3. Results and Discussion3.1 Coliform bacteria in fresh vegetables, four range produce and ready-to- eat saladsFirst, ten samples of the six selected fresh vegetables were tested for the presence of coliform bacteria. The termcoliform bacteria refers to Gram-negative bacilli that grow in the presence of bile and ferment lactose with productionof gas, although the methodology used also allows the detection of non-coliform species belonging to theEnterobacteriaceae family as well as some non-enterobacteria Gram-negative species, since mixed bacterialpopulations are found in vegetables and therefore non-coliform species present in positive cultures in BGBLB tubes arethen isolated on EMB-agar plates. In our study all colonies isolated on EMB plates were identified. Coliforms were isolated in 50% out of the 60 samples analyzed, although only one isolate was identified asEscherichia coli (Table 1). The identified species (n: 45) included enterobacteria: Klebsiella pneumoniae (n: 5),Klebsiella oxytoca (n: 10), Serratia marcescens (n: 1), Serratia rubidaea (n: 1), Enterobacter cloacae (n: 20), Kluyveraascorbata (n: 2), and Pantoea agglomerans (n: 3), as well as other bacterial species: Acinetobacter baumannii (n: 1)and Stenotrophomonas maltophilia (n: 1). As shown in Table 1, is some cases (12 out of 60) the bacterial burden_______________________________________________________________________________________(NMP) of the samples was over the detection limit of the method (>2400 coliforms/g), whereas in 50% of samples thepresence of coliform bacteria was under the detection limit (<3 coliforms/g). Carrots were the vegetables morecontaminated, followed by the three types of lettuce, whereas both types of tomatoes showed minor content of bacterialburden; these results correlate with the probability of the analysed vegetables to be in contact with the source ofcontamination during growth: soil, organic fertilisers and irrigation water [3-6]. It should be noted that the in the areaof Valencia, and in general in the Spanish Mediterranean coast, the use of manure as a fertilizer is a common practice.In addition, vegetables from supermarkets were less contaminated with coliform bacteria (11 samples out of 30) ascompared to vegetables from retail greengrocer’s shops (19 samples out of 30). Besides, previous standard washing ofvegetables with water did not significantly affect the results obtained (not shown) indicating that coliform bacteriapossess mechanisms for attachment to vegetal surfaces [3,5,6]. Preliminary results showed the presence of species ofEnterobacteriaceae (Pantoea agglomerans, Escherichia vulneri, and others) in vegetable samples collected directlyfrom the farm land (lettuce and spinach) (not shown).
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