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This study was designed to determine the antibiotic resistance patterns of Enterococcus sp. isolated from feedlot cattle supplemented with a novel direct-fed microbial (DFM) Lactobacillus salivarius (L28) in replacement of [...]

The effects of a novel direct-fed microbial (DFM) on feedlot performance, carcass characteristics, digestibility, ruminal morphology, and volatile fatty acid (VFA) profile of finishing steers were evaluated. Single-source Angus-crossbred yearling steers (n= 144; initial body weight (BW) = 371 ± 19 kg) were used in a randomized complete block design. Steers were blocked by initial BW and randomly assigned to treatments (12 pens/treatment; 4 steers/pen). Treatments included (A) CONTROL (no DFM, tylosin, or monensin, (B) MONTY (monensin sodium [330 mg/animal-daily] and tylosin phosphate [90 mg/animal-daily]), and (C) MONPRO (monensin sodium [same as previous] and Lactobacillus salivariusL28 [1 × 106CFU/animal-daily]). Treatments were included in a steam-flaked corn-based finisher diet offered once daily using a clean-bunk management for ~149 d. The digestibility assessment was performed from days 70 to 74. Ruminal fluid and rumen tissue samples were collected at the slaughter for VFA profile and papillae morphology analyses, respectively. Data were analyzed using the GLIMMIX procedure of SAS with pen serving as the experimental unit, treatment as fixed effect, and BW block as random effect. Steers offered MONPRO had on average 5.3% less (P< 0.01) dry matter intake (9.56 kg/d) compared with either CONTROL (10.16 kg/d) or MONTY (9.96 kg/d). The carcass-adjusted final BW (613 kg; P= 0.23), overall average daily gain (1.64 kg/d; P= 0.23), and gain-efficiency (0.165; P= 0.61) were not affected by treatments. Steers offered CONTROL had greater (P< 0.01) marbling score and tended (P= 0.06) to have less carcasses grading Select and tended (P= 0.10) to have more carcasses grading Upper-Choice, while other carcass characteristics and liver-abscesses were not affected (P≥ 0.23) by treatments. The digestibility of nutrients (P≥ 0.13) and the ruminal VFA profile (P≥ 0.12) were not affected by treatments. Steers offered MONPRO tended (P= 0.09) to have 16% greater average papillae number compared to other treatments. Yearlings offered finishing diets containing L. salivariusL28 plus monensin did not affect growth performance, digestibility, or ruminal VFA, but reduced feed intake. Carcass quality was negatively affected by treatments, while animals consuming L. salivariusL28 and monensin tended to improve ruminal morphology. Current findings in ruminal morphology and feed intake may warrant further assessment of diets containing L. salivariusL28 on beef cattle food safety aspects.Steers offered Lactobacillus salivariusL28 plus monensin consumed less feed, while other growth performance variables and nutrient digestibility were not affected. Carcass quality was negatively affected, while L. salivariusL28 plus monensin tended to improve ruminal morphology. Further food safety assessment is warranted.Antimicrobial resistance is a growing concern to public health and medically important antibiotics have been listed in the Veterinary Feed Directive. Nutritional technologies, such as direct-fed microbials, are being increasingly studied for the development of an effective use on beef cattle production systems. The newly isolated strain of Lactobacillus salivariusL28 has demonstrated pathogenic inhibition of Escherichia coli, Salmonella, and Listeria monocytogeneson in vitro assessments. The potential benefits have warranted the exploration of L. salivariusL28 in a feedlot setting. Single-source Angus-crossbred yearling steers were offered steam-flaked corn-based finishing diets containing no feed additive, or either a combination of tylosin plus monensin or L. salivariusL28 plus monensin. Steers offered L. salivariusL28 plus monensin consumed 5.3% less feed compared with other treatments, while other growth performance variables and the digestibility of nutrients were not affected. Carcasses from cattle supplemented with monensin had slightly lower carcass quality grades than those not supplemented with monensin. Lactobacillus salivariusL28 plus monensin tended to improve steers ruminal morphology. Current findings may warrant further food safety assessments when cattle are offered diets containing L. salivariusL28.

Listeriaspecies have been isolated from diverse environments, often at considerable prevalence, and are known to persist in food processing facilities. The presence of Listeriaspp. has been suggested to be a marker for Listeria monocytogenescontamination. Therefore, a study was conducted to (i) determine the prevalence and diversity of Listeriaspp. in produce production and natural environments and (ii) identify geographical and/or meteorological factors that affect the isolation of Listeriaspp. in these environments. These data were also used to evaluate Listeriaspp. as index organisms for L. monocytogenesin produce production environments. Environmental samples collected from produce production (n= 588) and natural (n= 734) environments in New York State were microbiologically analyzed to detect and isolate Listeriaspp. The prevalence of Listeriaspp. was approximately 33 and 34% for samples obtained from natural environments and produce production, respectively. Coisolation of L. monocytogenesand at least one other species of Listeriain a given sample was recorded for 3 and 9% of samples from natural environments and produce production, respectively. Soil moisture and proximity to water and pastures were highly associated with isolation of Listeriaspp. in produce production environments, while elevation, study site, and proximity to pastures were highly associated with isolation of Listeriaspp. in natural environments, as determined by randomForest models. These data show that Listeriaspp. were prevalent in both agricultural and nonagricultural environments and that geographical and meteorological factors associated with isolation of Listeriaspp. were considerably different between the two environments.

Studies were conducted to compare the decontamination efficacy of six chemical treatments against Escherichia coliO157:H7 and multidrug-resistant and antibiotic-susceptible Salmonellainoculated on beef trimmings. The inocula, comprising four-strain mixtures of rifampin-resistant E. coliO157:H7 and antibiotic-susceptible or multidrug-resistant (MDR and/or MDR-AmpC) SalmonellaNewport and SalmonellaTyphimurium, were inoculated (3 log CFU/cm2) separately onto samples (10 by 5 by 1 cm) derived from beef chuck rolls. Samples were left untreated (control), were immersed for 30 s in acidified sodium chlorite (0.1%, pH 2.5), peroxyacetic acid (0.02%, pH 3.8), sodium metasilicate (4%, pH 12.6), Bromitize Plus (0.0225% active bromine, pH 6.6), or AFTEC 3000 (pH 1.2), or were immersed for 5 s in SYNTRx 3300 (pH 1.0). Levels of surviving Salmonellaon treated trimmings were not influenced by serotype or antibiotic resistance phenotype and were generally similar (P≥ 0.05) or lower (P< 0.05) than levels of surviving E. coliO157:H7 regardless of antimicrobial treatment. Overall, depending on chemical treatment (reductions within each chemical treatment were similar among all tested inocula), initial counts of E. coliO157:H7 (2.7 to 3.1 log CFU/cm2) were reduced (P< 0.05) by 0.2 to 1.4 log CFU/cm2. Similarly, initial counts of the tested Salmonellainocula (2.8 to 3.3 log CFU/ cm2) were reduced (P< 0.05) by 0.4 to 1.4 (SalmonellaNewport, antibiotic susceptible), 0.3 to 1.4 (SalmonellaNewport, MDR-AmpC), 0.2 to 1.5 (SalmonellaTyphimurium, antibiotic susceptible), 0.4 to 1.3 (SalmonellaTyphimurium, MDR), and 0.4 to 1.5 (SalmonellaTyphimurium, MDR-AmpC) log CFU/cm2, depending on antimicrobial treatment. Reductions obtained with sodium metasilicate were 1.3 to 1.5 log CFU/cm2, regardless of inoculum, and reductions obtained with the five remaining antimicrobial treatments were 0.2 to 0.7 log CFU/cm2(depending on treatment). Findings of this study should be useful to regulatory authorities and the meat industry as they consider Salmonellacontamination on beef trimmings.

Studies were performed to determine whether lactic acid treatments used to reduce Escherichia coliO157:H7 on beef trimmings are also effective in controlling non-O157 Shiga toxin–producing E. coli(nSTEC), and multidrug-resistant and antibiotic-susceptible Salmonella. Beef trimming pieces (10 by 5 by 1 cm) were inoculated (3 log CFU/cm2) separately with four-strain mixtures of rifampin-resistant E. coliO157:H7, O26, O45, O103, O111, O121, and O145. Similarly, in a second study, trimmings were separately inoculated with rifampin-resistant E. coliO157:H7, and antibiotic-susceptible or multidrug-resistant (MDR and/or MDR-AmpC) SalmonellaNewport and SalmonellaTyphimurium. Inoculated trimmings were left untreated (control) or were immersed for 30 s in 5% lactic acid solutions (25 or 55°C). No differences (P≥ 0.05) were obtained among surviving counts of E. coliO157:H7 and those of the tested nSTEC serogroups on lactic acid–treated (25 or 55°C) samples. Counts (3.1 to 3.3 log CFU/cm2) of E. coliO157:H7 and nSTEC were reduced (P< 0.05) by 0.5 to 0.9 (25°C lactic acid) and 1.0 to 1.4 (55°C lactic acid) log CFU/cm2. Surviving counts of Salmonellaon treated trimmings were not influenced by serotype or antibiotic resistance phenotype and were similar (P≥ 0.05) or lower (P< 0.05) than surviving counts of E. coliO157:H7. Counts (3.0 to 3.3 log CFU/cm2) were reduced (P< 0.05) by 0.5 to 0.8 (E. coliO157:H7) and 1.3 to 1.5 (Salmonella) log CFU/cm2after treatment of samples with 25°C lactic acid. Corresponding reductions following treatment with lactic acid at 55°C were 1.2 to 1.5 (E. coliO157:H7) and 1.6 to 1.9 (Salmonella) log CFU/cm2. Overall, the results indicated that lactic acid treatments used against E. coliO157:H7 on beef trimmings should be similarly or more effective against the six nSTEC serogroups and against multidrug-resistant and antibiotic-susceptible SalmonellaNewport and SalmonellaTyphimurium.

Listeria monocytogenesis a human foodborne pathogen with a broad range of hosts. While the L. monocytogenesgenome encodes a number of internalins, which are leucine-rich repeat bacterial surface proteins with putative or confirmed roles in host cell attachment and invasion, the specific function of many internalins remains unclear. The distribution of 7 internalin genes (inlC, inlC2, inlD, inlE, inlF, inlG, and inlH) in 120 L. monocytogenesisolates from humans, foods, and animals was investigated to determine if the distribution of these proteins differed with respect to source or phylogenetic lineage. Isolates were classified into 6 different profiles based on internalin gene presence or absence, and a phylogeny based on one stress response (sigB) and two housekeeping (gapand prs) genes was used to correlate these profiles with L. monocytogenesphylogenetic lineages. All 69 isolates classified into L. monocytogeneslineage I, which is overrepresented among human disease cases, had the same internalin profile (presence of inlCand the inlC2DEoperon). Lineage II (48 isolates), which is common among food and environmental sources, represented 4 internalin gene profiles, with most isolates carrying inlGand inlFin addition to inlCand inlC2DE. Our data indicate that L. monocytogenesisolates show diverse and distinct patterns of internalin gene presenceabsence and L. monocytogenesinternalin profiles are associated with phylogenetic lineages.

Characterization of 80 Listeria monocytogenesisolates from urban and natural environments differentiated 7 and 26 EcoRI ribotypes, respectively. Whereas the majority of isolates from the natural environment represented L. monocytogeneslineage II (12 of 13 isolates), urban isolates grouped evenly into lineages I and II (32 and 33 isolates, respectively) and included two lineage III isolates. Multilocus sequence typing of all natural isolates and a randomly selected subset of 30 urban isolates showed a higher overall diversity (Simpson index of discrimination [D] of 0.987 and 0.920, respectively) than did EcoRI ribotyping (D= 0.872 and 0.911, respectively). Combined analysis with ribotype and lineage data for 414 isolates from farm sources, 165 isolates from foods and food-processing environments, and 342 human clinical isolates revealed that lineage I was significantly more common among human (P< 0.0001) isolates, whereas lineage II was more common among isolates from the natural environment, farms, and foods (P≤ 0.05). Among a total of 92 ribotypes, 31 showed significant associations with specific isolate sources. One ribotype (DUP-1039C) was significantly associated with both natural environments and farms. A spatial analysis showed a marginal association between locations in the natural environment positive for L. monocytogenesand a proximity to farms. Our data indicate that (i) L. monocytogenesstrains from different sources show a high level of diversity; (ii) L. monocytogenessubtypes differ significantly in their associations with different environments, even though populations overlap; and (iii) a higher proportion of isolates from environmental sources than from human clinical cases can be classified into L. monocytogeneslineage II, which supports the classification of this lineage as an environmentally adapted subgroup.