The isolation and genetic characterization of extrachromosomal chloramphenicol and oligomycin-resistant mutants from the petite-negative yeast Kluyveromyces lactis

1977 ◽  
Vol 152 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Aurora Brunner ◽  
Alba Tuena de Cobos ◽  
David E. Griffiths
Keyword(s):  
Genetic Characterization ◽  
Kluyveromyces Lactis ◽  
Resistant Mutants ◽  
Petite Negative Yeast

scholarly journals Genetic Characterization of Fluoroquinolone-Resistant Streptococcus pneumoniae Strains Isolated during Ciprofloxacin Therapy from a Patient with Bronchiectasis

2003 ◽  
Vol 47 (4) ◽  
pp. 1419-1422 ◽  
Author(s):  
Adela G. de la Campa ◽  
María-José Ferrandiz ◽  
Fe Tubau ◽  
Román Pallarés ◽  
Federico Manresa ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Genetic Characterization ◽  
Susceptible Strain ◽  
Low Level ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
High Level ◽  
Level Resistance

ABSTRACT Five Spain9V-3 Streptococcus pneumoniae strains were isolated from a patient with bronchiectasis who had received long-term ciprofloxacin therapy. One ciprofloxacin-susceptible strain was isolated before treatment, and four ciprofloxacin-resistant strains were isolated during treatment. The resistant strains were derived from the susceptible strain either by a parC mutation (low-level resistance) or by parC and gyrA mutations (high-level resistance). This study shows that ciprofloxacin therapy in a patient colonized by susceptible S. pneumoniae may select fluoroquinolone-resistant mutants.

scholarly journals Isolation and genetic characterization of polymyxin-resistant mutants ofSalmonella

1978 ◽  
Vol 3 (6) ◽  
pp. 323-326 ◽  
Author(s):  
P. Helena Mäkelä ◽  
M. Sarvas ◽  
Sinikka Calcagno ◽  
K. Lounatmaa
Keyword(s):  
Genetic Characterization ◽  
Resistant Mutants

scholarly journals Selection and Genetic Characterization of Streptococcus pneumoniae Mutants Resistant to the Des-F(6) Quinolone BMS-284756

2001 ◽  
Vol 45 (10) ◽  
pp. 2865-2870 ◽  
Author(s):  
Sandra Hartman-Neumann ◽  
Kenneth DenBleyker ◽  
Lenore A. Pelosi ◽  
Laura E. Lawrence ◽  
John F. Barrett ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Genetic Characterization ◽  
Pcr Primers ◽  
Type Ii ◽  
Chromosomal Dna ◽  
Dna Strands ◽  
Previous Round ◽  
Resistant Mutants ◽  
Four Levels

ABSTRACT Existing quinolones are known to target the type II topoisomerases in bacteria. In order to determine which of these targets are of key importance in Streptococcus pneumoniae treated with BMS-284756 (T-3811ME), a novel des-F(6) quinolone, resistant mutants were selected in several steps of increasing resistance by plating pneumococci on a series of blood agar plates containing serial twofold-increasing concentrations of drug. After incubation, colonies that arose were selected and passaged twice on antibiotic-containing media at the selection level. Mutants generally showed increases in resistance of four- to eightfold over the prior level of susceptibility. Mutants in the next-higher level of resistance were selected from the previous round of resistant mutants. Subsequently, chromosomal DNA was prepared from parental (R6) pneumococci and from at least three clones from each of four levels of increasing antibiotic resistance. Using PCR primers, 500- to 700-bp amplicons surrounding the quinolone resistance determining regions (QRDR) ofgyrA, gyrB, parC, andparE genes were prepared from each strain. Internal primers were used to sequence both DNA strands in the regions of approximately 400 bp centered on the QRDR. Mutations identified with increasing levels of resistance included changes in GyrA at Ser-81 and Glu-85 and changes in ParC at Ser-79 and Asp-83. Changes in GyrB and ParE were not observed at the levels of resistance obtained in this selection. The resistance to comparator quinolones (levofloxacin, ciprofloxacin, and moxifloxacin) also increased in four- to eightfold steps with these mutations. The intrinsically greater level of antibacterial activity and thus lower MICs of BMS-284756 observed at all resistance levels in this study may translate to coverage of these resistant pneumococcal strains in the clinic.

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