Addy Cembellin-Kao

All Publications

• Occult bromazolam exposure in patients presenting with opioid or stimulant overdose. Clinical toxicology (Philadelphia, Pa.) Cembellin-Kao, A., Aldy, K., Brent, J., Culbreth, R., LaBozzetta, C., Turcios, M. A., Wax, P., Yonamine, C., Stolbach, A. 2025; 63 (5): 330-336

  Abstract

  Bromazolam is a benzodiazepine, not approved for use in any North American or European jurisdiction that has emerged as an adulterant in the United States illicit drug supply.This is a case series of seven patients treated for an acute overdose and found to have bromazolam in their blood despite no self-reported exposure. Patients were enrolled from June 2023 to January 2024 as part of the Drug Overdose Toxico-Surveillance Reporting Program, a multi-center, prospective project including patients aged 13 years and older with a suspected life-threatening opioid and/or stimulant overdose. This case series is drawn from a single emergency department from that project. Patients were interviewed on their drug use, and clinical data were collected from electronic medical records. Whole blood was obtained and tested qualitatively for over 1,200 psychoactive substances using liquid chromatography quadrupole time-of-flight mass spectrometry and quantitative measurements using liquid chromatography-tandem quadrupole mass spectrometry.Patients presented with acute signs of excessive sedation (six of seven) or agitation (one of seven). The median blood bromazolam concentration was 29 µg/L (range <5-84 µg/L). Three patients were admitted to hospital or observed for more than 24 h in the emergency department. The reasons for admission/observation were advanced pregnancy, prolonged sedation, and the need for social services. No patients were placed in a critical care unit and all patients survived. During the structured interview, none of the patients reported bromazolam use.This case series demonstrated no poor clinical outcomes in patients with acute overdose who had detectable bromazolam concentrations despite no reported bromazolam use. In all cases of sedation, patients responded to naloxone (in all cases the patients admitted to taking opioids, which was confirmed analytically), and there was no ongoing sedation attributed to the detected bromazolam.Substances unknown to patients are present in the drug supply. Toxico-surveillance programs are essential to obtaining information about community patterns of drug use that cannot be obtained from patient history or from medical charts.

  View details for DOI 10.1080/15563650.2025.2490831

  View details for PubMedID 40387680

• Cathelicidin Peptides Restrict Bacterial Growth via Membrane Perturbation and Induction of Reactive Oxygen Species. mBio Rowe-Magnus, D. A., Kao, A. Y., Prieto, A. C., Pu, M., Kao, C. 2019; 10 (5)

  Abstract

  All metazoans produce antimicrobial peptides (AMPs) that have both broad antimicrobial and immunomodulatory activity. Cathelicidins are AMPs that preferentially kill Gram-negative bacteria in vitro, purportedly by assembling into higher-order structures that perforate the membrane. We utilized high-resolution, single-cell fluorescence microscopy to examine their mechanism of action in real time. Engineered cathelicidins rapidly bound to Gram-negative and Gram-positive cells and penetrated the cytoplasmic membrane. Rapid failure of the peptidoglycan superstructure in regions of active turnover caused leakage of cytoplasmic contents and the formation of membrane-bound blebs. A mutation anticipated to destabilize interactions between cathelicidin subunits had no effect on bactericidal activity, suggesting that cathelicidins have activities beyond perforating the membrane. Nanomolar concentrations of cathelicidins, although not bactericidal, reduced the growth rate of Gram-negative and Gram-positive bacteria. The cells exhibited expression changes in multiple essential processes, including protein synthesis, peptidoglycan biosynthesis, respiration, and the detoxification of reactive oxygen species (ROS). Time-lapse imaging revealed that ROS accumulation preceded bleb formation, and treatments that reduced cellular ROS levels overcame these bactericidal effects. We propose that that the primary effect of cathelicidins is to induce the production of ROS that damage bacterial molecules, leading to slowed growth or cell death. Given their low circulating levels in vivo, AMPs may serve to slow bacterial population expansion so that cellular immunity systems can respond to and battle the infection.IMPORTANCE Antimicrobial peptides (AMPs) are an important part of the mammalian innate immune system in the battle against microbial infection. How AMPs function to control bacteria is not clear, as nearly all activity studies use nonphysiological levels of AMPs. We monitored peptide action in live bacterial cells over short time frames with single-cell resolution and found that the primary effect of cathelicidin peptides is to increase the production of oxidative molecules that cause cellular damage in Gram-positive and Gram-negative bacteria.

  View details for DOI 10.1128/mBio.02021-19

  View details for PubMedID 31506312

  View details for PubMedCentralID PMC6737244