Tamra Tolen | Prairie View A&M University (original) (raw)

Papers by Tamra Tolen

Food protection trends, 2018

Small and Very Small meat harvest and products processing establishments warrant unique considera... more Small and Very Small meat harvest and products processing establishments warrant unique consideration with respect to development and utilization of food safety interventions. While industry best practices have been developed for the sanitary manufacture of beef products, similar practices are lacking for U.S. pork products manufacturers. To assist development of best practices for Small and Very Small pork slaughter and further processing establishments, a survey instrument asking for information on establishment and facility characteristics as well as current sanitary practices was distributed to establishments in the Southwest U.S. to gauge current industry practices and identify areas in need for improvement for food safety protection. Nineteen facilities returned fully or partially completed questionnaires, detailing use of antimicrobial interventions on pork carcasses or further processed not-ready-to-eat (NRTE) products, as well as sanitation schedules, selected sanitizers us...

Food Control, 2019

As a result of frequent outbreaks occurring due to poor hygiene and improper sanitation of proces... more As a result of frequent outbreaks occurring due to poor hygiene and improper sanitation of processing environments, there has been an increasing demand for the development of food-contact surface materials that intrinsically inhibit and reduce likelihood of potential microbial adherence and biofilm formation. Herein, we report the synergistic utilization of surface nanotexturing and chemical modifications with nonpolar functional groups on aluminum surfaces to produce coatings having bacterial super-repellant and mud anti-fouling characteristics. Using these coatings, the attachment of Salmonella Typhimurium LT2 and Listeria innocua as pathogen surrogates was reduced more than 99.0%, compared to the bare aluminum surfaces. In addition, the coating strongly resisted the adhesion of mud, showing a 10-fold reduction in the area of mud adhesion upon submerging in mud solution. Moreover, this method is both versatile and scalable, involving inert and biocompatible building blocks. Overall, this study contributes to the field of food safety through the design and development of novel coatings for achieving improved food safety and hygiene.

Foods (Basel, Switzerland), Jan 16, 2018

Microbiological safety of beef products can be protected by application of antimicrobial interven... more Microbiological safety of beef products can be protected by application of antimicrobial interventions throughout the beef chain. This study evaluated a commercial prototype antimicrobial intervention comprised of lytic bacteriophages formulated to reduce O157 and non-O157 Shiga-toxigenic (STEC) on beef cattle hide pieces, simulating commercial pre-harvest hide decontamination. STEC reduction in vitro by individual and cocktailed phages was determined by efficiency of plating (EOP). Following STEC inoculation onto hide pieces, the phage intervention was applied and hide pieces were analyzed to quantify reductions in STEC counts. Phage intervention treatment resulted in 0.4 to 0.7 log CFU/cm² ( < 0.01) O157, O121, and O103 reduction. Conversely, O111 and O45 did not show any significant reduction after application of bacteriophage intervention ( > 0.05). Multiplicity of infection (MOI) evaluation indicated O157 and O121 isolates required the fewest numbers of phages per host ce...

Foods, 2017

Beef safety may be compromised by O157 and non-O157 Shiga toxin-producing Escherichia coli (STEC)... more Beef safety may be compromised by O157 and non-O157 Shiga toxin-producing Escherichia coli (STEC) contamination. The capacity of surfactant micelles loaded with the plant-derived antimicrobial eugenol to reduce STEC on beef trimmings that were later ground and refrigerated for five days at 5 ± 1 • C was tested to determine their utility for beef safety protection. STEC-inoculated trimmings were treated with free eugenol, micelle-encapsulated eugenol, 2% lactic acid (55 • C), sterile distilled water (25 • C), or left untreated (control). Following treatment, trimmings were coarse-ground and stored aerobically at 5 ± 1 • C. Ground beef was then sampled for STEC immediately post-grinding, and again at three and five days of storage. STEC minimum inhibitory concentrations (MICs) in liquid medium for free eugenol and 1% sodium dodecyl sulfate (SDS)-loaded micelles were 0.5% and 0.125%, respectively. STEC numbers on beef trimmings treated by sterile water (6.5 log 10 CFU/g), free eugenol (6.5 log 10 CFU/g), micelle-loaded eugenol (6.4 log 10 CFU/g), and lactic acid (6.4 log 10 CFU/g) did not differ compared to untreated controls (6.6 log 10 CFU/g) (p = 0.982). Conversely, STEC were significantly reduced by refrigerated storage (0.2 and 0.3 log 10 CFU/g at three and five days of storage, respectively) (p = 0.014). Antimicrobial treatments did not significantly decontaminate ground beef, indicating their low utility for beef safety protection.

International journal of food science, 2017

Because of their antagonistic activity towards pathogenic and spoilage bacteria, some members of ... more Because of their antagonistic activity towards pathogenic and spoilage bacteria, some members of the lactic acid bacteria (LAB) have been evaluated for use as food biopreservatives. The objectives of this study were to assess the antimicrobial utility of a commercial LAB intervention against O157 and non-O157 Shiga-toxigenic E. coli (STEC) on intact beef strip loins during refrigerated vacuum aging and determine intervention efficacy as a function of mode of intervention application. Prerigor strip loins were inoculated with a cocktail (8.9 ± 0.1 log10 CFU/ml) of rifampicin-resistant (100.0 μg/ml; Rif(R)) O157 and non-O157 STEC. Inoculated loins were chilled to ≤4°C and treated with 8.7 ± 0.1 log10 CFU/ml LAB intervention using either a pressurized tank air sprayer (conventional application) or air-assisted electrostatic sprayer (ESS). Surviving STEC were enumerated on tryptic soy agar supplemented with 100.0 μg/ml rifampicin (TSAR) to determine STEC inhibition as a function of inte...

Genome announcements, Jan 9, 2015

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a leading cause of foodborne illness ... more Salmonella enterica serovar Typhimurium (S. Typhimurium) is a leading cause of foodborne illness worldwide. Over the past two decades, strains resistant to antibiotics have begun to emerge, highlighting the need for alternative treatment strategies such as bacteriophage therapy. Here, we present the complete genome of Mushroom, an S. Typhimurium myophage.

Nature, 2001

Salmonella enterica subspecies I, serovar Typhimurium (S. typhimurium), is a leading cause of hum... more Salmonella enterica subspecies I, serovar Typhimurium (S. typhimurium), is a leading cause of human gastroenteritis, and is used as a mouse model of human typhoid fever. The incidence of non-typhoid salmonellosis is increasing worldwide, causing millions of infections and many deaths in the human population each year. Here we sequenced the 4,857-kilobase (kb) chromosome and 94-kb virulence plasmid of S. typhimurium strain LT2. The distribution of close homologues of S. typhimurium LT2 genes in eight related enterobacteria was determined using previously completed genomes of three related bacteria, sample sequencing of both S. enterica serovar Paratyphi A (S. paratyphi A) and Klebsiella pneumoniae, and hybridization of three unsequenced genomes to a microarray of S. typhimurium LT2 genes. Lateral transfer of genes is frequent, with 11% of the S. typhimurium LT2 genes missing from S. enterica serovar Typhi (S. typhi), and 29% missing from Escherichia coli K12. The 352 gene homologues ...

Journal of Food Protection

The purpose of this study was to compare the efficacy of different antimicrobial interventions ap... more The purpose of this study was to compare the efficacy of different antimicrobial interventions applied via either conventional spray (CS) or handheld electrostatic spray (ESS) to reduce Shiga toxin–producing Escherichia coli (STEC) on fresh beef surfaces. Hot-boned outside rounds (ORs) were inoculated within 1 h after harvest with a cocktail of eight isolates consisting of 8 O157 and non-O157 serogroups of STEC (STEC8). ORs were hung on sterile meat hooks at 4°C for 36 h to simulate a contaminated full carcass side in the chiller. ORs were then treated with lactic acid (LA; 4.5%, w/v), 3.0% lauric arginate ester (LAE), 0.8% cetylpyridinium chloride, 200 mg/L peracetic acid, 3 mg/L chlorine dioxide, 5 mg/L ClO2, or tap water by using CS or ESS. Temperatures of LA and peracetic acid were set at 55 and 42°C before spraying, whereas all other solutions were applied at room temperature (25°C). Pretreatment and posttreatment STEC8-inoculated beef tissue samples were aseptically collected ...

Food protection trends, 2018

Small and Very Small meat harvest and products processing establishments warrant unique considera... more Small and Very Small meat harvest and products processing establishments warrant unique consideration with respect to development and utilization of food safety interventions. While industry best practices have been developed for the sanitary manufacture of beef products, similar practices are lacking for U.S. pork products manufacturers. To assist development of best practices for Small and Very Small pork slaughter and further processing establishments, a survey instrument asking for information on establishment and facility characteristics as well as current sanitary practices was distributed to establishments in the Southwest U.S. to gauge current industry practices and identify areas in need for improvement for food safety protection. Nineteen facilities returned fully or partially completed questionnaires, detailing use of antimicrobial interventions on pork carcasses or further processed not-ready-to-eat (NRTE) products, as well as sanitation schedules, selected sanitizers us...

Food Control, 2019

As a result of frequent outbreaks occurring due to poor hygiene and improper sanitation of proces... more As a result of frequent outbreaks occurring due to poor hygiene and improper sanitation of processing environments, there has been an increasing demand for the development of food-contact surface materials that intrinsically inhibit and reduce likelihood of potential microbial adherence and biofilm formation. Herein, we report the synergistic utilization of surface nanotexturing and chemical modifications with nonpolar functional groups on aluminum surfaces to produce coatings having bacterial super-repellant and mud anti-fouling characteristics. Using these coatings, the attachment of Salmonella Typhimurium LT2 and Listeria innocua as pathogen surrogates was reduced more than 99.0%, compared to the bare aluminum surfaces. In addition, the coating strongly resisted the adhesion of mud, showing a 10-fold reduction in the area of mud adhesion upon submerging in mud solution. Moreover, this method is both versatile and scalable, involving inert and biocompatible building blocks. Overall, this study contributes to the field of food safety through the design and development of novel coatings for achieving improved food safety and hygiene.

Foods (Basel, Switzerland), Jan 16, 2018

Microbiological safety of beef products can be protected by application of antimicrobial interven... more Microbiological safety of beef products can be protected by application of antimicrobial interventions throughout the beef chain. This study evaluated a commercial prototype antimicrobial intervention comprised of lytic bacteriophages formulated to reduce O157 and non-O157 Shiga-toxigenic (STEC) on beef cattle hide pieces, simulating commercial pre-harvest hide decontamination. STEC reduction in vitro by individual and cocktailed phages was determined by efficiency of plating (EOP). Following STEC inoculation onto hide pieces, the phage intervention was applied and hide pieces were analyzed to quantify reductions in STEC counts. Phage intervention treatment resulted in 0.4 to 0.7 log CFU/cm² ( < 0.01) O157, O121, and O103 reduction. Conversely, O111 and O45 did not show any significant reduction after application of bacteriophage intervention ( > 0.05). Multiplicity of infection (MOI) evaluation indicated O157 and O121 isolates required the fewest numbers of phages per host ce...

Foods, 2017

Beef safety may be compromised by O157 and non-O157 Shiga toxin-producing Escherichia coli (STEC)... more Beef safety may be compromised by O157 and non-O157 Shiga toxin-producing Escherichia coli (STEC) contamination. The capacity of surfactant micelles loaded with the plant-derived antimicrobial eugenol to reduce STEC on beef trimmings that were later ground and refrigerated for five days at 5 ± 1 • C was tested to determine their utility for beef safety protection. STEC-inoculated trimmings were treated with free eugenol, micelle-encapsulated eugenol, 2% lactic acid (55 • C), sterile distilled water (25 • C), or left untreated (control). Following treatment, trimmings were coarse-ground and stored aerobically at 5 ± 1 • C. Ground beef was then sampled for STEC immediately post-grinding, and again at three and five days of storage. STEC minimum inhibitory concentrations (MICs) in liquid medium for free eugenol and 1% sodium dodecyl sulfate (SDS)-loaded micelles were 0.5% and 0.125%, respectively. STEC numbers on beef trimmings treated by sterile water (6.5 log 10 CFU/g), free eugenol (6.5 log 10 CFU/g), micelle-loaded eugenol (6.4 log 10 CFU/g), and lactic acid (6.4 log 10 CFU/g) did not differ compared to untreated controls (6.6 log 10 CFU/g) (p = 0.982). Conversely, STEC were significantly reduced by refrigerated storage (0.2 and 0.3 log 10 CFU/g at three and five days of storage, respectively) (p = 0.014). Antimicrobial treatments did not significantly decontaminate ground beef, indicating their low utility for beef safety protection.

International journal of food science, 2017

Because of their antagonistic activity towards pathogenic and spoilage bacteria, some members of ... more Because of their antagonistic activity towards pathogenic and spoilage bacteria, some members of the lactic acid bacteria (LAB) have been evaluated for use as food biopreservatives. The objectives of this study were to assess the antimicrobial utility of a commercial LAB intervention against O157 and non-O157 Shiga-toxigenic E. coli (STEC) on intact beef strip loins during refrigerated vacuum aging and determine intervention efficacy as a function of mode of intervention application. Prerigor strip loins were inoculated with a cocktail (8.9 ± 0.1 log10 CFU/ml) of rifampicin-resistant (100.0 μg/ml; Rif(R)) O157 and non-O157 STEC. Inoculated loins were chilled to ≤4°C and treated with 8.7 ± 0.1 log10 CFU/ml LAB intervention using either a pressurized tank air sprayer (conventional application) or air-assisted electrostatic sprayer (ESS). Surviving STEC were enumerated on tryptic soy agar supplemented with 100.0 μg/ml rifampicin (TSAR) to determine STEC inhibition as a function of inte...

Genome announcements, Jan 9, 2015

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a leading cause of foodborne illness ... more Salmonella enterica serovar Typhimurium (S. Typhimurium) is a leading cause of foodborne illness worldwide. Over the past two decades, strains resistant to antibiotics have begun to emerge, highlighting the need for alternative treatment strategies such as bacteriophage therapy. Here, we present the complete genome of Mushroom, an S. Typhimurium myophage.

Nature, 2001

Salmonella enterica subspecies I, serovar Typhimurium (S. typhimurium), is a leading cause of hum... more Salmonella enterica subspecies I, serovar Typhimurium (S. typhimurium), is a leading cause of human gastroenteritis, and is used as a mouse model of human typhoid fever. The incidence of non-typhoid salmonellosis is increasing worldwide, causing millions of infections and many deaths in the human population each year. Here we sequenced the 4,857-kilobase (kb) chromosome and 94-kb virulence plasmid of S. typhimurium strain LT2. The distribution of close homologues of S. typhimurium LT2 genes in eight related enterobacteria was determined using previously completed genomes of three related bacteria, sample sequencing of both S. enterica serovar Paratyphi A (S. paratyphi A) and Klebsiella pneumoniae, and hybridization of three unsequenced genomes to a microarray of S. typhimurium LT2 genes. Lateral transfer of genes is frequent, with 11% of the S. typhimurium LT2 genes missing from S. enterica serovar Typhi (S. typhi), and 29% missing from Escherichia coli K12. The 352 gene homologues ...

Journal of Food Protection

The purpose of this study was to compare the efficacy of different antimicrobial interventions ap... more The purpose of this study was to compare the efficacy of different antimicrobial interventions applied via either conventional spray (CS) or handheld electrostatic spray (ESS) to reduce Shiga toxin–producing Escherichia coli (STEC) on fresh beef surfaces. Hot-boned outside rounds (ORs) were inoculated within 1 h after harvest with a cocktail of eight isolates consisting of 8 O157 and non-O157 serogroups of STEC (STEC8). ORs were hung on sterile meat hooks at 4°C for 36 h to simulate a contaminated full carcass side in the chiller. ORs were then treated with lactic acid (LA; 4.5%, w/v), 3.0% lauric arginate ester (LAE), 0.8% cetylpyridinium chloride, 200 mg/L peracetic acid, 3 mg/L chlorine dioxide, 5 mg/L ClO2, or tap water by using CS or ESS. Temperatures of LA and peracetic acid were set at 55 and 42°C before spraying, whereas all other solutions were applied at room temperature (25°C). Pretreatment and posttreatment STEC8-inoculated beef tissue samples were aseptically collected ...