Vegetables and Restaurant Salads as a Reservoir for Shiga Toxigenic Escherichia coli: Distribution of Virulence Factors, O-Serogroups, and Antibiotic Resistance Properties

Abstract

Close contact of vegetables with soil, polluted water, and animal manure and unsanitary conditions during processing of restaurant salads led us to study the distribution of virulence factors, O-serogroups, and antibiotic resistance properties in Shiga toxigenic Escherichia coli (STEC) isolated from vegetables and salads. Samples of vegetables and salad (n = 420) were collected and evaluated for the presence of E. coli using culture and a PCR assay. Total prevalence of E. coli in studied samples was 49.5%. E. coli was found in 49.6% of vegetable samples and 49% of salad samples. Leek and traditional salad had the highest incidence of E. coli. Significant differences in the incidence of E. coli were found between the hot and cold seasons. Of the 149 E. coli isolates from vegetable samples, 130 (87%) were STEC, and of the 59 E. coli isolates from salad samples, 50 (84%) were STEC. The most commonly detected virulence factors were stx1 and eaeA. A significant difference was found between the frequency of the attaching and effacing and the enterohemorrhagic E. coli subtypes. Serogroups O26 (46% of isolates), O157 (14%), O121 (10%), and O128 (9%) were the most commonly detected serogroups among the STEC strains. The tetA, sul1, aac(3)-IV, dfrA1, blaSHV, and CITM antibiotic resistance genes were found in 96, 47.7, 90, 51, 27, and 93% of isolates, respectively. The highest levels of resistance were found against ampicillin (96.6% of isolates), tetracycline (87%), and gentamicin (90%). This study shows the importance of vegetables and salads as potential sources of E. coli infection.

Escherichia coli O157:H7 in Retail Lettuce (Lactuca sativa) in Addis Ababa City: Magnitude of Contamination and Antimicrobial Susceptibility Pattern

“…On the other hand, among the two E. coli O157:H7 isolates from lettuce, one isolate showed multidrug resistance to ampicillin and tetracycline. Comparable to the present study, multidrug resistance was recorded from Iran (Shah et al, 2015;Shakerian et al, 2016). However, no studies have been found in Ethiopia.…”

“…Studies have reported zero prevalence 7 in Spain and Mexico (Canizalez-Roman et al, 2013;Castro-Ibáñez et al, 2015). Higher prevalence has been reported in Pakistan (2.0%) (Shah et al, 2015) and in Iran (10.0%) (Shakerian et al, 2016). The prevalence of E. coli O157:H7 was not statistically significant (p > 0.05) among the subcities of vegetable retail outlets.…”

“…There are no other similar studies in Ethiopia. However, resistance to the same antibiotics has been reported in studies in Iran [ampicillin (100%) and tetracycline (87%)] (Shakerian et al, 2016) and in Pakistan [ampicillin (87%) and tetracycline (92%)] (Shah et al, 2015). On the other hand, among the two E. coli O157:H7 isolates from lettuce, one isolate showed multidrug resistance to ampicillin and tetracycline.…”

Genomic features and antimicrobial resistance patterns of Shiga toxin‐producing Escherichia coli strains isolated from food in Chile

“…In vegetables, contact with contaminated soil, use of contaminated waters and animal manure, and unsanitary conditions during processing have been contributing for STEC prevalence (Shakerian et al., 2016). In this study, we detected STEC pathogens in 0.3% of the lettuce samples, in a similar way that a previous report from Argentina, where 0.5% of 373 vegetable samples were contaminated with STEC (González et al., 2017).…”

Unraveling the Role of Vegetables in Spreading Antimicrobial-Resistant Bacteria: A Need for Quantitative Risk Assessment

“…The majority of studies reported pronounced resistance to streptomycin and tetracyclines—a finding of limited significance, given the fact that clinical breakpoints cut within natural populations. However, studies also reported significant resistance to amoxicillin combined with clavulanic acid (>15%) (e.g., Araújo et al , 2017) or resistance to carbapenems (Shakerian et al , 2016 ) and third- or fourth-generation cephalosporin as well as presence of bla TEM 1-genes (Araújo et al , 2017). Remarkably, Gómez-Aldapa et al ( 2016 ) reported 100% resistance to amikacin and colistin in diarrheagenic E. coli pathotypes from Mexican cactus salads.…”