Shiga-toxin producing Escherichia coli (STEC) serogroups exhibit varied thermal susceptibility in marinated beef products (original) (raw)
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Journal of Food Protection, 2012
Although numerous antimicrobial interventions targeting Escherichia coli O157:H7 have been developed and implemented to decontaminate meat and meat products during the harvesting process, the information on efficacy of these interventions against the so-called Big Six non-O157 Shiga toxin-producing E. coli (STEC) strains is limited. Prerigor beef flanks (160) were inoculated to determine if antimicrobial interventions currently used by the meat industry have a similar effect in reducing non-O157 STEC serogroups O26, O45, O103, O111, O121, and O145 compared with E. coli O157:H7. A high (10 4 CFU/cm 2 ) or a low (10 1 CFU/cm 2 ) inoculation of two cocktail mixtures was applied to surfaces of fresh beef. Cocktail mixture 1 was composed of O26, O103, O111, O145, and O157, while cocktail mixture 2 was composed of O45, O121, and O157. The inoculated fresh beef flanks were subjected to spray treatments by the following four antimicrobial compounds: acidified sodium chlorite, peroxyacetic acid, lactic acid, and hot water. High-level inoculation samples were enumerated for the remaining bacteria populations after each treatment and compared with the untreated controls, while low-level inoculation samples were chilled for 48 h at 4uC before enrichment, immunomagnetic separation, and isolation. Spray treatments with hot water were the most effective, resulting in mean pathogen reductions of 3.2 to 4.2 log CFU/cm 2 , followed by lactic acid. Hot water and lactic acid also were the most effective interventions with the low-level inoculation on surfaces of fresh beef flanks after chilling. Peroxyacetic acid had an intermediate effect, while acidified sodium chlorite was the least effective in reducing STEC levels immediately after treatment. Results indicate that the reduction of non-O157 STEC by antimicrobial interventions on fresh beef surfaces were at least as great as for E. coli O157:H7. However, the recovery of these low inoculation levels of pathogens indicated that there is no single intervention to eliminate them.
2012
Although numerous antimicrobial interventions targeting Escherichia coli O157:H7 have been developed and implemented to decontaminate meat and meat products during the harvesting process, the information on efficacy of these interventions against the so-called Big Six non-O157 Shiga toxin–producing E. coli (STEC) strains is limited. Prerigor beef flanks (160) were inoculated to determine if antimicrobial interventions currently used by the meat industry have a similar effect in reducing nonO157 STEC serogroups O26, O45, O103, O111, O121, and O145 compared with E. coli O157:H7. A high (10 CFU/cm) or a low (10 CFU/cm) inoculation of two cocktail mixtures was applied to surfaces of fresh beef. Cocktail mixture 1 was composed of O26, O103, O111, O145, and O157, while cocktail mixture 2 was composed of O45, O121, and O157. The inoculated fresh beef flanks were subjected to spray treatments by the following four antimicrobial compounds: acidified sodium chlorite, peroxyacetic acid, lactic...
Journal of Food Protection, 2012
Although numerous antimicrobial interventions targeting Escherichia coli O157:H7 have been developed and implemented to decontaminate meat and meat products during the harvesting process, the information on efficacy of these interventions against the so-called Big Six non-O157 Shiga toxin–producing E. coli (STEC) strains is limited. Prerigor beef flanks (160) were inoculated to determine if antimicrobial interventions currently used by the meat industry have a similar effect in reducing non-O157 STEC serogroups O26, O45, O103, O111, O121, and O145 compared with E. coli O157:H7. A high (104 CFU/cm2) or a low (101 CFU/cm2) inoculation of two cocktail mixtures was applied to surfaces of fresh beef. Cocktail mixture 1 was composed of O26, O103, O111, O145, and O157, while cocktail mixture 2 was composed of O45, O121, and O157. The inoculated fresh beef flanks were subjected to spray treatments by the following four antimicrobial compounds: acidified sodium chlorite, peroxyacetic acid, l...
Meat science, 2018
In Argentina, Shiga toxin producing Escherichia coli (STEC) serogroups O157, O26, O103, O111, O145 and O121 are adulterant in ground beef. In other countries, the zero-tolerance approach to all STEC is implemented for chilled beef. Argentinean abattoirs are interested in implementing effective interventions against STEC on carcasses. Pre-rigor beef carcasses were used to determine whether nine antimicrobial strategies effectively reduced aerobic plate, coliform and E. coli counts and stx and eae gene prevalence. These strategies were: citric acid (2%; automated), acetic acid (2%; manual and automated), lactic acid (LA 2%; manual and automated), LA (3%; automated), electrolytically-generated hypochlorous acid (400 ppm; manual), hot water (82 °C; automated) and INSPEXX (0.2%; automated). Automated application of 2% LA after 30-60-min aeration and 3% LA at 55 °C were the most effective interventions. Automated application was more effective than manual application. Decontamination of b...
2013
Compared to planktonic cells, bacterial biofilms are more resistant to sanitizing agents, causing crucial challenges for their inactivation in various food environments. The first study of this dissertation investigated biofilm formation of seven pathogenic Escherichia coli serogroups (i.e., O157, O26, O45, O103, O111, O121, O145) and two or three phenotypes of Salmonella Newport and S. Typhimurium (i.e., susceptible, multidrug-resistant [MDR], and/or multidrugresistant with acquired ampC gene [MDR-AmpC]). One-week mature biofilms were also exposed to water and to two commercially available quaternary ammonium compound-based (QAC) and acid-based (AB) sanitizers. Specifically, seven strain mixtures of the abovementioned pathogen groups were separately spot-inoculated onto the surface of stainless steel coupons for target inoculation of 2 log CFU/cm 2. Coupons were then stored statically and partially submerged in non-sterilized meat (10% w/v) homogenate at 4, 15, and 25°C. Microbial counts on days 0, 1, 4, and 7 and survivors after exposure (submersion in 30 ml for 1 min) to water, QAC and AB of one-week mature biofilms were enumerated using selective and nonselective media. At 4°C, pathogen counts on inoculation day ranged from 1.6±0.4 log CFU/cm 2 to 2.4±0.6 and changed to 1.2±0.8 to 1.9±0.8 on day-7 with no appreciable differences among the pathogen groups. After treatment with QAC and AB on day-7, counts were reduced (P<0.05) to less than 0.7±0.6 and 1.2±0.5, respectively, with similar trends among the inoculated pathogen groups. Biofilm formation at higher temperatures was more enhanced. E. coli O157:H7, as an coli O157:H7. Overall, the results of this acid challenge showed, for nearly all strains and time intervals, that individual strains of wild-type and rifampicin-resistant non-O157 E. coli and of S. Newport and Typhimurium were less (P<0.05) acid tolerant than the E. coli O157:H7. The vast majority of non-O157 E. coli strains showed similar (P≥0.05) acid tolerance and also the majority of drug resistant and susceptible Salmonella strains were similarly (P≥0.05) acid tolerant. The third study of this dissertation investigated decontamination of beef trimming inoculated with shiga toxin-producing Escherichia coli and Salmonella using lactic acid (LA). The efficacy of LA was compared against (i) six non-O157 Shiga toxin-producing E. coli (nSTEC) serogroups and (ii) antibiotic susceptible and multidrug resistant S. Newport and S. Typhimurium serovars. The antimicrobial effects against these pathogens were compared to those obtained against E. coli O157:H7. Four-strain mixture inocula of rifampicin-resistant E. coli O157:H7, O26, O45, O103, O111, O121 and O145, and antibiotic susceptible and multidrug resistant (MDR and/or MDR-AmpC) S. Newport and S. Typhimurium were evaluated on beef trimmings (100-g pieces). The inoculated (3 log CFU/cm 2) trimmings were immersed (30 s) in solutions of LA (5%, 25 or 55°C). Pathogen populations on untreated and treated samples were enumerated (two or three repetitions, three samples each), and data were analyzed as a complete randomized block design. Initial levels (3.1-3.3 log CFU/cm 2) of E. coli O157:H7 and nSTEC serogroups were reduced (P<0.05) by 0.7 (E. coli O157:H7) and 0.4-0.9 (nSTEC) log CFU/cm 2 in 25°C LA-treated samples, and 1.4 (E. coli O157:H7) and 1.0-1.3 (nSTEC) log CFU/cm 2 in 55°C LA-treated samples. No differences (P≥0.05) were obtained between surviving counts of the six nSTEC serogroups and those of E. coli O157:H7. LA at 25°C and 55°C reduced (P<0.05) Salmonella counts (3.0-3.3 log CFU/ cm 2) by 1.2-1.5 and 1.5-1.9 log CFU/cm 2 , respectively, while v corresponding E. coli O157:H7 reductions were 0.5 and 1.2 log CFU/cm 2 , respectively. Reductions of Salmonella counts were not influenced by serovar or antibiotic resistance phenotype, and were similar (P≥0.05) or higher (P<0.05) than reductions of E. coli O157:H7. The results indicated that LA decontamination of beef trimmings can be as effective against the six nSTEC serogroups and antibiotic susceptible and multidrug resistant S. Newport and S. Typhimurium as it is against E. coli O157:H7. The fourth study of this dissertation was conducted with the objective of evaluating survival and multiplication of L. monocytogenes inoculated on cooked chicken breasts which were stored aerobically at 7°C for 7 days. Reduction of pathogen cells by microwave, domestic oven, and stove top reheating was also evaluated. L. monocytogenes populations increased from 3.7±0.1 to 7.8±0.2 log CFU/g after 7 days. Microwave oven reheating for 90 s, and stove-top and ovenreheating to 70°C internal temperature reduced pathogen populations to <0.4-2.6, <0.4-4.8, and 1.4-5.9 log CFU/g, respectively; numbers of survivors after reheating were higher (P<0.05) in products stored for increasing length of time up to 7 days. At shorter microwaving times and lower product internal temperatures (stove-top and oven-reheating), similar reduction trends were observed but with higher levels of survivors after treatment. Although reheating methods in this study reduced L. monocytogenes contamination by 2-5 log CFU/g, growth of the pathogen during previous storage allowed high numbers of survivors after reheating, especially after 2 days of storage. This indicates that storage period, and type and intensity of reheating need to be considered for safe consumption of leftovers. The last study of this dissertation was designed to evaluate growth of L. monocytogenes inoculated on cooked chicken meat with different marinades and survival of the pathogen as affected by microwave oven reheating during aerobic storage at 7°C. Raw chicken breast meat vi samples were treated with three commercially-formulated and three domestically-available marinades, and then cooked (74.4°C internal temperature), cooled to 4°C, and surface-inoculated with L. monocytogenes. During storage at 7°C, on days 0, 1, 2, 4, and 7, samples were reheated by microwave oven (1100 W) for 45 or 90 s and analyzed microbiologically. L. monocytogenes counts on non-marinated control samples increased (P<0.05) from 2.7±0.1 to 6.9±0.1 log CFU/g during storage. At day-7 of storage, pathogen levels on samples marinated with tomato juice were not different (P≥0.05; 6.9±0.1 log CFU/g) from those of the control, whereas for samples treated with the remaining marinades, pathogen counts were 0.7 to 2.0 log CFU/g lower (P<0.05) than those of control samples. Microwave reheating reduced L. monocytogenes by 1.9 to 4.1 (at 45 s) and 2.1 to 5.0 (at 90 s) log CFU/g. With similar trends across different marinates, the high levels of L. monocytogenes survivors found after microwave reheating, especially after two days of storage, indicate that length of storage and reheating time need to be considered for safe consumption of leftover cooked chicken. vii ACKNOWLEDGMENTS Most gratefully, I would like to thank Dr. John Sofos, for being a mentor throughout my journey of exploring beauties of food and agricultural sciences. Thank you very much for seeing potential in me, and opportunity of research assistantship that in addition to be a great educational journey, it covered all the expenses of my doctorate, even the very expensive out-ofstate tuitions. My most sincere appreciation also goes to Drs. Kendra Nightingale, Patricia Kendall, Keith Belk, and Dale Woerner for all their additional direction, suggestions, and comments. My best regards and appreciation is also necessary for Dr. Martha Stone, I won't be able to complete my education without her advice, positive attitude, and encouragements. I need to express my special gratitude to Dr. Marisa Bunning, for her kindness and advice during my education and to Dr. John Avens and Dr. Cecil Stushnoff, for their additional support, encouragement, and kindness throughout my stay in Colorado State University. I am thankful of Dr. Jana Anderson and Charlene Spencer for their direction and professionalism during my enrollment in their on-line certification program. My most sincere appreciation also goes to Becky Kinsinger and Daniel Berlin from Microbac Laboratories and Custom Blending Inc for their expertise and advice and providing the opportunity of internship during my education. I am sincerely appreciative of Dr. Janet Landreth and Vladimir Ostromensky for providing the opportunity to learn from them during their busy days and introducing me to many beauties that I would not be able to explore on my own.
Journal of food protection, 2015
Several antimicrobial compounds have been used in commercial meat processing plants for decontamination of pathogens on beef carcasses, but there are many commercially available, novel antimicrobial compounds that may be more effective and suitable for use in beef processing pathogen-reduction programs. Sixty-four prerigor beef flanks (cutaneous trunci) were used in a study to determine whether hypobromous acid, neutral acidified sodium chlorite, and two citric acid-based antimicrobial compounds effectively reduce seven Shiga toxin-producing Escherichia coli (STEC) serogroups and Salmonella on the surface of fresh beef. Two cocktail mixtures were inoculated onto prerigor beef flank surfaces. Cocktail mixture 1 was composed of STEC serogroups O26, O103, O111, O145, and O157; and cocktail mixture 2 was composed of STEC serogroups O45, O121, and O157 and Salmonella. The inoculated fresh beef flanks were subjected to spray treatments with four antimicrobial compounds. Following antimicr...
Journal of Food Processing & Beverages
Escherichia coli O157:H7 and Non-O157 shiga toxin producing E. coli (STEC) serogroups O26, O45, O103, O111, O121, or O145 are both considered adulterated in non-intact beefs. Forty to fifty-eight percent of U.S. consumers prefer to order beef steaks of medium rare to rare status. From 2000 to 2007, undercooked non-intact beef products have been involved in several outbreaks in the United States due to contamination with E. coli O157:H7.Traditional cooking practices of non-intact beef steaks contaminated with Non-O157 STEC may result in the same food safety risks as shown in E. coli O157:H7 through consumption of undercooked contaminated products. This mini-review focuses on the research advances in recent 10 years to evaluate the effectiveness of cooking inactivation of E. coli O157:H7 and Non-O157 STEC contaminated in ground beef, mechanical tenderized beef, and moisture enhanced non-intact beef.
This study evaluated the decontamination efficacy of water (W; 25° or 55 o C), 2% acetic acid (AA), 0.001% acidified chlorine (AC), 2% lactic acid (LA; 55 o C), 0.02% acidified sodium chlorite (ASC), 0.5% cetylpyridinium chloride (CPC), 1% lactoferricin B (LB), and 0.02% peroxyacetic acid (PAA) on Escherichia coli O157:H7 when applied to fresh beef carcass tissue (BCT) surfaces (40 cm 2 ) and lean tissue pieces (LTP; 300 g). Samples were inoculated with a five-strain composite of E. coli O157:H7 and then immersed in the treatment solutions for 30 s. Viable cell counts were enumerated by plating on sorbitol MacConkey (SMAC) agar. Overall, CPC was most effective (P < 0.05) and reduced bacterial populations by 4.8 log CFU/cm 2 and 2.1 log CFU/g on BCT and LTP, respectively. Of the treatments commonly used by industry, LA was the most effective (P < 0.05), as it reduced pathogen populations by 3.3 log CFU/cm 2 and 1.3 log CFU/g on BCT and LTP, respectively. Additionally, ASC, AA, PAA, LB, AC and W reduced pathogen populations when plated on SMAC by 1.9, 1.6, 1.4, 0.7, 0.4 and 1.2 log CFU/cm 2 , when applied to BCT, while corresponding reductions following the above treatment applications to LTP were 1.8, 1.1, 1.0, 0.4, 0.5 and 0.3 log CFU/g, respectively. Results from this study indicated that LA and ASC were the most effective pathogen decontamination solutions currently approved for commercial use. Information regarding the antibacterial efficacy of decontamination solutions should prove beneficial to industry personnel as a means of improving microbiological quality as well as potentially improving the quality of non-intact beef tissue.
Journal of food protection, 2016
Several antimicrobial compounds are in commercial meat processing plants for pathogen control on beef carcasses. However, the efficacy of the method used is influenced by a number of factors, such as spray pressure, temperature, type of chemical and concentration, exposure time, method of application, equipment design, and the stage in the process that the method is applied. The objective of this study was to evaluate effectiveness of time of exposure of various antimicrobial compounds against nine strains of Shiga toxin-producing Escherichia coli (STEC) and four strains of Salmonella in aqueous antimicrobial solutions with and without organic matter. Non-O157 STEC, STEC O157:H7, and Salmonella were exposed to the following aqueous antimicrobial solutions with or without beef purge for 15, 30, 60, 120, 300, 600, and 1,800 s: (i) 2.5% lactic acid, (ii) 4.0% lactic acid, (iii) 2.5% Beefxide, (iv) 1% Aftec 3000, (v) 200 ppm of peracetic acid, (vi) 300 ppm of hypobromous acid, and (vii)...