Progressive Sub-MIC Exposure of Klebsiella pneumoniae 43816 to Cephalothin Induces the Evolution of Beta-Lactam Resistance without Acquisition of Beta-Lactamase Genes.

Bacterial exposure to antibiotic concentrations below the minimum inhibitory concentration (MIC) may result in a selection window allowing for the rapid evolution of resistance. These sub-MIC concentrations are commonly found in soils and water supplies in the greater environment. This study aimed to evaluate the adaptive genetic changes in Klebsiella pneumoniae 43816 after prolonged but increasing sub-MIC levels of the common antibiotic cephalothin over a fourteen-day period. Over the course of the experiment, antibiotic concentrations increased from 0.5 µg/mL to 7.5 µg/mL. At the end of this extended exposure, the final adapted bacterial culture exhibited clinical resistance to both cephalothin and tetracycline, altered cellular and colony morphology, and a highly mucoid phenotype. Cephalothin resistance exceeded 125 µg/mL without the acquisition of beta-lactamase genes. Whole genome sequencing identified a series of genetic changes that could be mapped over the fourteen-day exposure period to the onset of antibiotic resistance. Specifically, mutations in the rpoB subunit of RNA Polymerase, the tetR/acrR regulator, and the wcaJ sugar transferase each fix at specific timepoints in the exposure regimen where the MIC susceptibility dramatically increased. These mutations indicate that alterations in the secretion of colanic acid and attachment of colonic acid to LPS may contribute to the resistant phenotype. These data demonstrate that very low sub-MIC concentrations of antibiotics can have dramatic impacts on the bacterial evolution of resistance. Additionally, this study demonstrates that beta-lactam resistance can be achieved through sequential accumulation of specific mutations without the acquisition of a beta-lactamase gene.

Comparison of Migraine Characteristics in Patients With and Without Inflammatory Bowel Disease: A Retrospective Cohort Study.

BACKGROUND: Survey studies have found an increased prevalence of migraine in patients with inflammatory bowel disease (IBD). However, the clinical characteristics of migraines in this population are unknown. We conducted a retrospective medical record review study to characterize migraines in the IBD population. METHODS: Six hundred seventy-five migraine patients (280 with IBD, 395 without IBD) who were evaluated at Mayo Clinic Rochester, Mayo Clinic Arizona, or Mayo Clinic Florida between July 2009 and March 2021 were included. Patients with ICD codes for migraine and either Crohn's disease (CD) or ulcerative colitis (UC) were selected. Electronic health care records were reviewed. Patients confirmed to have IBD and migraine were included. Demographic, IBD, and migraine characteristics were collected. Statistical analysis was completed using SAS. RESULTS: Patients with IBD were less often male (8.6% vs 21.3%, P < .001) and had a higher Charlson Comorbidity Index (>2: 24.6% vs 15.7%, P = .003); 54.6% had CD and 39.3% had UC. Patients with IBD had migraine with aura and without aura more frequently ( OR 2.20, P < .001 and OR 2.79, P < .001, respectively) than non-IBD patients. Additionally, those with IBD less commonly had chronic migraine (OR 0.23, P < .001) and less commonly had chronic migraine or treatment for migraine (ORs 0.23-0.55, P ≤ .002). CONCLUSIONS: Migraine with and without aura have increased prevalence in IBD patients. Further study of this topic will be helpful to clarify the prevalence of migraine, establish this population's response to treatment, and better understand the reason(s) for a low rate of treatment.