The presence of multidrug-resistant pathogenic bacteria in food is a significant public health concern. Diarrheagenic Escherichia coli pathotypes (DEPs) are foodborne bacteria. In Mexico, DEPs have been associated with diarrheal illness. There is no information about the presence of multidrug-resistant DEPs on fresh vegetables and in cooked vegetable salads in Mexico. "Nopalitos" (Opuntia ficus-indica L.) is a Cactacea extensively used as a fresh green vegetable throughout Mexico. The presence of generic E. coli and multidrug-resistant DEPs on raw whole and cut nopalitos and in nopalitos salad samples was determined. One hundred raw whole nopalitos (without prickles) samples, 100 raw nopalitos cut into small square samples, and 100 cooked nopalitos salad samples were collected from markets. Generic E. coli was determined using the most probable number procedures. DEPs were identified using two multiplex polymerase chain reaction procedures. Susceptibility to 16 antibiotics was tested for the isolated DEP strains by standard test. Of the 100 whole nopalitos samples, 100 cut nopalitos samples, and 100 nopalitos salad samples, generic E. coli and DEPs were identified, respectively, in 80% and 10%, 74% and 10%, and 64% and 8%. Eighty-two DEP strains were isolated from positive nopalitos samples. The identified DEPs included Shiga toxin-producing E. coli (STEC), enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC). All isolated strains exhibited resistance to at least six antibiotics. To the best of our knowledge, this is the first report of the presence of multidrug-resistant and antibiotic resistance profiles of STEC, ETEC, and EPEC on raw nopalitos and in nopalitos salads in Mexico.

Presence of antibiotic‐resistant Salmonella strains on raw carrots was evaluated, as was the antibacterial activity of roselle calyx extracts against any identified resistant Salmonella strains. One hundred samples of carrots were collected from markets in Pachuca, Mexico. Salmonella was isolated from the carrot samples by culture procedure. Susceptibilities to sixteen antibiotics were determined for the isolated Salmonella strains by standard test. Antibacterial activity versus the isolated strains was measured for roselle extracts produced with water, methanol, acetone and ethyl acetate. Finally, the antibacterial effect of roselle extracts, sodium hypochlorite, acetic acid and colloidal silver against Salmonella strains isolated from carrots was evaluated on contaminated carrots. Thirteen Salmonella strains were isolated from 11% of the carrot samples. All strains exhibited resistance to at least two of the tested antibiotics. Roselle extracts caused a greater reduction in concentration of Salmonella than the sodium hypochlorite, acetic acid and colloidal silver on contaminated carrots. Practical Applications Roselle Hibiscus sabdariffa calyx extracts exhibited antimicrobial activity on culture media and on carrots against multidrug‐resistant Salmonella strains. The information presented shows that water extract of roselle calyx may be a potentially useful addition to disinfection procedures of raw carrots in field, carrot processor plants, restaurants and home.

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The presence of multidrug-resistant Salmonella in vegetables is a significant public health concern. Multidrug-resistant Salmonella strains were isolated from raw tomatoes purchased in public markets in Mexico and challenged with roselle Hibiscus sabdariffa calyx extracts, sodium hypochlorite and acetic acid. On tomatoes, the extracts caused a greater reduction in the concentration of antibiotic-resistant Salmonella strains than sodium hypochlorite and acetic acid. Roselle calyx extracts are a potentially useful addition to disinfection procedures of raw tomatoes in the field, processing plants, restaurants and homes.

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