Efficacy of the thin agar layer method for the recovery of stressed Cronobacter spp. (Enterobacter sakazakii)

Cronobacter spp. (Enterobacter sakazakii) are emerging opportunistic pathogens for all age groups, and are of particular concern when it comes to infants. Prior to contaminating food, the organism may be exposed to a variety of stresses, leading to a generation of sublethally injured cells that may not be detected by selective media unless a protracted recovery period is included in the isolation procedure. This study evaluated the efficacy of the thin agar layer (TAL) method for the recovery of Cronobacter cells that had been exposed to various stress conditions. Five strains of C. sakazakii and C. muytjensii were exposed to starvation, heat, cold, acid, alkaline, chlorine, or ethanol, with or without further exposure to desiccation stress. The recovery of the stressed cells was determined on tryptone soy agar (TSA; nonselective control medium), violet red bile glucose agar (VRBGA; selective agar), Druggan-Forsythe-Iversen (DFI; selective agar), and TAL media (viz., VRBGA overlaid with TSA, and DFI overlaid with TSA). Regardless of stress type, there were no significant differences among the recoveries of stressed desiccated Cronobacter spp. cultures on TSA, DFI+TSA, and VRBGA+TSA, but there was significantly less recovery on VRBGA. The recovery of prestressed desiccated Cronobacter spp. on DFI+TSA was similar to that on TSA, whereas the recovery on VRBGA+TSA was lower. DFI+TSA performed better than VRBGA+TSA did in differentiating Cronobacter spp. within mixed bacterial cultures. The results of this study suggest the use of the TAL method DFI+TSA as an improved method for the direct recovery of stressed Cronobacter spp.     

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.     

Technical control of nanoparticle emissions from desktop 3D printing

Material extrusion (ME) desktop 3D printing is known to strongly emit nanoparticles (NP), and the need for risk management has been recognized widely. Four different engineering control measures were studied in real-life office conditions by means of online NP measurements and indoor aerosol modeling. The studied engineering control measures were general ventilation, local exhaust ventilation (LEV), retrofitted enclosure, and retrofitted enclosure with LEV. Efficiency between different control measures was compared based on particle number and surface area (SA) concentrations from which SA concentration was found to be more reliable. The study found out that for regular or long-time use of ME desktop 3D printers, the general ventilation is not sufficient control measure for NP emissions. Also, the LEV with canopy hood attached above the 3D printer did not control the emission remarkably and successful position of the hood in relation to the nozzle was found challenging. Retrofitted enclosure attached to the LEV reduced the NP emissions 96% based on SA concentration. Retrofitted enclosure is nearly as efficient as enclosure attached to the LEV (reduction of 89% based on SA concentration) but may be considered more practical solution than enclosure with LEV.     

Thermal inactivation of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in breaded pork patties

ABSTRACT:  Decimal reduction times ( D -values) and thermal resistance constants ( z -values) for 3 foodborne pathogenic bacteria in formulated ready-to-eat breaded pork patties were determined with thermal inactivation studies. Meat samples, inoculated with Escherichia coli O157:H7, Salmonella , and Listeria monocytogenes cultures or uninoculated controls, were packaged in sterile bags, immersed in circulated water bath, and held at 55, 57.5, 60, 62.5, 65, 67.5, and 70 °C for different durations of time. The D - and z -values were determined by using a linear regression model. Average calculated D -values for E. coli O157:H7, Salmonella , and L . monocytogenes at a temperature range of 55 to 70 °C were 32.11 to 0.08 min, 69.48 to 0.29 min, and 150.46 to 0.43 min, respectively. Calculated z -values for E. coli O157:H7, Salmonella , and L. monocytogenes were 5.4, 6.2, and 5.9 °C, respectively. The results of this study will be useful to food processors to validate thermal lethality of the studied foodborne pathogens in ready-to-eat breaded pork patties.     

Thermal lethality of salmonella in chicken leg quarters processed via an air/steam impingement oven

Chicken leg quarters were injected with 0.1 ml of the cocktail culture per cm2 of the product surface area to contain about 7 log(CFU/g) of Salmonella. The inoculated leg quarters were processed in an air/steam impingement oven at an air temperature of 232 degrees C, an air velocity of 1.4 m/s, and a relative humidity of 43%. The endpoint product temperatures were correlated with the cooking times. A model was developed for pathogen thermal lethality up to 7 log(CFU/g) reductions of Salmonella in correlation to the product mass (140 to 540 g) and cooking time (5 to 35 min). The results from this study are useful for validating thermal lethality of pathogens in poultry products that are cooked via impingement ovens.     

Heavy metals in vegetables sold in the local market in Jordan

Heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) in various vegetables (cabbage, green onion, lettuce, parsley, rocket, spinach, carrot, onion, potato and cauliflower) from the market in Jordan were measured using inductively coupled plasma-mass spectrometry. As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn ranged from 0.009–0.275 mg kg^?1 wet weight, 0.004–0.060 mg kg^?1, 0.003–0.401 mg kg^?1, 0.105–3.51 mg kg^?1, 0.15–1.15 mg kg^?1, 0.93–14.39 mg kg^?1, 0.044–0.702 mg kg^?1, 0.072–0.289 mg kg^?1 and 2.23–6.65 mg kg^?1, respectively. Parsley, followed by spinach, contained the highest concentration of heavy metals. Onion contained high levels of toxic heavy metals. The content of Cu in parsley and spinach and Pb in onion exceeded the Codex limits. However, the daily intake of heavy metals from the tested vegetables was lower than the maximum limits for allowable intake.     

Inhibition of Cronobacter sakazakii by Heat Labile Bacteriocins Produced by Probiotic LAB Isolated from Healthy Infants

Cronobacter sakazakii is an opportunistic pathogen that can cause bacteremia, meningitis, and necrotizing enterocolitis, most often in neonates with case‐fatality rates that may reach 80%. The antimicrobial activity of lactic acid bacteria against a wide range of foodborne pathogens is well‐established in different types of food products. The objective of the current study was to investigate the antibacterial activity of Lactobacillus acidophilus and L. casei isolated from feces of healthy infants against different strains of C. sakazakii in agar and a rehydrated infant milk formula (RIMF) model. The inhibition zones of C. sakazakii around L. acidophilus or L. casei ranged from 22 to 32 mm on eMan Rogosa Sharpe (MRS) agar under aerobic conditions, while a slight reduction in antibacterial activity was noted on modified MRS (0.2% glucose) under anaerobic conditions. It was observed that pH‐neutralized cell‐free supernatant (CFS) of L. acidophilus or L. casei was inhibitory against tested C. sakazakii strains. The inhibition zones of neutralized CFS were lower than the antibacterial activities of live cultures. The antibacterial activity of CFS was abolished when CFS from L. acidophilus or L. casei was heated at 60 or 80 °C for either 10 min or 2 h, or treated with trypsin or pepsin. This was considered strong evidence that the inhibition was due to the production of bacteriocins by L. casei and L. acidophilus. Both the CFS and active growing cells of L. casei and L. acidophilus were able to reduce the viability of C. sakazakii in the RIMF model. The results may extend the use of natural antimicrobials instead of conventional preservation methods to improve the safety of RIMF.     

Arsenic pollution in groundwater: a self-organizing complex geochemical process in the deltaic sedimentary environment,Bangladesh

The presence of considerable concentrations of As (Sonargon: below detection limit (bdl)-1.46 mg/l; Faridpur: bdl-1.66 mg/l) and some other elements (like B, F, U) in groundwater of the Ganges-Meghna-Brahmaputra (G-M-B) rivers flood plain indicate that several millions of people are consuming contaminated water. Conditions regulating the mobilization and diagenetic behavior of arsenic in sediments are not well characterized, although understanding these conditions is essential in order to predict the modes of transfer of this contaminant from sediments to groundwater. Analyses of vertical profiles of total arsenic and iron as well as easily soluble As and reducible (reactive) iron concentrations in sediments of the Ganges and Meghna flood plains show no arsenic-enriched layer up to 36-m depth. However, arsenic content in sediments is relatively higher than mean crustal concentration, showing some peaks (Sonargaon: 27.9 mg/kg; 3 m, 31.5 mg/kg; 9 m, 27.30 mg/kg; 16 m, 37.70 mg/kg; 29.5 m, Faridpur: 19.80 mg/kg; 6 m, 26.60 mg/kg; 14.5 m, 29.40 mg/kg; 25 m) depending on the periodical differences in sedimentary cycling of arsenic, metal (hydr)oxides and organic matter. Seasonal changes have no clear or consistent effect on the groundwater arsenic concentrations; with the exception of a small-scale localized irregular change (10-16%). However, easily reducible metal oxides and hydroxides were significant factors affecting the retention of arsenic by sediments during leaching. The biogeochemical cycling of arsenic and iron is closely coupled in deltaic systems where iron oxy-hydroxides provide a carrier phase for the deposition of arsenic in sediments. Analytical results of mimic leaching experiments strongly supported the reduction (Fe oxy-hydroxides) mechanism for arsenic mobilization in alluvial aquifer of deltaic sedimentary environment of G-M-B rivers flood plain.