Mutations in 23S rRNA Account for Intrinsic Resistance to Macrolides in Mycoplasma hominis and Mycoplasma fermentans and for Acquired Resistance to Macrolides in M. hominis

Abstract

The mechanisms of intrinsic resistance of Mycoplasma hominis to 14-and 15-membered macrolides were investigated in comparison with those of M. pneumoniae, which is naturally susceptible to macrolides. Radiolabeled erythromycin was not accumulated by M. hominis PG21, but addition of an ABC transporter inhibitor increased the level of erythromycin uptake more than two times, suggesting the existence of an active efflux process. The affinity of [ 14 C]erythromycin to ribosomes isolated from M. hominis was dramatically reduced relative to that to ribosomes isolated from M. pneumoniae. The nucleotide sequences of 23S rRNA of both ribosomal operons rrnA and rrnB and ribosomal proteins L4 and L22 of M. hominis were obtained. Compared to the sequence of M. pneumoniae, M. hominis harbored a G2057A transition in its 23S rRNA sequence, as did M. fermentans, another mycoplasma that is erythromycin resistant. An additional C2610U change was also found in the sequence of M. hominis. Moreover, two M. hominis clinical isolates with acquired resistance to 16-membered macrolides were examined for mutations in domain II and domain V of 23S rRNA and in ribosomal proteins L4 and L22. Compared to the sequence of reference strain PG21, one isolate harbored a A2059G transition and a C2611U transition in one of the two rrn operons, while the other one was mutated only at position 2059, also on the same operon. No mutation was found in the two ribosomal protein sequences. Overall, the present study is an exhaustive characterization of the intrinsic resistance of M. hominis to 14-and 15-membered macrolides and the first description of mycoplasma clinical isolates resistant to macrolide, lincosamide, and streptogramin antibiotics harboring a mutation at position 2611 in the 23S rRNA.Human mycoplasmas are responsible for urogenital and respiratory tract infections. Macrolide, lincosamide, and streptogramin antibiotics (MLSs) are a class of antimicrobials commonly used for the treatment of these infections. The MICs of ketolides, a new class of antimicrobials derived from erythromycin, are low for these microorganisms (3). The MLSs and ketolide antibiotics (MLSKs) inhibit protein synthesis by binding to domain V and domain II of 23S rRNA (13, 21). Three main mechanisms of resistance have been reported: drug inactivation, active efflux, and modification of the target sites by methylation or mutation (46, 49). Resistance by ribosomal mutations in domain II and domain V of 23S rRNA has been described, and recently, mutations in ribosomal proteins L4 and L22 were also associated with resistance to MLSKs (7,30,33,42,43).Mycoplasmas present different phenotypes of intrinsic resistance to macrolides. Mycoplasma pneumoniae, a respiratory mycoplasma, is susceptible to all MLSKs. In contrast, M. hominis, a genital species, is naturally resistant to 14-and 15-membered macrolides and ketolides but is susceptible to josamycin, a 16-membered macrolide, and lincosamides. Intrinsic resistance to 14-membered macrolides has been observed in other mycoplasma s...

In Vitro Selection and Characterization of Resistance to Macrolides and Related Antibiotics in Mycoplasma pneumoniae

“…In M. pneumoniae, resistance by mutation is the most expected mechanism of resistance, and so far it is the only one described in this species (20,22), since this mycoplasma harbors only one copy of the rRNA gene operon (18). Thus, heterozygous strains or gene dosage effect, previously described for Mycoplasma hominis (13,23) or other bacteria (19,25) with at least two copies of rRNA, could not exist in M. pneumoniae.…”

“…Mutations in domains II and V of 23S rRNA and in ribosomal proteins L4 and L22 were involved in resistance to MLSKs, first in bacteria with a small number of rrn operons and more recently in bacteria like Streptococcus pneumoniae and Staphylococcus aureus with four and six rrn operons, respectively (25,29,32). In mycoplasmas, gram-positive related bacteria which possess one or two copies of 23S rRNA, only resistance by point mutations in the peptidyltransferase loop of domain V of 23S rRNA has been described (13,20,22,23). The genome of M. pneumoniae is entirely sequenced (18) and possesses only one copy of the rRNA gene operon.…”

ANTIBIOTICS TARGETING RIBOSOMES: Resistance, Selectivity, Synergism, and Cellular Regulation

“…Mutations in proteins L22 and L4 that cause resistance to telithromycin in ribosomes with A2058G mutation or methylation were detected in several pathogens (108,109) as well as in a genetically engineered pathogen model (E. Boettger and N. Corti, private communication). In its complex with D50S, the position of telithromycin allows interactions with Arg 90 of L22 through its carbamate ring (R. Berisio, private communication).…”

Micoplasmas y antibióticos

“…Por otra parte, se ha demostrado que este micoplasma es sensible in vitro a la tetraciclina, la doxiciclina, el cloramfenicol, la clindamicina y la ciprofloxacina. 9,10 Es importante señalar que en la práctica clínica no es muy común que se solicite el diagnóstico de micoplasmas, lo cual es un factor importante para que otros grupos de bacterias desarrollen resistencia, ya que el tratamiento que se da a un paciente se basa en antibióticos diseñados comúnmente para gram positivos y gram negativos, sin considerar que los micoplasmas carecen de pared celular. Así, la selección de diversos microorganismos resistentes puede ocurrir durante o después de tratamientos, ya que los residuos de antibióticos pueden establecerse durante grandes periodos de tiempo posteriores al tratamiento, lo que favorece la inactivación de los antibióticos y la diseminación de genes de resistencia.…”