Salmonella Biofilm Formation under Fluidic Shear Stress on Different Surface Materials.

This study characterized biofilm formation of various Salmonella strains on common processing plant surface materials (stainless steel, concrete, rubber, polyethylene) under static and fluidic shear stress conditions. Surface-coupons were immersed in well-plates containing 1 mL of Salmonella (6 log CFU/mL) and incubated aerobically for 48 h at 37 °C in static or shear stress conditions. Biofilm density was determined using crystal violet assay, and biofilm cells were enumerated by plating on tryptic soy agar plates. Biofilms were visualized using scanning electron microscopy. Data were analyzed by SAS 9.4 at a significance level of 0.05. A surface-incubation condition interaction was observed for biofilm density (p < 0.001). On stainless steel, the OD600 was higher under shear stress than static incubation; whereas, on polyethylene, the OD600 was higher under static condition. Enumeration revealed surface-incubation condition (p = 0.024) and surface-strain (p < 0.001) interactions. Among all surface-incubation condition combinations, the biofilm cells were highest on polyethylene under fluidic shear stress (6.4 log/coupon; p < 0.001). Biofilms of S. Kentucky on polyethylene had the highest number of cells (7.80 log/coupon) compared to all other strain-surface combinations (p < 0.001). Electron microscopy revealed morphological and extracellular matrix differences between surfaces. Results indicate that Salmonella biofilm formation is influenced by serotype, surface, and fluidic shear stress.

Effects of broiler genetic strain and dietary amino acid reduction on (part I) growth performance and internal organ development.

Genetic selection in broilers has resulted in improved growth performance, meat yield, and feed conversion efficiency. However, consumers have become increasingly concerned about modern broiler welfare that is related to their rapid growth rate, which may be alleviated by nutrient dilution. This study was conducted to investigate the effects of dietary amino acid (AA) reduction on the growth performance and internal organ development of different genetic strains of broilers. A randomized completed block design with a factorial arrangement of 10 treatments (5 strains × 2 AA levels) was used. The 5 different strains of broilers were fed either a control diet, with digestible AA (lysine, total sulfur AA, and threonine) at the highest recommended levels for the 5 strains, or an AA-reduced diet, with the digestible AA being 20% lower than the control diet. Feed conversion ratio was increased by AA reduction in all 5 strains during day 0-14, 14-28, and 28-41 but was not affected from day 41-55. Body weight and feed intake responses to AA reduction varied in the different strains and ages of birds. Liver weight relative to BW on day 40, and weights of the duodenum and jejunum relative to BW on day 60 were increased by decreasing the dietary AA concentration. These results indicate that the birds had adjusted their organ growth and metabolism in response to increases in digestion, absorption, and utilization efficiency to accommodate a decrease in dietary AA content. Surprisingly, the cost of feed required to produce the same BW was decreased in 4 of 5 strains on both day 41 and 55, which was largely because of the lower price of the diets containing reduced AA levels and the later compensatory growth experienced by the birds fed AA-reduced diets. In the future, when dietary AA levels need to be adjusted to control growth rate and improve welfare status, the genetic strain, age of the birds, and targeted goals need to be taken into consideration.

Technological characteristics of pre- and post-rigor deboned beef mixtures from Holstein steers and quality attributes of cooked beef sausage.

The objective of this study was to determine the effects of deboning time (pre- and post-rigor), processing steps (grinding - GB; salting - SB; batter formulation - BB), and storage time on the quality of raw beef mixtures and vacuum-packaged cooked sausage, produced using a commercial formulation with 0.25% phosphate. The pH was greater in pre-rigor GB and SB than in post-rigor GB and SB (P < .001). However, deboning time had no effect on metmyoglobin reducing activity, cooking loss, and color of raw beef mixtures. Protein solubility of pre-rigor beef mixtures (124.26 mg/kg) was greater than that of post-rigor beef (113.93 mg/kg; P = .071). TBARS were increased in BB but decreased during vacuum storage of cooked sausage (P ≤ .018). Except for chewiness and saltiness being 52.9 N-mm and 0.3 points greater in post-rigor sausage (P = .040 and 0.054, respectively), texture profile analysis and trained panelists detected no difference in texture between pre- and post-rigor sausage.

Salmonella enterica growth and biofilm formation in flesh and peel cantaloupe extracts on four food-contact surfaces.

Salmonella enterica is responsible for the highest number of foodborne disease outbreaks pertaining to cantaloupe industry. The objective of this study was to examine the growth and biofilm formation by outbreak strains of S. enterica ser. Poona (S. Poona), S. enterica ser. Stanley (S. Stanley) and S. enterica ser. Montevideo (S. Montevideo) on different food-contact processing surfaces in cantaloupe flesh and peel extracts at 22 °C and 10 °C. The generation time of all S. enterica strains tested was shorter in the high concentration (50 mg/ml) of cantaloupe extract and high temperature. In 50 mg/ml of cantaloupe flesh or peel extract, the populations of S. enterica were increased by 5 log CFU/ml in 24 h at 22 °C and 1 log CFU/ml in 72 h at 10 °C. In 2 mg/ml of cantaloupe flesh or peel extracts, the populations of S. enterica were increased by 3.5 log CFU/ml in 56 h at 22 °C, but there were no changes in 72 h at 10 °C. The biofilm production of S. enterica was greater at 50 mg/ml of cantaloupe extract and 22 °C, but no major differences (P ≥ 0.05) were found among the strains tested. In 50 mg/ml cantaloupe extract, S. enterica produced 5-6 log CFU/cm2 biofilm in 4-7 d at 22 °C and approximately 3.5-4 log CFU/cm2 in 7 d at 10 °C. In 2 mg/ml of cantaloupe extract, S. enterica produced 4-4.5 log CFU/cm2 biofilms in 4-7 d at 22 °C and 3 log CFU/cm2 in 7 d at 10 °C. Biofilm formation by S. Poona (01A4754) was lowest on buna-n rubber compared to stainless steel, polyethylene and polyurethane surfaces under the majority of conditions tested. Overall, these findings show that S. enterica strains can grow rapidly and form biofilms on different cantaloupe processing surfaces in the presence of low concentrations of cantaloupe flesh or peel extracts.

Scanning electron microscopy of Salmonella biofilms on various food-contact surfaces in catfish mucus.

The objective of this study was to determine the growth and survival of Salmonella enterica in the presence of high and low concentrations (375 µg/ml and 15 µg/ml) of catfish mucus extract at 10 °C and 22 °C for 63 days. The second objective of this study was to investigate the biofilm formation of Salmonella enterica serovar Blockley (7175) in catfish mucus extract for 48 h at 22 °C on four food-contact surfaces and to observe the biofilm populations using Scanning Electron Microscopy (SEM). The surface properties, surface roughness and surface energies were determined using contact angle measurement and atomic force microscopy. In 375 µg/ml of catfish mucus extract that was inoculated with 3 log CFU/ml, the growth of Salmonella counts were increased to a maximum of 6-7 log CFU/ml at 10 °C and 7-8 log CFU/ml at 22 °C in 7-14 d and decreased by 1-2 log CFU/ml from these peak levels at both 10 °C and 22 °C from 21 to 63 d. In 15 µg/ml of catfish mucus extract, Salmonella counts were in the range of 4-5 log CFU/ml at 10 °C and 5-6 log CFU/ml at 22 °C over 7-63 d of storage. By contrast, Salmonella counts were non-detectable in the absence of catfish mucus by 21-28 d of storage at 10 °C or 22 °C. The biofilm counts of S. Blockley (7175) on a stainless steel surface were 4 log CFU/cm2 and 5.5 log CFU/cm2 in 15 µg/ml and 375 µg/ml of catfish mucus extract respectively after 48 h incubation at 22 °C. SEM revelead that biofilm formation by S. Blockley (7175) was less in 15 µg/ml than 375 µg/ml of catfish mucus extract on stainless steel. In addition, SEM indicated that the visible biofilms were least on buna-N rubber as compared to stainless steel, polyethylene and polyurethane surfaces. Contact angle and atomic force microscopy confirmed that buna-N rubber was highly hydrophobic with low surface energy and low roughness when compared to other three surfaces. These findings indicate that Salmonella can utilize catfish mucus as a nutrient source to survive for longer periods and promote biofilm formation for its persistence on different food-contact surfaces.

Effect of deboning time on the growth of Salmonella, E. coli, aerobic, and lactic acid bacteria during beef sausage processing and storage.

The objective of the current study was to determine the effects of deboning time, three steps of sausage processing (grinding, salting, and batter formulation), and storage time (of raw materials and cooked sausage) on the growth (log CFU/g) of aerobic bacteria, lactic acid bacteria, and inoculated Salmonella and E. coli. Beef deboning time did not influence bacterial counts (P≥0.138). However, salting of raw ground beef resulted in a 0.4-log reduction in both aerobic plate count (APC) and Salmonella (P≤0.001). Lactic acid bacteria were increased from non-detectable concentration (0.54 log) on d 0 to 3.8 log on d 120 of vacuum storage (P≤0.019). Salmonella counts were increased (P<0.001) over storage time (3.2 to 3.3 log CFU/g from d 0 to 10). Results indicated that salting and batter formulation had a greater impact on bacterial counts than rigor state of raw beef.

Growth and Biofilm Formation by Listeria monocytogenes in Catfish Mucus Extract on Four Food Contact Surfaces at 22 and 10°C and Their Reduction by Commercial Disinfectants.

The objective of this study was to determine the effect of strain and temperature on growth and biofilm formation by Listeria monocytogenes in high and low concentrations of catfish mucus extract on various food contact surfaces at 10 and 22°C. The second objective of this study was to evaluate the efficacy of disinfectants at recommended concentrations and contact times for removing L. monocytogenes biofilm cells from a stainless steel surface covered with catfish mucus extract. Growth and biofilm formation of all L. monocytogenes strains increased with higher concentrations of catfish mucus extract at both 10 and 22°C. When 15 µg/mL catfish mucus extract was added to 3 log CFU/mL L. monocytogenes, the biofilm levels of L. monocytogenes on stainless steel reached 4 to 5 log CFU per coupon at 10°C and 5 to 6 log CFU per coupon at 22°C in 7 days. With 375 µg/mL catfish mucus extract, the biofilm levels of L. monocytogenes on stainless steel reached 5 to 6 log CFU per coupon at 10°C and 6 to 7.5 log CFU per coupon at 22°C in 7 days. No differences ( P > 0.05) were observed between L. monocytogenes strains tested for biofilm formation in catfish mucus extract on the stainless steel surface. The biofilm formation by L. monocytogenes catfish isolate HCC23 was lower on Buna-N rubber than on stainless steel, polyethylene, and polyurethane surfaces in the presence of catfish mucus extract ( P < 0.05). Contact angle analysis and atomic force microscopy confirmed that Buna-N rubber was highly hydrophobic, with lower surface energy and less roughness than the other three surfaces. The complete reduction of L. monocytogenes biofilm cells was achieved on the stainless steel coupons with a mixture of disinfectants, such as quaternary ammonium compounds with hydrogen peroxide or peracetic acid with hydrogen peroxide and octanoic acid at 25 or 50% of the recommended concentration, in 1 or 3 min compared with use of the quaternary ammonium compounds, chlorine, or acid disinfectants alone, which were ineffective for removing all the L. monocytogenes biofilm cells.

Biofilm formation by Salmonella spp. in catfish mucus extract under industrial conditions.

The objective of this study was to determine the effect of strain and temperature on the growth and biofilm formation of Salmonella spp. in high and low concentrations of catfish mucus extract on different food-contact surfaces at 22 °C and 10 °C. The second objective of this study was to evaluate the efficacy of disinfectants at recommended concentrations and contact times for removing Salmonella biofilms cells on a stainless steel surface containing catfish mucus extract. Growth and biofilm formation of all Salmonella strains increased with higher concentrations of catfish mucus extract at both 10 °C and 22 °C. In 15 µg/ml of catfish mucus extract inoculated with 3 log CFU/ml, the biofilm levels of Salmonella on stainless steel surface reached to 3.5 log CFU/cm2 at 10 °C or 5.5 log CFU/cm2 at 22 °C in 7 days. In 375 µg/ml of catfish mucus extract inoculated with 3 log CFU/ml, the biofilm levels of Salmonella on the stainless steel surface reached 4.5 log CFU/cm2 at 10 °C and 6.5 log CFU/cm2 at 22 °C in 7 days. No differences were observed between Salmonella strains tested for biofilm formation in catfish mucus extract on the stainless steel surface. The biofilm formation by Salmonella Blockley (7175) in catfish mucus extract was less (P < 0.05) on buna-N rubber when compared to stainless steel, polyethylene and polyurethane surfaces. Salmonella biofilm cells were not detectable on the stainless steel surface after treatment with a mixture of disinfectants but were still present when single compound disinfectants were used.