Eli Perencevich notes that we’re underestimating the effect of healthcare-associated infections (boldface mine):
The CDC estimates that 23,000 deaths are caused by antibiotic resistant pathogens annually and as many as 14,000 of these deaths are linked to C. difficile. Every time I look at those numbers, they make me incredibly sad. First, they include all C. difficile deaths and not just those attributed to fluoroquinolone-resistant C. difficile, for example. This tends to incorrectly overweight the importance of C. difficile relative to other pathogens. Second, and you’ve heard me rant about this before, they only count deaths caused by the small proportion of bacterial pathogens that happen to be resistant, as narrowly-defined. This would tend to diminish the importance of bacterial pathogens compared to other causes of death (e.g. accidents)….
The CDC estimates that 80,000 infections and 11,000 deaths are attributed to MRSA each year. In 2005, they also estimated that MRSA was associated with 18,650 deaths, but I’ll be conservative and stick with 11,000. Per this 2013 NHSN report, the proportion of S. aureus that were MRSA ranged from 43.8% (SSI) to 58.7% for CAUTI. I’ll use the lower proportion (44%) since this allows for some mortality secondary to more community (less MRSA) infections. However, I suspect most patients that die from S. aureus infection will ultimately be hospitalized. For simplicity, I will also assume that MRSA is twice as lethal as MSSA (AKA penicillin-resistant S. aureus).
Taking the above numbers, if there were 80,000 MRSA infections, we would expect 102,648 MSSA infections. If the mortality rate for MRSA was 13.75% (11,000/80,000) then MSSA’s mortality rate would be half of that or 6.875%. So there would be 7057 deaths from MSSA. If you add that to the 11,000 you get 18,057 deaths due to S. aureus. We can quibble about numbers, but I suspect that 7,000 deaths caused by MSSA, passes the so-called giggle test.
Thus, if we used the CDC rankings to fund research and prevention activities, we would rank C. difficile at the top of the report. However, if we used my ranking system, S. aureus (MSSA+MRSA) ranks ahead of CDI. Since most interventions to prevent MRSA deaths would also work against MSSA (vaccines, new antibiotics) shouldn’t both types be included in burden of disease estimates?
While the public discussion typically focuses on resistance, ultimately, this is a matter of infection:
…too often, proposed solutions to antibiotic resistance are posed as a combination of drug discovery and smarter use of antibiotics (which, to be clear, are critical).
…the lack of emphasis on preventing unnecessary infections, whether they be susceptible or resistant to antibiotics, should be (and hopefully, is) part of the solution. To put this another way, every time we have to treat an unnecessary infection, we use antibiotics when we shouldn’t have. At the same time, we potentially create an asymptomatic carrier (‘MRSA Mary’) of either the disease-causing resistant organism (obviously, only if it was resistant), or potentially enable the transfer of resistance into another organism (or strain) which can then serve as a reservoir of resistance.
We shouldn’t forget that infection control is a key factor. Antibiotic resistance is a serious problem, but, as Perencevich notes, there is a lot of death due to boring, unsexy, and susceptible bacterial infections.