RESUMEN
Mandelate racemase (MR) catalyzes the 1,1-proton transfer that interconverts the enantiomers of mandelate. The transition state/intermediate analogues N-hydroxyformanilide (K(i)=2.79+/-0.19 microM) and cupferron (K(i)=2.67+/-0.09 microM) are identified as potent competitive inhibitors of MR. The pH-pK(i) profile indicates that MR can bind either the protonated or deprotonated forms of N-hydroxyformanilide, with a 10-fold greater affinity for the latter form.
Asunto(s)
Inhibidores Enzimáticos/química , Formamidas/química , Nitrosaminas/química , Pseudomonas putida/enzimología , Racemasas y Epimerasas/antagonistas & inhibidores , Concentración de Iones de Hidrógeno , Racemasas y Epimerasas/química , Especificidad por SustratoRESUMEN
Mandelate racemase has been studied as a paradigm for enzyme-catalyzed abstraction of a proton from carbon acids with relatively high pKa values. 1,1-Diphenyl-1-hydroxymethylphosphonate is a substrate-intermediate-product analogue and is a modest competitive inhibitor of the enzyme (Ki=1.41+/-0.09 mM), suggesting that simultaneous binding of the two phenyl groups obviates mimicry of the aci-carboxylate function of the intermediate by the phosphonate group.
Asunto(s)
Inhibidores Enzimáticos/química , Compuestos Organofosforados/química , Pseudomonas putida/enzimología , Racemasas y Epimerasas/antagonistas & inhibidores , Proteínas Bacterianas/antagonistas & inhibidores , Sitios de Unión , Unión Competitiva , Inhibidores Enzimáticos/farmacología , Ligandos , Estructura Molecular , Compuestos Organofosforados/síntesis química , Compuestos Organofosforados/farmacología , Relación Estructura-ActividadRESUMEN
The motile enterococci with the vanC gene have intrinsic low-level resistance to vancomycin, but have not been implicated in a nosocomial outbreak. We determined the colonization rate of motile enterococci in hospitalized and nonhospitalized patients. Perianal or stool specimens were cultured in Enterococcosel broth supplemented with 6 micrograms of vancomycin per mL. Rapid motility and pigment tests were performed on all enterococci isolated. A total of 82 motile and/or pigmented enterococci were isolated from 679 patients for a colonization rate of 12.1%. There were 43 Enterococcus gallinarum, 32 Enterococcus casseliflavus, 4 Enterococcus flavescens, and 3 Enterococcus mundtii identified. The E. gallinarum vancomycin MIC90 was 32 micrograms/mL and the E. casseliflavus vancomycin MIC90 was 8 micrograms/mL.
Asunto(s)
Canal Anal/microbiología , Enterococcus/crecimiento & desarrollo , Heces/microbiología , Antibacterianos/farmacología , Farmacorresistencia Microbiana , Enterococcus/efectos de los fármacos , Enterococcus/aislamiento & purificación , Enterococcus/fisiología , Hospitalización , Humanos , Pruebas de Sensibilidad Microbiana , Movimiento , Vancomicina/farmacologíaRESUMEN
Brain heart infusion-6-micrograms/ml vancomycin agar plates obtained from five commercial sources (B-D Microbiology Systems, Carr-Scarborough Microbiologicals, MicroBio Products, PML Microbiologicals, and REMEL) were evaluated with 714 enterococci for detection of vancomycin resistance. All 465 (100%) vancomycin-resistant enterococci (MIC > or = 32 micrograms/ml) were detected by each manufacturer's agar screen plate, and each manufacturer's agar screen plate detected at least 99% of the 177 vancomycin-susceptible enterococci (MIC < or = 4 micrograms/ml). Detection of the 72 vancomycin-intermediate enterococci (MIC = 6 to 16 micrograms/ml) ranged from 94% for B-D Microbiology Systems to 99% for PML Microbiologicals.
Asunto(s)
Antibacterianos/farmacología , Medios de Cultivo , Enterococcus/efectos de los fármacos , Pruebas de Sensibilidad Microbiana/métodos , Vancomicina/farmacología , Farmacorresistencia Microbiana , Estudios de Evaluación como Asunto , Infecciones por Bacterias Grampositivas/microbiología , HumanosRESUMEN
Broth formulations of two media selective for enterococci, Enterococcel, M-Enterococcosel broths were supplemented with 6 micrograms of vancomycin per ml and evaluated for isolation of vancomycin-resistant enterococci (VRE). Each broth was challenged with various concentrations of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and vancomycin-susceptible and vancomycin-resistant enterococci and with 193 perianal specimens obtained from patients at risk in our institution for VRE colonization. Both the Enterococcosel and M-Enterococcus broths with vancomycin detected as few as 1 to 9 CFU of VRE while inhibiting growth of the other organisms tested. Enterococcus faecium organisms (MIC, > 256 micrograms/ml) were recovered from 66 perianal swab cultures in the enterococcosel-vancomycin broth, and VRE were recovered from 62 perianal swab cultures in the M-Enterococcus-vancomycin broth. Enterococcosel-vancomycin broth detected VRE in perianal specimens 48 h earlier than did M-Enterococcus-vancomycin broth. Enterococcosel broth with 6 micrograms of vancomycin per ml can be used for the rapid and selective isolation of VRE from surveillance specimens.