Application of gelatin-based zinc oxide nanoparticles bionanocomposite coatings to control Listeria monocytogenes in Talaga cheese and camel meat during refrigerated storage.

Listeria monocytogenes is a concerning foodborne pathogen incriminated in soft cheese and meat-related outbreaks, highlighting the significance of applying alternative techniques to control its growth in food. In the current study, eco-friendly zinc oxide nanoparticles (ZnO-NPs) were synthesized using Rosmarinus officinalis, Punica granatum, and Origanum marjoram extracts individually. The antimicrobial efficacy of the prepared ZnO-NPs against L. monocytogenes was assessed using the agar well diffusion technique. Data indicated that ZnO-NPs prepared using Origanum marjoram were the most effective; therefore, they were used for the preparation of gelatin-based bionanocomposite coatings. Furthermore, the antimicrobial efficacy of the prepared gelatin-based bionanocomposite coatings containing eco-friendly ZnO-NPs was evaluated against L. monocytogenes in Talaga cheese (an Egyptian soft cheese) and camel meat during refrigerated storage at 4 ± 1 oC. Talaga cheese and camel meat were inoculated with L. monocytogenes, then coated with gelatin (G), gelatin with ZnO-NPs 1% (G/ZnO-NPs 1%), and gelatin with ZnO-NPs 2% (G/ZnO-NPs 2%). Microbiological examination showed that the G/ZnO-NPs 2% coating reduced L. monocytogenes count in the coated Talaga cheese and camel meat by 2.76 ± 0.19 and 2.36 ± 0.51 log CFU/g, respectively, by the end of the storage period. Moreover, G/ZnO-NPs coatings controlled pH changes, reduced water losses, and improved the sensory characteristics of Talaga cheese and camel meat, thereby extending their shelf life. The obtained results from this study indicate that the application of gelatin/ZnO-NPs 2% bionanocomposite coating could be used in the food industry to control L. monocytogenes growth, improve quality, and extend the shelf life of Talaga cheese and camel meat.

Rapid and sensitive in situ detection of heavy metals in fish using enhanced Raman spectroscopy.

Heavy metals have been widely applied in industry, agriculture, and other fields because of their outstanding physics and chemistry properties. They are non-degradable even at low concentrations, causing irreversible harm to the human and other organisms. Therefore, it is of great significance to develop high accuracy and sensitivity as well as stable techniques for their detection. Raman scattering spectroscopy and atomic absorption spectrophotometer (AAS) were used parallelly to detect heavy metal ions such as Hg, Cd, and Pb of different concentrations in fish samples. The concentration of the heavy metals is varied from 5 ppb to 5 ppm. Despite the satisfactory recoveries of AAS, their drawbacks are imperative for an alternative technique. In Raman scattering spectroscopy, the intensities and areas of the characteristic peaks are increased with increasing the concentration of the heavy metals. For Hg concentration ≥ 1 ppm, a slight shift is observed in the peak position. The obtained values of peak intensity and peak area are modeled according to Elvoich, Pseudo-first order, Pseudo-second order, and asymptotic1 exponential model. The best modeling was obtained using the Elovich model followed by the asymptotic1 exponential model. The introduced Raman spectroscopy-based approach for on-site detection of trace heavy metal pollution in fish samples is rapid, low-cost, and simple to implement, increasing its visibility in food safety and industrial applications.

Effect of chitosan-gelatin coating fortified with papaya leaves and thyme extract on quality and shelf life of chicken breast fillet and Kareish cheese during chilled storage.

A novel antimicrobial chitosan-gelatin based edible coating fortified with papaya leaves and thyme extract was prepared for improving the quality and shelf-life of chicken breast fillet and Kareish cheese during chilled storage at 4 ± 1 °C. The samples were dipped for 10 min in distilled water (control), chitosan-gelatin (CG), chitosan-gelatin +2% papaya leaves extract (CG + P) and chitosan-gelatin +2% thyme extract (CG + Th). The coated and uncoated samples were examined periodically for sensory attributes, pH, TBARs, total aerobic mesophilic (TAM), total Enterobacteriaceae (TE), and total yeasts and molds counts (TYM). Sensory evaluation revealed that chicken breast fillet and Kareish cheese samples coated with CG + P were the best in terms of tenderness, juiciness, body & texture and flavor. CG + Th exhibited the highest antimicrobial and antioxidant effect, followed by CG + P. The results of microbiological, physicochemical and sensory analysis of this study demonstrated that the application of CG + P or CG + Th could be a promising method for increasing the shelf life and improving the quality of chicken breast fillet and Kareish cheese.

Subclinical Mastitis in Selected Bovine Dairy Herds in North Upper Egypt: Assessment of Prevalence, Causative Bacterial Pathogens, Antimicrobial Resistance and Virulence-Associated Genes.

Mastitis is a significant disease affecting dairy cattle farms in Egypt. The current study aimed to investigate the prevalence and major bacterial pathogens causing subclinical mastitis (SCM) in three bovine dairy herds, with a history of SCM, at three Governorates in North Upper Egypt. The antimicrobial resistance profiles and specific virulence-associated genes causing bovine SCM were investigated. One thousand sixty-quarter milk samples (QMS) were collected aseptically from 270 apparently healthy cows in three farms and examined. The total prevalence of SCM was 46% and 44.8% based on California Mastitis Test (CMT) and Somatic Cell Count (SCC), respectively. Bacteriological examination of CMT positive quarters revealed that the prevalence of bacterial isolation in subclinically mastitic quarters was 90.4% (26 and 64.3% had single and mixed isolates, respectively). The most frequent bacterial isolates were E. coli (49.8%), Staphylococcus aureus (44.9%), streptococci (44.1%) and non-aureus staphylococci (NAS) (37.1%). Antimicrobial susceptibility testing of isolates revealed a high degree of resistance to the most commonly used antimicrobial compound in human and veterinary medicine. Implementation of PCR revealed the presence of mecA and blaZ genes in 60% and 46.7% of S. aureus isolates and in 26.7% and 53.3% of NAS, respectively. Meanwhile 73.3% of streptococci isolates harbored aph(3')-IIIa gene conferring resistance to aminoglycosides and cfb gene. All E. coli isolates harbored tetA gene conferring resistance to tetracycline and sul1 gene conferring resistance to sulfonamides. The fimH and tsh genes were found in 80% and 60%, respectively. A significant association between the phenotypes and genotypes of AMR in different bacteria was recorded. The presence of a high prevalence of SCM in dairy animals impacts milk production and milk quality. The coexistence of pathogenic bacteria in milk is alarming, threatens human health and has a public health significance. Herd health improvement interventions are required to protect human health and society.

Prevalence, Characterization, and Control of Campylobacter jejuni Isolated from Raw Milk, Cheese, and Human Stool Samples in Beni-Suef Governorate, Egypt.

Our study aimed to determine the prevalence of Campylobacter jejuni isolated from raw milk, cheese, and human stool samples in Beni-Suef Governorate, Egypt, and to characterize the antibiotic resistance profile and virulence genes of the isolates. An additional objective was to evaluate the effectiveness of cinnamon oil and Lactobacillus acidophilus La5 for controlling C. jejuni in cheese. A total of 200 samples of raw milk and dairy products, including 50 samples of raw milk and 150 samples of three different types of cheese were used. Fifty-three human stool samples were also collected. The samples were tested for the presence of C. jejuni using culture and molecular methods. Campylobacter spp. were isolated from 9.5% (19/200) of the raw milk and cheese samples. The highest prevalence was observed in milk samples (18%), followed by Kareish cheese (14%) and Talaga cheese (6%). In contrast, C. jejuni was not found in any of the Feta cheese samples. Of the human stool samples, 21 (39.6%) were positive for C. jejuni. Of the isolates, 60-90% were highly resistant to the antimicrobial agents tested, that is, nalidixic acid, ciprofloxacin, and tetracycline. Virulent cadF and cdtA genes were detected in all isolates. As milk and dairy products are important sources of contamination, reducing the level of C. jejuni in them will lower the risk to consumers. We showed that L. acidophilus La5 was able to control C. jejuni in Kareish cheese, but cinnamon oil was less effective.

Prevalence and Survival of Stenotrophomonas Species in Milk and Dairy Products in Egypt.

Stenotrophomonas maltophilia is a nosocomial, multidrug-resistant pathogen that causes significant economic losses in milk production and deterioration of dairy product quality. This study investigates the prevalence and the survival of S. maltophilia under different food preservation conditions. A total of 240 samples, including farm-sourced milk, dairy shop purchased milk, Kareish cheese, Domiati cheese, ice cream, yoghurt, cooking butter, and unpasteurized cream were collected from various locations in Beni-Suef Governorate, Egypt. Thirty samples of each product were analyzed by standard biochemical tests for the presence of Stenotrophomonas spp., which was isolated from 36% (87/240) of the examined samples. The highest prevalence was observed in ice cream (80%), followed by unpasteurized cream (67%), whereas the lowest incidence was in Domiati cheese (3.3%). S. maltophilia, identified by PCR, was found only in unpasteurized cream (13%), cooking butter (10%), ice cream (6.7%), and dairy shop milk (3.3%). We also studied the viability of S. maltophilia in laboratory manufactured cream, butter, and cheese under different preservation conditions. S. maltophilia was able to survive for 30, 30, 28, 30, and 8 d in the inoculated cream, butter 0% salt, butter 3% salt, cheese 0% salt, and cheese 6% salt, respectively. Thus, S. maltophilia was able to survive more than predicted in all products in this study. This suggests that strains of S. maltophilia may develop adaptive strategies that enable survival under different food preservation conditions, which contradicts previous knowledge about the sensitivity of this microbe to environmental stress conditions. Our overall aim was to draw attention to the prevalence and future potential for increased public health significance of Stenotrophomonas spp.

Treatment of Brucellosis in Guinea Pigs via a Combination of Engineered Novel pH-Responsive Curcumin Niosome Hydrogel and Doxycycline-Loaded Chitosan-Sodium Alginate Nanoparticles: an In Vitro and In Vivo Study.

Brucellosis is a common zoonotic infection, particularly in the developing world. The recommended treatment regimens for brucellosis involve the use of two medications such as doxycycline and curcumin in order to avoid relapses and prolonged use of these drugs. Doxycycline has excellent activity in the acidic phagolysosomal environment, while curcumin modulates the immune system function and macrophage activity. Due to the intracellular existence of Brucellae and the different anti-immune mechanisms of Brucella, the treatment of Brucella infection faces many limitations. The design of nanosystems is a promising treatment approach for brucellosis. The objective of this study was to design and evaluate the efficacy of in situ pH-responsive curcumin-loaded niosome hydrogel and doxycycline-loaded chitosan-sodium alginate nanoparticles as chemotherapeutic agents against brucellosis. The prepared formulae showed a spherical nano shape with a slow drug release pattern and small particle size. The prepared formulae were evaluated in vivo using Guinea pigs experimentally infected with Brucella melitensis biovar3. The prepared formula combination gave a significant high reduction rate of Brucella spleen viable count compared with that of untreated controls at p < 0.05. The results showed that the treatment schemes were not fully successful in eliminating Brucella infection in Guinea pigs; however, they significantly (p < 0.05) reduced the viable Brucella count in a shorter time and sub-therapeutic doses. Collectively the novel prepared formulae could be a successful therapy for the effective treatment of brucellosis infection at the recommended therapeutic doses. Graphical abstract.

Nanozyme-Mediated Dual Immunoassay Integrated with Smartphone for Use in Simultaneous Detection of Pathogens.

Nanozymes are an excellent class of optical reporters for the development of sensitive biosensors for widespread applications. In this study, mesoporous core-shell palladium@platinum (Pd@Pt) nanoparticles were synthesized and then applied as signal amplifier in a dual lateral flow immunoassay (LFIA) and integrated with a smartphone-based device for use in simultaneous detection of Salmonella Enteritidis and Escherichia coli O157:H7. After optimization, the limit of detections were calculated to be ∼20 cfu/mL for S. Enteritidis and ∼34 cfu/mL for E. coli O157:H7, respectively. The greatly improved sensitivity was contributed by the peroxidase-like catalytic activity of the Pd@Pt nanoparticles for signal enhancement and the parallel design of dual detection for eliminating the cross-interference. The estimated recoveries of the dual LFIA range from 91.44 to 117.00%, which indicated that the developed method is capable of detecting live bacteria in food samples. This approach provides an attractive platform for S. Enteritidis and E. coli O157:H7 detection using a smartphone-based device as the sole piece of equipment, indicating great promise for foodborne pathogen analysis or in-field food safety tracking.

A 3D-Printed, Portable, Optical-Sensing Platform for Smartphones Capable of Detecting the Herbicide 2,4-Dichlorophenoxyacetic Acid.

Onsite rapid detection of herbicides and herbicide residuals in environmental and biological specimens are important for agriculture, environmental concerns, food safety, and health care. The traditional method for herbicide detection requires expensive laboratory equipment and a long turnaround time. In this work, we developed a single-stripe microliter plate smartphone-based colorimetric device for rapid and low-cost in-field tests. This portable smartphone platform is capable of screening eight samples in a single-stripe microplate. The device combined the advantages of small size (50 × 100 × 160 mm3) and low cost ($10). The platform was calibrated by using two different dye solutions, i.e. methyl blue (MB) and rhodamine B, for the red and green channels. The results showed good correlation with results attained from a traditional laboratory reader. We demonstrated the application of this platform for detection of the herbicide 2,4-dichlorophenoxyacetic acid in the range of 1 to 80 ppb. Spiked samples of tap water, rat serum, plasma, and human serum were tested by our device. Recoveries obtained varied from 95.6% to 105.2% for all of the spiked samples using the microplate reader and from 93.7% to 106.9% for all of the samples using the smartphone device. This work validated that the smartphone optical-sensing platform is comparable to the commercial microplate reader; it is eligible for onsite, rapid, and low-cost detection of herbicides for environmental evaluation and biological monitoring.

Impact of Seasonal Conditions on Quality and Pathogens Content of Milk in Friesian Cows.

Heat stress negatively affects milk quality altering its nutritive value and cheese making properties. This study aimed at assessing the impact of seasonal microclimatic conditions on milk quality of Friesian cows. The study was carried out in a dairy farm from June 2013 to May 2014 at Beni-Suef province, Egypt. Inside the barn daily ambient temperature and relative humidity were recorded and used to calculate the daily maximum temperature-humidity index (mxTHI), which was used as indicator of the degree of heat stress. The study was carried out in three periods according to the temperature-humidity index (THI) recorded: from June 2013 to September 2013 (mxTHI>78), from October 2013 to November 2013 (mxTHI 72-78) and from December 2013 to April 2014 (mxTHI<72). Eighty Friesian lactating dairy cows were monitored in each period. The three groups of cows were balanced for days in milk and parity. Milk quality data referred to somatic cell count, total coliform count (TCC), faecal coliform count (FCC), Escherichia coli count, percentage of E. coli, and Staphylococcus aureus, percentage of fat, protein, lactose, total solid and solid non-fat. Increasing THI was associated with a significant decrease in all milk main components. An increase of TCC, FCC, and E. coli count from mxTHI<72 to mxTHI>78 was observed. In addition, the isolation rate of both S. aureus and E. coli increased when the mxTHI increased. The results of this study show the seriousness of the negative effects of hot conditions on milk composition and mammary gland pathogens. These facts warrant the importance of adopting mitigation strategies to alleviate negative consequences of heat stress in dairy cows and for limiting related economic losses.

Heavy Metal Dietary Intake and Potential Health Risks for University Hostel Students.

The study was conducted to determine the residual concentration of Cd, Pb, Asand Hg in some foodstuffs served to university students living at hostels of Beni-Suef University (BSU), Egypt, and to estimate the dietary intake of such metals, as well as to assess the potential health risks associated with the consumption of such foods. Therefore, a total of 200 samples, 50 each of, soft cheese, UHT milk, raw broiler carcasses and canned tuna, were periodically collected from university hostels of BSU and examined for the residual levels of these metals using atomic absorption spectrophotometer. The obtained results revealed that the mean residual levels of Cd in soft cheese, UHT milk, broiler's meat and canned tuna samples were 0.37, 0.26, 0.089 and 0.093 mg/kg, respectively, while those of Pb were 0.187, 0.20, 0.181 and 0.164 mg/kg, respectively. Regarding As, they were 0.196, 0.24, 0.14 and 0.201 mg/kg, respectively, and Hg mean residual concentration accounted for 0.05, 0.05, 0.117 and 0.235 mg/kg, respectively. Some of the examined food samples had heavy metals' concentrations above the international standards. The total weekly dietary intakes of Cd, Pb, As and Hg were 4.99, 5.38, 4.77 and 2.76 µg/kg bw/week, respectively, that were comparable to the provisional tolerable weekly intake recommended by the Joint Expert Committee on Food Additives (JECFA). The total target hazard quotient (TTHQ) of broiler's meat was over 1 (1.686), thus indicating possible health risks in contrast to the TTHQs of other foodstuffs that were below one.

The Use of Multiplex PCR to Determine the Prevalence of Enterotoxigenic Staphylococcus aureus Isolated from Raw Milk, Feta Cheese, and Hand Swabs.

Staphylococcus aureus (S. aureus) can cause mastitis in cattle and, therefore, can be present in milk. This study was undertaken to determine the prevalence of coagulase positive S. aureus and its enterotoxin genes sea, seb, and sec in isolates recovered from raw milk, feta cheese, and human hand swabs of milk and cheese handlers in Beni-Suef province, Egypt. A total of 100 samples of raw milk and 50 samples of pasteurized-milk feta cheese were collected. In addition, 50 hand swabs from milk handlers and 25 hand swabs from cheese handlers were examined for the presence of coagulase positive S. aureus. The isolates were characterized by multiplex PCR for detection of sea, seb, and sec genes, and for resistance to 5 classes of commonly used antibiotics. Twelve (12/100), 12 (6/50), and 17% (13/75) of milk, cheese, and hand swab samples, respectively, were positive for coagulase positive S. aureus. One isolate was obtained from each positive sample (31 isolates), and none contained genes for SEA or SEC production. Twenty-five percent, 33%, and 31%, respectively, of the isolates contained the genes for SEB, resulting in 3%, 4%, and 5% of samples being positive for toxin producing coagulase positive S. aureus, respectively. At least one isolate was resistant to each of the antibiotics tested. Despite the low potential for SEB production shown, preventative measures, such as maintenance of the cold-chain and good hygienic practices should be implemented to further reduce the potential risk to public health from SEB, and to reduce the spread of antimicrobial resistance.