Inactivation of Salmonella spp., Escherichia coli O157:H7 and Listeria monocytogenes in Tahini by Microwave Heating.

Tahini (sesame paste) is a traditional food. Numerous foodborne outbreaks have been associated with it. This study aimed to (i) explore the efficiency of 2450 MHz microwave heating at 220, 330, 440, 550, and 660 W on the inactivation of Salmonella spp, Escherichia coli O157:H7, and Listeria monocytogenes in tahini; (ii) determine the impact of desiccation and starvation stresses on pathogen survival; (iii) assess the impact of microwave heating on the physicochemical characteristics of tahini. The inoculated microorganisms in tahini were reduced with higher microwave power levels (p < 0.05) and longer exposure times. The D-values of unstressed Salmonella spp., Escherichia coli O157:H7, and L. monocytogenes ranged from 6.18 to 0.50 min, 6.08 to 0.50 min, and 4.69 to 0.48 min, respectively, at power levels of 220 to 660 W, with z-values of 410, 440, and 460 W, respectively. Generally, desiccation and starvation stress levels prior to heating increased microbial resistance to heat treatment. Microwave heating did not affect acid, peroxide, p-anisidine, or color values of tahini up to 90 °C. These findings reveal microwave heating as a potential method for lowering the risk of Salmonella spp., E. coli O157:H7 and L. monocytogenes in tahini with no compromise on quality.

Congenital abnormalities in dead-in-shell chicks associated with mixed bacterial infections.

Determination of the chick embryonic developmental period at which embryonic mortalities occur could help in establishing the cause of such mortalities. The late stage of embryonic development has particular importance due to its dramatic effect on life after hatching. This study was conducted to investigate the occurrence, frequency and bacterial isolates from dead-in-shell chick embryos in Northern Jordan. A total of 1,000 unhatched eggs were collected at hatching day from 10 hatcheries located in Northern Jordan. Out of 1,000 eggs, 357 (35.7%) were fertile, of which 210 (58.8%) were dead-in-shell embryos. Approximately 50.5% of the dead embryos displayed abnormalities, including neck muscles with subcutaneous petechial haemorrhages (44.3%), beak abnormalities (3.8%), eye deformities (1.9%) and anencephaly (0.5%). Sixty-six bacterial isolates were identified from 82 samples from the dead-in-shell embryos. The isolates were 22 (33.3%) Escherichia coli, 18 (27.3%) Klebsiella pneumoniae, 14 (21.2%) Staphylococcus aureus, 5 (7.6%) Pseudomonas aeruginosa, 4 (6.1%) Salmonella enteritidis, 2 (3%) Bacillus cereus and 1 (1.5%) Proteus vulgaris. Mixed growth was also recorded in 16 (19.5%) samples. There was a significant (P < 0.05) association between Escherichia coli as a bacterial isolate and the occurrence of neck and beak abnormalities. In this study, infection of check embryos with several bacterial species, particularly Escherichia coli, was identified as an important cause of multiple congenital abnormalities involving the neck and beak of unhatched chicks.

Microbial safety of oily, low water activity food products: A review.

Oily, low water activity (OL aw) products including tahini (sesame seed paste), halva (tahini halva), peanut butter, and chocolate, have been recently linked to numerous foodborne illness outbreaks and recalls. This review discusses the ingredients used and processing of OL aw products with a view to provide greater understanding of the routes of their contamination with foodborne pathogens and factors influencing pathogen persistence in these foods. Adequate heat treatment during processing may eliminate bacterial pathogens from OL aw foods; however, post-processing contamination commonly occurs. Once these products are contaminated, their high fat and sugar content can enhance pathogen survival for long periods. The physiological basis and survival mechanisms used by pathogens in these products are comprehensively discussed here. Foodborne outbreaks and recalls linked to OL aw foods are summarized and it was observed that serotypes of Salmonella enterica were the predominant pathogens causing illnesses. Further, intervention strategies available to control foodborne pathogens such as thermal inactivation, use of natural antimicrobials, irradiation and hydrostatic pressure are assessed for their usefulness to achieve pathogen control and enhance the safety of OL aw foods. Sanitation, hygienic design of manufacturing facilities, good hygienic practices, and environmental monitoring of OL aw food industries were also discussed.

Prevalence, antibiotic resistance and genotypes of Campylobacter jejuni and Campylobacter coli isolated from chickens in Irbid governorate, Jordan.

Campylobacter is the world's leading cause of bacterial gastroenteritis, causing nearly 9 million cases of food poisoning in Europe every year. Poultry is considered the main source of Campylobacter infection to humans. The objectives of the study were to determine occurrence of C. jejuni and C. coli in chickens, the antimicrobial resistance, genotypes, and relatedness of the isolates. A total of 177 chicken samples obtained from informal butcher shops (fresh), formal poultry slaughterhouses (refrigerated) and retail market (frozen) were analyzed. Isolation of Campylobacter spp. was conducted according to the ISO 10272-2006 method. Multiplex PCR was used for confirmation and identification of the isolates. The disk diffusion method was used to determine the antimicrobial resistance of the isolates and multilocus sequence typing was used for genotyping. The proportion of samples with Campylobacter spp. was 31.6% among all chicken samples (fresh and refrigerated 47.5%, frozen 0%) C. coli was isolated from 42.4% of chicken samples obtained from butcher shops and from 18.6% of samples obtained in formal slaughterhouses. C. jejuni was isolated from 17.0% of samples obtained in butcher shops and formal slaughterhouses. Campylobacter spp. was not isolated in frozen chicken samples. All tested isolates showed resistance toward ciprofloxacin and susceptibility toward imipenem and all of the isolates were multidrug resistant toward 5 or more antimicrobials. Three sequence types were identified among 10 C. coli isolates and seven sequence types were identified among 10 C. jejuni isolates. Among sequence types, chicken isolates shared similarities of both phenotypic and genetic levels.

Pesticides (Hexachlorocyclohexane, Aldrin, and Malathion) Residues in Home-Grown Eggs: Prevalence, Distribution, and Effect of Storage and Heat Treatments.

The abuse of pesticides in home gardens may lead to contamination of home-grown eggs. This study aimed to determine the prevalence of hexachlorocyclohexane (HCH), aldrin, and malathion pesticides residues in egg white and egg yolk of home-grown eggs in Jordan; and the effect of refrigerated storage and heat treatment (boiling and frying) on residues level. High-performance liquid chromatography was used to detect pesticide residues in egg samples (n = 200) obtained from households that raise laying hens in Jordan. About 96% of the tested eggs showed pesticide residues. None of the tested egg samples showed residual level above maximum residue limit (MRL 0.02 mg/kg) for HCH, whereas 33% and 44% of samples were above MRL for aldrin and malathion, respectively. All studied pesticide residues were detected from both egg yolk and egg white. The concentrations of malathion and aldrin (0.075 and 0.067 mg/kg) in egg yolk were higher than those (0.049 and 0.058 mg/kg) in egg white samples. Pesticide residue levels were quite stable during refrigeration storage whereas heat treatment (boiling at 100 °C and frying at 160 °C) significantly reduced contamination levels to values below MRL. The high level of pesticide residues in home-grown egg in Jordan may reflect the improper use of pesticides in home gardens and thus exposing the environment to unwanted pollution and the risk they may pose on human health. PRACTICAL APPLICATION: Home-grown eggs could be exposed to pesticides more than commercial eggs as free-range hens interact directly with the environment and ingest soil or materials on/in the soil that might be contaminated with pesticides used in home gardens or farms. Exploring pesticides residues in home-grown eggs and effect of refrigerated storage and heat treatment (boiling and frying) on residue levels would be useful to consumers and health authorities.

Decontamination and survival of Enterobacteriaceae on shredded iceberg lettuce during storage.

Enterobacteriaceae family can contaminate fresh produce at any stage of production either at pre-harvest or post-harvest stages. The objectives of the current study were to i) identify Enterobacteriaceae species on iceberg lettuce, ii) compare the decontamination efficiency of water, sodium hypochlorite (free chlorine 200 ppm), peroxyacetic acid (PA 80 ppm; Kenocid 2100®) or their combinations and ionizing radiation against Enterobacteriaceae on shredded iceberg lettuce and iii) determine the survival of Enterobacteriaceae post-treatment storage of shredded iceberg lettuce at 4, 10 and 25 °C, for up to 7 days. Klebsiella pneumonia spp. pneumonia, Enterobacter cloacae, Klebsiella oxytoca, Pantoea spp., Leclercia adecarboxylata and Kluyvera ascorbate were identified on iceberg lettuce. No significant difference (P≥ 0.05) among Enterobacteriaceae survival after washing with water or sanitizing with sodium hypochlorite or Kenocid 2100® (reduction ≤ 0.6 log CFU/g) were found. Combined sanitizer treatments were more effective against Enterobacteriaceae than single washing/sanitizing treatments. Sanitization of iceberg lettuce with combined washing/sanitizing treatments reduced Enterobacteriaceae by 0.85-2.24 CFU/g. Post-treatment growth of Enterobacteriaceae during storage on samples sanitized with sodium hypochlorite and Kenocid 2100® was more than on samples washed with water. The D10-value of Enterobacteriaceae on shredded iceberg lettuce was 0.21 KGy. The reduction of Enterobacteriaceae populations on iceberg after gamma radiation (0.6 KGy) was 3 log CFU/g, however, Enterobacteriaceae counts increased post-irradiation storage by 4-5 log CFU/g. Therefore, washing shredded iceberg lettuce with combined sanitizing treatment (sodium hypochlorite/sodium hypochlorite, sodium hypochlorite/Kenocid 2100®, or Kenocid 2100®/Kenocid 2100®) for total time of 6 min or exposing it to gamma irradiation (0.6 KGy) can decrease the risk of Enterobacteriaceae (reduction ≥ 2 log). Post-washing storage of sliced iceberg lettuce (4, 10, 25 °C) could increase the risk of Enterobacteriaceae as their counts increased during storage even at low temperatures.

Resistance of Campylobacter jejuni Isolated from Layer Farms in Northern Jordan Using Microbroth Dilution and Disc Diffusion Techniques.

Campylobacter jejuni is an important pathogen of significant public health importance. This pathogen is associated with human infection and has been isolated from mammals and birds. Ninety-two cloacal C. jejuni isolates were identified from 35 layer farms in Northern Jordan. Antimicrobial susceptibility was determined using minimal inhibitory concentration (MIC) and disc diffusion techniques with variable suggested breakpoints. Using MIC and EUCAST cut-off values, the study revealed a significantly high resistance level (100%) among the layers' isolates against ciprofloxacin and tetracycline. A relatively high resistance (41%) toward gentamicin and amoxicillin and low resistance to nalidixic acid (21%), erythromycin (14%), and florfenicol (6.5%) were also found. This high level of resistance may indicate abuses in the handling of antibiotics, which may require stricter control in the local layer industry. A good agreement between the 2 techniques used was demonstrated and the disc diffusion technique could be used as a rapid screening test for antimicrobial susceptibility of C. jejuni to many antibiotics using specific Campylobacter breakpoints.

Feasibility of Using Gamma Irradiation for Inactivation of Starvation-, Heat-, and Cold-Stressed Salmonella in Tahini.

Salmonella continues to be the leading cause of acute gastroenteritis and recently has been involved in infections related to edible seeds and their products, including tahini. This study investigated the (i) effectiveness of using gamma irradiation to inactivate starvation- and heat- or cold-stressed Salmonella in tahini, (ii) effect of storage on the sensitivity of stressed Salmonella to irradiation, and (iii) effect of irradiation on the chemical and physical characteristics of tahini. Tahini samples were inoculated with a cocktail of unstressed or stressed (starvation and heat or cold stress) Salmonella isolates and then exposed after storage at 21°C for 0, 7, and 30 days to gamma irradiation for up to 2.0 kGy. Additionally, the effect of irradiation on the color, peroxide, p-anisidine, and acid values of tahini were assessed. The initial level of unstressed and starvation- and heat-stressed Salmonella in tahini decreased by ca. 4.6 log CFU/g after exposure to 2.0 kGy, while cold-stressed cultures decreased by 4.5 log after exposure to 0.6 kGy. Irradiation doses of 1.0 kGy after 7 days of storage or 0.75 kGy after 30 days of storage decreased the populations of the unstressed and starvation- and heatstressed Salmonella by ca. 3.4 or 2.6 log, respectively. The D10-value of the unstressed Salmonella was 0.43 kGy. Starvation and heat stresses showed no significant effect (P > 0.05) on the calculated D10-value, whereas cold stress significantly (P < 0.05) decreased the D10-value to 0.14 kGy. Preirradiation storage for 7 and 30 days significantly decreased the D10-value to 0.31 and 0.28 kGy, respectively. An irradiation dose of 2.0 kGy did not significantly affect the color, peroxide, p-anisidine, and acid values of tahini when compared with nonirradiated samples. Therefore, this study lays the foundation for using irradiation as an effective means for minimizing the risk of Salmonella in tahini without compromising its quality.

Detection, Identification, and Prevalence of Pathogenic Vibrio parahaemolyticus in Fish and Coastal Environment in Jordan.

Vibrio parahaemolyticus is widely distributed in the marine environments and considered the leading cause of human gastroenteritis in Asian countries. A total of 150 marketed fish and 50 water and sediment samples from the Gulf of Aqaba were examined for the prevalence of pathogenic strains of V. parahaemolyticus. A total of 132 typical isolates obtained from the primary selective medium (thiosulfate-citrate bile salt sucrose agar) and showed positive biochemical properties were subjected to confirmation by polymerase chain reaction targeting the gyrB and toxR genes. These genes were confirmed at rates of 82% (108 isolates) and 72% (95 isolates), respectively. The toxR positive isolates were tested for the presence of thermolabile hemolysin (tlh), thermostable direct hemolysin (tdh), and tdh-related hemolysin (trh) virulence genes. Accordingly, the prevalence rates of pathogenic V. parahaemolyticus were 4%, 8%, and 12% in sediment, water, and fish samples, respectively. The 16S rRNA amplification and sequences were conducted for confirmation of the isolates and showing the relatedness among these isolates. The results showed that both 16S rRNA and toxR assays had same sensitivity and tested isolates had high nucleotide similarity irrespective of their sources.

Survival and growth of Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus in eggplant dip during storage.

Eggplant dip is an internationally popular appetizer, prepared in some instances under uncertain hygienic conditions with inconsistent refrigeration. This study examined the effects of citric acid on the survival of pathogenic microorganisms (Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus) and naturally present organisms (lactic acid bacteria, LAB, aerobic bacteria, APC and yeast and mold, YM) in eggplant dip during storage. Eggplant dip with 0, 0.2, 0.4, 0.6 or 0.8% citric acid was inoculated with S. Typhimurium, E. coli O157:H7 or S. aureus and stored at 4, 10 and 21 °C for ≤15 d. Throughout the study, the survival of the inoculated microorganisms was monitored, and LAB, APC, YM numbers and pH were determined. There was no significant (p>0.05) effect of citric acid on inoculated S. Typhimurium and E. coli O157:H7. Salmonella and E. coli O157:H7 survived >7d with little reduction in viability. Reduction of S. aureus viability increased with citric acid concentration and reached>3.0 log10 CFU/g by 15 d at 4 °C. Citric acid had no effect (p>0.05) on the background YM during storage at 4, 10 and 21 °C or LAB stored at 4 and 10 °C, while at 21 °C, 0.6 and 0.8% citric acid significantly reduced LAB. Citric acid had no effect (p>0.05) on the APC in samples stored at 4 °C but it had significant effects on samples stored at 10 and 21 °C. Work reported showed that the use of citric acid at 0.4-0.8% can inhibit the growth of S. aureus in eggplant dip, but adequate refrigeration is essential to minimize risk from this and other pathogens in this product.

Prevalence and antimicrobial susceptibility of Escherichia coli O157:H7 on beef cattle slaughtered in Amman abattoir.

Cattle are the main asymptomatic reservoir of Escherichia coli O157:H7 which can cause illness to human. The objectives of the study were to measure the prevalence of E. coli O157:H7 on cattle slaughtered in Amman abattoir, detect virulence factors in the isolates, determine antibacterial resistance of the isolates, and know how the isolates are different or similar when compared to characterized isolates from developed countries. A total of 540 samples (feces, hide, and carcass) were tested for E. coli O157:H7 using the method of ISO 16654:(E). Conventional and multiplex PCR assays were used for serotype confirmation and virulence factor detection, respectively. Fifty E. coli O157:H7 isolates were identified and virulence factors eaeA and hlyA were present in all of the isolates. 60%, 12%, and 22% of the isolates harbored stx(1), stx(2), and stx(1) and stx(2), respectively. The prevalence rates of enterotoxigenic E. coli O157:H7 (n=47) were 8.3%, 10%, and 7.8% in feces, hides and carcasses, respectively. The antimicrobial profiles of the isolates showed an extensive resistance to erythromycin, neomycin and vancomycin and high sensitivity to ampicillin, ciprofloxacin, gentamicin, kanamycin and tetracycline.

Occurrence and antimicrobial susceptibility of Listeria monocytogenes isolated from brined white cheese in Jordan.

Listeria monocytogenes is a serious foodborne pathogen that has been isolated from different dairy food products. Several foodborne outbreaks of listeriosis have been associated with consumption of cheese. The aims of this study were to determine the occurrence of L. monocytogenes and Listeria spp. in brined white cheese (BWC) sold in Jordan, and to determine the susceptibility of isolated L. monocytogenes to antimicrobials. Three hundred and fifty samples of 5 different types of BWC (akkawi, boiled, halloumi, pasteurized, and shellal) were collected from a local market in Jordan. The ISO (11290-1) procedure was followed for isolation and identification of Listeria spp. from cheese samples and a polymerase chain reaction (PCR) technique was used for confirmation of L. monocytogenes isolates. The VITEK2 automated system was used for testing antimicrobial susceptibility of L. monocytogenes isolates. The overall prevalence of Listeria spp. in cheese sample was 27.1%. L. monocytogenes was isolated from 39 (11.1%) samples. Other isolated species were L. grayi (6.9%), L. innocua (2%), L. ivanovii (4%), L. seeligeri (2%), and L. welshimeri (0.3%). The pH values and salt concentrations of L. monocytogenes positive cheese samples ranged from 5.10 to 6.32 and 5.64 to 13.16, respectively. L. monocytogenes isolates were sensitive or intermediate susceptible to imipenem, gentamicin, linezolid, teicoplanin, vancomycin, fusidic acid, trimethoprim/sulfamethoxazole, benzylpenicillin, ciprofloxacin, erythromycin, tetracycline, and rifampicin, but resistant to fosfomycin, oxacillin, and clindamycin.

Prevalence and antimicrobial susceptibility of Campylobacter spp. in live and dressed chicken in Jordan.

A total of 140 broiler flocks presented for slaughtering at Amman slaughterhouse were tested for Campylobacter spp. via collection of cloacal swabs from live birds, feathered skin samples at prescalding, and skin samples at postscalding (62°C or 57°C scalding temperature), postevisceration, and postchilling. The results indicated that 40% of the flocks tested by cloacal swabs, 34% at prescalding, 32% at post 57°C scalding, and 32% postevisceration were harboring Campylobacter jejuni. None of the skin samples collected from dressed birds at postscalding (62°C) or postwashing-chilling steps (regardless of scalding temperature) revealed the presence of C. jejuni. Thirty eight isolates were tested for susceptibility to ten antimicrobials by using the microbroth dilution method. Almost 50% of the isolates were multidrug resistant to 9 or 10 out of the ten tested antimicrobials. The other half of tested isolates were sensitive to erythromycin, tetracycline, doxycyclin, chlortetracycline, ciprofloxacin, enorfloxacin, gentamycin, tilmicosin, amoxicillin, and trimethoprim.

Escherichia coli O157:H7 facilitates the penetration of Staphylococcus aureus into table eggs.

Fresh eggshells collected from a local farm were subjected to different levels of surface contamination with feces containing different levels (3 to 5 log10) of Escherichia coli O157:H7 or Staphylococcus aureus and incubated at 3 different temperatures (10, 25, and 32 °C). The penetration rates of contaminating bacteria were followed throughout the incubation period by tracing bacterial presence in shell, shell membranes, albumen, and yolk. The study revealed the ability of both E. coli O157:H7 and enterotoxigenic S. aureus to grow on shell in feces, penetrate the shell, and move and multiply within egg contents at different rates and periods depending on bacterial type and incubation conditions. High temperatures (25 and 32 °C) increased penetration rate, whereas storage at 10 °C decreased significantly the rate of penetration. High levels of contamination with E. coli O157:H7 also shortened the time needed for the penetration process. Results showed that when eggshells were contaminated with both organisms simultaneously, the penetration of E. coli O157:H7 preceded that of S. aureus and facilitated the invasion of the latter bacteria.