Browsing by Subject "Susceptibility"

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    Criticality of Benzoyl Peroxide and Antibiotic Fixed Combinations in Combating Rising Resistance in Cutibacterium acnes
    (Dove Press, 2025-03-31) Ghannoum, Mahmoud; Gamal, Ahmed; Kadry, Ahmed; Del Rosso, James Q.; Stein Gold, Linda; Kircik, Leon H.; Harper, Julie C.; Dermatology, School of Medicine
    Background: Antibiotic resistance is growing globally, with multiple countries reporting resistance in >50% of Cutibacterium acnes (C. acnes) strains. Combination formulations of an antibiotic and the antimicrobial benzoyl peroxide (BPO) may reduce this resistance risk, especially with prolonged use. This 4-part study tested susceptibility of 31 C. acnes clinical strains and development of resistance to antibiotics alone or combined with BPO. Methods: C. acnes susceptibility to single-drug antibiotics was assessed via minimum inhibitory concentration (MIC) values obtained from epsilometer tests, with lower MIC indicating higher susceptibility. Susceptibility to fixed-dose antibiotic/BPO combination products was determined by measuring the zone of inhibition using the agar diffusion method, with larger diameter indicating increased bacterial inhibition. The effect (synergistic, additive, antagonistic, or indifferent [no interaction]) of combining clindamycin with BPO on C. acnes inhibition was evaluated using a checkerboard assay, wherein 2 test compounds are combined in varying concentrations. Resistance development was assessed using serial passage of bacterial cultures in increasing concentrations of clindamycin alone or in combination with BPO. Results: All tested antibiotics (clindamycin, doxycycline, erythromycin, and minocycline) exhibited similar activity. C. acnes susceptibility was variable, with some strains having elevated MIC values-an indication of resistance-against different antibiotics. For 6 strains resistant to clindamycin alone (inhibitory zone=0 cm), formulations with BPO enhanced activity against the same isolates (range: 0.8-2.2 cm). Of 7 acne-associated strains, combining clindamycin and BPO had an additive effect against 4, and no interaction against 3. Bacterial cultures repeatedly exposed to the combination of clindamycin and BPO did not develop antibiotic resistance, which occurred with exposure to clindamycin alone. Conclusion: Overall, antibiotic susceptibility was highly dependent on the C. acnes strain, and antibiotic formulations with BPO exhibited enhanced activity against less susceptible strains. Fixed combinations of BPO with an antibiotic may improve antimicrobial activity and protect against resistance development.
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    L1 coupling to ankyrin and the spectrin-actin cytoskeleton modulates ethanol inhibition of L1 adhesion and ethanol teratogenesis
    (Federation of American Society of Experimental Biology, 2018-03) Dou, Xiaowei; Menkari, Carrie; Mitsuyama, Rei; Foroud, Tatiana; Wetherill, Leah; Hammond, Peter; Suttie, Michael; Chen, Xiaopan; Chen, Shao-Yu; Charness, Michael E.; Collaborative Initiative on Fetal Alcohol Spectrum Disorders; Medical and Molecular Genetics, School of Medicine
    Ethanol causes fetal alcohol spectrum disorders (FASDs) partly by inhibiting cell adhesion mediated by the L1 neural cell adhesion molecule. Ethanol interacts with an alcohol binding pocket in the L1 extracellular domain (ECD), and dephosphorylation of S1248 in the L1 cytoplasmic domain (CD) renders L1 adhesion insensitive to inhibition by ethanol (L1 insensitive). The mechanism underlying this inside-out signaling is unknown. Here we show that phosphorylation of the human L1-CD at S1152, Y1176, S1181, and S1248 renders L1 sensitive to ethanol by promoting L1 coupling with ankyrin-G and the spectrin-actin cytoskeleton. Knockdown of ankyrin-G or L1 mutations that uncouple L1 from ankyrin reduce L1 sensitivity to ethanol, but not methanol, consistent with a small conformational change in the extracellular alcohol binding pocket. Phosphorylation of Y1176 and ankyrin-G coupling with L1 are higher in NIH/3T3 clonal cell lines in which ethanol inhibits L1 adhesion than in ethanol-resistant NIH/3T3 clonal cell lines. Similarly, phosphorylation of Y1176 is higher in C57BL/6J mice that are sensitive to ethanol teratogenesis than in ethanol resistant C57BL/6N mice. Finally, polymorphisms in genes that encode ankyrin-G and p90rsk, a kinase that phosphorylates S1152, are linked to facial dysmorphology in children with heavy prenatal ethanol exposure. These findings indicate that genes that regulate L1 coupling to ankyrin may influence susceptibility to FASD.-Dou, X., Menkari, C., Mitsuyama, R., Foroud, T., Wetherill, L., Hammond, P., Suttie, M., Chen, X., Chen, S.-Y., Charness, M. E., Collaborative Initiative on Fetal Alcohol Spectrum Disorders. L1 coupling to ankyrin and the spectrin-actin cytoskeleton modulates ethanol inhibition of L1 adhesion and ethanol teratogenesis.