Thursday, November 03, 2011

Important topics in ID for 2011

A Medscape Expert Review and Commentary from Dr. John Bartlett.

A few points of interest:

There's yet another new betalactamase causing resistance to multiple antibiotics including the penems. It's from India and Pakistan but has reached the US. It's very nasty and although tygecycline may show activity generally you have to use colistin. No new gram negative drugs are in the pipeline for the near future:

Two bills introduced in Congress (the GAIN bill in the House and the STARR Act in the Senate) include proposals for financial incentives for the pharmaceutical industry to produce new antibiotics. Nevertheless, no antibiotics currently in phase 3 development are likely to resolve the problem of gram-negative bacilli resistance, so it will continue to evolve with no anticipated deterrence until 2016 at the earliest, considering the snail speed of the regulatory process.

Antibiotic stewardship will need to rise to a new level.

New Hep C drugs here or in the pipeline. This section of the article is a nice perspective of the current status of Hep C evaluation and treatment.

The central line bundle and reduction in central catheter related infections. This is a remarkable story. Very soon after the bundle was rolled out came the ridiculous claim that central line infections would “go to zero.” Well, it's been a decade now. It didn't happen. Instead we have reductions in infections on the order of 50% to 70%. As laudable as that is there is no warrant for the claim that a central line infection is a “never event.”

What does this tell us about bundles in general? In the experience to date it appears that bundles can work. We're talking about the effectiveness of the central line bundle. We've seen the effectiveness of the sepsis bundle. The VAP bundle has had mixed results. As Dr. Bartlett pointed out the success of bundles is getting the attention of regulatory agencies, which means there may be a future push to turn them into performance measures. That is a concerning trend because in my view incorporating them into the performance measures will do little more than diminish their effectiveness for reasons I've stated previously here.

Rapid detection of MRSA in blood cultures by PCR. Sometimes fancy new technology really does reduce costs! Dr. Bartlett also discusses other molecular techniques along with some general principles of microbiologic diagnosis. Study question: name some pathogens that often colonize the airways of healthy individuals and some that should never be there.

Point of care testing for Hep C and other infections. Dr. Bartlett gives an update on this new test along with some background on the enormously successful track record of other point of care tests, such as HIV.

Anti-vaccination and the outbreak of measles and other pediatric infectious diseases. Some parents refuse vaccination for their children or surreptitiously avoid vaccination. This ignorant and nasty practice is not only child abuse; it has caused an enormous public health problem. Despite waning immunity we old farts, up until recently, were protected by herd immunity. Not so much anymore. Measles is a big deal. It can be fatal. Remember the case definition:

The standard case definition of measles is: fever (over 38.3ÂșC), a characteristic generalized maculopapular rash lasting more than 3 days, cough, coryza, and/or conjunctivitis. A patient with these symptoms needs prompt isolation and diagnostic testing.

So think of it in someone who has a really bad cold and a rash.

Vanc update. Dr. Bartlett references the vancomycin guidelines---a couple of years old but still very useful. Key points include the waxing and waning concerns surrounding vancomycin nephrotoxicity, to what extent it exists, a possible re-emergence due to newer more aggressive dosing recommendations, and its case definition. There's also the concern, as I've blogged before, about treatment failures with MRSA MICs in the higher range of “sensitivity.” Some higher MICs, despite being below the breakpoint, warrant switching to an alternative anti-MRSA agent. Vancomycin is the most frequently ordered antibiotic in hospitals today.

This was not the highly feared (and probably much more lethal) H5N1 strain we were watching out for.

We were under a non-evidence based mandate to wear N-95 masks. Subsequent findings confirmed that surgical masks were just as good.

What causes respiratory deaths in pandemic flu? Is it viral or bacterial pneumonia? Although well known for some time that both exist, controversy dates all the way back to the 1918 pandemic when it was widely believed that a bacterium then known as Pfeiffer's bacillus (now known as Haemophilus influenzae) was the primary etiologic agent. During that pandemic Dr. Ernest Goodpasture, who probably later insisted that there's no such thing as Goodpasture syndrome, published a report of two autopsies on cases which had negative bacterial cultures, thus giving credence to a viral etiology of influenza pneumonia. One of the patients also had glomerular lesions, which later led to the inappropriate association of Goodpasture's name with pulmonary renal syndrome due to anti-GBM antibody. (You can view the first page of Goodpasture's paper here). All that being said, it is believed that then and in 2009-2010 bacterial superinfection was important. According to Dr. Bartlett:

Ambitious gumshoe detective work with historic reports and autopsy studies determined that the major cause of death was bacterial infection with the following pathogens: S pneumoniae, N meningitidis, H influenzae type B, S aureus, and group A streptococci.[48] Translated to the 2011 experience, the major bacterial superinfecting pathogens were S pneumoniae, group A streptococci, and S aureus, which proved prophetic in the subsequent CDC review.[49]