RT Journal Article SR Electronic(1) A1 Helander, Ilkka M. A1 Alakomi, Hanna-Leena A1 Latva-Kala, KyÖsti A1 Koski, PerttiYR 1997 T1 Polyethyleneimine is an effective permeabilizer of Gram-negative bacteria JF Microbiology, VO 143 IS 10 SP 3193 OP 3199 DO https://doi.org/10.1099/00221287-143-10-3193 PB Microbiology Society, SN 1465-2080, AB The effect of the polycation polyethyleneimine (PEI) on the permeability properties of the Gram-negative bacterial outer membrane was investigated using Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium as target organisms. At concentrations of less than 20 µg ml−1, PEI increased the bacterial uptake of 1-N-phenylnaphthylamine, which is a hydrophobic probe whose quantum yield is greatly increased in a lipid environment, indicating increased hydrophobic permeation of the outer membrane by PEI. The effect of PEI was comparable to that brought about by the well-known permeabilizer EDTA. Permeabilization by PEI was retarded but not completely inhibited by millimolar concentrations of MgCl2. PEI also increased the susceptibility of the test species to the hydrophobic antibiotics clindamycin, erythromycin, fucidin, novobiocin and rifampicin, without being directly bactericidal. PEI sensitized the bacteria to the lytic action of the detergent SDS in assays where the bacteria were pretreated with PEI. In assays where PEI and SDS were simultaneously present, no sensitization was observed, indicating that PEI and SDS were inactivating each other. In addition, a sensitizing effect to the nonionic detergent Triton X-100 was observed for P. aeruginosa. In conclusion, PEI was shown to be a potent permeabilizer of the outer membrane of Gram-negative bacteria., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-143-10-3193