In Vitro Activity of Five Quinolones and Analysis of the Quinolone Resistance-Determining Regions of gyrA , gyrB , parC , and parE in Ureaplasma parvum and Ureaplasma urealyticum Clinical Isolates from Perinatal Patients in Japan

Abstract

g Ureaplasma spp. cause several disorders, such as nongonococcal urethritis, miscarriage, and preterm delivery with lung infections in neonates, characterized by pathological chorioamnionitis in the placenta. Although reports on antibiotic resistance in Ureaplasma are on the rise, reports on quinolone-resistant Ureaplasma infections in Japan are limited. The purpose of this study was to determine susceptibilities to five quinolones of Ureaplasma urealyticum and Ureaplasma parvum isolated from perinatal samples in Japan and to characterize the quinolone resistance-determining regions in the gyrA, gyrB, parC, and parE genes. Out of 28 clinical Ureaplasma strains, we isolated 9 with high MICs of quinolones and found a single parC gene mutation, resulting in the change S83L. Among 158 samples, the ParC S83L mutation was found in 37 samples (23.4%), including 1 sample harboring a ParC S83L-GyrB P462S double mutant. Novel mutations of ureaplasmal ParC (S83W and S84P) were independently found in one of the samples. Homology modeling of the ParC S83W mutant suggested steric hindrance of the quinolone-binding pocket (QBP), and de novo prediction of peptide structures revealed that the ParC S84P may break/kink the formation of the ␣4 helix in the QBP. Further investigations are required to unravel the extent and mechanism of antibiotic resistance of Ureaplasma spp. in Japan.Ureaplasma spp. are among the smallest self-replicating organisms, in terms of both genome size and cellular dimensions. They lack cell walls and are thus resistant to penicillin and other ␤-lactams. These organisms exist in association with eukaryotic cells, mainly colonizing mucosal surfaces of the respiratory and urogenital tracts (1, 2). Ureaplasma spp. are common inhabitants of the lower genital tract and can be isolated from 40% to 80% of women of child-bearing age (1, 3). Ureaplasma spp. have been associated with a range of pathologies, including nongonococcal urethritis (NGU), miscarriage, preterm delivery, neonatal pneumonia, and chronic lung disease in preterm neonates (4, 5). Many reports have suggested that Ureaplasma parvum and/or Ureaplasma urealyticum may be associated with urogenital infections, infertility, and adverse pregnancy outcomes (6). Regarding the management of ureaplasmal infections, only a limited number of reports are available on the surveillance of antimicrobial resistance in clinical Ureaplasma strains, which is crucial for providing therapy empirically (6). The treatment of ureaplasmal infections is limited to tetracyclines, macrolides, and quinolones (5, 7). Resistance to all the three antibiotic classes in clinical Ureaplasma isolates has been documented, with unique nucleic acid substitutions identified as potential molecular mechanisms for each (5,(8)(9)(10).Quinolones are used for treating urogenital infections and interact in bacteria with the type II topoisomerases DNA gyrase and topoisomerase IV, both of which are composed of two A and two B subunits; these subunits are encoded by the gyrA and gyrB genes for DNA...

Susceptibility and Antimicrobial Resistance of Genital Ureaplasma Parvum

“…1). The results of the present study were similar to those of other studies on the rates of susceptibility of U. parvum to antibiotics [5,9,12].…”

“…According to previous studies, eight antibiotic agents including DOX, AZM, gentamicin (GEN), CIP, TET, levofloxacin (LVX), ERY and CLR were tested on 35 samples of U. parvum, as they are the major antibiotics used in the treatment of genital tract infection caused by U. parvum. A further purpose of choosing these antimicrobial agents was they are conventionally being used for the routine treatment of sexually transmitted infections [6,9,10,12]. In addition, a new macrolide CLR was also tested.…”

“…U. parvum had higher mutation rate than conventional bacteria which meant it could rapidly develop resistance to drugs including quinolone, ERY and AZM. Resistance developed in U. parvum by point mutation in parC (Pro-57 Leu), and two novel mutations in parE (Ile-73Thr and a methionine insertion at codon 86) were found in an ofloxacin-resistant strain [9,10,15].…”

Antibiotic Susceptibility and Sequence Type Distribution of Ureaplasma Species Isolated from Genital Samples in Switzerland

“…In Croatia, U. urealyticum strains showed nonsusceptibility rates of 22%, 8%, and 3% for OFL, AZI, and DOX, respectively (14). However, we emphasize that possible inconsistencies in resistance rates among the aforementioned studies could occur due to the use of different methodologies (i.e., Mycoplasma IST 2 kit [10,12,13] versus broth microdilution [25]) and/or different criteria for interpretation for the susceptibility results (i.e., those used for the Mycoplasma IST 2 kit [10,12,13] versus those of the CLSI [9,11,19]). As shown in this work (Table 1), conflicting results from the IST 2 kit and standard broth microdilution were observed for CIP and AZI (i.e., most of the isolates routinely reported as nonsusceptible to these antibiotics were actually fully sensitive).…”

“…This phenomenon was observed previously and was ascribed to mechanisms not yet recognized (e.g., altered membrane permeability); however, we emphasize that the IST 2 kit might overrate the FQ resistance (i.e., high MICs that are actually in the susceptible range with the microdilution method). With regard to the QRDR substitutions found in the five isolates, only the well-described Ser83Leu substitution in ParC (U. parvum ID141 [ST22 and serovar 6]) conferred resistance to CIP (MIC of 4 g/ml with the microdilution method) (25,28), whereas both Thr417Val (for U. urealyticum) and Val417Thr (for U. parvum) ParE substitutions had predicted small effects on the MICs (Table 1) (27). Mutations in the two copies of 23S rRNA or, more frequently, amino acid substitutions in the L4 and L22 ribosomal proteins were linked previously to macrolide resistance.…”