Presence of Multidrug-Resistant Shiga Toxin-ProducingEscherichia coli, EnteropathogenicE. coliand EnterotoxigenicE. coli, on Raw Nopalitos (Opuntia ficus-indicaL.) and in Nopalitos Salads from Local Retail Markets in Mexico

Abstract

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.

Behavior of thirteen foodborne bacteria on whole Hass avocado and potential of roselle calyx extracts as alternative disinfectant agents of avocado

“…Typhi (strain SS6 isolated from raw tomatoes [Gutiérrez‐Alcántara, Rangel‐Vargas, et al, ]), S . Montevideo (strain Z6 isolated from raw carrots [Gutiérrez‐Alcántara, Gómez‐Aldapa, et al, ]), E. coli O157:H7 (E09; donated by E.F. Escartín of the Universidad Autónoma de Querétaro, México) , Vibrio cholerae O1 (87151, serotipe Inaba; donated by E.F. Escartín); E. coli pathotypes comprised three strains of each non‐O157‐STEC, EPEC, ETEC, and EIEC strains, and one of EAEC strain. EIEC strains were EISCM13, isolated from ready‐to‐eat salads (Castro‐Rosas et al, ), EICJB121 isolated from carrot juice (Torres‐Vitela et al, ), and EIMS79 isolated from mung bean sprout (Cerna‐Cortes, Gómez‐Aldapa, Rangel‐Vargas, Ramirez‐Cruz, & Castro‐Rosas, ).…”

“…Avocados were inoculated as previously described (Gutiérrez‐Alcántara, Gómez‐Aldapa, et al, ). Briefly, trypticase soy broth tubes (TSB; 3 ml) were inoculated with individual rifampicin resistant (R+) S .…”

“…Disinfectant solutions were prepared as previously described (Gutiérrez‐Alcántara, Gómez‐Aldapa, et al, ). In brief, 1 L of sodium hypochlorite solution (pH 5.0; 200 mg L −1 free chlorine) was prepared from a sodium hypochlorite solution (10%, Sigma‐Aldrich) by dilution in deionized water.…”

“…Disinfection treatments and microbiological counts were performed as previously described (Gutiérrez‐Alcántara, Gómez‐Aldapa, et al, ). Briefly, aliquots (50 ml) of each calyx extract, sodium hypochlorite, acetic acid, colloidal silver, or isotonic saline solution (ISS; control) were placed in individual trays.…”

“…Previous studies used only aqueous roselle calyx extracts to disinfect romaine lettuce and alfalfa sprouts contaminated with Escherichia coli O157:H7, Salmonella and L. monocytogenes (Jaroni & Ravishankar, ) and organic iceberg lettuce and adult and baby spinach contaminated with Salmonella (Moore, Patel, Jaroni, Friedman, & Ravishankar, ). Recently, we reported the antimicrobial effect of four‐roselle calyx extracts (water, methanol, acetone, and ethyl acetate) against multidrug‐resistant Salmonella strains on carrots (Gutiérrez‐Alcántara, Gómez‐Aldapa, et al, ) and tomatoes (Gutiérrez‐Alcántara, Rangel‐Vargas, et al, ). However, no data are available regarding the activity of these roselle calyx extracts against S .…”