Daptomycin non-susceptible enterococcus

There was a time, way back in the 1990's, back before quinupristin/dalfopristin (1999), linezolid (2000) or daptomycin (2003), that we had to treat VRE with an antibiotic called chloramphenicol. You remember chloramphenicol and its association with reversible bone marrow suppression and fatal aplastic anemia. Even then, VRE developed resistance to chloramphenicol, but we didn't have many other options.

So, it was an exciting time a decade ago when we suddenly had three new treatment options for the always resistant enterococcus.  Those good times have passed us by quickly.  In a new study published in ARIC, Jeremy Storm (COI alert: an ID fellow in Dan's ID division) analyzed a case-series of daptomycin non-susceptible enterococci from a 6-year period (2005-2011) at the University of Iowa.  This is a case-series, so risk factors can't specifically be measured; however, 60% of the 25 patients had prior daptomycin exposure. I've pasted Table 3 below, so you can look at the resistance profile of the isolates. Hopefully, we won't have to dig out chloramphenicol anytime soon, but I'm brushing up on its dosing just in case.

If you need more depressing enterococcal news, you can also read about a high-prevalence (61 patients) of vanB containing E. faecium in a southwest Germany neonatal ICU.

VRE Forever!

Without despair we will share
And the joys of caring will not be replaced
What has been must never end
And with the strength we have won't be erased
When the truths of love are planted firm, they won't be hard to find
And the words of love I speak to you will echo in my mind

I believe when I fall in love with you
It will be forever
I believe when I fall in love this time
It will be forever

Stevie Wonder  -  I Believe (When I Fall in Love It Will Be Forever), 1972

One of the most consistent obstacles to halting the spread of MDROs in hospitals is the ability for the organisms to persist in the environment.  Nosocomial outbreak pathogens such as MDR-Acinetobacter baumannii have been shown to persist for up to a year in vitro. Vancomycin-resistant Enterococcus faecium (VREFm) has been shown to persist for up to 4 months.  Now a new letter to the editor in the March issue of Journal of Hospital Infection suggests that we may have underestimated VREFm.

Researchers at the University Medical Centre Utrecht took an outbreak CC17 VREFm strain and a non-outbreak but concurrently isolated non-CC17 VREFm strain recovered during a year 2000 outbreak and placed 1ml at 10^9 cfu/ml of each strain in 104 bottles to dry. They then tested for recovery weekly and then quarterly.  I have pasted the survival curve below.  Survival for both strains was gradual to 10^4 at 9 months and 10^2 during the next 30 months.  Out to week 170-194 between 1-7 colonies were detected. Thus, these strains survived almost 4 years!!!

Certainly gives you something to think about.  Just another reason to love the enterococcus and Stevie Wonder - the pride of Saginaw, Michigan.

Reference: Wagenvoort et al, JHI March 2011

Another reason to wear a wide-brimmed hat to the beach

Attacking seagulls Dewey Beach, Delaware 2007

These days, with everyone worried about skin cancer, one shouldn't go to the beach without plenty of sun screen and one of those wide-brimmed floppy hats that protects your cabeza. Now you have another reason to look totally awesome at the beach - VRE protection.  That's right.  Researchers collected 57 faecal samples of Seagulls (Larus cachinnans) of Berlengas Natural Reserve in Portugal.  Using a combined proteomic and genomic approach they found that 95% of the gulls had detectable Enterococcus isolates with 50% being E. faecium and 10% E. faecalis with the remainder being other species. Around 10% had vanA containing VRE (Four E. faecium and two E. durans). Other resistance genes were detected including tet(M) and erm(B).

Of course finding VRE in other species isn't the true discovery here as the authors state they've identified proteins involved in both antibiotic resistance and the stress response in vanA-containing enterococci. They also suggest that their results may reflect the expression of a few membrane proteins involved in resistance which could be targets for the development of novel antibiotics.  I can't comment much on that, but I am going to wear my large-brimmed hat to the beach.

Radhouani et al. Proteome Science 2010.

New glycopeptide resistance gene cluster (VanM) found in E. faecium

Originally recovered in 2006 from a Shanghai patient with an intra-abdominal infection, the new Enterococcus faecium was highly resistant to Vancomycin(MIC, >256 µg/ml) and teicoplanin (MIC, 96 µg/ml).  The novel vanM cluster shares a similar DNA sequence to vanA, but is arranged more like vanD. At least the VanM, like VanA, confers glycopeptide resistance by the inducible synthesis of precursor ending in D-Ala-D-Lac. One less thing to learn. So now we have to remember vanA, vanB, vanC, vanD, vanE, vanG, vanL and vanM. The enterococcus sure has been busy making new VREs.

November 2010 AAC article Xu X., et al.