RESUMEN
Background. Blood culture contamination (BCC) is an important quality concern in clinical microbiology as it can lead to unnecessary antimicrobial therapy in patients and increased workload for laboratory scientists. The Clinical Laboratory and Standards Institute recommend BCC rates to be <3â% and recently updated guidelines have set a new goal of 1â%. The aim of this project was to design and implement interventions to reduce BCC rates at our institution. Methods. We introduced a combined education and skin antisepsis intervention in a large Model 4 academic teaching hospital in the South of Ireland. BD ChloraPrep skin antisepsis applicators (2â% chlorhexidine gluconate/70â% isopropyl alcohol), licensed for use for blood culture specimen collection, were introduced, replacing Clinell (2â% chlorhexidine gluconate/70â% isopropyl alcohol) wipes. In addition, a multimodal education programme was designed and delivered. This consisted of a video demonstrating the recommended blood culture specimen collection technique using the new applicators as well as simulation training for all interns. The video was uploaded to the intranet as an educational resource available to all staff. Results. The interventions were implemented in July 2022 and BCC rates pre- and post-intervention were calculated. The average BCC rate for the 12 months preceding the intervention (July 2021 to July 2022) was 2.56â% with highest rates in the Emergency Department. This compared to an average rate of 2.2â% in the 12 months post-intervention (July 2022 to July 2023). In comparing the two rates the reduction in BCC rates between the two periods was not statistically significant (P=0.30). Conclusion. Overall BCC rates reduced but the difference between the two periods did not reach statistical significance. The resource-intensive nature of providing regular and timely feedback of contamination rates and the larger impact of in-person education and training over virtual modalities may explain the modest reduction. Further investments in these areas, particularly in the Emergency Department, will be necessary to further reduce rates in line with new recommendations.
RESUMEN
The factors influencing the virulence of P. aeruginosa in the development of invasive infection remain poorly understood. Here, we investigated the role of the host microenvironment in shaping pathogen virulence and investigated the mechanisms involved. Comparing seven paired genetically indistinguishable clinical bloodstream and peripheral isolates of P. aeruginosa, we demonstrate that isolates derived from bloodstream infections are more virulent than their peripheral counterparts (p = 0.025). Bloodstream and peripheral isolates elicited similar NF-kB responses in a THP-1 monocyte NF-kappaB reporter cell line implicating similar immunogenicity. Proteomic analysis by mass spectrometry identified multiple virulence and virulence-related factors including LecA and RpoN in significantly greater abundance in the bacterial supernatant from the bloodstream isolate in comparison to that from the corresponding peripheral isolate. Investigation by qPCR revealed that control of expression of these virulence factors was not due to altered levels of transcription. Based on these data, we hypothesize a post-transcriptional mechanism of virulence regulation in P. aeruginosa bloodstream infections influenced by surrounding microenvironmental conditions.
Asunto(s)
Bacteriemia/microbiología , Regulación Bacteriana de la Expresión Génica , Infecciones por Pseudomonas/microbiología , Pseudomonas aeruginosa/patogenicidad , Factores de Virulencia/biosíntesis , Medios de Cultivo/química , Perfilación de la Expresión Génica , Humanos , Inmunidad Innata , Espectrometría de Masas , Proteoma/análisis , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/inmunología , Pseudomonas aeruginosa/aislamiento & purificación , Reacción en Cadena en Tiempo Real de la Polimerasa , Células THP-1 , Virulencia , Factores de Virulencia/genéticaRESUMEN
Our understanding of how the course of opportunistic bacterial infection is influenced by the microenvironment is limited. We demonstrate that the pathogenicity of Pseudomonas aeruginosa strains derived from acute clinical infections is higher than that of strains derived from chronic infections, where tissues are hypoxic. Exposure to hypoxia attenuated the pathogenicity of strains from acute (but not chronic) infections, implicating a role for hypoxia in regulating bacterial virulence. Mass spectrometric analysis of the secretome of P. aeruginosa derived from an acute infection revealed hypoxia-induced repression of multiple virulence factors independent of altered bacterial growth. Pseudomonas aeruginosa lacking the Pseudomonas prolyl-hydroxylase domain-containing protein, which has been implicated in bacterial oxygen sensing, displays reduced virulence factor expression. Furthermore, pharmacological hydroxylase inhibition reduces virulence factor expression and pathogenicity in a murine model of pneumonia. We hypothesize that hypoxia reduces P. aeruginosa virulence at least in part through the regulation of bacterial hydroxylases.