We have a mutually beneficial relationship with the trillions of microorganisms inhabiting our gastrointestinal tract. However, maintaining this relationship requires recognizing these organisms as affable and restraining inflammatory responses to these organisms when encountered in hostile settings. How and when the immune system develops tolerance to our gut microbial members is not well understood. Here we identify a specific pre-weaning interval in which gut microbial antigens are encountered by the immune system to induce antigen specific tolerance to gut bacteria. Intriguingly for some bacterial taxa, physiologic encounters with the immune system are restricted to this interval, despite abundance of these taxa in the gut lumen at later times outside this interval. Antigen specific tolerance to gut bacteria induced during this pre-weaning interval is stable and maintained even if these taxa are encountered later in life in an inflammatory setting. However, inhibiting microbial antigen encounter during this interval or extending these encounters beyond the normal interval, results in a failure to induce tolerance and robust antigen specific effector responses to gut bacteria upon reencounter in an inflammatory setting. Thus, we have identified a defined pre-weaning interval critical for developing tolerance to gut bacteria and maintaining the mutually beneficial relationship with our gut microbiota.

Late-onset sepsis (LOS) is a highly consequential complication of preterm birth and is defined by a positive blood culture obtained after 72 h of age. The causative bacteria can be found in patients’ intestinal tracts days before dissemination, and cohort studies suggest reduced LOS risk in breastfed preterm infants through unknown mechanisms. Reduced concentrations of epidermal growth factor (EGF) of maternal origin within the intestinal tract of mice correlated to the translocation of a gut-resident human pathogenEscherichia coli, which spreads systemically and caused a rapid, fatal disease in pups. Translocation ofEscherichia coliwas associated with the formation of colonic goblet cell-associated antigen passages (GAPs), which translocate enteric bacteria across the intestinal epithelium. Thus, maternally derived EGF, and potentially other EGFR ligands, prevents dissemination of a gut-resident pathogen by inhibiting goblet cell-mediated bacterial translocation. Through manipulation of maternally derived EGF and alteration of the earliest gut defenses, we have developed an animal model of pathogen dissemination which recapitulates gut-origin neonatal LOS.

Nonprovisional Application Serial No. 15/880,658 Compositions And Methods For Modulation Of Dietary And Microbial Exposure. PIT discloses a financial conflict of interest with MediBeacon Inc (member of their Scientific Advisory Board, consultant, and equity holder) and is a potential recipient of royalties from a patent to test human gut permeability noninvasively.

Levetiracetam is a Food and Drug Administration (FDA)-approved drug for partial, generalized, and myoclonic seizures. Its mechanism of action as an antiepileptic involves the release of neurotransmitters from synaptic vesicles. The common side effects of levetiracetam include sleepiness, weakness, dizziness, and infection. We present a case of levetiracetam-induced hypokalemia, which was refractory to multiple repletion attempts. A 73-year-old woman with a history of seizures, heart failure, and previous stroke was admitted to the hospital due to witnessed seizure-like activity as a result of medication non-compliance. Her serum potassium prior to the start of antiepileptic medication was 4.5 mmol/L. She was restarted on her home dose of levetiracetam 1000 mg twice daily. Twenty-four hours after starting levetiracetam, the patient was found to have hypokalemia, and the patient’s potassium levels failed to correct, dropping as low as 2.0 mmol/L despite continued repletion and normalized magnesium levels. A decision was made to switch the levetiracetam to lacosamide. Thirty-six hours after this change was made, the patient’s potassium level corrected to 3.3 mmol/L and then corrected to 3.9 mmol/L five days later without requiring further repletion. Based on her clinical course, a diagnosis of levetiracetam-induced refractory hypokalemia was made. She was discharged home on lacosamide as her new antiepileptic medication, along with a close follow-up with neurology. Our case highlights the importance of considering Levetiracetam as a cause of refractory hypokalemia. Cases of levetiracetam-induced hypokalemia and hypomagnesemia are rarely reported in the literature, and those that have been reported vary greatly in onset and the resolution of electrolyte derangements. Given that levetiracetam is a widely used antiepileptic medication, we suggest that in cases of refractory hypokalemia, a change in antiepileptic medication should be considered.

Late-onset neonatal sepsis (LOS), an important cause of morbidity and mortality in prematurely born infants, results from a bloodstream infection by bacteria of gut origin. It remains unclear how such bacteria translocate from the intestine, though it has been repeatedly observed that breastfed infants, particularly those fed mother’s own milk (MOM), have reduced risk of LOS compared to formula fed infants. Epidermal growth factor (EGF) promotes intestinal barrier function in infants and is present at high concentrations in breast milk post-partum and decreases throughout lactation. We found reduced concentrations of EGF in the stool of premature formula-fed infants compared to MOM-fed infants, and observed a similar decrease in EGF concentrations of stool of neonatal mice asynchronously cross-fostered (ACF) to dams that had delivered two weeks prior. LOS bloodstream isolates of E. coli colonized the tracts of all pups but translocated and disseminated systemically only in ACF mice resulting in bacteremia and rapid death. Oral gavage of recombinant EGF reduced bacteria translocation and prevented the development of systemic disease in ACF mice. Thus, disruption of maternally delivered EGF in ACF mice results in translocation of pathogens from the gut, and a sepsis-like disease. In conclusion we have identified a mechanism whereby gut-residing pathogens gain systemic access and have developed a novel animal model replicating this mechanism to explore the protective effect of breastmilk and EGF in LOS.