Escherichia coli antibiotic sensitivity

The first report of a specific screening technique designed to search for p-lactam antibiotic-producing cultures was described by Kitano et al. (1975). A mutant of Pseudomonas aeruginosa highly and specifically sensitive to p-lactam antibiotics was isolated. A similar mutant strain of Escherichia coli highly sensitive to p-lactam antibiotics was used in the detection of nocardicins (Aoki et al., 1976). 

Empiric antibiotic therapy is an appropriate approach to traveler s diarrhea. Eradication of the causal microbe depends on the etiologic agent and its antibiotic sensitivity. Most cases of traveler s diarrhea and other community-acquired infections result from enterotoxigenic (ETEC) or enteropathogenic (EPEC) Escherichia coli. Routine stool cultures do not identify these strains primary empiric antibiotic choices include fluoroquinolones such as ciprofloxacin or levofloxacin. Azithromycin may be a feasible option when fluoroquinolone resistance is encountered. 

However, recent investigations on the effect of the tissue matrix on the detection limits attained by this test have indicated that ceftiofur, sulfonamides, streptomycin, and some macrolide antibiotics cannot be detected in intact meat with the plates and the bacterial strains prescribed in the European four-plate test (81, 82). Two plates of this system were not found suitable for screening sulfamethazine or streptomycin at levels far above the MRL the third plate detected tetracyclines and -lactams up to the MRL levels whereas the fourth was sensitive to -lactams and some but not all macrolides. Detection, on the other hand, of the fluoroquinolones enrofloxacin and ciprofloxacin could only be made possible by an additional Escherichia coli plate not included in the four-plate test. 

LC—MS) analysis of culture broth extracts, and reporter gene activation have all been successfully used as readouts in high-throughput assays designed to find small-molecule-producing clones (see Section 2.13.4). The most frequently used functional assays have been color production and antibacterial activity. While any assay strain can he selected for an overlay assay, Bacillus subtilis is commonly used due to its sensitivity to most known classes of antibiotics. Using simple functional assays, clones that produce new natural products have been recovered from both Escherichia coli- and Streptomyces lividans-h seA eDNA libraries (see Section 2.13.4). 

Escherichia coli K12 R5 (which produced this enzyme) was weakly resistant to kanamycins A and B, but sensitive to kanamycin C, which has no 6 -amino group to be acetylated. The involvement of this enzyme in the mechanism of resistance was shown by the resistance of this organism to kanamycin A and 3, 4 -dideoxykanamycin B, and by its sensitive behavior to the 6 -iV-methyl derivatives of these antibiotics. 

The mild reaction conditions that can be employed in the cleavage of such amide linkages means, once again, that sensitive bonds can be preserved. This is relevant to the commercially important process which converts fermentated penicillins (e.g. penicillin G) into 6-aminopenicillanic acid (6-APA), a precursor of the semi-synthetic penicillin antibiotics. The enzyme used for this transformation is the acylase from the bacterium Escherichia coli (Scheme 3.11) (see also Chapter 6, Section 6.5). 

Brehm-Stecher BF, Johnson EA (2003) Sensitization of Staphylococcus aureus and Escherichia coli to antibiotics by the sesquiterpenoids nerolidol, famesol, bisabolol, and apritone. Antimicrob Agents Chemother 47 3357-3360... 

Chlamydomonas reinhardi is sensitive to the protein synthesis inhibitor, erythromycin. At the time, some erythromycin-resistant strains had been isolated and described, and we were considering experimental approaches to locate the sites of structural genes for proteins of plastid ribosomes. It seemed reasonable to use erythromycin resistance as a genetic marker if we could be certain that the antibiotic interacts with some part of the chloroplast ribosome and was not lethal for some other reason. Erythromycin was known to bind to the large subunit of Escherichia coli ribosomes, and the alteration leading to resistance in the bacteria was found to reside in a single protein in the 50 S subunit. ... 

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