A study on prevalence of multi-drug-resistant (MDR) Salmonella in water sprinkled on fresh vegetables in Bareilly, Moradabad, and Kanpur (northern Indian cities)

Abstract

Water-borne and food-borne diseases are common in summers and monsoons in India. This study between March 2004 to September 2004 on microbiological quality of water used by vegetable vendors to keep their vegetables fresh was conducted to asses the role of water as a source of Salmonella. Of the 309 samples collected from Bareilly (80 vegetable vendors, 47 ponds, five municipal water taps), Moradabad (74 vegetable vendors, three ponds, five municipal water taps) and Kanpur (84 vegetable vendors, six ponds, five municipal water taps), 82 (26.5%) and 27 (8.7%) had Escherichia coli and Salmonella enterica strains, respectively. The study revealed that sprinkling water was contaminated with 0.00–6.81 log₁₀ cfu ml⁻¹ of coliforms, 4.16 log₁₀ to 9.46 log₁₀ cfu ml⁻¹ of heterotrophic aerobic bacteria, 0.00 to 7.23 log₁₀ cfu ml⁻¹ of non-lactose fermenters, 0.00 to 5.56 log₁₀ cfu ml⁻¹ of Salmonella and 0.00 to 7.77 log₁₀ cfu ml⁻¹ of yeast and moulds. Similarly, microbial counts in pond water samples (Bareilly) were 0.00 to 6.06 log₁₀ cfu ml⁻¹ of faecal coliforms, 5.12 log₁₀ to 8.09 log₁₀ cfu ml⁻¹ of heterotrophic aerobic bacteria, 0.00 to 6.37 log₁₀ cfu ml⁻¹ of non-lactose fermenters, 0.00 to 5.73 log₁₀ cfu ml⁻¹ of Salmonella and 0.00 to 7.82 cfu log₁₀ ml⁻¹ of yeasts and moulds. Presence of Salmonella in water sample had negative correlation with number of coliforms and positive correlation with number of non-lactose fermenters, as of the 16 (6.7%) Salmonella positive samples of water from vegetable vendors, ten were negative for coliforms. Similarly, of the 11 pond-water samples positive for Salmonella, six were negative for coliforms, and negative correlation (−0.55) between coliform count and Salmonella was statistically significant (r_0.01). On the other hand, Salmonella counts could be positively correlated (r_0.01) with counts of non-lactose fermenters. Salmonella isolates from water for sprinkling on vegetables belonged to S. Anatum (1), S. Newport (1), S. Saintpaul (6), S. Virchow (4) and S. Weltevreden (4) serovars while isolates pond water samples belonged to S. Saintpaul (9) and S. Newport (2) serovars. Except two Salmonella isolates (one each of serovar S. Anatum and S. Weltevreden), all had multiple drug resistance and could be classified into 21 resistotypes. All the Salmonella isolates were sensitive to ceftriaxone and streptomycin while resistant to sulphamethizole. The study indicated that pond water (used by farmers for washing vegetables) and water used by vegetable vendors for sprinkling on vegetables might have an important role as a source of multiple-drug-resistant zoonotic Salmonella.