Mecanismos de Resistencia de Quinolonas
-
Upload
eduardo-alvarado -
Category
Documents
-
view
213 -
download
0
Transcript of Mecanismos de Resistencia de Quinolonas
-
7/31/2019 Mecanismos de Resistencia de Quinolonas
1/8
MECANISMOS DERESISTENCIA DE
QUINOLONAS
-
7/31/2019 Mecanismos de Resistencia de Quinolonas
2/8
MECANISMOS DE RESISTENCIA A
LAS QUINOLONAS
MECANISMO DE ACCION
INGRESO POR PORINAS
SITIO DE ACCION
DNA GIRASA (SUBUNIDAD GRUPO A GRUPO
BTOPOISOMERASA IV SUBUNIDAD GRUPO C
GRUPO E
CAMBIOS EN EL SUPERENROLLAMIENTO
-
7/31/2019 Mecanismos de Resistencia de Quinolonas
3/8
MECANISMOS DE RESISTENCIA A
LAS QUINOLONAS
MECANISMO DE RESISTENCIA
IMPERMEABILIDAD POR ALTERACIN DEUNA PORINA
EFLUJO
ALTERACIN DEL SITIO DE ACCIN(GIRASA, TOPOISOMERASA)
CROMOSOMICAS NO PLASMIDICASDEPENDE DEL USO DEL ATB
-
7/31/2019 Mecanismos de Resistencia de Quinolonas
4/8
MECANISMOS DE RESISTENCIA A
LAS QUINOLONASMUTACIONES POR PASOS
1ERA MUTACIONR A ACIDO NAL.
S A CIPRO
FRACASO DE
TTO
2DA MUTACION R ACIDO NAL
R A CIPRO
-
7/31/2019 Mecanismos de Resistencia de Quinolonas
5/8
MECANISMOS DE RESISTENCIA A
LAS QUINOLONASBACILOS GRAM NEGATIVOS
PUNTO DE CORTE ACIDONALIDIXICOSENSIBLE > 19 mm RESISTENTE < 13 mm
PUNTO DE CORTE PARA CIPROFLOXACINO
SENSIBLE > 21mm RESISTENTE < 15 mm
Criterio farmacocintico NCCLS
Disco de acido nalidixico < 13 mm Sensibilidaddisminuda a ci rofloxacino
-
7/31/2019 Mecanismos de Resistencia de Quinolonas
6/8
. - .
The quinolones are a potent class of antimicrobial agents that target two essential enzymes
of bacterial cells: DNA gyrase and topoisomerase IV. Resistance is mediated chiefly through
stepwise mutations in the genes that encode these enzymes, leading to alterations of the
target site. These mutations occur in an area called the "quinolone resistance determining
region". In gram-positive organisms, mutations occur more often in topoisomerase IV thanin DNA gyrase. This target preference appears to depend upon two factors: the species of
organism and the selecting drug. Resistance can be enhanced by a decrease in intracellular
drug concentration, which is mediated through efflux pumps. The newer generation of
fluoroquinolones and non-fluorinated quinolones exhibits enhanced activity against gram-
positive organisms compared to the older members of this drug class, although development
of resistance to these drugs has been demonstrated in vitro. This review gives a
chronological perspective of the literature on the action of DNA gyrase and topoisomerase
IV and the mechanisms of resistance to quinolones in staphylococci, streptococci and
enterococci.
-
7/31/2019 Mecanismos de Resistencia de Quinolonas
7/8
2002 Feb;115:49-54 Related Articles,Links
Nalidixic acid susceptibility test to screen ciprofloxacin resistance in Salmonella typhi.
Kapil A, Renuka, Das B.
Department of Microbiology, All India Institute of Medical Sciences, New Delhi, India.
BACKGROUND & OBJECTIVES: Clinical non response to ciprofloxacin therapy in enteric fever is increasingly being
encountered in endemic areas possibly due to the increase in the levels of resistance to ciprofloxacin in Salmonella typhi. The
antimicrobial susceptibility tests for S. typhi performed by the disc diffusion method using NCCLS breakpoints fail to detect
the increasing MIC of ciprofloxacin, leading to the inappropriate treatment of enteric fever with ciprofloxacin. We explored
the possibility of testing S. typhi strains for their susceptibility to nalidixic acid by disc diffusion method as a marker for highMIC to ciprofloxacin. METHODS: Isolates (94) of S. typhi were tested for in vitro susceptibility to nalidixic acid (30
micrograms) and ciprofloxacin (5 micrograms) by disc diffusion method using NCCLS guidelines. The MIC of these strains
to ciprofloxacin was also determined by E-test. RESULTS: Of the 94 strains tested, 56 were NARST (nalidixic acid resistant
S. typhi) and 34 were NASST (nalidixic acid sensitive S. typhi). MIC of ciprofloxacin in the NASST strains varied from
0.002-0.125 microgram/ml while that for NARST strains varied from 0.023-0.38 microgram/ml, which is about 10-folds
higher than that of NASST strains. INTERPRETATION & CONCLUSION: Our study shows that resistance to nalidixic acid
is associated with a high MIC to ciprofloxacin in S. typhi. These strains would have been interpreted as ciprofloxacin
sensitive by routine antimicrobial susceptibility testing by disc diffusion method. Hence screening of S. typhi isolates by thenalidixic acid susceptibility test may be incorporated in a clinical bacteriology laboratory to alert the treating physicians of
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Display&dopt=pubmed_pubmed&from_uid=12138664http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Display&dopt=pubmed_pubmed&from_uid=12138664 -
7/31/2019 Mecanismos de Resistencia de Quinolonas
8/8