Journal:

Article Title: Quality Control Guidelines for MIC Susceptibility Testing of Omiganan Pentahydrochloride (MBI 226), a Novel Antimicrobial Peptide

doi: 10.1128/JCM.42.3.1386-1387.2004

Figure Lengend Snippet: Proposed MIC QC ranges for omiganan listed by medium type a

Article Snippet: The proposed omiganan MIC QC ranges also were 1 log 2 dilution higher for CA-MHB when E. coli ATCC 25922 was used (Table ). table ft1 table-wrap mode="anchored" t5 caption a7 QC organism Omiganan MIC (μg/ml) QC range (% in range) for: CA-MHB MHB RPMI 1640 E. faecalis ATCC 29212 32-128 (100.0) 32-128 (100.0) S. aureus ATCC 29213 8-64 (99.5) 4-32 (100.0) S. pneumoniae ATCC 49619 b 32-128 (100.0) 16-64 (100.0) E. coli ATCC 25922 16-64 (99.0) 8-32 (100.0) P. aeruginosa ATCC 27853 64-256 (100.0) 8-64 (100.0) C. parapsilosis ATCC 22019 32-128 (99.0) C. krusei ATCC 6258 16-64 (100.0) Open in a separate window a RPMI 1640 was used for all tests of yeast. b Lysed horse blood (2 to 5%) was added to CA-MHB for testing this QC strain.

Techniques:

Journal: Journal of Clinical Microbiology

Article Title: Antimicrobial Susceptibility Testing for Polymyxins: Challenges, Issues, and Recommendations

doi: 10.1128/JCM.01390-18

Figure Lengend Snippet: Mechanisms of LPS modification involved in polymyxin resistance in Gram-negative bacilli. In Salmonella spp., Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa, the sensing of various stress conditions, such as the presence of cationic compounds (polymyxins), low Mg2+ and Ca2+ concentrations, acidic pH, and high Fe3+ concentrations, by the histidine kinases PhoQ and PmrB activates the two-component systems (TCSs) PhoP-PhoQ and PmrA-PmrB, respectively. Subsequent activation of the arnBCADTEF and pmrCAB operons leads to the synthesis and addition of 4-amino-4-deoxy-l-arabinose (l-Ara4N) and phosphoethanolamine (PEtN) to lipid A, respectively. In addition, PmrAB is activated by PhoP-PhoQ via the product of the pmrD gene, which in turn activates pmrA for activation of the arnBCADTEF operon. Inactivation of MgrB (a negative regulator of the PhoP-PhoQ system) by amino acid substitutions leads to overexpression of the phoP-phoQ operon as well, causing activation of the pmrHFIJKLM operon, thus leading to the production of l-Ara4N. On the other hand, polymyxin resistance in Acinetobacter baumannii is due to alterations in PmrB or the response regulator PmrA, which activates the PmrAB TCS. The subsequent upregulation of the pmrCAB operon and the naxD gene promotes the addition of PEtN and galactosamine to lipid A, respectively. In addition, a recently identified mcr-1 gene, encoding phosphoethanolamine transferase, has been shown to be the main mechanism of polymyxin resistance.

Article Snippet: Polymyxin B and colistin interpretative breakpoints according to CLSI and EUCAST guidelines in 2018 Both CLSI and EUCAST recommend use of the quality control (QC) organisms E. coli ATCC 25922 (MIC range, 0.25 to 2 μg/ml) and P. aeruginosa ATCC 27853 (MIC range, 0.5 to 4 μg/ml) for polymyxin susceptibility testing to standardize the procedures ( 82 , 85 ).

Techniques: Modification, Activation Assay, Over Expression