Análise bacteriológica de hortaliças em três sistemas de cultivo em Presidente Prudente SP

Abstract

The aim of this study was to quantitatively evaluate Listeria monocytogenes, Salmonella spp, Escherichia coli and Staphylococcus aureus in garden lettuce (Lactuca sativa) produced in the region of Presidente Prudente, using three cultivation systems: conventional, hydroponic and organic. One hundred and eighty samples of lettuce were collected for six months, sixty in each cultivation system. The lettuces were diluted in fractions 10-1 10-2 and 10-3 and plated on chromogenic agar for Listeria (Aloa Agar - Laborclin ), Baird-Parker agar supplemented with egg yolk (Oxoid ) and potassium tellurite (Laborclin ) for isolation of S. aureus, eosin methylene blue agar (Kasvi ) for isolating thermotolerant fecal coliforms (E. coli) and Rappaport-Vassilaidis broth (Himedia ) and sodium tetrathionate (Himedia ) followed by plating on Rambach agar for isolation of Salmonella. The production systems did not differ with regard to the E. coli (p = 0.582) or L. monocytogenes counts (p = 0.526). The counts of S. aureus in the lettuces cultivated in the organic system were statistically higher than the counts registered in the hydroponic system (p <0.05). The systems evaluated did not differ in relation to the isolation frequencies of the investigated bacterial species. Positive and statistically significant correlations were found between E. coli and S. aureus counts for the hydroponic and conventional systems. The results suggest that lettuces, regardless of the cultivation system, may contain food-borne infectious agents. Thus, improvements in the management system for these crops are recommended in order to strengthen the prevention of infections spread through consumption of raw vegetables.