[Formation of M. hominis and A. laidlawii resistance to fluoroquinolones]. / O formirovanii rezistentnosti k ftorkhinolonam u M. hominis i A. laidlawii.

Mycoplasma hominis and Acholeplasma laidlawii cultures resistant to antibacterial fluoroquinolone drugs ciprofloxacin (Cpf), ofloxacin (Ofl), and lomefloxacin (Lmf) were prepared by selection in liquid nutrient medium with ascending concentrations of Cpf. Resistant mycoplasma clones contained point mutations in the gyrase. A gene region determining quinolone resistance (QRDR gyrA): M. hominis contained C-->T transition resulting in substitution of Ser(83) for Leu and A. laidlawii G-->A resulting in substitution of Asp (91) for Asn. The phenomena of mutation formation during mycoplasma culturing in the presence of fluoroquinolones is studied. In the presence of Cpf in culture medium in concentrations of up to 10 micrograms/ml (for M. hominis) and 1 microgram/ml (for A. laidlawii) the mycoplasma populations contained cells with both altered and wild genotype. Culturing in the presence of higher Cpf concentrations resulted in elimination of cells nonmutant for QRDR gyrA. Besides in vitro studies, we analyzed clinical strains of M. hominis in the presence of different Cpf concentrations. M. hominis clones resistant to Cpf varying in genotypes were detected. These data permit a conclusion that the mechanism of fluoroquinolone resistance formation in mycoplasma includes several stages.

[Use of a method of single-stranded DNA fragment conformation polymorphism (SSCP) for detecting resistance of Mycoplasm hominis to fluoroquinolones]. / Ispol'zovanie metoda konformatsionnogo polimorfizma odnotsepochechnykh fragmentov DNK (SSCP) dlia vyiavleniia rezistentnosti Mycoplasma hominis k ftorkhinolonam.

Single-strand conformation polymorphism (SSCP) method was used for nucleotide sequence variation analysis of the gyrase A subunit quinolone resistance determining region (gyrA QRDR) in a laboratory and clinical strains of M. hominis. The couple of primers selected for this region amplified specific product in clinical material. M. hominis cultures growing in the presence of different concentrations of ciprofloxacin were studied by the SSCP method. Ser(83) to Leu mutation described previously was detected in the presence of quinolone in concentrations of at least 10 mcg/ml. In addition, 11 clinical samples were tested. In all cases the results of SSCP were confirmed by direct sequencing of the region. In 2 cases the sequences of gyrA QRDR in clinical strains were the same as in the laboratory strain. A Ser(83)-Leu mutation was identified in 1 clinical sample, while in others nucleotide substitutes did not lead to changes in amino acid sequences. These data demonstrate high informative value of the SSCP method for evaluating nucleotide variation in gyrA QRDR and quinolone resistance of M. hominis.