Pesticides residues in leafy green vegetables and irrigation waters in Accra, Ghana.

Pesticides are used in vegetable farming to control pests and diseases, reduce crop losses and improve yield. The study examined pesticide residues in irrigation waters and leafy green vegetables grown in some farming areas in Accra, Ghana. Three types of irrigation water sources (n = 23) and two exotic and four indigenous Ghanaian leafy vegetables (n = 34) from 10 farming areas in Accra, Ghana were collected and examined for 15 organochlorines, 13 organophosphorus and 9 synthetic pyrethroids pesticide residues using the modified QuEChERS procedure. Pesticide residues were detected on 50% (17/34) of the leafy vegetable and 52% (12/23) of the irrigation water samples analysed. Chlorpyrifos and deltamethrin were the most detected pesticide residues in the vegetables and irrigation water. About 26.5% of the vegetables contained pesticide residues exceeding the EU maximum residue limits, so vegetable farmers should be encouraged to comply with appropriate measures on pesticide use to enhance food safety.

Effect of Pre-Exposure to Chlorine Dioxide on the Susceptibility of Fecal Coliforms to Antibiotics.

Adaptive exposure to sub-lethal concentrations of sanitizers was previously reported to offer cross-protection to bacteria against antibiotics. This study was undertaken to determine whether the pre-exposure of fecal coliforms to suboptimal concentrations of a chemical sanitizer, chlorine dioxide (ClO2), alters their susceptibility to certain antibiotics. Fecal coliforms isolated from fresh fruit packing facilities (n = 12) were adapted in ½ or » of the manufacturer-recommended concentration of ClO2. The susceptibility of the adapted and non-adapted cells to 13 different antibiotics was determined by observing the changes in their minimal inhibitory concentrations (MICs). The results showed that preadaptation to the suboptimal concentrations of ClO2, in general, either decreased or did not change the MICs of the antibiotics against selected fecal coliform isolates, with only two exceptions; preadaptation increased the MICs of kanamycin against two of the fecal coliform isolates, and of nalidixic acid against one of the fecal coliform isolates. The results suggest that the use of ClO2 has a relatively low risk of inducing the resistance of fecal coliforms to antibiotics.

Validating the Efficacy of Sanitation Methods Commonly Used by Ghanaian Households in Inactivating Artificially Inoculated Salmonella enterica on Leafy Green Vegetables.

ABSTRACT: Our previous survey revealed the poor microbial quality of leafy green vegetables and the presence of Salmonella on these vegetables grown and sold in Accra, Ghana. This study validated the efficacy of some cleaning and sanitation methods (tap water, salt solution, lemon juice, and vinegar) commonly used by Ghanaian households, by comparing them with the performance of several sanitation approaches used by the U.S. fresh produce industry (chlorine, peracetic acid, and ozonated water) in reducing Salmonella populations on leafy green vegetables. Cabbage and lettuce leaves inoculated with each of three Salmonella cocktails were treated with sterile water and the previously mentioned six sanitizers. The efficacies of the treatments were evaluated by using the standard plate count assay. The effect of the treatments on the sensory quality of treated vegetables was evaluated by a 97-member consumer panel in the United States. Treatments with citric and acetic acid were as effective as chlorine and peracetic acid in reducing Salmonella counts on vegetable leaves. Ozonated water was less effective than the two organic acids but equally as effective as treatment with the salt solution. Rinsing vegetables with water did not significantly reduce Salmonella counts (P > 0.05). Cabbage leaves treated with citric acid, vinegar, and water were more preferred (P ≤ 0.05) by the consumer panel, while chlorine-treated cabbage leaves were the least preferred. Lettuce samples treated with citric acid and water were more preferred, and salt-treated samples were least preferred. Among the vegetable sanitation methods used by Ghanaian households, treatments with citric and acetic acid are effective in inactivating Salmonella without adversely affecting the sensory quality of treated vegetables.

Antibiotic Resistance Profile of Salmonella enterica Isolated from Exotic and Indigenous Leafy Green Vegetables in Accra, Ghana.

ABSTRACT: Fresh produce-borne enteric bacterial pathogens that are resistant to antibiotics have posed serious challenges to food safety and public health worldwide. This study was conducted to evaluate the antibiotic resistance profiles of Salmonella enterica isolates (n = 33) recovered from exotic and indigenous leafy green vegetable samples (n = 328) collected from 50 vegetable farms in 12 farming areas and 37 vegetable sellers in four market centers in Accra, Ghana, from March 2016 to March 2017 and to determine the distribution of integrons among antibiotic-resistant isolates. The susceptibility of the Salmonella isolates to 12 antibiotics was assayed with the standard disk diffusion assay. The MICs of the five most resisted antibiotics were determined with a twofold macrodilution method. A PCR assay was used to detect the presence of integrons in Salmonella isolates, and PCR products with the amplified integron gene cassette were purified and sequenced with the Sanger sequencing technology. The Salmonella isolates used in the study were resistant to at least one tested antibiotic, and 30.3% (10 of 33) of the isolates were multidrug resistant. Most isolates (81.8%) were resistant to sulfisoxazole. The MICs of tetracycline, cefoxitin, streptomycin, ampicillin, and sulfisoxazole were 16, 32, 64, 64, and >1,024 µg/mL, respectively. Five patterns of multidrug resistance were observed among the Salmonella isolates, and the most common patterns were AAuFox (30.3%) and AAuFoxSSu (18.1%). One (3.0%) of the 33 Salmonella isolates tested positive for the class 1 integron, with a gene cassette of about 800 bp. Nucleotide sequencing revealed that this class 1 integron carried a single gene, dfrA7. Further studies are needed to determine whether the consumption of contaminated leafy green vegetables is a route for acquiring antibiotic-resistant Salmonella in Accra, Ghana.

The effect of thermal and ultrasonic treatment on amino acid composition, radical scavenging and reducing potential of hydrolysates obtained from simulated gastrointestinal digestion of cowpea proteins.

The effect of thermal and ultrasonic treatment of cowpea proteins (CP) on amino acid composition, radical scavenging and reducing potential of hydrolysates (CPH) obtained from in vitro simulated gastrointestinal digestion of CP was evaluated. Hydrolysis of native and treated CP with gastrointestinal pepsin and pancreatin yielded CPH that displayed antioxidant activities based on oxygen radical scavenging capacity (ORAC), ferric reducing antioxidant power (FRAP) and superoxide radical scavenging activity (SRSA). CPH derived from the treated CP yielded higher ORAC values than CPH from untreated proteins. However, lower significant FRAP and SRSA values were observed for these samples compared to untreated CPH (p < 0.05). Amino acid analysis indicated that CP processing decreased total sulphur-containing amino acids in the hydrolysates, particularly cysteine. The amount of cysteine appeared to be positively related to FRAP and SRSA values of CPH samples, but not ORAC. The results indicated that thermal and ultrasonic processing of CP can reduce the radical scavenging and reducing potential of the enzymatic hydrolysates possibly due to the decreased amounts of cysteine. Since the hydrolysates were generated with gastrointestinal enzymes, it is possible that the resulting compounds are produced to exert some health functions during normal consumption of cowpea.