Mechanism of action
Moxifloxacin is a bactericidal antibacterial broad-spectrum drug, 8-methoxy fluoroquinolone. The bactericidal effect of the drug is due to the inhibition of bacterial topoisomerases II and IV, which leads to a disruption in the processes of replication, repair and transcription of the biosynthesis of the microbial cell DIC and, as a consequence, to its death.
The minimum bactericidal concentrations of the preparation as a whole are comparable to its minimum inhibitory concentrations.
Mechanisms of resistance
Mechanisms that lead to the development of resistance to penicillins, cephalosporins, aminoglycosides, macrolides and tetracyclines, do not affect the antibacterial activity of moxifloxacin. Cross-resistance between these groups of antibacterial drugs and moxifloxacin is not noted. So far, no cases of plasmid resistance have been observed. The overall frequency of development of resistance is very low (10-7- 10-10). Resistance to moxifloxacin develops slowly by multiple mutations. Multiple effects of moxifloxacin on microorganisms at concentrations below the minimum inhibitory concentration (MIC) are accompanied by only a slight increase in MIC. There are cases of cross-resistance to quinolones. Nevertheless, some Gram-positive and anaerobic microorganisms resistant to other quinolones retain sensitivity to moxifloxacin.
It has been established that the addition of the methoxyfloxacin methoxy group in the C8 position to the molecule structure increases the activity of moxifloxacin and reduces the formation of resistant mutant strains of Gram-positive bacteria. The addition of the bicycloamine group in position C7 prevents the development of active efflux, - the mechanism of resistance to fluoroquinolones.
Moxifloxacin in vitro is active against a wide range of Gram-positive and Gram-negative microorganisms, anaerobes, acid-fast bacteria and atypical bacteria such as Mycoplasma spp., Chlamydia spp., Legionella spp., and also bacteria resistant to β-lactam and macrolide antibiotics.
Influence on human intestinal microflora
In two studies conducted on volunteers, the following changes in the intestinal microflora were observed after oral administration of moxifloxacin: a decrease in concentrations Escherichia coli, Bacillus spp., Bacteroides vulgatus, Enterococcus spp., Klebsiella spp., as well as anaerobes Bifidobacterium spp., Eubacterium spp., Peptostreptococcus spp. These changes were reversible within two weeks. Toxin Clostridium difficile Not found.
Sensitivity testing in vitro
The spectrum of antibacterial activity of moxifloxacin includes the following microorganisms:
Sensitive
- Gram-positive: Gardnerella vaginalis, Streptococcus pneumoniae* (including penicillin resistant strains and strains with multiple antibiotic resistance), as well as strains resistant to two or more antibiotics, such as penicillin (MIC> 2 μg / ml), cephalosporins of the second generation (for example, cefuroxime), macrolides, tetracyclines, trimethoprim / sulfamethoxazole), Streptococcus pyogenes (group A) *, group Streptococcus milleri (S. anginosus*, S. constellatus*, and S. intermedius*), Group Streptococcus viridians (S. viridians, S. mu tans, S. mitis, S. sanguinis, S. salivarius, S. thermophilus, S. constellatus), Streptococcus agalactiae, Streptococcus dysgalactiae, Staphylococcus aureus (including methicillin-sensitive strains) *, coagulase-negative staphylococci (S. cohnii, S. epidermidis, S. haemolyticus, S. hominis, S. saprophyticus, S. simulans, (including strains sensitive to methicillin).
- Gram-negative: Haemophilus influenzae (including strains, producing and non-producing β-lactamases) *, Haemophilus parainfluenzae*, Moraxella catarrhalis (including strains producing and not producing β-lactamases) *, Bordetella pertussis, Acinetobacter baumanii, Proteus vulgaris.
- anaerobes: Fusobacterium spp., Porphyromonas spp., Prevotella spp., Propionibacterium spp.
- atypical: Chlamydia pneumoniae *, Chlamydia trachomatis *, Mycoplasma pneumoniae *, Mycoplasma hominis, Mycoplasma genitalium, Legionella pneumophila *, Coxiella burnettii.
Moderately sensitive - Gram-positive:
Enterococcus faecalis (only strains sensitive to vancomycin and gentamicin), Enterococcus avium*, Enterococcus faecium.
- gram-negativeьfollowing:
Escherichia coli *, Klebsiella pneumoniae *, Klebsiella oxytoca, Citrobacter freundii **, Enterobacter spp. (E. aerogenes, E. intermedins, E. sakazakii), Enterobacter cloacae *, Pantoea agglomerans, Neisseria gonorrhoeae, Pseudomonas fluorescens, Burkholderia cepacia, Stenotrophomonas maltophilia, Proteus mirabilis *, Morganella morganii, Providencia spp. (P. rettgeri, P. stuartii).
- anaerobes:
Bacteroides spp. (B. distasonis *, B. fragilis *, B. ovatus *, B. thetaiotaomicron *, B. uniform is *, B. vulgatus *), Peptostreptococcus spp. *, Clostridium spp. *.
Resistant
- Gram-positive:
Staphylococcus aureus (methicillin / ofloxacin-resistant strains) **, coagulase-negative staphylococci (S. cohnii, S. epidermidis, S. haemolyticus, S. hominis, S. saprophyticus, S. simulans), resistant to methylpenicilliny strains).
Gram-negative:
Pseudomonas aeruginosa.
* - sensitivity to moxifloxacin is confirmed by clinical data.
** - use of the drug is not recommended for the treatment of infections caused by strains S. aureus, resistant to methicillin (MRSA). In the case of suspected or confirmed infections caused by MRSA, should be prescribed treatment with appropriate antibacterial drugs.
For certain strains, the spread of acquired resistance may vary depending on the geographical region and over time. In this regard, when testing the sensitivity of a strain, it is desirable to have local information on resistance, especially when treating severe infections.
If patients undergoing treatment in a hospital, the area under the pharmacokinetic curve "concentration-time" (AUC)/MANDK90, exceeds 125, and the maximum concentration in the blood plasma (Cmax) / MIC90 is within the range of 8-10, this implies a clinical improvement. In outpatients, the values of these surrogate parameters are usually less: AUC/MANDK90 > 30-40.
Parameter (average value) | AUIC * (h) | FROMmOh** / MIC90 |
MIC90 0,125 mg / l | 279 | 23,6 |
MIC90 0.25 mg / l | 140 | 11,8 |
MIC90 0.5 mg / l | 70 | 5,9 |
*AUIC - area under the inhibitory curve (ratio AUC***/MHK90).
** - The maximum concentration of the drug in the blood plasma.
*** - area under the pharmacokinetic curve "concentration-time".