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Infections
Published in Evelyne Jacqz-Aigrain, Imti Choonara, Paediatric Clinical Pharmacology, 2021
Evelyne Jacqz-Aigrain, Imti Choonara
Alteration in access to the target site. This mechanism is found in Gram-negative cells where beta-lactams gain access to their target PBPs by diffusion through protein channels (porins) in the outer membrane. Mutations in porin genes result in a decrease in permeability of the outer membrane, and hence, resistance. Strains resistant to this mechanism may exhibit cross-resistance to unrelated antibiotics which use the same porins.
A Biophysical View on the Function and Activity of Endotoxins
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Ulrich Seydel, Andre Wiese, Andra B. Schromm, Klaus Brandenburg
The outer membrane of gram-negative bacteria serves as a molecular sieve, allowing small hydrophilic molecules (≤600 daltons) to permeate through particular pores that are formed by special outer membrane proteins (Omp) termed porins (61). The porins, in general, have characteristic molecular weights between 30 and 50 kDa and normally form trimers within the outer membrane (62,63).
Antimicrobial Compounds from Medicinal Plants: Effects on Antibiotic Resistance to Human Pathogens
Published in Megh R. Goyal, Hafiz Ansar Rasul Suleria, Ademola Olabode Ayeleso, T. Jesse Joel, Sujogya Kumar Panda, The Therapeutic Properties of Medicinal Plants, 2019
Olutoyin Omolara Bamigboye, Idowu Jesulayomi Adeosun
Antibiotic resistance can also occur when the penetrable ability of the bacteria outer membrane is reduced due to suppressed porin expression; hence, access of antibiotic to bacteria target is reduced. Antimicrobial agents make use of porin and other protein channels to reach the bacterial targets. Loss of certain protein from the outer membrane has been associated with antibiotic resistance in some bacteria species [32].
Strengths and caveats of identifying resistance genes from whole genome sequencing data
Published in Expert Review of Anti-infective Therapy, 2022
Brian M. Forde, David M. P. De Oliveira, Caitlin Falconer, Bianca Graves, Patrick N. A. Harris
Drug efflux systems are a major mediator of AMR. These systems encoded by genes either on the chromosome or within mobile genetic elements (MGEs) mediate the active removal of antimicrobial agents from the cytoplasmic and periplasmic space [14]. To date, six drug efflux systems have been characterized. These include resistance-nodulation-division (RND), major facilitator superfamily (MFS), multidrug and toxic compound extrusion (MATE), small multidrug resistance (SMR), ATP-binding cassette (ABC), and proteobacterial antimicrobial compound efflux (PACE) families [15,16]. In conjunction with these systems, mutations in outer membrane protein channels (porins) further act to reduce antibiotic penetration and accumulation in bacterial cells. Mutations leading to the downregulation, or complete loss of porins are known to result in the decreased penetration of hydrophilic agents such as β-lactams (including carbapenems) and fluoroquinolones [17,18].
Multidrug-resistant Klebsiella pneumoniae: mechanisms of resistance including updated data for novel β-lactam-β-lactamase inhibitor combinations
Published in Expert Review of Anti-infective Therapy, 2021
Irene Galani, Ilias Karaiskos, Helen Giamarellou
Porins are transmembrane β-barrel proteins that exist as trimers, creating channels of defined size and are found in the outer membrane of Gram-negative bacteria. Porins regulate the nonspecific diffusion of hydrophilic solutes and other small molecules through the outer membrane. Enterobacterales commonly express two major nonspecific porins with similar functions, differing in their permeability to small molecules. These nonspecific porins play an important role in nutrient acquisition but also mediate the passive diffusion of antibiotics across the outer membrane and are closely associated with antibiotic resistance in the Gram-negative bacteria [75,76]. Decreased outer membrane porin expression in antibiotic resistant isolates has been correlated with an increased minimum inhibitory concentration (MIC) to multiple antibiotics, most commonly those that target peptidoglycan synthesis [77–79].
Chlamydia trachomatis vaccines for genital infections: where are we and how far is there to go?
Published in Expert Review of Vaccines, 2021
Luis M. de la Maza, Toni L Darville, Sukumar Pal
MOMP is highly antigenic, contains B- and T-cell epitopes and accounts for ~60% of the outer membrane protein mass [34,87]. MOMP belongs to a group of proteins called porins important for the passive transport of ions, sugars and nucleotides across the outer membrane of Gram-negative bacteria [88,89]. Porins have a structural topology comprised of antiparallel β-strands spanning the outer membrane, a water-filled inner channel, tight β-turns extending into the periplasmic region and flexible loops reaching beyond the extracellular surface. Because of their DNA sequence heterogeneity, that is used to classify C. trachomatis into different serovars, the extracellular loops of MOMP are called variable domains (VD) [85,90]. The VD are the main target of the antibody responses while the T-cell epitopes are mostly located in the β-strands [91–93]. MOMP has a monomeric molecular weight of 39.5 kDa, a hydrophobic residue content of ~40% and migration patterns on SDS-PAGE gels consistent with trimeric oligomerization [94].