe and tolerable levels of the natural contaminants (14,23,24).…”

“…The prevalence of the endophytic cultivable bacterial community like Salmonella spp., Escherichia coli, Bacillus cereus, Campylobacter spp., Yersinia enterocolitica, Listeria monocytogenes, Clostridium botulinum, yeasts, molds, some viruses and parasites in the salad vegetables like carrots, cucumbers, tomatoes or onions are not unlikely (22,(25)(26)(27). The incidents of Listeriosis, the E. coli 0157 outbreak, and the Salmonella outbreak upon consumption of mixed salad vegetables unfortunately seem to be common (23). As mentioned in the earlier reports, besides the potential health offers from the fresh vegetables, the point of safety and the quality of vegetables is of clinical significance due to an array of disease outbreaks (23).…”

The Incidence of Extended-Spectrum Beta-Lactamase (ESBL)-Producing Bacteria in Salad Vegetables in Ondo City, Nigeria

“…These bacteria could adapt and persist in plant environment and increase the chance of transmitting to humans via consumption of plants or plant-derived products. Nithya and Babu [23] reported the existence of Stenotrophomonas rhizophila, Arthrobacter mysorens, Xanthomonas axonopodis, and Aeromonas hydrophila that were not encountered in this study. The findings of this study also differ from the results of Kemajou et al [26] who reported Escherichia coli as the predominant (29.3%) and which was followed by Staphylococcus aureus (22.9%).…”

“…In this part of the country, domestic sewage, industrial and municipal waste water is used for irrigating vegetable crops. This could be responsible for the presence of human pathogenic bacterial load observed in salad vegetables, in addition to contamination through human and farm animal waste in agricultural lands, postharvest handling, transport, storage and poor hygiene conditions prevailing in market places [23].…”

“…These changes are mainly due to change in the ecology of human pathogens to persist in non-host environments. Fresh vegetables, generally, are known to harbour huge bacterial populations [2], which could be of plant endophytes, plant pathogenic and human pathogenic in nature. The most important features of plant host colonization is by the adaptation of pathogens to the host defence response, physiology, immunity, native microflora, physical barriers, mobility and temperature.…”