Microbial load, prevalence and antibiograms of <i>Salmonella</i> and <i>Shigella</i> in lettuce and green peppers

Abstract

BackgroundHuman food borne infections traditionally are acquired through the ingestion of foods of animal origin. Fresh fruits and vegetables are major vehicles for the transmission of the food-borne infections. In Ethiopia, there is a tradition of consuming raw vegetables, particularly lettuce and green pepper, without adequate treatment. The objective of this study was to investigate the microbial load of fresh lettuce and green pepper, used as salad vegetables, and to assess the prevalence and antibiotic resistance of Salmonella and Shigella spp. isolated from lettuce and green pepper.MethodsA total of eighty samples of lettuce and green peppers were purchased from different outlets in Addis Ababa and analyzed for their load of various microbial groups and flora analysis was conducted following standard microbiological methods. The presence of Salmonella and Shigella and their antibiotic resistance was also determined.ResultsOver 90% of the vegetable samples had aerobic mesophilic counts of ≥ log 6 cfu/g. Ninety seven percent of the lettuce and 58% of the green pepper samples had enterobacteraceae counts of ≥ log 5 cfu/g. Coliforms were encountered at counts ≥ log 4 cfu/g in 48% and 35% of lettuce and green pepper samples, respectively. Over 80% of vegetable samples harbored staphylococci with counts ranging from log 4 to log 6 cfu/g. More than 88% of lettuce and 18% of green pepper samples had yeast and mold counts ≥ log 4 cfu/g. The aerobic mesophilic flora of the vegetable samples was dominated by Bacillus and Micrococcus spp. Salmonella and Shigella were isolated from eight (10%) and 24 (30%) samples, respectively. All of the Salmonella and 97% of Shigella isolates showed resistance to penicillin. Ampicillin resistance was observed in 42% of Salmonella and 79% of Shigella isolates. Multiple drug resistance was seen in 8 and 24 isolates of Salmonella and Shigella isolates, respectively.ConclusionThe majority of lettuce and green pepper samples had high microbial load and multiple drug resistant pathogens were also isolated from some samples. As lettuce and green pepper, when used as salad vegetables, do not get any further heat treatment, thorough washing and considerably longer exposure of the vegetables to food grade chemicals is recommended to kill pathogens and significantly reduce the microbial load.

Microbiological quality of lettuce (Lactuca sativa) irrigated with wastewater in Addis Ababa, Ethiopia and effect of green salads washing methods

“…Based on the analysis and recommendations from Guchi and Ashenafi (2010) to thoroughly wash vegetables eaten raw in Addis Ababa and/or to dip them in food grade antibacterial chemicals for a considerable time, a short survey of 200 households was undertaken to understand how green salads are commonly washed at home. This short survey was carried out in 5 sub-city administrative areas (Kolfe Keraniyo, Chirkos, Bole, Nefas Silk Lafto and Akaki Kaliti).…”

“…Information on the bacteriological and parasitological aspects of wastewater cropping system and potential health risks associated with the practice is scanty (Guchi and Ashenafi 2010;Habtu 2011). Aside excreta borne pathogens, also heavy metals can be a potential risk factor where industrial effluent enters the common water sources as discussed by Itanna (1998Itanna ( , 2002, Fitamo et al (2007) and Weldegebriel et al (2012).…”

Effect of the irrigation regime on the susceptibility of pepper and tomato to post-harvest proliferation of Salmonella enterica

“…The presence of these human pathogens was also reported on fruits and vegetables (including tomatoes and peppers) in the market place (Arthur et al, 2007;Benjamin et al, 2013;Gallegos-Robles et al, 2008;Greene et al, 2008;Guchi and Ashenafi, 2010;Micallef et al, 2012;Weber et al, 2006;Butterfield, 1997, 1999). Even though human pathogens are fairly uncommon in the crop production environment, fresh produce has been implicated in at least 130 outbreaks of gastroenteritis in the U.S. since 1996.…”

A Comprehensive Review on Śākavarga-group of Vegetables from Classical Texts of Ayurveda

“…29 Therefore, it is always recommended that vegetables should be washed thoroughly and treated with food grade chemicals to reduce the microbial load on them. 30 Thorough washing followed by boiling and/ or cooking processes is also quite effective in reducing the pesticide and insecticide residues.…”