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1.
BMC Genomics ; 23(1): 275, 2022 Apr 07.
Artículo en Inglés | MEDLINE | ID: mdl-35392797

RESUMEN

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a pathogen known to reside in cattle feedlots. This retrospective study examined 181 STEC O157:H7 strains collected over 23 years from a closed-system feedlot. All strains were subjected to short-read sequencing, with a subset of 36 also subjected to long-read sequencing. RESULTS: Over 96% of the strains fell into four phylogenetically distinct clades. Clade membership was associated with multiple factors including stx composition and the alleles of a well-characterized polymorphism (tir 255 T > A). Small plasmids (2.7 to 40 kb) were found to be primarily clade specific. Within each clade, chromosomal rearrangements were observed along with a core phageome and clade specific phages. Across both core and mobile elements of the genome, multiple SNP alleles were in complete linkage disequilibrium across all strains within specific clades. Clade evolutionary rates varied between 0.9 and 2.8 SNP/genome/year with two tir A allele clades having the lowest evolutionary rates. Investigation into possible causes of the differing rates was not conclusive but revealed a synonymous based mutation in the DNA polymerase III of the fastest evolving clade. Phylogenetic trees generated through our bioinformatic pipeline versus the NCBI's pathogen detection project were similar, with the two tir A allele clades matching individual NCBI SNP clusters, and the two tir T allele clades assigned to multiple closely-related SNP clusters. CONCLUSIONS: In one ecological niche, a diverse STEC O157:H7 population exhibited different rates of evolution that associated with SNP alleles in linkage disequilibrium in the core genome and mobile elements, including tir 255 T > A.


Asunto(s)
Infecciones por Escherichia coli , Escherichia coli O157 , Alelos , Animales , Bovinos , Ecosistema , Infecciones por Escherichia coli/epidemiología , Escherichia coli O157/genética , Filogenia , Estudios Retrospectivos
2.
Appl Environ Microbiol ; 87(7)2021 03 11.
Artículo en Inglés | MEDLINE | ID: mdl-33483306

RESUMEN

Microbial resistance to processing treatments poses a food safety concern, as treatment tolerant pathogens can emerge. Occasional foodborne outbreaks caused by pathogenic Escherichia coli have led to human and economic losses. Therefore, this study screened for the extreme heat resistance (XHR) phenotype as well as one known genetic marker, the locus of heat resistance (LHR), in 4,123 E. coli isolates from diverse meat animals at different processing stages. The prevalences of XHR and LHR among the meat-borne E. coli were found to be 10.3% and 11.4%, respectively, with 19% agreement between the two. Finished meat products showed the highest LHR prevalence (24.3%) compared to other processing stages (0 to 0.6%). None of the LHR+E. coli in this study would be considered pathogens based on screening for virulence genes. Four high-quality genomes were generated by whole-genome sequencing of representative LHR+ isolates. Nine horizontally acquired LHRs were identified and characterized, four plasmid-borne and five chromosomal. Nine newly identified LHRs belong to ClpK1 LHR or ClpK2 LHR variants sharing 61 to 68% nucleotide sequence identity, while one LHR appears to be a hybrid. Our observations suggest positive correlation between the number of LHR regions present in isolates and the extent of heat resistance. The isolate exhibiting the highest degree of heat resistance possessed four LHRs belonging to three different variant groups. Maintenance of as many as four LHRs in a single genome emphasizes the benefits of the LHR in bacterial physiology and stress response.IMPORTANCE Currently, a "multiple-hurdle" approach based on a combination of different antimicrobial interventions, including heat, is being utilized during meat processing to control the burden of spoilage and pathogenic bacteria. Our recent study (M. Guragain, G. E. Smith, D. A. King, and J. M. Bosilevac, J Food Prot 83:1438-1443, 2020, https://doi.org/10.4315/JFP-20-103) suggests that U.S. beef cattle harbor Escherichia coli that possess the locus of heat resistance (LHR). LHR seemingly contributes to the global stress tolerance in bacteria and hence poses a food safety concern. Therefore, it is important to understand the distribution of the LHRs among meat-borne bacteria identified at different stages of different meat processing systems. Complete genome sequencing and comparative analysis of selected heat-resistant bacteria provide a clearer understanding of stress and heat resistance mechanisms. Further, sequencing data may offer a platform to gain further insights into the genetic background that provides optimal bacterial tolerance against heat and other processing treatments.


Asunto(s)
Escherichia coli/fisiología , Genoma Bacteriano , Carne/microbiología , Escherichia coli/genética , Calor , Secuenciación Completa del Genoma
3.
BMC Microbiol ; 20(1): 250, 2020 08 12.
Artículo en Inglés | MEDLINE | ID: mdl-32787780

RESUMEN

BACKGROUND: Mannheimia haemolytica strains isolated from North American cattle have been classified into two genotypes (1 and 2). Although members of both genotypes have been isolated from the upper and lower respiratory tracts of cattle with or without bovine respiratory disease (BRD), genotype 2 strains are much more frequently isolated from diseased lungs than genotype 1 strains. The mechanisms behind the increased association of genotype 2 M. haemolytica with BRD are not fully understood. To address that, and to search for interventions against genotype 2 M. haemolytica, complete, closed chromosome assemblies for 35 genotype 1 and 34 genotype 2 strains were generated and compared. Searches were conducted for the pan genome, core genes shared between the genotypes, and for genes specific to either genotype. Additionally, genes encoding outer membrane proteins (OMPs) specific to genotype 2 M. haemolytica were identified, and the diversity of their protein isoforms was characterized with predominantly unassembled, short-read genomic sequences for up to 1075 additional strains. RESULTS: The pan genome of the 69 sequenced M. haemolytica strains consisted of 3111 genes, of which 1880 comprised a shared core between the genotypes. A core of 112 and 179 genes or gene variants were specific to genotype 1 and 2, respectively. Seven genes encoding predicted OMPs; a peptidase S6, a ligand-gated channel, an autotransporter outer membrane beta-barrel domain-containing protein (AOMB-BD-CP), a porin, and three different trimeric autotransporter adhesins were specific to genotype 2 as their genotype 1 homologs were either pseudogenes, or not detected. The AOMB-BD-CP gene, however, appeared to be truncated across all examined genotype 2 strains and to likely encode dysfunctional protein. Homologous gene sequences from additional M. haemolytica strains confirmed the specificity of the remaining six genotype 2 OMP genes and revealed they encoded low isoform diversity at the population level. CONCLUSION: Genotype 2 M. haemolytica possess genes encoding conserved OMPs not found intact in more commensally prone genotype 1 strains. Some of the genotype 2 specific genes identified in this study are likely to have important biological roles in the pathogenicity of genotype 2 M. haemolytica, which is the primary bacterial cause of BRD.


Asunto(s)
Proteínas de la Membrana Bacteriana Externa/genética , Enfermedades de los Bovinos/microbiología , Mannheimia haemolytica/genética , Infecciones del Sistema Respiratorio/veterinaria , Secuenciación Completa del Genoma/métodos , Animales , Bovinos , Cromosomas Bacterianos/genética , Genotipo , Mannheimia haemolytica/clasificación , Mannheimia haemolytica/aislamiento & purificación , Mutación , Filogenia
4.
BMC Genomics ; 17(1): 982, 2016 11 29.
Artículo en Inglés | MEDLINE | ID: mdl-27894259

RESUMEN

BACKGROUND: Mannheimia haemolytica typically resides in cattle as a commensal member of the upper respiratory tract microbiome. However, some strains can invade their lungs and cause respiratory disease and death, including those with multi-drug resistance. A nucleotide polymorphism typing system was developed for M. haemolytica from the genome sequences of 1133 North American isolates, and used to identify genetic differences between isolates from the lungs and upper respiratory tract of cattle with and without clinical signs of respiratory disease. RESULTS: A total of 26,081 nucleotide polymorphisms were characterized after quality control filtering of 48,403 putative polymorphisms. Phylogenetic analyses of nucleotide polymorphism genotypes split M. haemolytica into two major genotypes (1 and 2) that each were further divided into multiple subtypes. Multiple polymorphisms were identified with alleles that tagged genotypes 1 or 2, and their respective subtypes. Only genotype 2 M. haemolytica associated with the lungs of diseased cattle and the sequence of a particular integrative and conjugative element (ICE). Additionally, isolates belonging to one subtype of genotype 2 (2b), had the majority of antibiotic resistance genes detected in this study, which were assorted into seven combinations that ranged from 1 to 12 resistance genes. CONCLUSIONS: Typing of diverse M. haemolytica by nucleotide polymorphism genotypes successfully identified associations with diseased cattle lungs, ICE sequence, and antibiotic resistance genes. Management of cattle by their carriage of M. haemolytica could be an effective intervention strategy to reduce the prevalence of respiratory disease and supplemental needs for antibiotic treatments in North American herds.


Asunto(s)
Conjugación Genética , Farmacorresistencia Bacteriana , Genoma Bacteriano , Genómica , Mannheimia haemolytica/efectos de los fármacos , Mannheimia haemolytica/fisiología , Neumonía Enzoótica de los Becerros/microbiología , Animales , Antibacterianos/farmacología , Bovinos , Ligamiento Genético , Genómica/métodos , Genotipo , Secuenciación de Nucleótidos de Alto Rendimiento , Mannheimia haemolytica/clasificación , Polimorfismo de Nucleótido Simple
5.
Appl Environ Microbiol ; 81(2): 713-25, 2015 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-25398858

RESUMEN

Specific concerns have been raised that third-generation cephalosporin-resistant (3GC(r)) Escherichia coli, trimethoprim-sulfamethoxazole-resistant (COT(r)) E. coli, 3GC(r) Salmonella enterica, and nalidixic acid-resistant (NAL(r)) S. enterica may be present in cattle production environments, persist through beef processing, and contaminate final products. The prevalences and concentrations of these organisms were determined in feces and hides (at feedlot and processing plant), pre-evisceration carcasses, and final carcasses from three lots of fed cattle (n = 184). The prevalences and concentrations were further determined for strip loins from 103 of the carcasses. 3GC(r) Salmonella was detected on 7.6% of hides during processing and was not detected on the final carcasses or strip loins. NAL(r) S. enterica was detected on only one hide. 3GC(r) E. coli and COT(r) E. coli were detected on 100.0% of hides during processing. Concentrations of 3GC(r) E. coli and COT(r) E. coli on hides were correlated with pre-evisceration carcass contamination. 3GC(r) E. coli and COT(r) E. coli were each detected on only 0.5% of final carcasses and were not detected on strip loins. Five hundred and 42 isolates were screened for extraintestinal pathogenic E. coli (ExPEC) virulence-associated markers. Only two COT(r) E. coli isolates from hides were ExPEC, indicating that fed cattle products are not a significant source of ExPEC causing human urinary tract infections. The very low prevalences of these organisms on final carcasses and their absence on strip loins demonstrate that current sanitary dressing procedures and processing interventions are effective against antimicrobial-resistant bacteria.


Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana , Infecciones por Escherichia coli/veterinaria , Escherichia coli/aislamiento & purificación , Carne/microbiología , Salmonelosis Animal/microbiología , Salmonella enterica/aislamiento & purificación , Animales , Cadáver , Bovinos , Microbiología Ambiental , Escherichia coli/efectos de los fármacos , Escherichia coli/genética , Infecciones por Escherichia coli/microbiología , Heces/microbiología , Manipulación de Alimentos , Pruebas de Sensibilidad Microbiana , Salmonella enterica/efectos de los fármacos , Salmonella enterica/genética , Factores de Virulencia/genética
6.
Appl Environ Microbiol ; 79(7): 2273-83, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23354706

RESUMEN

In the United States, the blaCMY-2 gene contained within incompatibility type A/C (IncA/C) plasmids is frequently identified in extended-spectrum-cephalosporin-resistant (ESC(r)) Escherichia coli strains from both human and cattle sources. Concerns have been raised that therapeutic use of ceftiofur in cattle may increase the prevalence of ESC(r) E. coli. We report that herd ESC(r) E. coli fecal and hide prevalences throughout the residency of cattle at a feedlot, including during the period of greatest ceftiofur use at the feedlot, were either not significantly different (P ≥ 0.05) or significantly less (P < 0.05) than the respective prevalences at arrival. Longitudinal sampling of cattle treated with ceftiofur demonstrated that once the transient increase of ESC(r) E. coli shedding that follows ceftiofur injection abated, ceftiofur-injected cattle were no more likely than untreated members of the same herd to shed ESC(r) E. coli. Pulsed-field gel electrophoresis (PFGE) genotyping, antibiotic resistance phenotyping, screening for presence of the blaCMY-2 gene, and plasmid replicon typing were performed on 312 ESC(r) E. coli isolates obtained during six sampling periods spanning the 10-month residence of cattle at the feedlot. The identification of only 26 unique PFGE genotypes, 12 of which were isolated during multiple sampling periods, suggests that clonal expansion of feedlot-adapted blaCMY-2 E. coli strains contributed more to the persistence of blaCMY-2 than horizontal transfer of IncA/C plasmids between E. coli strains at this feedlot. We conclude that therapeutic use of ceftiofur at this cattle feedlot did not significantly increase the herd prevalence of ESC(r) E. coli.


Asunto(s)
Antibacterianos/administración & dosificación , Cefalosporinas/administración & dosificación , Escherichia coli/efectos de los fármacos , Heces/microbiología , Piel/microbiología , Resistencia betalactámica , beta-Lactamasas/metabolismo , Animales , Portador Sano/epidemiología , Portador Sano/microbiología , Portador Sano/veterinaria , Bovinos , Electroforesis en Gel de Campo Pulsado , Escherichia coli/clasificación , Escherichia coli/genética , Escherichia coli/aislamiento & purificación , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/microbiología , Infecciones por Escherichia coli/veterinaria , Epidemiología Molecular , Tipificación Molecular , Prevalencia , beta-Lactamasas/genética
7.
Appl Environ Microbiol ; 79(15): 4744-50, 2013 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-23793628

RESUMEN

Lymph nodes (mandibular, mesenteric, mediastinal, and subiliac; n = 68) and fecal (n = 68) and hide (n = 35) samples were collected from beef carcasses harvested in an abattoir in Mexico. Samples were analyzed for Salmonella, and presumptive colonies were subjected to latex agglutination. Of the isolates recovered, a subset of 91 was characterized by serotyping, pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility phenotyping. Salmonella was isolated from 100% (hide), 94.1% (feces), 91.2% (mesenteric), 76.5% (subiliac), 55.9% (mandibular), and 7.4% (mediastinal) of samples. From the 87 typeable isolates, eight Salmonella enterica serotypes, including Kentucky (32.2%), Anatum (29.9%), Reading (17.2%), Meleagridis (12.6%), Cerro (4.6%), Muenster (1.1%), Give (1.1%), and Mbandaka (1.1%), were identified. S. Meleagridis was more likely (P = 0.03) to be recovered from lymph nodes than from feces or hides, whereas S. Kentucky was more likely (P = 0.02) to be recovered from feces and hides than from lymph nodes. The majority (59.3%) of the Salmonella isolates were pansusceptible; however, multidrug resistance was observed in 13.2% of isolates. Typing by PFGE revealed that Salmonella strains generally clustered by serotype, but some serotypes (Anatum, Kentucky, Meleagridis, and Reading) were comprised of multiple PFGE subtypes. Indistinguishable PFGE subtypes and, therefore, serotypes were isolated from multiple sample types, and multiple PFGE subtypes were commonly observed within an animal. Given the overrepresentation of some serotypes within lymph nodes, we hypothesize that certain Salmonella strains may be better at entering the bovine host than other Salmonella strains or that some may be better adapted for survival within lymph nodes. Our data provide insight into the ecology of Salmonella within cohorts of cattle and offer direction for intervention opportunities.


Asunto(s)
Enfermedades de los Bovinos/microbiología , Polimorfismo Genético , Salmonelosis Animal/microbiología , Salmonella/clasificación , Salmonella/genética , Mataderos , Animales , Bovinos , Enfermedades de los Bovinos/epidemiología , Farmacorresistencia Bacteriana Múltiple , Electroforesis en Gel de Campo Pulsado/veterinaria , Heces/microbiología , Ganglios Linfáticos/microbiología , México , Pruebas de Sensibilidad Microbiana/veterinaria , Filogenia , Salmonella/efectos de los fármacos , Salmonella/aislamiento & purificación , Salmonelosis Animal/epidemiología , Serotipificación/veterinaria , Piel/microbiología
8.
Foodborne Pathog Dis ; 10(4): 368-74, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23566273

RESUMEN

Bovine peripheral lymph nodes (LNs), including subiliac LNs, have been identified as a potential source of human exposure to Salmonella enterica, when adipose trim containing these nodes is incorporated into ground beef. In order to gain a better understanding of the burden of S. enterica in peripheral LNs of feedlot and cull cattle, a cross-sectional study was undertaken in which 3327 subiliac LNs were collected from cattle at harvest in seven plants, located in three geographically distinct regions of the United States. Samples were collected in three seasons: Fall 2010, Winter/Spring 2011, and Summer/Fall 2011. A convenience sample of 76 LNs per day, 2 days per season (approximately 1 month apart), was collected per plant, from carcasses held in the cooler for no less than 24 h. Every 10(th) carcass half on a rail was sampled, in an attempt to avoid oversampling any single cohort of cattle. Median point estimates of S. enterica contamination were generally low (1.3%); however, median Salmonella prevalence was found to be greater in subiliac LNs of feedlot cattle (11.8%) compared to those of cull cattle (0.65%). Enumeration analysis of a subset of 618 feedlot cattle LNs showed that 67% of those harboring S. enterica (97 of 144) did so at concentrations ranging from <0.1 to 1.8 log10 CFU/g, while 33% carried a higher burden of S. enterica, with levels ranging from 1.9 to >3.8 log10 CFU/g. Serotyping of S. enterica isolated identified 24 serotypes, with the majority being Montevideo (44.0%) and Anatum (24.8%). Antimicrobial susceptibility phenotypes were determined for all isolates, and the majority (86.1%) were pansusceptible; however, multidrug-resistant isolates (8.3%) were also occasionally observed. As Salmonella contained within LNs are protected from carcass interventions, research is needed to define opportunities for mitigating the risk of Salmonella contamination in LNs of apparently healthy cattle.


Asunto(s)
Portador Sano , Bovinos/microbiología , Farmacorresistencia Bacteriana Múltiple , Ganglios Linfáticos/microbiología , Salmonella enterica/aislamiento & purificación , Animales , Enfermedades de los Bovinos/microbiología , Recuento de Colonia Microbiana , Estudios Transversales , Pruebas de Sensibilidad Microbiana , Fenotipo , Salmonelosis Animal/microbiología , Salmonella enterica/clasificación , Estaciones del Año , Serotipificación , Estados Unidos
9.
Appl Environ Microbiol ; 78(8): 2716-26, 2012 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-22327585

RESUMEN

The objective of this study was to characterize Salmonella enterica contamination on carcasses in two large U.S. commercial pork processing plants. The carcasses were sampled at three points, before scalding (prescald), after dehairing/polishing but before evisceration (preevisceration), and after chilling (chilled final). The overall prevalences of Salmonella on carcasses at these three sampling points, prescald, preevisceration, and after chilling, were 91.2%, 19.1%, and 3.7%, respectively. At one of the two plants, the prevalence of Salmonella was significantly higher (P < 0.01) for each of the carcass sampling points. The prevalences of carcasses with enumerable Salmonella at prescald, preevisceration, and after chilling were 37.7%, 4.8%, and 0.6%, respectively. A total of 294 prescald carcasses had Salmonella loads of >1.9 log CFU/100 cm(2), but these carcasses were not equally distributed between the two plants, as 234 occurred at the plant with higher Salmonella prevalences. Forty-one serotypes were identified on prescald carcasses with Salmonella enterica serotypes Derby, Typhimurium, and Anatum predominating. S. enterica serotypes Typhimurium and London were the most common of the 24 serotypes isolated from preevisceration carcasses. The Salmonella serotypes Johannesburg and Typhimurium were the most frequently isolated serotypes of the 9 serotypes identified from chilled final carcasses. Antimicrobial susceptibility was determined for selected isolates from each carcass sampling point. Multiple drug resistance (MDR), defined as resistance to three or more classes of antimicrobial agents, was identified for 71.2%, 47.8%, and 77.5% of the tested isolates from prescald, preevisceration, and chilled final carcasses, respectively. The results of this study indicate that the interventions used by pork processing plants greatly reduce the prevalence of Salmonella on carcasses, but MDR Salmonella was isolated from 3.2% of the final carcasses sampled.


Asunto(s)
Farmacorresistencia Bacteriana , Salmonelosis Animal/epidemiología , Salmonelosis Animal/microbiología , Salmonella enterica/aislamiento & purificación , Porcinos/microbiología , Mataderos , Animales , Carga Bacteriana , Manipulación de Alimentos , Fenotipo , Prevalencia , Salmonella enterica/clasificación , Salmonella enterica/efectos de los fármacos , Serotipificación , Estados Unidos/epidemiología
10.
Appl Environ Microbiol ; 77(5): 1783-96, 2011 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-21239549

RESUMEN

The prevalence and diversity of multidrug-resistant (MDR) Salmonella enterica strains associated with cattle at harvest in the United States were examined. Hides and carcasses of cattle were sampled at processing plants (n = 6) located in four geographically distant regions from July 2005 to April 2006. The mean prevalences of Salmonella on hides, preevisceration carcasses (immediately after hide removal), and postintervention carcasses (in the chiller and after the full complement of interventions) were 89.6%, 50.2%, and 0.8%, respectively. The values for MDR Salmonella enterica strains (defined as those resistant to two or more antimicrobials) as percentages of Salmonella prevalence were 16.7% (95% confidence interval [CI], 8.3 to 25.1%; median percent prevalence, 6.9%), 11.7% (95% CI, 4.4 to 19.0%; median, 4.8%), and 0.33% (95% CI, -0.3 to 0.70%; median, 0%), respectively. In this study, 16,218 Salmonella hide and carcass isolates were screened for antimicrobial resistance. Of these, 978 (6.0%) unique MDR S. enterica isolates were identified and serotyped and their XbaI pulsed-field gel electrophoresis (PFGE) profiles determined. The predominant MDR S. enterica serotypes observed were Newport (53.1%), Typhimurium (16.6%), and Uganda (10.9%). Differences in MDR S. enterica prevalence were detected, and PFGE analysis revealed both epidemic clusters (profiles found in plants in multiple regions/seasons) and endemic clusters (profiles observed in plants in limited regions/seasons) within several of the MDR serotypes examined. Despite these differences, multiple-hurdle processing interventions employed at all plants were found to be quite effective and decreased Salmonella carcass contamination by 98.4% (95% CI, 97.6 to 99.7%).


Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana Múltiple , Variación Genética , Salmonelosis Animal/microbiología , Salmonella enterica/efectos de los fármacos , Salmonella enterica/aislamiento & purificación , Animales , Técnicas de Tipificación Bacteriana , Bovinos , Análisis por Conglomerados , Electroforesis en Gel de Campo Pulsado , Genotipo , Tipificación Molecular , Salmonella enterica/clasificación , Serotipificación , Estados Unidos
11.
Foodborne Pathog Dis ; 8(4): 535-40, 2011 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-21453118

RESUMEN

It is thought that antimicrobial resistance imposes a fitness cost on bacteria, so that a reduction in antimicrobial use may reduce the incidence of resistant bacteria. The objectives of the present study were to determine (1) whether multidrug resistant (MDR) Escherichia coli field strains with different plasmid profiles show disparate plasmid loss when grown over time without selection pressure; (2) whether the number of plasmids present in the cell affects growth. Nine ß-hemolytic E. coli strains from swine (n=8) and cattle (n=1) were grown in separate continuous-flow vessels for 36 days without antimicrobial selection. Populations were enumerated on brain heart infusion agar and brain heart infusion agar with tetracycline on days 2, 5, 8, 15, 22, 29, and 36. Growth rates, plasmid profiles and susceptibility profiles of the strains were compared, and day 36 isolates (n=40, five for each MDR strain) were compared with their corresponding day 0 strains. Plasmid content of the nine field strains ranged from zero to eight with sizes from 3.2 to 165 kb. Changes in susceptibility profiles of day 36 isolates were observed among 20% (8 of 40) of the isolates. MDR E. coli largely maintained their original plasmid profiles, replicon types, and susceptibility profiles over 36 days of continuous culture. There was no significant difference in maximum specific growth rate among strains when compared with the plasmid-free strain or when day 36 isolates were compared with their own day 0 strain. This suggests that there is little fitness cost in the maintenance of multiple plasmids of various sizes under the conditions of this study. Other strategies rather than merely reducing antimicrobial usage are needed to combat the emergence of MDR bacteria.


Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana/genética , Escherichia coli/efectos de los fármacos , Escherichia coli/genética , Factores R/genética , Farmacorresistencia Bacteriana Múltiple/genética , Escherichia coli/crecimiento & desarrollo , Fermentación , Genotipo , Hemólisis , Pruebas de Sensibilidad Microbiana , Reacción en Cadena de la Polimerasa , Secuencias Repetitivas de Ácidos Nucleicos , Replicón , Selección Genética , Factores de Tiempo
12.
Appl Environ Microbiol ; 75(20): 6515-23, 2009 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-19684164

RESUMEN

The objectives of the study described here were (i) to investigate the dynamics of Escherichia coli O157:H7 fecal and hide prevalence over a 9-month period in a feedlot setting and (ii) to determine how animals shedding E. coli O157:H7 at high levels affect the prevalence and levels of E. coli O157:H7 on the hides of other animals in the same pen. Cattle (n = 319) were distributed in 10 adjacent pens, and fecal and hide levels of E. coli O157:H7 were monitored. When the fecal pen prevalence exceeded 20%, the hide pen prevalence was usually (25 of 27 pens) greater than 80%. Sixteen of 19 (84.2%) supershedder (>10(4) CFU/g) pens had a fecal prevalence greater than 20%. Significant associations with hide and high-level hide (>/=40 CFU/100 cm(2)) contamination were identified for (i) a fecal prevalence greater than 20%, (ii) the presence of one or more high-density shedders (>/=200 CFU/g) in a pen, and (iii) the presence of one or more supershedders in a pen. The results presented here suggest that the E. coli O157:H7 fecal prevalence should be reduced below 20% and the levels of shedding should be kept below 200 CFU/g to minimize the contamination of cattle hides. Also, large and unpredictable fluctuations within and between pens in both fecal and hide prevalence of E. coli O157:H7 were detected and should be used as a guide when preharvest studies, particularly preharvest intervention studies, are designed.


Asunto(s)
Bovinos/microbiología , Escherichia coli O157/aislamiento & purificación , Microbiología de Alimentos , Carne/microbiología , Alimentación Animal , Crianza de Animales Domésticos , Animales , Recuento de Colonia Microbiana , Heces/microbiología , Femenino , Contaminación de Alimentos/prevención & control , Modelos Logísticos , Estudios Longitudinales , Masculino , Modelos Biológicos , Estaciones del Año , Piel/microbiología , Microbiología del Suelo
13.
J Food Prot ; 72(1): 151-6, 2009 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-19205477

RESUMEN

1,3-Dibromo-5,5-dimethylhydantoin (DBDMH; 25 degrees C) and hot water (85 degrees C) spray treatments were evaluated for efficacy in decontamination of pathogenic bacteria attached to beef carcass surfaces represented by cutaneous trunci (CT) muscle sections and beef hearts. Treatments were evaluated using two different systems, a commercial carcass wash cabinet and a model carcass washer. The effects were measured immediately after treatment and again after 48 h of storage at 4 degrees C. Section of CT and beef hearts were inoculated with bovine fecal solution containing approximately 6 log CFU/cm2 of Escherichia coli O157:H7 and Salmonella. After DBDMH or hot water spray treatments, bacterial populations were enumerated immediately and after storage for 48 h at 4 degrees C. DBDMH treatments reduced aerobic plate counts, Enterobacteriaceae, E. coli O157: H7, and Salmonella by the same or slightly lower amounts relative to hot water treatment. DBDMH reduced aerobic plate counts and Enterobacteriaceae by 2.8 to 3.6 log CFU/cm2, E. coli O157:H7 by 1.6 to 2.1 log CFU/cm2, and Salmonella by 0.7 to 2.3 log CFU/cm2 on CT sections and beef hearts. Hot water treatment reduced aerobic plate counts and Enterobacteriaceae by 3.0 to 4.1 log CFU/cm2, E. coli O157:H7 by 1.8 to 2.3 log CFU/cm2, and Salmonella by 2.5 to 2.8 log CFU/cm2. After 48 h of storage, the reductions of organisms by DBDMH and hot water treatments were not different. This study demonstrated that DBDMH spray washing could be effective as an antimicrobial intervention for beef carcasses and variety meats.


Asunto(s)
Antibacterianos/farmacología , Escherichia coli O157/efectos de los fármacos , Manipulación de Alimentos/métodos , Hidantoínas/farmacología , Carne/microbiología , Salmonella/efectos de los fármacos , Animales , Bovinos , Recuento de Colonia Microbiana , Enterobacteriaceae/efectos de los fármacos , Enterobacteriaceae/crecimiento & desarrollo , Escherichia coli O157/crecimiento & desarrollo , Contaminación de Alimentos/análisis , Contaminación de Alimentos/prevención & control , Corazón/microbiología , Salmonella/crecimiento & desarrollo , Temperatura , Factores de Tiempo
14.
J Food Prot ; 72(6): 1267-71, 2009 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-19610338

RESUMEN

The prevalence rates of Escherichia coli O157:H7 and Salmonella at different sampling sites on cattle hides were determined at a feedlot and a processing plant. Sponge samples were collected from six hide surface sites at the feedlot (left and right shoulders, left and right ribs, back, and belly) and four sites at the processing plant (left and right shoulders, back, and belly). The prevalence of E. coli O157:H7 was approximately 80% for left and right shoulder and rib samples, 68% for back samples, and 92% for belly samples collected at the feedlot. At the processing plant, the prevalences of E. coli O157:H7 at all four sites were between 76 and 79%. Salmonella prevalence in feedlot samples was too low to allow for accurate analysis. The prevalence of Salmonella at processing was 49% for left shoulder samples, 48% for right shoulder samples, 40% for back samples, and 68% for belly samples. The results of this study indicate that the site most likely to be naturally contaminated with E. coli O157:H7 and Salmonella simultaneously was the belly.


Asunto(s)
Crianza de Animales Domésticos , Bovinos/microbiología , Escherichia coli O157/aislamiento & purificación , Industria de Procesamiento de Alimentos , Salmonella/aislamiento & purificación , Animales , Recuento de Colonia Microbiana , Microbiología Ambiental , Contaminación de Alimentos/análisis , Contaminación de Alimentos/prevención & control , Microbiología de Alimentos , Cabello/microbiología , Prevalencia , Estaciones del Año , Piel/microbiología
15.
J Food Prot ; 72(6): 1272-8, 2009 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-19610339

RESUMEN

A significant portion (15 to 20%) of beef in the United States is produced in small beef processing plants that harvest fewer than 1000 cattle per day. However, there are little data on the prevalence and levels of Escherichia coli O157:H7 and Salmonella in these processing plants. To address this lack of data, hides (n=1995) and carcasses (n=1995) of cattle at seven small processing plants located across the United States were analyzed for E. coli O157:H7 and Salmonella. Across all plants, hide prevalence of E. coli O157:H7 and Salmonella was 71 and 91%, respectively. Twelve percent of hides had E. coli O157:H7 at enumerable levels (> or =40 CFU/100 cm2), while 36% of hides had Salmonella at enumerable levels. Across all plants, the prevalence of E. coli O157:H7 on preevisceration carcasses was 33%, with 2% at an enumerable level (> or = 0.8 CFU/ 100 cm2). Across all plants, Salmonella prevalence on preevisceration carcasses was 58%, with 8% at an enumerable level. Significant plant-to-plant variations in levels and prevalence of pathogens on carcasses were detected. Reduced levels of pathogens on carcasses were noted among small processors that had incorporated a hide-directed intervention. The results obtained are comparable to those observed previously for larger processors, showing that smaller beef processors face and address the same challenges as do larger beef processors.


Asunto(s)
Mataderos/estadística & datos numéricos , Bovinos/microbiología , Escherichia coli O157/aislamiento & purificación , Contaminación de Alimentos/análisis , Industria de Procesamiento de Alimentos/estadística & datos numéricos , Salmonella/aislamiento & purificación , Mataderos/normas , Animales , Recuento de Colonia Microbiana , Industria de Procesamiento de Alimentos/normas , Cabello/microbiología , Carne/microbiología , Prevalencia , Estados Unidos/epidemiología
16.
Foodborne Pathog Dis ; 6(10): 1185-94, 2009 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19743926

RESUMEN

The objective of this study was to understand the conjugative transmissibility of resistance plasmids present in 205 Salmonella enterica isolates from bovine sources. Polymerase chain reaction (PCR)-based replicon typing was used to type plasmid replicons. Conjugation experiments were preformed in triplicate at 30 degrees C and 37 degrees C on solid medium. PCR mapping of the A/C transfer gene operon was done on 17 Salmonella Newport isolates that were only positive for A/C. Eighty-six percent (n = 177) of the Salmonella isolates were multidrug resistant (MDR) with resistance to 3-12 antimicrobial agents. Of these, 82% (n = 146) were resistant to extended-spectrum cephalosporins and possessed a bla(CMY) gene. A/C was the predominant replicon detected, present in 90% (n = 160) of the MDR isolates. Twenty-three percent (n = 37) of the A/C-positive strains were positive for a second replicon. Replicons coresident with A/C included I1, N, B/O, HI1, and HI2. Only 31% (n = 54) of the MDR isolates produced transconjugants, and most of these donors carried multiple replicons. A/C cotransferred with B/O, N, and I1 at both 30 degrees C and 37 degrees C and with HI2 at 30 degrees C. Seven Salmonella Newport isolates that produced transconjugants possessed only the single A/C replicon and lacked bla(CMY). PCR mapping of the A/C transfer gene operon in ten Salmonella Newport isolates that carried bla(CMY) revealed a bla(CMY) inverted repeat element integrated between the traA and traC genes. These results suggest that A/C may have been a conjugative plasmid before the integration of bla(CMY) into the transfer gene operon. Additionally, transfer deficient A/C replicons may be mobilized in the presence of certain compatible conjugative plasmids.


Asunto(s)
Conjugación Genética , Transferencia de Gen Horizontal , Plásmidos/genética , Salmonella enterica/genética , beta-Lactamasas/genética , Animales , Bovinos , Escherichia coli/genética , Heces/microbiología , Femenino , Genes MDR , Genotipo , Masculino , Pruebas de Sensibilidad Microbiana , Fenotipo , Plásmidos/química , Reacción en Cadena de la Polimerasa , Replicón/genética , Salmonella enterica/efectos de los fármacos , Salmonella enterica/aislamiento & purificación , Salmonella enterica/fisiología , Piel/microbiología , Resistencia betalactámica/genética
17.
Appl Environ Microbiol ; 74(20): 6289-97, 2008 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-18723661

RESUMEN

The hide and carcass hygiene of cull cattle at slaughter in four geographically distant regions of the United States was examined from July 2005 to April 2006 by measuring the aerobic plate counts (APC) and the prevalences and loads of Salmonella and Escherichia coli O157:H7. The geometric mean log(10) APC CFU/100 cm(2) levels on hides and preevisceration and postintervention carcasses ranged from 6.17 to 8.19, 4.24 to 6.47, and 1.46 to 1.96, respectively, and were highest in the summer (P < 0.0001). The average prevalences of Salmonella on hides and preevisceration and postintervention carcasses were 89.6% (95% confidence interval [CI], 85.1 to 94.0), 50.2% (95% CI, 40.9 to 59.5), and 0.8% (95% CI, 0.18 to 1.42), respectively. The prevalences of E. coli O157:H7 were 46.9% (95% CI, 37.3 to 56.6) and 16.7% (95% CI, 9.8 to 23.6) on hides and preevisceration carcasses, respectively. Examination of the concomitant incidence of Salmonella and E. coli O157:H7 showed that, on average, 33.3% (95% CI, 15.9 to 69.8) of cattle hide and 4.1% (95% CI, 0.98 to 17.3) of preevisceration carcass samples were contaminated with both pathogens. The pathogen prevalence on hides and carcasses was not significantly affected by the season; however, significant differences were observed between plants with respect to the incoming pathogen load and the ability to mitigate hide-to-carcass transfer. In spite of these differences, postintervention carcass contamination was significantly reduced (P < 0.001), likely as a result of the use of one or more of the processing interventions employed at each of the four processing plants examined.


Asunto(s)
Escherichia coli O157/aislamiento & purificación , Microbiología de Alimentos , Salmonella/aislamiento & purificación , Mataderos , Animales , Bovinos , Recuento de Colonia Microbiana , Contaminación de Alimentos , Separación Inmunomagnética , Estaciones del Año , Estados Unidos
18.
J Food Prot ; 71(11): 2177-81, 2008 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-19044258

RESUMEN

Several strains of Salmonella have been identified as resistant to multiple antibiotics. What is not known is whether strains possessing multidrug resistance properties also have the ability to resist the killing effects of the antimicrobial interventions used in beef processing. The research project described herein was designed to determine whether antimicrobial interventions currently in place in beef processing facilities are adequate for reducing the foodborne pathogen loads on beef carcass surfaces contaminated with multidrug-resistant (MDR) Salmonella. The data presented here indicate that MDR Salmonella is reduced at least as effectively as are Escherichia coli O157:H7 and susceptible Salmonella when treated with antimicrobial interventions currently in use at most U.S. beef processing plants. The E. coli O157:H7 strains used in this study were divided into two groups, strains that have a genetic polymorphism associated with human disease and strains not typically found to cause human disease. No differences were detected in the abilities of these two strain types to survive antimicrobial interventions. These results indicate that neither the drug resistance status of a particular Salmonella strain nor the likelihood that a particular E. coli O157:H7 strain will cause human illness influences the antimicrobial efficacy of the interventions utilized by the modern beef processing plants.


Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana Múltiple , Escherichia coli O157/efectos de los fármacos , Contaminación de Alimentos/análisis , Carne/microbiología , Salmonella/efectos de los fármacos , Animales , Bovinos , Recuento de Colonia Microbiana , Seguridad de Productos para el Consumidor , Escherichia coli O157/crecimiento & desarrollo , Escherichia coli O157/patogenicidad , Contaminación de Alimentos/prevención & control , Microbiología de Alimentos , Humanos , Pruebas de Sensibilidad Microbiana , Salmonella/crecimiento & desarrollo , Salmonella/patogenicidad
19.
J Food Prot ; 71(9): 1752-60, 2008 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-18810858

RESUMEN

Transportation from the feedlot and lairage at the processing plant have been identified as potential sources of Escherichia coli O157:H7 and Salmonella hide contamination. The objective of this study was to perform a comprehensive tracking analysis of E. coli O157:H7 and Salmonella associated with beef cattle from the feedlot through processing. Cattle (n = 581) were sampled in a feedlot, then transported in multiple lots to three commercial, fed beef processing plants in the United States, where they were sampled again. Samples were collected from the tractor trailers prior to loading cattle and from the lairage environment spaces prior to entry of the study cattle. Pathogen prevalence on cattle hides increased on every lot of cattle between exiting the feedlot and beginning processing. Prior to loading cattle, E. coli O157:H7 was found in 9 (64%) of 14 tractor trailers. E. coli O157:H7 was detected in over 60% of the samples from each lairage environment area, while Salmonella was detected in over 70% of the samples from each lairage environment area. E. coli O157:H7 and Salmonella isolates (n = 3,645) were analyzed using pulsed-field gel electrophoresis. The results of the pulsed-field gel electrophoresis tracking indicate that the transfer of bacteria onto cattle hides that occurs in the lairage environments of U.S beef processing plants accounts for a larger proportion of the hide and carcass contamination than does the initial bacterial population found on the cattle exiting the feedlot. Finally, the results of this study indicate that hide wash cabinets are effective in removing contamination derived from the lairage environment.


Asunto(s)
Escherichia coli O157/aislamiento & purificación , Contaminación de Alimentos/análisis , Microbiología de Alimentos , Industria de Procesamiento de Alimentos/normas , Salmonella/aislamiento & purificación , Mataderos , Crianza de Animales Domésticos/métodos , Crianza de Animales Domésticos/normas , Animales , Bovinos , Recuento de Colonia Microbiana , Microbiología Ambiental , Femenino , Industria de Procesamiento de Alimentos/métodos , Humanos , Masculino , Prevalencia , Piel/microbiología , Transportes/métodos , Transportes/normas
20.
J Food Prot ; 71(3): 621-4, 2008 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-18389711

RESUMEN

The effectiveness of electrolyzed oxidizing water, FreshFx, hot water, DL-lactic acid, and ozonated water was determined using a model carcass spray-washing cabinet. A total of 140 beef heads obtained from a commercial processing line were inoculated with Escherichia coli O157:H7 on the cheek areas. Each head was exposed to a simulated preevisceration wash and then had antimicrobial wash treatments. Hot water, lactic acid, and FreshFx treatments reduced E. coli O157:H7 on inoculated beef heads by 1.72, 1.52, and 1.06 log CFU/cm2, respectively, relative to the simulated preevisceration wash. Electrolyzed oxidizing water and ozonated water reduced E. coli O157:H7 less than 0.50 log CFU/cm2. Hot water, lactic acid, and FreshFx could be used as decontamination washes for the reduction of E. coli O157:H7 on bovine head and cheek meat.


Asunto(s)
Desinfectantes/farmacología , Desinfección/métodos , Escherichia coli O157/crecimiento & desarrollo , Manipulación de Alimentos/métodos , Industria de Procesamiento de Alimentos/normas , Cabeza/microbiología , Animales , Bovinos , Recuento de Colonia Microbiana , Seguridad de Productos para el Consumidor , Escherichia coli O157/efectos de los fármacos , Microbiología de Alimentos , Humanos , Ácido Láctico/farmacología , Ozono/farmacología , Agua/farmacología
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