Reducing Gram-negative BSI…by accident


We have precious little data on what works to prevent the transmission of MDR-GNR. An interesting article published recently in CID provides invaluable data that an infection control programme aimed at reducing MRSA (and succeeding) was also effective in reducing GNR BSI!

The MRSA Prevention Initiative was launched in 2007 and was effective in reducing MRSA in the US VA hospitals. The question of today’s study was whether the measures aimed at reducing MRSA may result in a ‘collateral’ reduction in GNR BSI. The “headline” intervention of the MRSA Prevention Initiative was targeted MRSA screening and contact precautions. On the face of it, this ought to have little impact on GNR BSI. However, MRSA colonisation is probably a pretty effective epidemiological marker for MDR-GNR colonisation. Also, and perhaps more importantly, there were a number of important universal interventions, which ought to reduce the transmission of any pathogen, including:

  • An emphasis on hand hygiene,
  • Expanded educational activities,
  • Cultural transformation, and
  • More IPC staff.

The bottom line finding is a 43% reduction in the incidence of hospital-onset GNR BSI. Importantly, community-onset GNR BSI did not change, which acted as a pretty compelling natural control. I was reassured by the larger scale of reductions in Klebsiella species and Pseudomonas species compared with E. coli, since the Klebsiella species and Pseudomonas species are probably better markers of horizontal transmission. The fact that both MDR and non-MDR GNR BSI was reduced suggests that it was the universal interventions rather than collateral from the targeted MRSA screening and contact precautions that drove this reduction.

It’s worth reflecting on what an enormous study this was. It was performed in 130 VA hospitals across the US over the course of a decade, including 55 million patients, and 30 million patient days of acute care. Put another way, this was a 10 year study at the scale of around 2/3 of the entire NHS. Of course, over a decade, healthcare has changed. As would be the trend in most developed healthcare systems, the number of admissions increased by 16%, and the average length of stay reduced from 6 to less than 5. This also raises the question of what else changed that may explain this reduction? In general, patients are getting sicker, we are using more invasive devices, multidrug resistance is increasing, and we are using more anti-infectives, so this reduction bucks the trend. Indeed, the rate of hospital-onset GNR BSI was trending upwards before the intervention. The only niggle is the various initiatives implemented to reduce CLABSI during the decade. It would be useful to see what happened to the rate of infections at other sites with GNR during this period, which may help to confirm that CLABSI initiatives did not wholly explain the reduction.

Finally, the study raises an interesting question about the original MRSA reduction study: did this have anything to do with screening and contact precautions or was this reduction, too, explained by improved universal interventions to prevent the transmission of hospital pathogens?

Image: Wikipedia.

2 thoughts on “Reducing Gram-negative BSI…by accident

  1. Dr. Otter,
    Thank you very much for highlighting our study in this blog post, and I appreciate your suggestions about future study. Our study demonstrated that steady and collective infection control efforts could substantially reduce GNR infections, although I also do think there is no easy “short-cut” to tackle to these challenging pathogens. However, as you correctly mentioned, it is difficult to disintegrate the bundle and quantify the effect of each component by quasi-experimental study (also, presumably, those components have synergistic effects on each other). One clue may be in the difference between MDR and non-MDR, where we saw immediate intercept change in MDR but delayed onset in non-MDR. In addition, the difference between E. coli and other species again raises the decade-old question of “what is preventable, and what is not”.
    Michi Goto (Iowa City VAMC/Univ. of Iowa)


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