@article{monte_nethery_berman_keelara_lincopan_fedorka-cray_barrangou_landgraf_2022, title={Clustered Regularly Interspaced Short Palindromic Repeats Genotyping of Multidrug-Resistant Salmonella Heidelberg Strains Isolated From the Poultry Production Chain Across Brazil}, volume={13}, ISSN={["1664-302X"]}, DOI={10.3389/fmicb.2022.867278}, abstractNote={Salmonella enterica subsp. enterica serovar Heidelberg has been associated with a broad host range, such as poultry, dairy calves, swine, wild birds, environment, and humans. The continuous evolution of S. Heidelberg raises a public health concern since there is a global dispersal of lineages harboring a wide resistome and virulome on a global scale. Here, we characterized the resistome, phylogenetic structure and clustered regularly interspaced short palindromic repeats (CRISPR) array composition of 81 S. Heidelberg strains isolated from broiler farms (n = 16), transport and lairage (n = 5), slaughterhouse (n = 22), and retail market (n = 38) of the poultry production chain in Brazil, between 2015 and 2016 using high-resolution approaches including whole-genome sequencing (WGS) and WGS-derived CRISPR genotyping. More than 91% of the S. Heidelberg strains were multidrug-resistant. The total antimicrobial resistance (AMR) gene abundances did not vary significantly across regions and sources suggesting the widespread distribution of antibiotic-resistant strains from farm to market. The highest AMR gene abundance was observed for fosA7, aac(6′)-Iaa, sul2, tet(A), gyrA, and parC for 100% of the isolates, followed by 88.8% for blaCMY–2. The β-lactam resistance was essentially driven by the presence of the plasmid-mediated AmpC (pAmpC) blaCMY–2 gene, given the isolates which did not carry this gene were susceptible to cefoxitin (FOX). Most S. Heidelberg strains were classified within international lineages, which were phylogenetically nested with Salmonella strains from European countries; while CRISPR genotyping analysis revealed that the spacer content was overall highly conserved, but distributed into 13 distinct groups. In summary, our findings underscore the potential role of S. Heidelberg as a key pathogen disseminated from farm to fork in Brazil and reinforce the importance of CRISPR-based genotyping for salmonellae. Hence, we emphasized the need for continuous mitigation programs to monitor the dissemination of this high-priority pathogen.}, journal={FRONTIERS IN MICROBIOLOGY}, author={Monte, Daniel F. M. and Nethery, Matthew A. and Berman, Hanna and Keelara, Shivaramu and Lincopan, Nilton and Fedorka-Cray, Paula J. and Barrangou, Rodolphe and Landgraf, Mariza}, year={2022}, month={Jun} }
 @article{hempstead_gensler_keelara_brennan_urie_wiedenheft_marshall_morningstar-shaw_lantz_fedorka-cray_et al._2022, title={Detection and molecular characterization of Salmonella species on US goat operations}, volume={208}, ISSN={["1873-1716"]}, DOI={10.1016/j.prevetmed.2022.105766}, abstractNote={Salmonella species are an important cause of gastrointestinal disease in animals, including goats. Additionally, Salmonella species are among the top five U.S. foodborne pathogens causing illness to humans. The goat industry is rapidly expanding in the U.S. yet estimates of Salmonella prevalence within these populations is lacking. The aim of this study was to investigate the fecal prevalence, antimicrobial resistance (AMR), biofilm potential, and virulence profile of Salmonella species isolated from goat feces as part of the United States Department of Agriculture (USDA) National Animal Health Monitoring System (NAHMS) Goat 2019 study, enteric microbe component. A total of 4917 fecal samples were collected from 332 operations, from September 2019-March 2020. Salmonella were isolated using standard enrichment and culture methods; antimicrobial susceptibility was determined by broth microdilution. Biofilm production was assessed using a crystal violet assay and normalized to a positive control strain, and PCR was used to detect virulence genes. Overall, we detected a low prevalence (0.7%, n = 35/4917) of Salmonella in goat feces and identified a broad range of serotypes including S. Bareilly (35%) and a single rare S. Sharon. All isolates were pansusceptible to 14 antimicrobials except one, which was resistant to only tetracycline (MIC ≥ 32 µg/mL). All strains were found to possess the majority of virulence determinants screened, and 40% (14 of 35) formed weak, moderate, or strong biofilm. We found a low prevalence of Salmonella, and characteristics of Salmonella in the U.S. goat population informs ongoing public health efforts to manage risk of animal food products and animal interactions.}, journal={PREVENTIVE VETERINARY MEDICINE}, author={Hempstead, Stephanie C. and Gensler, Catherine A. and Keelara, Shivaramu and Brennan, Matthew and Urie, Natalie J. and Wiedenheft, Alyson M. and Marshall, Katherine L. and Morningstar-Shaw, Brenda and Lantz, Kristina and Fedorka-Cray, Paula J. and et al.}, year={2022}, month={Nov} }
 @article{atlaw_keelara_correa_foster_gebreyes_aidara-kane_harden_thakur_fedorka-cray_2022, title={Evidence of sheep and abattoir environment as important reservoirs of multidrug-resistant Salmonella and extended-spectrum beta-lactamase Escherichia coli}, volume={363}, ISSN={["1879-3460"]}, url={http://dx.doi.org/10.1016/j.ijfoodmicro.2021.109516}, DOI={10.1016/j.ijfoodmicro.2021.109516}, abstractNote={The increase in antimicrobial-resistant (AMR) foodborne pathogens, including E. coli and Salmonella in animals, humans, and the environment, is a growing public health concern. Among animals, cattle, pigs, and chicken are reservoirs of these pathogens worldwide. There is a knowledge gap on the prevalence and AMR of foodborne pathogens in small ruminants (i.e., sheep and goats). This study investigates the prevalence and antimicrobial resistance of extended-spectrum beta-lactamase (ESBL) E. coli and Salmonella from sheep and their abattoir environment in North Carolina. We conducted a year-round serial cross-sectional study and collected a total of 1128 samples from sheep (n = 780) and their abattoir environment (n = 348). Sheep samples consisted of feces, cecal contents, carcass swabs, and abattoir resting area feces. Environmental samples consisted of soil samples, lairage swab, animal feed, and drinking water for animals. We used CHROMAgar EEC with 4 μg/ml of Cefotaxime for isolating ESBL E. coli, and ESBL production was confirmed by double-disk diffusion test. Salmonella was isolated and confirmed using standard methods. All of the confirmed isolates were tested against a panel of 14 antimicrobials to elucidate susceptibility profiles. The prevalence of ESBL E. coli and Salmonella was significantly higher in environmental samples (47.7% and 65.5%) compared to the sheep samples (19.5% and 17.9%), respectively (P < 0.0001). We recovered 318 ESBL E. coli and 368 Salmonella isolates from sheep and environmental samples. More than 97% (310/318) of ESBL E. coli were multidrug-resistant (MDR; resistant to ≥3 classes of antimicrobials). Most Salmonella isolates (77.2%, 284/368) were pansusceptible, and 10.1% (37/368) were MDR. We identified a total of 24 different Salmonella serotypes by whole genome sequencing (WGS). The most common serotypes were Agona (19.8%), Typhimurium (16.2%), Cannstatt (13.2%), Reading (13.2%), and Anatum (9.6%). Prevalence and percent resistance of ESBL E. coli and Salmonella isolates varied significantly by season and sample type (P < 0.0001). The co-existence of ESBL E. coli in the same sample was associated with increased percent resistance of Salmonella to Ampicillin, Chloramphenicol, Sulfisoxazole, Streptomycin, and Tetracycline. We presumed that the abattoir environment might have played a great role in the persistence and dissemination of resistant bacteria to sheep as they arrive at the abattoir. In conclusion, our study reaffirms that sheep and their abattoir environment act as important reservoirs of AMR ESBL E. coli and MDR Salmonella in the U.S. Further studies are required to determine associated public health risks.}, journal={International Journal of Food Microbiology}, publisher={Elsevier BV}, author={Atlaw, N.A. and Keelara, S. and Correa, M. and Foster, D. and Gebreyes, W. and Aidara-Kane, A. and Harden, L. and Thakur, S. and Fedorka-Cray, P.J.}, year={2022}, month={Feb}, pages={109516} }
 @article{hornsby_ibitoye_keelara_harris_2022, title={Validation of a modified IDEXX defined-substrate assay for detection of antimicrobial resistant E. coli in environmental reservoirs}, volume={12}, ISSN={["2050-7895"]}, url={https://doi.org/10.1039/D2EM00189F}, DOI={10.1039/d2em00189f}, abstractNote={Antimicrobial resistant organisms can be transmitted to humans through multiple environmental pathways. Monitoring these organisms in multiple environmental reservoirs is an important step towards mitigating adverse health impacts.}, journal={ENVIRONMENTAL SCIENCE-PROCESSES & IMPACTS}, author={Hornsby, Gracie and Ibitoye, Temitope D. and Keelara, Shivaramu and Harris, Angela}, year={2022}, month={Dec} }
 @article{atlaw_keelara_correa_foster_gebreyes_aidara-kane_harden_thakur_fedorka-cray_2021, title={Identification of CTX-M type ESBL E. coli from sheep and their abattoir environment using whole-genome sequencing}, volume={10}, ISSN={["2076-0817"]}, url={https://doi.org/10.3390/pathogens10111480}, DOI={10.3390/pathogens10111480}, abstractNote={Widespread dissemination of extended-spectrum beta-lactamase (ESBL) Escherichia coli (E. coli) in animals, retail meats, and patients has been reported worldwide except for limited information on small ruminants. Our study focused on the genotypic characterization of ESBL E. coli from healthy sheep and their abattoir environment in North Carolina, USA. A total of 113 ESBL E. coli isolates from sheep (n = 65) and their abattoir environment (n = 48) were subjected to whole-genome sequencing (WGS). Bioinformatics tools were used to analyze the WGS data. Multiple CTX-M-type beta-lactamase genes were detected, namely blaCTX-M-1, blaCTX-M-14, blaCTX-M-15, blaCTX-M-27, blaCTX-M-32, blaCTX-M-55, and blaCTX-M-65. Other beta-lactamase genes detected included blaCMY-2, blaTEM-1A/B/C, and blaCARB-2. In addition, antimicrobial resistance (AMR) genes and/or point mutations that confer resistance to quinolones, aminoglycosides, phenicols, tetracyclines, macrolides, lincosamides, and folate-pathway antagonists were identified. The majority of the detected plasmids were shared between isolates from sheep and the abattoir environment. Sequence types were more clustered around seasonal sampling but dispersed across sample types. In conclusion, our study reported wide dissemination of ESBL E. coli in sheep and the abattoir environment and associated AMR genes, point mutations, and plasmids. This is the first comprehensive AMR and WGS report on ESBL E. coli from sheep and abattoir environments in the United States.}, number={11}, journal={Pathogens}, publisher={MDPI AG}, author={Atlaw, N.A. and Keelara, S. and Correa, M. and Foster, D. and Gebreyes, W. and Aidara-Kane, A. and Harden, L. and Thakur, S. and Fedorka-Cray, P.J.}, year={2021}, pages={1480} }
 @article{jacob_keelara_aidara-kane_alvarez_fedorka-cray_2020, title={Optimizing a Screening Protocol for Potential Extended-Spectrum beta-Lactamase Escherichia coli on MacConkey Agar for Use in a Global Surveillance Program}, volume={58}, ISSN={["1098-660X"]}, DOI={10.1128/JCM.01039-19}, abstractNote={
            The increasing prevalence of extended-spectrum beta-lactamase (ESBL)-producing
            Escherichia coli
            is worrisome. Coordinated efforts to better understand global prevalence and risk factors are needed. Developing lower- and middle-income countries need reliable, readily available, and cost-effective solutions for detecting ESBL
            E. coli
            to contribute to global surveillance. We evaluated MacConkey agar supplemented with ceftriaxone or cefotaxime as a screening method for accurately detecting and quantifying potential ESBL
            E. coli
            .
          }, number={9}, journal={JOURNAL OF CLINICAL MICROBIOLOGY}, author={Jacob, Megan E. and Keelara, Shivaramu and Aidara-Kane, Awa and Alvarez, Jorge R. Matheu and Fedorka-Cray, Paula J.}, year={2020}, month={Sep} }
 @article{monte_lincopan_berman_cerdeira_keelara_thakur_fedorka-cray_landgraf_2019, title={Genomic Features of High-Priority Salmonella enterica Serovars Circulating in the Food Production Chain, Brazil, 2000-2016}, volume={9}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-019-45838-0}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Monte, Daniel F. . and Lincopan, Nilton and Berman, Hanna and Cerdeira, Louise and Keelara, Shivaramu and Thakur, Siddhartha and Fedorka-Cray, Paula J. and Landgraf, Mariza}, year={2019}, month={Jul} }
 @article{monte_nelson_cerdeira_keelara_greene_griffin_rath_hall_page_fedorka-cray_et al._2019, title={Multidrug- and colistin-resistant Salmonella enterica 4,[5],12:i:- sequence type 34 carrying the mcr-3.1 gene on the IncHI2 plasmid recovered from a human}, volume={68}, ISSN={0022-2615 1473-5644}, url={http://dx.doi.org/10.1099/jmm.0.001012}, DOI={10.1099/jmm.0.001012}, abstractNote={A colistin-resistant Salmonella enterica 4, [5],12:i:- sequence type (ST) 34 harbouring mcr-3.1 was recovered from a patient who travelled to China 2 weeks prior to diarrhoea onset. Genomic analysis revealed the presence of the mcr-3.1 gene located in the globally disseminated IncHI2 plasmid, highlighting the intercontinental dissemination of the colistin-resistant S. enterica 4, [5],12:i:- ST34 pandemic clone.}, number={7}, journal={Journal of Medical Microbiology}, publisher={Microbiology Society}, author={Monte, Daniel F. and Nelson, Valerie and Cerdeira, Louise and Keelara, Shivaramu and Greene, Shermalyn and Griffin, Denise and Rath, Shadia and Hall, Robbie and Page, Nichole and Fedorka-Cray, Paula J. and et al.}, year={2019}, month={Jul}, pages={986–990} }
 @article{monte_nelson_cerdeira_keelara_greene_griffin_rath_hall_page_lawson_et al._2019, title={Multidrug- and colistin-resistant Salmonella enterica 4,[5],12:i:- sequence type 34 carrying the mcr-3.1 gene on the IncHI2 plasmid recovered from a human (vol 68, pg 986, 2019)}, volume={68}, ISSN={["1473-5644"]}, DOI={10.1099/jmm.0.001057}, abstractNote={Microbiology Society journals contain high-quality research papers and topical review articles. We are a not-for-profit publisher and we support and invest in the microbiology community, to the benefit of everyone. This supports our principal goal to develop, expand and strengthen the networks available to our members so that they can generate new knowledge about microbes and ensure that it is shared with other communities.}, number={11}, journal={JOURNAL OF MEDICAL MICROBIOLOGY}, author={Monte, Daniel F. and Nelson, Valerie and Cerdeira, Louise and Keelara, Shivaramu and Greene, Shermalyn and Griffin, Denise and Rath, Shadia and Hall, Robbie and Page, Nichole and Lawson, Thomas and et al.}, year={2019}, month={Nov}, pages={1694–1694} }
 @article{nayakvadi_alemao_kumar_rajkumar_rajkumar_chakurkar_keelara_2018, title={Detection and molecular characterization of sorbitol fermenting non-O157 Escherichia coli from goats}, volume={161}, ISSN={["1879-0941"]}, DOI={10.1016/j.smallrumres.2018.02.008}, abstractNote={Abstract Shiga toxigenic Escherichia coli (STEC) O157 and several other serogroups of non-O157 STEC strains present as commensalism bacteria in small ruminants that possess a high potential of attaining pathogenic virulent genetic elements. The pathogenicity of non-O157 strains is emerging progressively in animals as well as in humans especially in the rural areas as they get transmitted through unsanitary practices of living, consumption of uncooked meat and milk, human-livestock close proximity as well as within livestock pathogenic bacterial transmission. The present study was carried out to determine the prevalence of non-O157 E.coli isolates and characterize based on clinical history, antibiotic sensitivity testing, multiplex PCR (mPCR) detection of virulence genes, genotype identification using pulse field gel electrophoresis (PFGE) and polyacrylamide gel electrophoretic separation of antigenic proteins to determine their prevalence, virulence and genetic comparison between host and environment for epidemiological significance. A total of 300 E.coli isolates were recovered from rectal swabs of goats and their surrounding environment over a period of one year (2016–2017) by selective isolation. Among which 50 isolates were confirmed to be from the non-O157 E.coli family. The mPCR analysis of these 50 isolates revealed the presence of two or more virulent genes, viz., hylA (90%), fliC (74%), eaeA (56%), stx1 (48%) and stx2 (22%).Four isolates exhibited multidrug-resistance to amoxiclav, doxycycline, ciprofloxacin and ceftriazone. The PFGE fingerprint profile showed six major clusters at 100% similarity from the 50 isolates. The major antigenic proteins identified from the isolates were stx1A, stx2B and fliC. This study has significant implications for understanding the molecular diversity of emerging pathotypes of non-O157 in young goats in terms of virulence and epidemiological aspects.}, journal={SMALL RUMINANT RESEARCH}, author={Nayakvadi, Shivasharanappa and Alemao, Charlotte Alison and Kumar, H. B. Chethan and Rajkumar, R. S. and Rajkumar, Susitha and Chakurkar, Eaknath B. and Keelara, Shivaramu}, year={2018}, month={Apr}, pages={7–12} }
 @article{patel_keelara_green_2018, title={Inactivation of Escherichia coli O157:H7 and Salmonella on Fresh Herbs by Plant Essential Oils}, volume={15}, ISSN={["1556-7125"]}, DOI={10.1089/fpd.2017.2377}, abstractNote={Consumer awareness of fresh herbs and its demand has increased in recent years due to health benefits and distinct aroma in prepared food. There are specific markets for local growers, especially for organically grown herbs. Shiga-toxigenic Escherichia coli and Salmonella spp. have been detected and associated with foodborne outbreaks from fresh herbs. Limited treatment options are available in the processing of fresh herbs to prevent the spread of foodborne pathogens. In this study, plant-based essential oils were evaluated on fresh herbs for their antimicrobial activities against Salmonella and E. coli O157:H7. Fresh herbs (basil, cilantro, dill, parsley, and tarragon) were inoculated with cocktails of either Salmonella or E. coli O157:H7 and then dip treated with chlorine (50 ppm), cinnamaldehyde (0.3 and 0.5%), and carvacrol (0.1 and 0.3%). Control herb samples were dipped in sterile water. Samples were collected on days 0, 2, 7, and 14 for enumeration of pathogens during 4°C storage. The bactericidal efficacy differed with herbs and antimicrobial concentrations. Treatments with 0.3% carvacrol or 0.5% cinnamaldehyde reduced E. coli O157:H7 and Salmonella by 5 log CFU/g (p > 0.05%) on cilantro and dill leaves from their initial inoculum level. Bactericidal efficacy of 0.1% carvacrol and 0.3% cinnamaldehyde was significant against Salmonella compared with chlorine on all herb leaves. E. coli O157:H7 and Salmonella populations were reduced further during storage of treated herbs. There was no visual difference in herbs treated with 0.3% cinnamaldehyde or 0.1% carvacrol from control samples. Results indicate that 0.3% cinnamaldehyde and 0.1% carvacrol are effective against E. coli O157:H7 and Salmonella, retain color attributes of fresh herbs, and, therefore, may be an alternative wash treatment for fresh herbs.}, number={6}, journal={FOODBORNE PATHOGENS AND DISEASE}, author={Patel, Jitendra and Keelara, Shivramu and Green, Jennifer}, year={2018}, month={Jun}, pages={332–338} }
 @article{keelara_thakur_patel_2016, title={Biofilm Formation by Environmental Isolates of Salmonella and Their Sensitivity to Natural Antimicrobials}, volume={13}, ISSN={["1556-7125"]}, DOI={10.1089/fpd.2016.2145}, abstractNote={The objective of this study was to determine reduction of Salmonella in biofilms by essential oils. Biofilm formation of 15 Salmonella isolates from conventional swine farm environment was evaluated by 96-well microtiter plate crystal violet and minimum biofilm eradication concentration (MBEC) assays. Only one of the 15 isolates was a strong biofilm producer as classified by crystal violet assay. All Salmonella isolates formed biofilm on MBEC assay. The curli expression was robust among strains S322 and S435 (Salmonella Infantis), S644, S777, S931, S953, and S977 (Salmonella Typhimurium) as observed by Congo red dye binding assay. The cell hydrophobicity varied with strains and growth phase of the strain; however, there was no significant difference in hydrophobicity of these strains. Natural antimicrobials were evaluated with MBEC assay for their bactericidal efficacy in reducing Salmonella in biofilms. Cinnamaldehyde and sporran at 1000 ppm significantly reduced Salmonella in biofilms. The bactericidal effect of these antimicrobials increased with their concentrations. Salmonella were reduced by 6 log CFU from their initial populations of 7-7.5 log CFU/cm(2) when 2000 ppm concentration of these antimicrobials were used. Salmonella were undetectable when 3000 ppm of cinnamaldehyde or sporran was used. Natural antimicrobials such as cinnamaldehyde and sporran can be used to reduce Salmonella in biofilms.}, number={9}, journal={FOODBORNE PATHOGENS AND DISEASE}, author={Keelara, Shivaramu and Thakur, Siddhartha and Patel, Jitendra}, year={2016}, month={Sep}, pages={509–516} }
 @article{borst_suyemoto_keelara_dunningan_guy_barnes_2014, title={A Chicken Embryo Lethality Assay for Pathogenic Enterococcus cecorum}, volume={58}, ISSN={["1938-4351"]}, DOI={10.1637/10687-101113-reg.1}, abstractNote={SUMMARY Pathogenic strains of Enterococcus cecorum cause outbreaks of arthritis and osteomyelitis in chickens worldwide. Enterococcal spondylitis (ES) is a specific manifestation of E. cecorum-associated disease of broilers and broiler breeders characterized by increased flock mortality, resulting from unresolved infection of the free thoracic vertebra by pathogenic E. cecorum. A study of 22 ES outbreaks in the southeast United States revealed that pathogenic E. cecorum strains isolated from spinal lesions were genetically clonal. Here, we compare the virulence of previously genotyped pathogenic strains (n  =  8) isolated from spinal lesions and nonpathogenic strains (n  =  9) isolated from ceca of unaffected birds in a chicken embryo lethality model. Strains were inoculated into the allantoic cavity of 12-day-old broiler and specific-pathogen-free (SPF) layer embryos; embryo survival was determined by candling eggs daily for 4 days. Significantly decreased survival occurred in both broiler and SPF embryos inoculated with pathogenic genotype strains compared with embryos inoculated with nonpathogenic genotype strains (broiler embryos, 23% vs. 60%; SPF embryos, 9% vs. 61%). Embryos infected with pathogenic strains were unable to control infection and consistently showed gross changes typical of sepsis, including hemorrhage and edema. After 48 hr, similar changes were not observed in embryos infected with nonpathogenic strains. This embryo lethality assay provides a useful tool for understanding the genetic basis of E. cecorum virulence. RESUMEN Ensayo de letalidad en embriones de pollo para cepas de Enterococcus cecorum patogénicas. Las cepas patógenas de Enterococcus cecorum causan brotes de artritis y osteomielitis en pollos a nivel mundial. La espondilitis enterococócica (ES) es una manifestación específica de la enfermedad asociada con E. cecorum en pollos de engorde y en reproductoras pesadas que es caracterizada por alta mortalidad de la parvada, como resultado de la infección no resuelta en la vértebra torácica móvil causada por cepas de E. cecorum patógenas. Un estudio de 22 brotes de espondilitis enterococócica en el sureste de los Estados Unidos reveló que las cepas patógenas de E. cecorum aisladas de lesiones de la médula eran genéticamente provenientes de un clon. En este estudio, se comparó mediante un modelo de letalidad del embrión de pollo, la virulencia de las cepas patógenas previamente genotipificadas (n = 8) aisladas de lesiones de la columna vertebral y cepas no patógenas (n = 9) aisladas del ciego de las aves no afectadas. Las cepas fueron inoculadas en la cavidad alantoidea de embriones de pollo de 12 días de edad, de pollos de engorde y en aves libres de patógenos específicos (SPF); la supervivencia de los embriones se determinó por ovoscopía diariamente por cuatro días. De manera significativa se presentó una disminución en la supervivencia en ambos tipo embriones de pollos de engorde y de aves libres de patógenos específicos inoculados con cepas de genotipo patógeno en comparación con los embriones inoculados con cepas de genotipo no patógeno (embriones de pollos de engorde, 23% contra 60%; y en los embriones libres de patógenos específicos, 9% frente a 61%). Los embriones infectados con cepas patógenas fueron incapaces de controlar la infección y mostraron consistentemente cambios macroscópicos típicos de sepsis, incluyendo hemorragia y edema. Después de 48 horas, no se observaron cambios similares en los embriones infectados con cepas no patógenas. Este ensayo de letalidad del embrión proporciona una herramienta útil para la comprensión de la base genética de la virulencia de E. cecorum.}, number={2}, journal={AVIAN DISEASES}, author={Borst, Luke B. and Suyemoto, M. Mitsu and Keelara, Shivaramu and Dunningan, Sarah E. and Guy, James S. and Barnes, H. John}, year={2014}, month={Jun}, pages={244–248} }
 @article{keelara_thakur_2014, title={Dissemination of plasmid-encoded AmpC beta-lactamases in antimicrobial resistant Salmonella serotypes originating from humans, pigs and the swine environment}, volume={173}, ISSN={["1873-2542"]}, DOI={10.1016/j.vetmic.2014.07.018}, abstractNote={The aim of this study was to characterize and determine the inter-serovar exchange of AmpC β-lactamase conferring plasmids isolated from humans, pigs and the swine environment. Plasmids isolated from a total of 21 antimicrobial resistant (AMR) Salmonella isolates representing human clinical cases (n = 6), pigs (n = 6) and the swine farm environment (n = 9) were characterized by replicon typing and restriction digestion, inter-serovar transferability by conjugation, and presence of AmpC β-lactamase enzyme encoding gene blaCMY-2 by southern hybridization. Based on replicon typing, the majority (17/21, 81%) of the plasmids belonged to the I1-Iγ Inc group and were between 70 and 103 kb. The potential for inter-serovar plasmid transfer was further confirmed by the PCR detection of AMR genes on the plasmids isolated from trans-conjugants. Plasmids from Salmonella serovars Anatum, Ouakam, Johannesburg and Typhimurium isolated from the same cohort of pigs and their environment and S. Heidelberg from a single human clinical isolate had identical plasmids based on digestion with multiple restriction enzymes (EcoRI, HindIII and PstI) and southern blotting. We demonstrated likely horizontal inter-serovar exchange of plasmid-encoding AmpC β-lactamases resistance among MDR Salmonella serotypes isolated from pigs, swine farm environment and clinical human cases. This study provides valuable information on the role of the swine farm environment and by extension other livestock farm environments, as a potential reservoir of resistant bacterial strains that potentially transmit resistance determinants to livestock, in this case, swine, humans and possibly other hosts by horizontal exchange of plasmids.}, number={1-2}, journal={VETERINARY MICROBIOLOGY}, author={Keelara, Shivaramu and Thakur, Siddhartha}, year={2014}, month={Sep}, pages={76–83} }
 @article{keelara_scott_morrow_gebreyes_correa_nayak_stefanova_thakur_2013, title={Longitudinal Study of Distributions of Similar Antimicrobial-Resistant Salmonella Serovars in Pigs and Their Environment in Two Distinct Swine Production Systems}, volume={79}, ISSN={0099-2240 1098-5336}, url={http://dx.doi.org/10.1128/AEM.01419-13}, DOI={10.1128/aem.01419-13}, abstractNote={ABSTRACT}, number={17}, journal={Applied and Environmental Microbiology}, publisher={American Society for Microbiology}, author={Keelara, Shivaramu and Scott, H. Morgan and Morrow, William M. and Gebreyes, Wondwossen A. and Correa, Maria and Nayak, Rajesh and Stefanova, Rossina and Thakur, Siddhartha}, year={2013}, month={Jun}, pages={5167–5178} }