Maryn McKenna

Journalist and Author

Brand-new research: Vast increase MRSA, CA-MRSA diagnoses among kids

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I’m on the road today and have what feels like seconds between commitments, but there’s a brand new piece of research this morning that I think you folks should know about. It’s an early-online release from Pediatrics by researchers from 3 states. It uses a database called the Pediatric Health Information Systems analyze diagnosis codes and antibiotic treatment of kids treated for staph at 25 US children’s hospitals  from 1999 to 2008, and it finds:

The incidence of methicillin-resistant S aureus (MRSA) infections during this period increased 10-fold, from 2 to 21 cases per 1000 admissions, whereas the methicillin-susceptible S aureus infection rate remained stable. Among patients with S aureus infections, antibiotics that treat MRSA increased from 52% to 79% of cases, whereas those that treat only methicillin-susceptible S aureus declined from 66% to <30% of cases. Clindamycin showed the greatest increase, from 21% in 1999 to 63% in 2008. 

To translate, for those not used to reading scientific literature:

  • a 10-fold increase in MRSA diagnoses over 10 years
  • a 3-fold increase in what was not the most commonly prescribed drug, one useful for the different resistance profile of community infections 
  • clindamycin (used in mild and also invasive infections) eclipsing vancomycin (last-resort drug for invasive cases) as the most-used drug — which could be a sign of changes in prescribing patterns, changes in seriousness of the cases seen, or a warning that with so much use, clindamycin resistance could emerge more quickly, as happened when vancomycin came off the shelf in the 1990s and began to be used more.

It will take me a while to download and read the paper (hard to do in the car), but that’s the topline news. Update to come.

“Alarming” increase in MRSA infections in children

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I’ve been waiting to post on this paper from last week because there was something odd about the math in it. It’s an important and troubling finding, though, so even though I haven’t heard back from the authors, I’m going to describe it for you and explain where I think the error is. (NB, When corrected the error makes their findings more significant, not less.)

So: Authors from Emory University in Atlanta reviewed a national database of head and neck infections in children that were reported by 300 hospitals between 2001 and 2006. In those years, there were 21,009 S. aureus infections: ear infections, sinus infections and so on. But, in 2001, the proportion of S. aureus that was MRSA was 11.8%. In 2006, it was 28.1%. That’s more than a doubling — it’s a 138% increase. (Here’s the error: The authors say it was a “16.3% increase“. I believe they mean “16.3 percentage points,” which would be correct but significantly undersells their finding.)

Because 60% of the infections were outpatient, the authors make the reasonable assumption that these are community-associated MRSA (CA-MRSA). CA-MRSA is generally resistant to fewer drug than the hospital (HA-MRSA) variety. Unfortunately, they also find that this community strain is gaining additional resistance factors: More than 48% of all MRSA stains in this study were resistant to clindamycin, which is not a traditional resistance for CA-MRSA but recently has been reported more and more. Also, head and neck infections are not traditional presentations for MRSA, suggesting the bug is expanding its range.

Their comment:

…[T]he results of this study depict an alarming increase in MRSA in the United States. There is an increasing trend of clindamycin resistance among MRSA isolates. Expeditious culture of suspected head and neck infections leading to more appropriate antimicrobial drug selection is highly recommended to avoid further resistant patterns.

The cite is: Iman Naseri; Robert C. Jerris; Steven E. Sobol. Nationwide Trends in Pediatric Staphylococcus aureus Head and Neck Infections. Arch Otolaryngol Head Neck Surg. 2009;135(1):14-16.