RESUMEN
To compare two culture methods [nylon fiber flocked swabs with broth enrichment versus RODAC ('replicate organism detection and counting') plates] for recovery of multidrug-resistant organisms, 780 environmental surfaces in 63 rooms of patients on contact precautions in four intensive care units at one hospital were examined. Among sites that had at least one positive culture, swab culture with broth enrichment detected the target organisms more frequently than RODAC plates (37.5% vs 26.0%, P = 0.06). There was moderate agreement between the two methods (κ = 0.44) with agreement better for small or flat surfaces compared to large or irregular surfaces.
Asunto(s)
Bacterias/aislamiento & purificación , Técnicas Bacteriológicas/métodos , Farmacorresistencia Bacteriana Múltiple , Microbiología Ambiental , Manejo de Especímenes/métodos , Bacterias/efectos de los fármacos , Medios de Cultivo/química , Unidades de Cuidados IntensivosRESUMEN
In vitro, ciprofloxacin can select for dual resistance to fluoroquinolones and imipenem in Pseudomonas aeruginosa via a mutation in the regulatory gene, mexT, which downregulates OprD and upregulates MexEF-OprN. We performed a nested case-control study of patients in two medical intensive care units participating in an observational cohort study. Patients colonized or infected with P. aeruginosa resistant to both ciprofloxacin and imipenem (cases) were compared to controls. The presence of OprD and OprN from cases was evaluated by Western blot. In total, 44 cases were compared to 132 controls. Imipenem exposure [adjusted odds ratio (AOR) = 11.4, p = 0.044] was significantly associated with case status, but fluoroquinolone use was not (AOR = 1.0, p = 0.998). Neither OprD nor OprN were detected in any isolate. Fluoroquinolone use was not a risk factor for acquisitions of dually resistant P. aeruginosa. The absence of OprN in these isolates suggests that dual resistance is not due to mexT mutations.
Asunto(s)
Antibacterianos/farmacología , Ciprofloxacina/farmacología , Infección Hospitalaria/transmisión , Farmacorresistencia Bacteriana , Imipenem/farmacología , Infecciones por Pseudomonas/transmisión , Pseudomonas aeruginosa/efectos de los fármacos , Proteínas de la Membrana Bacteriana Externa/biosíntesis , Western Blotting , Estudios de Casos y Controles , Ciprofloxacina/uso terapéutico , Infección Hospitalaria/microbiología , Femenino , Humanos , Imipenem/uso terapéutico , Unidades de Cuidados Intensivos , Masculino , Persona de Mediana Edad , Porinas/biosíntesis , Infecciones por Pseudomonas/microbiología , Pseudomonas aeruginosa/aislamiento & purificaciónRESUMEN
This study examined the contribution of AmpC over-expression to beta-lactam resistance in clinical isolates of Pseudomonas aeruginosa obtained from a hospital in Houston, TX, USA. Seventy-six non-repeat bloodstream isolates obtained during 2003 were screened for ceftazidime resistance in the presence and absence of clavulanic acid 4 mg/L. AmpC was identified by isoelectric focusing (with and without cloxacillin inhibition); stable derepression was ascertained phenotypically by a spectrophotometric assay (with and without preceding induction by imipenem) using nitrocefin as the substrate, and was confirmed subsequently by quantitative RT-PCR of the ampC gene. The clonal relatedness of the AmpC-over-expressing isolates was assessed by pulsed-field gel electrophoresis. In addition, the ampC and ampR gene sequences were determined by PCR and sequencing. For comparison, two standard wild-type strains (PAO1 and ATCC 27853) and three multidrug-susceptible isolates were used as controls. AmpC over-expression was confirmed in 14 ceftazidime-resistant isolates (overall prevalence rate, 18.4%), belonging to seven distinct clones. The most prevalent point mutations in ampC were G27D, V205L and G391A. Point mutations in ampR were also detected in eight ceftazidime-resistant isolates. AmpC over-expression appears to be a significant mechanism of beta-lactam resistance in P. aeruginosa. Understanding the prevalence and mechanisms of beta-lactam resistance in P. aeruginosa may guide the choice of empirical therapy for nosocomial infections in hospitals.
Asunto(s)
Bacteriemia/microbiología , Proteínas Bacterianas/genética , Pseudomonas aeruginosa/enzimología , Resistencia betalactámica , beta-Lactamasas/genética , Electroforesis en Gel de Campo Pulsado , Humanos , Focalización Isoeléctrica , Mutación Puntual , Pseudomonas aeruginosa/efectos de los fármacos , Pseudomonas aeruginosa/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , EspectrofotometríaRESUMEN
Daptomycin is a new lipopeptide antibiotic that is rapidly bactericidal against Staphylococcus aureus. We report daptomycin resistance and treatment failure in 2 patients with osteomyelitis due to methicillin-resistant S. aureus. Disk diffusion susceptibility testing failed to detect resistance. Daptomycin at high concentration retained bactericidal activity against resistant isolates.
Asunto(s)
Antibacterianos/farmacología , Daptomicina/farmacología , Farmacorresistencia Bacteriana , Resistencia a la Meticilina , Staphylococcus aureus/efectos de los fármacos , Anciano , Anciano de 80 o más Años , Antibacterianos/uso terapéutico , Bacteriemia/microbiología , Femenino , Humanos , Vértebras Lumbares/microbiología , Región Lumbosacra/microbiología , Pruebas de Sensibilidad Microbiana/métodos , Persona de Mediana Edad , Osteomielitis/microbiología , Infecciones Estafilocócicas/microbiología , Insuficiencia del TratamientoRESUMEN
Carbapenemases are rare in the United States. This is the first report of a United States nosocomial outbreak of pan-resistant Pseudomonas aeruginosa infections due to an integron-borne metallo-beta-lactamase, VIM-2. This emergence of carbapenemases on mobile genetic elements in the United States warrants surveillance.
