doi: 10.15389/agrobiology.2024.6.1221eng
UDC: 619:636.2:577.21:579.62
Acknowledgements:
Conducted within the framework of the Russian Foundation for Basic Research grant (No. 20-416-660004) “Molecular genetic and phenotypic characteristics of the reproductive tract microbiota of cattle”
ANTIBIOTIC RESISTANCE, PATHOGENICITY AND VIRULENCE GENES OF Staphylococcus aureus AND Escherichia coli, ISOLATED FROM THE REPRODUCTIVE TRACT AND MAMMARY GLAND OF CATTLE (Bos taurus) DURING INFLAMMATION
O.V. Sokolova ✉, V.D. Zubareva, N.A. Bezborodova, M.V. Bytov,
I.A. Shkuratova
Ural Federal Agrarian Scientific Centre, Ural Branch RAS, 112a, ul. Belinskogo, Ekaterinburg, 620142 Russia, е-mail nauka_sokolova@mail.ru (✉ corresponding author), zzub97@mail.ru, n-bezborodova@mail.ru, bytovmaks@mail.ru, shkuratova@bk.ru
ORCID:
Sokolova O.V. orcid.org/0000-0002-1169-4090
Bytov M.V. orcid.org/0000-0002-3622-3770
Zubareva V.D. orcid.org/0000-0003-0284-0276
Shkuratova I.A. orcid.org/0000-0003-0025-3545
Bezborodova N.A. orcid.org/0000-0003-2793-5001
Final revision received October 25, 2023
Accepted November 14, 2023
Mastitis and metritis are the main diseases that cause significant economic damage to dairy cattle breeding, which is associated with a decrease in fertility and productivity, premature culling of highly productive cows, as well as the costs of diagnostics and treatment of affected animals. In this work, we have for the first time carried out genotyping of Staphylococcus aureus and Escherichia coli isolates obtained from cattle in the Sverdlovsk region for the genes of antibiotic resistance, pathogenicity, and virulence. The presence of isolates with a combination of genes determining resistance to antibiotics and the simultaneous manifestation of pathogenic and virulent properties was found. It was revealed that a high frequency of fimA and fimH virulence genes may be important for E. coli colonization of epithelial cells of the mammary gland and reproductive tract of cows. The aim of our research was to study the genetic profile of S. aureus and E. coli isolates for genes responsible for antibacterial resistance to drugs of the fluoroquinolone group, second-generation cephalosporins, macrolides, aminoglycosides, amphenicols, tetracyclines, oxazolidinones, glycopeptides, as well as for the pathogenicity and virulence genes of S. aureus (sea, seb, sec, seg, tst, luks-PV, lukED, fnbA, fnbB, cna) and E. coli (K99, fimA, fimH, F41, Sta, STΙa, STΙb, stx1, stx2). E. coli (n = 26) and S. aureus (n = 16) isolates from mammary gland secretion and cervicovaginal swabs of 29 Holstein cows with signs of inflammatory process in the reproductive tract and mammary gland were studied (2021,. Ready-made nutrient media were used for the microbiological study: Endo medium (State Research Center of Applied Microbiology and Biotechnology), salt broth, yolk-salt agar, elective salt medium (mannitol-salt agar) (OOO BioMedia, Russia), chromogenic medium for E. coli, chromogenic agar for uropathogenic bacteria (Condalab, Spain), Russell double sugar agar (HiMedia Laboratories Private Limited, India). DNA was isolated using the Ribosorb test system for bacterial DNA isolation (OOO InterLabservice, Russia). The sensitivity of isolates to antimicrobial drugs was determined by the disk diffusion method. Discs with antibiotics of known concentration of cefoxitin (30 μg), ciprofloxacin (5 μg), chloramphenicol (30 μg), tobramycin (10 μg), tigecycline (15 μg), linezolid (30 μg) (OOO NITsF, Russia) were used. Testing for resistance to linezolid by the disk diffusion method was performed only for S. aureus in accordance with EUCAST Clinical Breakpoint Tables V.12.0. Detection of antibiotic resistance genetic markers mecA, blaDHA, blaOXA-48, blaСTX-M was carried out in Real-time PCR using commercial kits (NPF Litech, Russia) on a QuantStudio 5 analyzer (Thermo Fisher Scientific, USA). To determine the antibiotic resistance genes mecA, tetM, vanA, blaFOX, blaEBC, blaACC, blaDHA, blaCITM, blaMOX, blaIMP, the pathogenicity genes of E. coli (stx1, stx2), as well as the virulence genes of E. coli (K99, fimA, fimH, F41, Sta, STIa, STIb) and S. aureus (sea, seb, sec, seg, tst, luks-PV, lukED, fnbA, fnbB, cna), specific oligonucleotide primers synthesized by OOO DNA-Synthesis (Russia) were used. By the PCR results, iIn 12.5 % of S. aureus isolates with the antibiotic resistance phenotype, the lukED genes encoding leukocidins were detected. The fnbA/B genes regulating fibronectin-binding proteins were detected in S. aureus: fnbA in 18.75 % of isolates, fnbB in 12.5 % (mastitis milk samples), fnbB in 6.25 % (endometritis swab samples). The studied S. aureus isolates showed combinations of antibiotic resistance genes with virulence and pathogenicity genes. The fnbA/fnbB/ermB combination was characteristic of 6.25 % isolates from the reproductive tract of cows. The lukED/fnbB/fnbA/ermB combination was found in 12.5 % isolates from mammary gland secretion. The ermB/ermC/fnbA combination was established in 6.25 % isolates from mammary gland secretion. The fimA gene was detected in 100 % of E. coli isolates with the antibiotic resistance phenotype, while the fimH gene was also detected in 88.46 % of cases; both genes encode adhesion factors. The stx2 gene was detected in one E. coli isolate from cervicovaginal swabs of a cow with endometritis. The most common combination was the fimA/fimH encoding adhesion factors and regulating biofilm formation; it was found in 92.31 % isolates. The fimA adhesin gene combined with the blaDHA antibiotic resistance gene were found in one E. coli isolate from mammary gland secretion. The fimA/fimH/blaDHA/blaOXA combination was detected in one E. coli isolate from mammary gland secretion of a cow with mastitis. The simultaneous presence of 5 genes in the adhesin/cytotoxin/AMP resistance combination fimA/fimH/stx2/ermA/ermB was found in one E. coli isolate from cervicovaginal swab from a cow with inflammation of the reproductive tract. The conducted microbiological monitoring is important for assessing factors of animal reproductive health, choosing rational therapy, and predicting changes in microbiocenoses to ensure high quality and safety of livestock products.
Keywords: genetic profile, antibiotic resistance, pathogenicity, virulence, Escherichia coli, Staphylococcus aureus, reproductive tract, mammary gland, cattle.
REFERENCES
- Rezanejad M., Karimi S., Momtaz H. Phenotypic and molecular characterization of antimicrobial resistance in Trueperella pyogenes strains isolated from bovine mastitis and metritis. BMC Microbiology, 2019, 19(1): 305 CrossRef
- Triadi B., Suwarno S., Sarudji S., Damayanti R., Sugihartuti R., Soelih Estoepangesti. A.T. Antibiotic sensitivity test of Escherichia coli and Staphylococcus aureus isolated from the reproductive tract of dairy cows. Ovozoa: Journal of Animal Reproduction, 2022, 11(2): 72-80 CrossRef
- Ying Y.-T., Yang J., Tan X., Liu R., Zhuang Y., Xu J.-X., Ren W.-J. Escherichia coli and Staphylococcus aureus differentially regulate Nrf2 pathway in bovine mammary epithelial cells: relation to distinct innate immune response. Cells, 2021, 10(12): 3426 CrossRef
- Patel K., Godden S.M., Royster E.E., Crooker B.A., Johnson T.J., Smith E.A., Sreevatsan S. Prevalence, antibiotic resistance, virulence and genetic diversity of Staphylococcus aureus isolated from bulk tank milk samples of U.S. dairy herds. BMC Genomics, 2021, 22(1): 367 CrossRef
- Mihailovskaya V.S., Remezovskaya N.B., Zhdanova I.N., Starcic Erjavec M., Kuznetsova M.V. Virulence potential of faecal Escherichia coli strains isolated from healthy cows and calves on farms in Perm Krai. Vavilovskii Zhurnal Genet. Selektsii, 2022, 26(5): 486-494 CrossRef
- Viñes J., Cuscó A., Napp S., Alvarez J., Saez-Llorente J.L., Rosàs-Rodoreda M., Francino O., Migura-Garcia L. Transmission of similar Mcr-1 carrying plasmids among different Escherichia coli lineages isolated from livestock and the farmer. Antibiotics, 2021, 10(3): 313 CrossRef
- Richardson E.J., Bacigalupe R., Harrison E.M., Weinert L.A., Lycett S., Vrieling M., Robb K., Hoskisson P.A., Holden M.T.G., Feil E.J., Paterson G.K., Tong S.Y.C., Shittu A., van Wamel W., Aanensen D.M., Parkhill J., Peacock S.J., Corander J., Holmes M., Fitzgerald J.R. Gene exchange drives the ecological success of a multi-host bacterial pathogen. Nature Ecology & Evolution, 2018, 2(9): 1468-1478 CrossRef
- Wielders C.L., Fluit A.C., Brisse S., Verhoef J., Schmitz F.J. mecA gene is widely disseminated in Staphylococcus aureus population. Journal of Clinical Microbiology, 2002, 40(11): 3970-3975 CrossRef
- Chai M., Sukiman M.Z., Kamarun Baharin A.H., Ramlan I., Lai L.Z., Liew Y., Malayandy P., Mohamad N.M., Choong S., Ariffin S.M.Z., Ghazali M.F. Methicillin-resistant Staphylococcus aureus from Peninsular Malaysian animal handlers: molecular profile, antimicrobial resistance, immune evasion cluster and genotypic categorization. Antibiotics, 2022, 11(1): 103 CrossRef
- Klotz M., Opper S., Heeg K., Zimmermann S. Detection of Staphylococcus aureus enterotoxins A to D by real-time fluorescence PCR assay. Journal of Clinical Microbiology, 2003, 41(10): 4683-4687 CrossRef
- Gholamzad M., Khatami M.R., Ghassemi S., Vaise Malekshahi Z., Shooshtari M.B. Detection of Staphylococcus enterotoxin B (SEB) using an immunochromatographic test strip. Jundishapur Journal of Microbiology, 2015, 8(9): e26793 CrossRef
- Saadati M., Barati B., Doroudian M., Shirzad H., Hashemi M., Hosseini S.M., Salehi Chaleshtari A.R., Bahmani M.-K., Hosseinzadeh S., Imani S. Detection of Sea, Seb, Sec, Seq genes in Staphylococcus aureus isolated from nasal carriers in Tehran province, Iran; by multiplex PCR. Archives of Advances in Biosciences, 1970, 2(2): 34-40 CrossRef
- Lee Y.-D., Moon B.Y., Park J.H., Chang H.I., Kim W.J. Expression of enterotoxin genes in Staphylococcus aureus isolates based on mRNA analysis. Journal of Microbiology and Biotechnology, 2007, 17(3): 461-467.
- Bzdil J., Zouharova M., Nedbalcova K., Sladecek V., Senk D., Holy O. Oxacillin (methicillin) resistant Staphylococci in domestic animals in the Czech Republic. Pathogens, 2021, 10(12): 1585 CrossRef
- He C., Xu S., Zhao H., Hu F., Xu X., Jin S., Yang H., Gong F., Liu Q. Leukotoxin and pyrogenic toxin Superantigen gene backgrounds in bloodstream and wound Staphylococcus aureus isolates from eastern region of China. BMC Infectious Diseases, 2018, 18(1): 395 CrossRef
- Drożdż K., Ochońska D., Ścibik L., Gołda-Cępa M., Biegun K., Brzychczy-Włoch M. The frequency of occurrence of resistance and genes involved in the process of adhesion and accumulation of biofilm in Staphylococcus aureus strains isolated from tracheostomy tubes. Microorganisms, 2022, 10(6): 1210 CrossRef
- Wood C., Sahl J., Maltinsky S., Coyne B., Russakoff B., Yague D.P., Bowers J., Pearson T. SaQuant: a real-time PCR assay for quantitative assessment of Staphylococcus aureus. BMC Microbiol, 2021, 21(1): 174 CrossRef
- Shahmoradi M., Faridifar P., Shapouri R., Mousavi S.F., Ezzedin M., Mirzaei B. Determining the biofilm forming gene profile of Staphylococcus aureus clinical isolates via multiplex colony PCR method. Reports of Biochemistry & Molecular Biology, 2019, 7(2): 181-188.
- Eslami M., Nourizadeh A., Salek Farrokhi A., Fallahi S. Detection of Amp-C type producing Escherichia coli using the clavulanic acid and boronic acid inhibitor and multiplex PCR method. Life Science Journal, 2013, 10(12s): 278-283.
- Narasanna R., Surwonse S., Chavadi M., Kelmani C. PCR detection of blaIMP gene in metallo-β-lactamase resistant E. coli isolated from clinical samples. International Journal of Current Microbiology and Applied Sciences, 2019, 8(2): 2696-2701 CrossRef
- Vittecoq M., Laurens C., Brazier L., Durand P., Elguero E., Arnal A., Thomas F., Aberkane S., Renaud N., Prugnolle F., Solassol J., Jean-Pierre H., Godreuil S., Renaud F. VIM-1 carbapenemase-producing Escherichia coli in gulls from southern France. Ecology and Evolution, 2017, 7(4): 1224-1232 CrossRef
- Cengiz M., Uslu M.O., Balcioglu I. Treatment of E. coli HB101 and the tetM gene by Fenton's reagent and ozone in cow manure. Journal of Environmental Management, 2010, 91(12): 2590-2593 CrossRef
- Gadou V., Guessennd N., Toty A., Fernique K., Ouattara M., Dosso M., Seydina D., Djaman J., Rolain J.-M. Molecular detection of the arr-2 gene in Escherichia coli and Klebsiella pneumoniae resistant to rifampicin in Abidjan, Côte D'Ivoire. Microbiology Research Journal International, 2018, 23(4): 1-8 CrossRef
- Sobhy N.M., Yousef S.G.A., Aboubakr H.A., Nisar M., Nagaraja K.V., Mor S.K., Valeris-Chacin R.J., Goyal S.M. Virulence factors and antibiograms of Escherichia coli isolated from diarrheic calves of Egyptian cattle and water buffaloes. PloS One, 2020, 15(5): e0232890 CrossRef
- Lee S.I., Kang S.G., Kang M.L., Yoo H.S. Development of multiplex polymerase chain reaction assays for detecting enterotoxigenic Escherichia coli and their application to field isolates from piglets with diarrhea. Journal of Veterinary Diagnostic Investigation, 2008, 20(4): 492-496 CrossRef
- Shams Z., Tahamtan Y., Pourbakhsh A., Hosseiny M.H., Kargar M., Hayati M. Detection of enterotoxigenic K99 (F5) and F41 from fecal sample of calves by molecular and serological methods. Comparative Clinical Pathology, 2012, 21(4): 475-478 CrossRef
- Andrade G.I., Coura F.M., Santos E.L., Ferreira M.G., Galinari G.C., Facury Filho E.J., de Carvalho A.U., Lage A.P., Heinemann M.B. Identification of virulence factors by multiplex PCR in Escherichia coli isolated from calves in Minas Gerais, Brazil. Tropical Animal Health and Production, 2012, 44(7): 1783-1790 CrossRef
- Bendary M.M., Abd El-Hamid M.I., Alhomrani M., Alamri A.S., Elshimy R., Mosbah R.A., Bahnass M.M., Omar N.N., Al-Sanea M.M., Elmanakhly A.R., Safwat N.A., Alshareef W.A. What is behind the correlation analysis of diarrheagenic E. coli pathotypes? Biology, 2022, 11(7): 1004 CrossRef
- Jinneman K.C., Yoshitomi K.J., Weagant S.D. Multiplex real-time PCR method to identify Shiga toxin genes stx1 and stx2 and Escherichia coli O157:H7/H-serotype. Applied and Environmental Microbiology, 2003, 69(10): 6327-6333 CrossRef
- Ghanbari F., Ghajavand H., Havaei R., Jami M.S., Khademi F., Heydari L., Shahin M., Havaei S.A. Distribution of erm genes among Staphylococcus aureus isolates with inducible resistance to clindamycin in Isfahan, Iran. Advanced Biomedical Research, 2016, 5: 62 CrossRef
- Talebi G., Hashemia A., Goudarzi H., Shariati A., Bostanghadiri N., Sharahi J.Y., Abbsi E. Survey of ermA, ermB, ermC and mecA genes among Staphylococcus aureus isolates isolated from patients admitted to hospitals in Tehran, Iran by PCR and sequencing. Biomedical Research, 2019, 30(2): 1-5 CrossRef
- Wong H., Louie L., Watt C., Sy E., Lo R.Y., Mulvey M.R., Simor A.E. Characterization of ermA in macrolide-susceptible strains of methicillin-resistant Staphylococcus aureus. Antimicrobial Agents and Chemotherapy, 2009, 53(8): 3602-3603 CrossRef
- Wan T.-W., Hung W.-C., Tsai J.-C., Lin Y.-T., Lee H., Hsueh P.-R., Lee T.-F., Teng L.-J. Novel structure of Enterococcus faecium-originated ermB-positive Tn1546-like element in Staphylococcus aureus. Antimicrobial Agents and Chemotherapy, 2016, 60(10): 6108-6114 CrossRef
- Bezborodova N.A., Sokolova O.V., Shkuratova I.A., Lysova Y.Y., Isakova M.N., Kozhukhovskaya V.V. Sensitivity and resistance of the microbiota of reproductive organs and mammary gland of cows to anti-microbial agents in cases of inflammation. International Journal of Biology and Biomedical Engineering, 2020, 14: 49-54 CrossRef
- Monistero V., Barberio A., Biscarini F., Cremonesi P., Castiglioni B., Graber H.U., Bottini E., Ceballos-Marquez A., Kroemker V., Petzer I.M., Pollera C., Santisteban C., Veiga Dos Santos M., Bronzo V., Piccinini R., Re G., Cocchi M., Moroni P. Different distribution of antimicrobial resistance genes and virulence profiles of Staphylococcus aureus strains isolated from clinical mastitis in six countries. Journal of Dairy Science, 2020, 103(4): 3431-3446 CrossRef
- Aklilu E., Hui Ying C. First mecC and mecA positive livestock-associated methicillin resistant Staphylococcus aureus (mecC MRSA/LA-MRSA) from dairy cattle in Malaysia. Microorganisms, 2020, 8(2): 147 CrossRef
- Reygaert W.C. An overview of the antimicrobial resistance mechanisms of bacteria. AIMS Microbiology, 2018, 4(3): 482-501 CrossRef
- Church D.L., Chow B.L., Lloyd T., Gregson D.B. Comparison of automated repetitive-sequence-based polymerase chain reaction and spa typing versus pulsed-field gel electrophoresis for molecular typing of methicillin-resistant Staphylococcus aureus. Diagnostic Microbiology and Infectious Disease, 2011, 69(1): 30-37 CrossRef
- Sheet O.H., Grabowski N.T., Klein G., Reich F., Abdulmawjood A. Characterisation of mecA gene negative Staphylococcus aureus isolated from bovine mastitis milk from Northern Germany. Folia Microbiologica, 2019, 64(6): 845-855 CrossRef
- Shrestha A., Bhattarai R.K., Luitel H., Karki S., Basnet H.B. Prevalence of methicillin-resistant Staphylococcus aureus and pattern of antimicrobial resistance in mastitis milk of cattle in Chitwan, Nepal. BMC Veterinary Research, 2021, 17(1): 239 CrossRef
- Mbindyo C.M., Gitao G.C., Plummer P.J., Kulohoma B.W., Mulei C.M., Bett R. Antimicrobial resistance profiles and genes of Staphylococci isolated from mastitic cow's milk in Kenya. Antibiotics, 2021, 10(7): 772 CrossRef
- Ndahetuye J.B., Leijon M., Bage R., Artursson K., Persson Y. Genetic characterization of Staphylococcus aureus from subclinical mastitis cases in dairy cows in Rwanda. Frontiers in Veterinary Science, 2021, 8: 751229 CrossRef
- Ingti B., Paul D., Maurya A.P., Bora D., Chanda D.D., Chakravarty A., Bhattacharjee A. Occurrence of bla (DHA-1) mediated cephalosporin resistance in Escherichia coli and their transcriptional response against cephalosporin stress: a report from India. Annals of Clinical Microbiology and Antimicrobials, 2017, 16(1): 13 CrossRef
- Moussa J., Panossian B., Nassour E., Salloum T., Abboud E., Tokajian S. Detailed characterization of an IncFII plasmid carrying blaOXA-48 from Lebanon. The Journal of Antimicrobial Chemotherapy, 2020, 75(9): 2462-2465 CrossRef
- Braun S.D., Ahmed M.F., El-Adawy H., Hotzel H., Engelmann I., Weiss D., Monecke S., Ehricht R. Surveillance of extended-spectrum beta-lactamase-producing Escherichia coli in dairy cattle farms in the Nile delta, Egypt. Frontiers in Microbiology, 2016, 7: 1020 CrossRef
- Jarraud S., Mougel C., Thioulouse J., Lina G., Meugnier H., Forey F., Nesme X., Etienne J., Vandenesch F. Relationships between Staphylococcus aureus genetic background, virulence factors, agr groups (alleles), and human disease. Infection and Immunity, 2002, 70(2): 631-641 CrossRef
- Vasquez M.T., Lubkin A., Reyes-Robles T., Day C.J., Lacey K.A., Jennings M.P., Torres V.J. Identification of a domain critical for Staphylococcus aureus LukED receptor targeting and lysis of erythrocytes. The Journal of Biological Chemistry, 2020, 295(50): 17241-17250 CrossRef
- Spaan A.N., van Strijp J.A.G., Torres V.J. Leukocidins: staphylococcal bi-component pore-forming toxins find their receptors. Nature Reviews Microbiology, 2017, 15(7): 435-447 CrossRef
- Terekhov V.I., Tishchenko A.S., Stepanenko A.V. Veterinariya Kubani, 2020, (5): 3-7 CrossRef (in Russ.).
- Murai M., Moriyama H., Hata E., Takeuchi F., Amemura-Maekawa J. Variation and association of fibronectin-binding protein genes fnbA and fnbB in Staphylococcus aureus Japanese isolates. Microbiology and Immunology, 2016, 60(5): 312-325 CrossRef
- Arciola C.R., Campoccia D., Gamberini S., Baldassarri L., Montanaro L. Prevalence of cna, fnbA and fnbB adhesin genes among Staphylococcus aureus isolates from orthopedic infections associated to different types of implant. FEMS Microbiology Letters, 2005, 246(1): 81-86 CrossRef
- Schröder A., Schröder B., Roppenser B., Linder S., Sinha B., Fässler R., Aepfelbacher M. Staphylococcus aureus fibronectin binding protein-A induces motile attachment sites and complex actin remodeling in living endothelial cells. Molecular Biology of the Cell, 2006, 17(12): 5198-5210 CrossRef
- Paharik A.E., Horswill A.R. The staphylococcal biofilm: adhesins, regulation, and host response. Microbiology Spectrum, 2016, 4(2) CrossRef
- Jung H.-R., Lee Y.J. Characterization of virulence factors in enterotoxin-producing Staphylococcus aureus from bulk tank milk. Animals, 2022, 12(3): 301 CrossRef
- Spier A., Stavru F., Cossart P. Interaction between intracellular bacterial pathogens and host cell mitochondria. Microbiology Spectrum, 2019, 7(2) CrossRef
- Guerra S.T., Orsi H., Joaquim S.F., Guimaraes F.F., Lopes B.C., Dalanezi F.M., Leite D.S., Langoni H., Pantoja J.C.F., Rall V.L.M., Hernandes R.T., Lucheis S.B., Ribeiro M.G. Short communication: Investigation of extra-intestinal pathogenic Escherichia coli virulence genes, bacterial motility, and multidrug resistance pattern of strains isolated from dairy cows with different severity scores of clinical mastitis. Journal of Dairy Science, 2020, 103(4): 3606-3614 CrossRef
- Silva V.O., Espeschit I.F., Moreira M.A. Clonal relationship of Escherichia coli biofilm producer isolates obtained from mastitic milk. Canadian Journal of Microbiology, 2013, 59(5): 291-293 CrossRef
- Zhou G., Mo W.J., Sebbel P., Min G., Neubert T.A., Glockshuber R., Wu X.R., Sun T.T., Kong X.P. Uroplakin Ia is the urothelial receptor for uropathogenic Escherichia coli: evidence from in vitro FimH binding. Journal of Cell Science, 2001, 114(22): 4095-4103 CrossRef
- Khalifeh O.M., Obaidat M.M. Urinary tract virulence genes in extended-spectrum beta-lactamase E. coli from dairy cows, beef cattle, and small ruminants. Acta Tropica, 2022, 234: 106611 CrossRef
- Donohue-Rolfe A., Acheson D.W.K., Keusch G.T. Shiga toxin: purification, structure, and function. Reviews of Infectious Diseases, 1991, 13(Supplement_4): S293-S297 CrossRef
- Jinnerot T., Tomaselli A.T.P., Johannessen G.S., Soderlund R., Urdahl A.M., Aspan A., Sekse C. The prevalence and genomic context of Shiga toxin 2a genes in E. coli found in cattle. PloS One, 2020, 15(8): e0232305 CrossRef
- Keykhaei N., Salari S., Rashki A. Frequency of k99, stx1, and stx2 virulence factors in Escherichia coli isolated from diarrheic and clinically healthy suckling calves in Sistan and Baluchistan Province, Iran. Archives of Razi Institute, 2021, 76(2): 283-291 CrossRef












