Genetic characterization of hydroxyurea-resistant mutants obtained from cell cultures of Nicotiana tabacum

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.

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Isolation and genetic characterization of polymyxin-resistant mutants of Salmonella

FEMS Microbiology Letters ◽

10.1016/0378-1097(78)90018-6 ◽

1978 ◽

Vol 3 (6) ◽

pp. 323-326 ◽

Cited By ~ 4

Author(s):

P HELENAMAKELA

Keyword(s):

Genetic Characterization ◽

Resistant Mutants

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Isolation and genetic characterization of polymyxin-resistant mutants ofSalmonella

FEMS Microbiology Letters ◽

10.1111/j.1574-6968.1978.tb01963.x ◽

1978 ◽

Vol 3 (6) ◽

pp. 323-326 ◽

Cited By ~ 20

Author(s):

P. Helena MÃ¤kelÃ¤ ◽

M. Sarvas ◽

Sinikka Calcagno ◽

K. Lounatmaa

Keyword(s):

Genetic Characterization ◽

Resistant Mutants

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Frequency and Genetic Characterization of Multidrug-Resistant Mutants of Staphylococcus aureus after Selection with Individual Antiseptics and Fluoroquinolones

Biological and Pharmaceutical Bulletin ◽

10.1248/bpb.25.1129 ◽

2002 ◽

Vol 25 (9) ◽

pp. 1129-1132 ◽

Cited By ~ 22

Author(s):

Norihisa Noguchi ◽

Maki Tamura ◽

Koji Narui ◽

Kazunori Wakasugi ◽

Masanori Sasatsu

Keyword(s):

Staphylococcus Aureus ◽

Genetic Characterization ◽

Multidrug Resistant ◽

Resistant Mutants

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Biochemical and genetic characterization of 5-fluoro-2?-deoxyuridine-resistant mutants of Arabidopsis thaliana

Planta ◽

10.1007/bf00201042 ◽

1994 ◽

Vol 194 (1) ◽

Cited By ~ 7

Author(s):

Keqiang Wu ◽

John King

Keyword(s):

Arabidopsis Thaliana ◽

Genetic Characterization ◽

Resistant Mutants

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

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.45.10.2865-2870.2001 ◽

2001 ◽

Vol 45 (10) ◽

pp. 2865-2870 ◽

Cited By ~ 17

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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