Genome sequence analysis and characterization of shiga toxin 2 production by escherichia coli O157:H7 strains associated with a laboratory infection

Authors: EPPINGER, MARK - University Of Texas At San Antonio; ALMERIA, SONIA - Food And Drug Administration(FDA); ALLURE-GUARDIA, ANNA - Texas Biomedical Institute; Bagi, Lori; KALALAH, ANWAR - University Of Texas At San Antonio; Gurtler, Joshua; FRATAMICO, PINA - Retired ARS Employee

Submitted to: Frontiers in Cellular and Infection Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2022
Publication Date: 6/13/2022
Citation: Eppinger, M., Almeria, S., Allure-Guardia, A., Bagi, L.K., Kalalah, A.A., Gurtler, J., Fratamico, P.M. 2022. Genome sequence analysis and characterization of shiga toxin 2 production by escherichia coli O157:H7 strains associated with a laboratory infection. Frontiers in Cellular and Infection Microbiology. 12. https://doi.org/10.3389/fcimb.2022.888568.
DOI: https://doi.org/10.3389/fcimb.2022.888568

Interpretive Summary: A scientist working with a mixture of six E. coli O157:H7 strains in the laboratory acquired an infection with two confirmed strains, and was treated with two antibiotics, which are often contraindicated in cases of Escherichia coli O157:H7 infection because this can result in an increased production of a deadly toxin (Shiga toxin) by the bacterium. The patient developed hemorrhagic colitis and hemolytic uremic syndrome, thus, the aim of this study was to investigate whether the two antibiotics administered to the patient resulted in increased production of the Shiga toxin, as well as to analyze the genome sequence (complete set of DNA) of the laboratory strains and the strains isolated from the patient. The results indicated a simultaneous co-infection with clinical strains (which had been isolated from previous O157:H7 outbreaks) in the laboratory, and further that the administration of sublethal concentrations of antibiotics likely exacerbated the severity of the disease. Additionally, the research furthers the understanding of the genetic makeup of E. coli O157:H7 strains that cause severe disease, providing information to develop improved treatment, detection, and control strategies.

Technical Abstract: A laboratory-acquired E. coli O157:H7 infection with associated severe sequelae including hemolytic uremic syndrome occurred in an individual working in the laboratory with a mixture of nalidixic acid-resistant (NalR) O157:H7 mutant strains in a soil-biochar blend. The patient was hospitalized and treated with an intravenous combination of metronidazole and levofloxacin. The present study investigated the source of this severe laboratory acquired infection and further examined the influence of the antibiotics used during treatment on the expression and production of Shiga toxin. The genomes of two Stx2a- and eae-positive O157:H7 strains isolated from the patient’s stool were sequenced along with two pairs of the wt strains and their derived NalR mutants used in the laboratory experiments. High-resolution SNP typing determined the strains’ individual genetic relatedness and unambiguously identified the two laboratory-derived NalR mutant strains as the source of the researcher’s life-threatening disease, rather than a conceivable ingestion of unrelated O157:H7 isolates circulating at the same time. It was further confirmed that in sublethal doses, the antibiotics increased toxin expression and production. Our results support a simultaneous co-infection with clinical strains in the laboratory, which were the causative agents of previous O157:H7 outbreaks, and further that the administration of antibiotics may likely have exacerbated the severity of the disease.