RESUMEN
Active surveillance is part of a multifaceted approach used to prevent the spread of vancomycin-resistant enterococci (VRE). The impact of fecal density, the vancomycin MIC of the isolate, and the vancomycin concentration in liquid medium on test performance are uncertain. Using fecal specimens spiked with a collection of 18 VRE (predominantly vanB) with a wide vancomycin MIC range, we compared the performances of commercial chromogenic agars (CHROMagar VRE, chromID VRE, Brilliance VRE, and VRE Select) and 1 liquid medium (Enterococcosel enrichment broth) for VRE detection. The specificity of solid media was excellent; however, the sensitivity at 48 h varied from 78 to 94%. Screening using liquid medium was less sensitive than screening with solid media, particularly as the vancomycin content increased. Sensitivity declined (i) as the fecal VRE density decreased, (ii) when the media were assessed at 24 h (versus 48 h), and (iii) for isolates with a low vancomycin MIC (sensitivity, 25 to 75% versus 100% for isolates with vancomycin MIC of <16 mg/liter versus >32 mg/liter on solid medium using 10(6) CFU/ml of feces). Depending on local epidemiology and in particular VRE vancomycin MICs, the sensitivity of culture-based methods for VRE screening of stool or rectal specimens may be suboptimal, potentially facilitating secondary transmission.
Asunto(s)
Antibacterianos/farmacología , Enterococcus/efectos de los fármacos , Heces/microbiología , Resistencia a la Vancomicina , Vancomicina/farmacología , Medios de Cultivo/química , Enterococcus/aislamiento & purificación , Infecciones por Bacterias Grampositivas/microbiología , Humanos , Pruebas de Sensibilidad Microbiana/métodos , Sensibilidad y EspecificidadRESUMEN
A large single-strain outbreak of vancomycin-resistant Enterococcus faecium (VREF) vanB occurred in Royal Perth Hospital from July to December 2001. When a VREF-carrying patient was discovered on a ward, all patients on the ward were screened with rectal swabs. A total of 172 patients were colonised, four with infections, but no deaths were attributable to VREF. The number of rectal swabs required to detect each carrier was recorded. On average four rectal swabs, each collected on separate days, were needed to detect more than 90 per cent of the 172 VREF carriers who were epidemiologically linked to the Royal Perth Hospital outbreak. An electronic alert system (Micro-Alert) was used to identify ward contacts of VREF carriers and enabled those who had not been screened before discharge to be followed-up and screened. Ninety-six contacts were actively followed-up in October 2001 and 32 (33.3%) were found to be VREF carriers. From 28 September 2001 to 30 April 2002, a total of 1,977 ward contacts were screened after discharge from hospital and 54 (2.73%) were found to be carrying VREF. We conclude that during single-strain outbreaks of vancomycin-resistant enterococci in hospitals, patient contacts need to be screened on more than three occasions in order to detect most of the carriers and control the outbreak. Secondly, electronic labelling and active follow-up of ward contacts of VREF carriers resulted in a significant number of carriers being detected who otherwise posed a risk of initiating further outbreaks in hospitals if they were readmitted.
Asunto(s)
Portador Sano/microbiología , Trazado de Contacto/métodos , Infección Hospitalaria/microbiología , Brotes de Enfermedades , Farmacorresistencia Bacteriana , Enterococcus faecium/aislamiento & purificación , Infecciones por Bacterias Grampositivas/diagnóstico , Vancomicina/farmacología , Portador Sano/diagnóstico , Portador Sano/epidemiología , Infección Hospitalaria/diagnóstico , Infección Hospitalaria/epidemiología , Enterococcus faecium/efectos de los fármacos , Infecciones por Bacterias Grampositivas/epidemiología , Infecciones por Bacterias Grampositivas/microbiología , Hospitales , Humanos , Tamizaje Masivo , Alta del Paciente , Recto/microbiología , Factores de RiesgoRESUMEN
BACKGROUND: Most breaches of endoscope disinfection result from inadequate manual cleaning or improper use of disinfectants. This is a description of how a quality assurance program identified rinse water as a source of bacterial contamination and how it facilitated the introduction of a novel means of delivering rinse water of high purity. METHODS: Between 1996 and 2001, weekly samples were obtained from accessory and suction channels of endoscopes as well as the internal chambers of automated washing machines. Samples were processed for routine bacterial and mycobacterial culture. RESULTS: Bacteria were isolated in 8.7% of samples collected between 1996 and 1998. Of 36 positive samples, 20 (54%) were Pseudomonas sp. Analysis of rinse water from pipework downstream from filters demonstrated high growth of Pseudomonas sp, suggesting biofilm within piping was contaminating rinse water. A system of hot water flushing of pipework was developed that maintains a temperature above 60 degrees C for 60 minutes on a daily basis. This resulted in a consistently low level of bacterial contamination. CONCLUSION: This report demonstrates the value of a quality assurance program for endoscope disinfection and shows how rinse water may contaminate disinfected endoscopes. A system of hot water purging of the rinse water delivery system markedly reduces this contamination.