Traceability and Characteristic Investigation of Burkholderia Gladioli Bloodstream Infection in Patients with Hematologic Malignancies

^{*Drs. Mei Hong and Qiuling Wu are co-corresponding authors}

Background and aims:

Bone marrow suppression and mucosal damage caused by high-dose chemotherapy, and the application of immunosuppressive agents after transplantation lead to immune deficiency of patients with hematologic malignancies, who are susceptibility to opportunistic pathogen infections . Burkholderia gladioli, widely known as B. cocovenenans in the public eye, is an extraordinary Burkholderia specie causing acute lethal food poisoning by producing toxoflavin (TF) and lethal bongkrekic acid (BA). It is also an opportunistic pathogen causing clinical infections in newborn infants and patients with cystic fibrosis, chronic granulomatous disease, mechanical ventilation and other immunocompromising conditions, but its source of infection and pathogenic mechanism are still not clear. This study investigated the source of B. gladioli bloodstream infection in patients with hematologic malignancies and demonstrated the antibiotic sensitivity, biological characteristics, and genetic characteristics of B. gladioli strains, providing guidance for clinical treatment and improving patient prognosis.

Methods:

Nanopore-targeted sequencing (NTS) was used to rapidly detect pathogens in the peripheral blood of patients, and MALDI-TOF MS was used to identify blood culture pathogens. Samples were taken from locations and things associated with patients including medical equipment, inpatient environment, food, and biological specimens. Multilocus sequence typing (MLST) analysis was used to detect the genotypes of B. gladioliDNA. The K-B assay was used to detect bacterial antibiotic sensitivity. The dilution-coated plate method was used in the in vitro phenotyping experiments. Whole-genome sequencing (WGS) was used for the identification and comparation of B. gladioli strains.

Results:

In this study, NTS and culture of peripheral blood were routinely carried out in patients with hematological malignancies when they gone through febrile neutropenia due to immune deficiency. When patients confirmed positive for B. gladioli bloodstream infection, traceability sampling and PCR verification were conducted from locations and things associated with patients including medical equipments, inpatient environments, food, and biological specimens. Results showed strong B. gladioli abundance in foods (rice, corn flour), but medical equipment and inpatient environment showed no B. gladioliexistence. Furthermore, MLST sequencing confirmed that B. gladiolibloodstream infections was originated from contaminated foods. More important, WGS analysis found that clinical B. gladioli strains isolated in this study were totally lacked of lethal bongkrekic acid (BA) gene clusters and partially lacked of the toxoflavin gene clusters. Antibiotic susceptibility tests revealed that the clinical strains were susceptible to cefazoxime, ciprofloxacin, levofloxacin, trimethoprim/sulfamethoxazole, cefalexin, cefoperazone/sulbactam, meropenem, imipenem, piperacillin/tazobactam, amikacin, tobramycin, minocycline hydrochloride, tigecycline and resistant to polymyxinB, ampicillin, cefazolin, cefuroxime, aztreonam, and cefoxitin. Phenotyping experiments found that B. gladioli strains didn't induce hemolysis but exhibited stronger thermal stability and ultraviolet (UV) stability compared with the standard B gladioli strain and lethal B gladioli strain.

Conclusions:

Foodborne B. gladioli strains in this study exhibited low toxicity and high thermal stability and caused opportunistic bloodstream infections of hematologic malignant patients in immunodeficient states, which deserves our attention. Its special biological characteristic might be attributed to whole and partial loss of toxigenic gene clusters. Clinical B gladioli strains are resistant to polymyxinB, but the standard B gladioli strain and lethal B gladioli strain are susceptible to it, indicating acquired resistance during colonization and empirical antibiotic therapy. Clinicians should strengthen the dietary management of inpatients to avoid the occurrence of foodborne infections.